OBJECTIVE: We conducted this systematic review to support the U.S. Preventive Services Task Force in updating its 2014 recommendation on screening for cognitive impairment in older adults. Our review addressed the direct evidence on the benefits and harms of screening for cognitive impairment versus no screening, the test accuracy of screening instruments to detect mild cognitive impairment (MCI) and dementia, and the benefits and harms of treatment for MCI and mild to moderate dementia among community-dwelling older adults age 65 years and older.
DATA SOURCES: We performed an updated search of MEDLINE, PubMed Publisher-Supplied, PsycINFO, and the Cochrane Central Register of Controlled Trials for studies published through January 2019. We supplemented searches by examining reference lists from related articles and expert recommendations and searched federal and international trial registries for ongoing trials.
STUDY SELECTION: Two researchers reviewed 11,644 titles and abstracts and 966 full-text articles against prespecified inclusion criteria. We included test accuracy studies that included screening instruments that could be delivered in primary care in 10 minutes or less by a clinician or self-administered in 20 minutes or less compared with a reference standard. We included trials of major pharmacologic and nonpharmacologic interventions in persons with MCI or mild to moderate dementia and large, observational studies examining adverse effects of these interventions. We conducted dual, independent critical appraisal of all provisionally included studies and abstracted all important study details and results from all studies rated fair or good quality. Data were abstracted by one reviewer and confirmed by another.
DATA ANALYSIS: We synthesized data separately for each key question and within subcategories of screening instruments and treatments. For diagnostic accuracy studies, we focused on sensitivity and specificity of instruments that were evaluated in more than one study. We conducted a qualitative synthesis of results using summary tables and figures to capture key study characteristics, sources of clinical heterogeneity, and overall results of each study. Quantitative synthesis was limited to test performance of the Mini Mental State Examination (MMSE) (due to insufficient number of homogeneous studies for other instruments) and U.S. Food and Drug Administration (FDA)–approved medications to treat Alzheimer’s Disease on global cognitive outcomes, global function, and harms; nonpharmacologic interventions aimed at the patient on global cognitive outcomes; and caregiver and caregiver-patient dyad interventions on caregiver burden and depression outcomes. We ran random-effects meta-analyses using the DerSimonian and Laird method and sensitivity analyses using a Restricted Likelihood Estimation Model with the Knapp-Hartung correction to calculate the pooled differences in mean changes (for continuous data) and pooled risk ratio (for binary data). We used meta-regression to explore potential effect modification by various study, population, and intervention characteristics in cases where 10 or more studies were pooled. We generated funnel plots and conducted tests for small-study effects for all pooled analyses. Using established methods, we assessed the strength of evidence for each question.
RESULTS: Screening (Key Questions 1–3): Only one trial was identified that examined the direct effect of screening for cognitive impairment on important patient outcomes, including potential harms. In that trial, at 12 months, there was no difference in health-related quality of life between those who were screened vs. not screened. Symptoms of depression and anxiety were also similar between groups at 1, 6, and 12 months as was health care utilization and advance care planning. We identified 59 studies that addressed the diagnostic accuracy of 49 screening instruments to detect cognitive impairment. Most instruments were only studied in a handful of well-designed diagnostic accuracy studies in primary care–relevant populations. The MMSE, a brief test taking 7 to 10 minutes to complete, remains the most thoroughly studied instrument. The pooled estimate across 15 studies (n=12,796) resulted in 89 percent sensitivity (95% CI, 0.85 to 0.92) and 89 percent specificity (95% CI, 0.85 to 0.93) to detect dementia at a cutoff of 23 or less or 24 or less. Other screening instruments evaluated in more than one study included the very brief instruments (≤5 minutes) of the CDT, MIS, MSQ, Mini-Cog, Lawton IADL, VF, AD8, and FAQ and the brief instruments (6 to 10 minutes) of the 7MS, AMT, MoCA, SLUMS, and TICS with sensitivity to detect dementia usually at 0.75 or higher and specificity at 0.80 or higher for all instruments. For self-administered, longer tests (>10 minutes), only the IQCODE was assessed in more than one study, with sensitivity to detect dementia ranging from 0.80 to 0.88 and specificity ranging from 0.51 to 0.91. Across all instruments, test performance was generally higher in the detection of dementia vs. mild cognitive impairment, although confidence intervals overlapped. No studies directly addressed the adverse psychological effects of screening or adverse effects from false-positive or false-negative testing. Treatment (Key Questions 4 and 5): We identified 224 trials and 3 observational studies representing more than 240,000 patients and/or caregivers that addressed the treatment or management of MCI or mild to moderate dementia. None of the treatment trials were linked with a screening program; in all cases, trial participants were persons with known MCI or dementia. Pharmacologic Interventions: Based on 45 trials (n=22,431) and three observational studies (n=190,076) that evaluated acetylcholinesterase inhibitors (AChEIs) (i.e., donepezil, galantamine, rivastigmine) and memantine, these medications may improve measures of global cognitive function in the short term, but the magnitude of change is small. In meta-analyses, the differences in changes between those on AChEIs or memantine compared with those on placebo ranged from approximately 1 to 2.5 points on the ADAS-Cog-11 and 0.5 to 1 point on the MMSE over 3 months to 3 years of followup. AChEIs and memantine appeared to increase the likelihood of improving or maintaining patients’ global function by 15 percent (for memantine) to 50 percent (for rivastigmine) in the short term (pooled 95% confidence interval range, 0.49 to 2.69). Other outcome measures were inconsistently reported. Total adverse events and discontinuation due to adverse events were more common with AChEIs, but not memantine, compared with placebo. Rates of serious adverse events overall were not higher among those taking medications vs. placebo, but individual studies noted increased rates of serious adverse events. Trials evaluating other medications or dietary supplements (k=29; n=6,489), including discontinuing antihypertensives, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (atorvastatin and simvastatin), nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen, indomethacin, and celecoxib), gonadal steroids (estrogen [plus or minus progesterone] and testosterone), and dietary supplements and vitamins (multivitamins, B vitamins, vitamin E, and omega-3 fatty acids) showed no benefit on global cognitive or physical function in persons with mild to moderate dementia or MCI. Nonpharmacologic Interventions: We identified 61 trials (n=7,847) that evaluated nonpharmacologic patient-level interventions, including cognitive-focused, exercise, and multicomponent and other interventions. Among all interventions, there was no clear benefit on global or domain-specific measures of cognitive function compared with control conditions at 3 months to 2 years followup. Effect estimates generally favored the intervention groups over control groups, but the magnitude of effect was inconsistent across trials and represented very wide confidence intervals (ranging from no effect to a large effect). Physical function outcomes, including change in activities of daily living and independent activities of daily living, as well as quality of life and mental and neuropsychiatric symptoms, were inconsistently reported. There was, however, a pattern of effect for exercise interventions, with small improvements seen in measures of physical function and symptoms for intervention groups, whereas control groups reported worsening function. Caregiver and caregiver-patient dyad interventions including psychoeducation for the caregiver and care and case management interventions, reported in 88 trials (n=14,880), resulted in a consistent benefit on caregiver burden and depression outcomes. Effect sizes were mostly small, however, and were of unclear clinical significance. Little harm was evident in the few nonpharmacologic intervention trials that reported harms.
LIMITATIONS: There is a lack of evidence around how screening for and treating MCI and early-stage dementia affects decision making outcomes. Furthermore, there has been little reproducibility in testing specific screening instruments in primary care populations. The treatment literature is limited by a lack of consistency in the specific outcomes reported and short followup duration. It is difficult to interpret the clinical importance of the small average effects seen among treatment trials, and many measures likely have limited responsiveness for patients with less pronounced cognitive impairment. Consistent and standardized reporting of results according to meaningful thresholds of clinical significance would be helpful in interpreting the small average effects on continuous outcome measures. Other important measures such as quality of life, physical function, and institutionalization, were inconsistently reported.
CONCLUSIONS: Several brief screening instruments can adequately detect cognitive impairment, especially in populations with a higher prevalence of underlying dementia. There is no empiric evidence, however, that screening for cognitive impairment or early diagnosis of cognitive impairment improves patient, caregiver, family, or clinician decision making or other important outcomes nor causes harm. In general, there is support that AChEIs and memantine and interventions that support caregivers, including those that help coordinate care for patients and caregivers, can result in small improvements in the short term. Unfortunately, the average effects of these benefits are quite small and likely not of clinical significance. Any benefits are further limited by the commonly experienced side effects of medications and the limited availability of complex caregiver interventions. Cognitive stimulation and training, exercise interventions, and other medications and supplements showed some favorable effects on patients’ cognitive and physical function, but trial evidence lacked consistency and the estimates of benefit were imprecise. There is less evidence related to screening for and treating MCI. The test performance of the few instruments evaluated to detect MCI was lower than the sensitivity and specificity to detect dementia and there is little evidence for any pharmacologic or nonpharmacologic interventions to preserve or improve patient functioning in persons with MCI.
IMPORTANCE: Early identification of cognitive impairment may improve patient and caregiver health outcomes.
OBJECTIVE: To systematically review the test accuracy of cognitive screening instruments and benefits and harms of interventions to treat cognitive impairment in older adults (≥65 years) to inform the US Preventive Services Task Force.
DATA SOURCES: MEDLINE, PubMed, PsycINFO, and Cochrane Central Register of Controlled Trials through January 2019, with literature surveillance through November 22, 2019.
STUDY SELECTION: Fair- to good-quality English-language studies of cognitive impairment screening instruments, and pharmacologic and nonpharmacologic treatments aimed at persons with mild cognitive impairment (MCI), mild to moderate dementia, or their caregivers.
DATA EXTRACTION AND SYNTHESIS: Independent critical appraisal and data abstraction; random-effects meta-analyses and qualitative synthesis.
MAIN OUTCOMES AND MEASURES: Sensitivity, specificity; patient, caregiver, and clinician decision-making; patient function, quality of life, and neuropsychiatric symptoms; caregiver burden and well-being.
RESULTS: The review included 287 studies with more than 280 000 older adults. One randomized clinical trial (RCT) (n = 4005) examined the direct effect of screening for cognitive impairment on patient outcomes, including potential harms, finding no significant differences in health-related quality of life at 12 months (effect size, 0.009 [95% CI, -0.063 to 0.080]). Fifty-nine studies (n = 38 531) addressed the accuracy of 49 screening instruments to detect cognitive impairment. The Mini-Mental State Examination was the most-studied instrument, with a pooled sensitivity of 0.89 (95% CI, 0.85 to 0.92) and specificity of 0.89 (95% CI, 0.85 to 0.93) to detect dementia using a cutoff of 23 or less or 24 or less (15 studies, n = 12 796). Two hundred twenty-four RCTs and 3 observational studies including more than 240 000 patients or caregivers addressed the treatment of MCI or mild to moderate dementia. None of the treatment trials were linked with a screening program; in all cases, participants were persons with known cognitive impairment. Medications approved to treat Alzheimer disease (donepezil, galantamine, rivastigmine, and memantine) improved scores on the ADAS-Cog 11 by 1 to 2.5 points over 3 months to 3 years. Psychoeducation interventions for caregivers resulted in a small benefit for caregiver burden (standardized mean difference, -0.24 [95% CI, -0.36 to -0.13) over 3 to 12 months. Intervention benefits were small and of uncertain clinical importance.
CONCLUSIONS AND RELEVANCE: Screening instruments can adequately detect cognitive impairment. There is no empirical evidence, however, that screening for cognitive impairment improves patient or caregiver outcomes or causes harm. It remains unclear whether interventions for patients or caregivers provide clinically important benefits for older adults with earlier detected cognitive impairment or their caregivers.
BACKGROUND: Cognitive impairment is a principal manifestation of Alzheimer disease (AD). To provide a clinical reference for the treatment of AD, a network meta-analysis (NMA) was performed to evaluate the effects of different anti-dementia drugs on the cognitive impairment exhibited by patients with AD.
METHODS: Relevant randomized controlled trials are found through the Pubmed database, Web of Science, Clinical Trials, Embase, Cohranne library, Chinese National Knowledge Infrastructure database, CBM databases, and Wanfang among others. A total of 33 articles were collected, with the earliest document collected having been published in February 2017. The included reports were screened for quality of papers by using strict inclusion and exclusion criteria. All analyses were based on previously published studies reporting de-identified data; thus, no ethical approval or patient consent were required. The Mini-Mental State Examination scores informed the classification of the 33 articles into a mild subgroup, which featured 11 articles, and 12 drugs (besides a placebo); a moderate subgroup, which featured 17 articles and 15 drugs (besides a placebo); and a severe subgroup, which featured 5 articles and 3 drugs (besides a placebo).
RESULTS: While donepezil, galanthamine, and huperzine demonstrated the highest efficacy in the mild cognitive dysfunction subgroup (mean difference = 5.2, 2.5, and 2.4, respectively). Donepezil, huperzine A, and rivastigmine achieved the most significant effects in the moderate cognitive dysfunction subgroup (MD = 3.8, 2.9, and 3.0 respectively). In the severe subgroup, donepezil was demonstrably superior to memantine. Donepezil was thus found to effectively address cognitive impairment in patients with AD regardless of the degrees of cognitive decline.
CONCLUSIONS: Evaluation of the clinically common anti-dementia drugs using NMA affirmed the utility of cholinesterase inhibitors, especially donepezil, in alleviating cognitive dysfunction of patients with AD. This study may therefore help to inform the clinical selection of pharmacotherapeutic interventions addressing cognitive dysfunction in patients with AD.
IMPORTANCE: Clinical trials in Alzheimer disease (AD) generally allow participants to continue receiving concomitant medications, including cholinesterase inhibitors (ChEIs) and memantine, if the dose is stable. Previous analysis of observational studies indicates such individuals experience greater rate of decline on cognitive testing than those not receiving such medications.
OBJECTIVE: To investigate whether concomitant use of ChEIs or memantine is associated with cognitive outcomes in AD clinical trials.
DATA SOURCES: Meta-database of 18 studies from the Alzheimer Disease Cooperative Study and Alzheimer Disease Neuroimaging Initiative.
STUDY SELECTION: All studies with data on ChEI and memantine use that included assessment of specified outcome measures.
DATA EXTRACTION AND SYNTHESIS: The analysis estimated annual rate of decline on the Alzheimer Disease Assessment Scale-cognitive subscale (ADAS-cog) using linear mixed-effects models, and compared rates for participants receiving ChEIs and memantine, alone and combined, with participants not receiving either medication using random-effects meta-analysis.
MAIN OUTCOMES AND MEASURES: Annual rate of change on the ADAS-cog.
RESULTS: Across 10 studies, of 2714 participants, the mean (SD) age was 75.0 (8.2) years, 58% were female, and 9% were racial/ethnic minorities. There were 906 participants (33.4%) receiving ChEIs, 143 (5.3%) receiving memantine, 923 (34.0%) receiving both, and 742 (27.3%) receiving neither. Meta-analysis showed those receiving ChEIs or memantine were associated with significantly greater annual rate of decline on the ADAS-cog than those receiving neither medication (1.4 points/y; 95% CI, 0.1-2.7).
CONCLUSIONS AND RELEVANCE: Similar to observational studies, many participants in AD clinical trials receiving ChEIs or memantine experience greater cognitive decline. This difference is nearly as large as the hypothesized effect sizes of the treatments investigated in the trials. Concomitant use of ChEIs or memantine may be confounded with outcomes on the ADAS-cog and should be considered in design of clinical trials of potential therapeutic agents for AD. Post hoc analyses stratifying by ChEIs or memantine must be interpreted cautiously given the potential for confounding.
BACKGROUND: In 2012, the United States Food and Drug Administration (FDA) issued a warning regarding potential adverse effects of HMG-CoA reductase inhibitors (statins) on cognition, based on the Adverse Events Reporting System and a review of the medical literature. We aimed to synthesize randomized clinical trial (RCTs) evidence on the association between statin therapy and cognitive outcomes.
METHODS: We searched MEDLINE, EMBASE, and Cochrane CENTRAL through December 2012, and reviewed published systematic reviews of statin treatment. We sought RCTs that compared statin treatment versus placebo or standard care, and reported at least one cognitive outcome (frequency of adverse cognitive events or measurements using standard neuropsychological cognitive test scores). Studies reporting sufficient information to calculate effect sizes were included in meta-analyses. Standardized and unstandardized mean differences were calculated for continuous outcomes for global cognition and for pre-specified cognitive domains. The main outcome was change in cognition measured by neuropsychological tests; an outcome of secondary interest was the frequency of adverse cognitive events observed during follow-up.
RESULTS: We identified 25 RCTs (all placebo-controlled) reporting cognitive outcomes in 46,836 subjects, of which 23 RCTs reported cognitive test results in 29,012 participants. Adverse cognitive outcomes attributable to statins were rarely reported in trials involving cognitively normal or impaired subjects. Furthermore, meta-analysis of cognitive test data (14 studies; 27,643 participants) failed to show significant adverse effects of statins on all tests of cognition in either cognitively normal subjects (standardized mean difference 0.01, 95 % confidence interval, CI, -0.01 to 0.03, p = 0.42) or Alzheimer's disease subjects (standardized mean difference -0.05, 95 % CI -0.19 to 0.10, p = 0.38).
CONCLUSIONS: Statin therapy was not associated with cognitive impairment in RCTs. These results raise questions regarding the continued merit of the FDA warning about potential adverse effects of statins on cognition.
BACKGROUND: Increasing evidence suggests vascular risk factors (VRF) play a role in the pathogenesis of Alzheimer's disease (AD). Epidemiological studies have found associations between VRF and risk of AD. Treating VRF in patients with AD offers a potential treatment option but ineffective treatments should be avoided in this group who are frequently on multiple medications and in whom compliance may be challenging.
METHODS: Studies containing information on the treatment of VRF in patients with a diagnosis of AD were identified using a defined search strategy. Randomised controlled trials and observational studies were included.
RESULTS: The pre-specified search strategy retrieved 11,992 abstract articles, and 25 papers including those identified on review of reference lists and reviews met the inclusion criteria. Of these, 11 were randomised controlled trials (RCTs) and 14 observational studies. Observational studies suggested that a VRF package and treatment of hypertension and statin therapy may be associated with improved outcome but these studies suffered from potential bias. The few RCTs performed were mostly small with short duration follow-up, and do not provide clear evidence either way.
CONCLUSIONS: Observational data raises the possibility that treating VRF could alter the rate of decline in AD. However RCT data are not yet available to support this hypothesis and to alter clinical practice. RCTs in larger numbers of individuals with longer follow-up, ideally in the early stages of AD, are required to address this potentially important treatment question.
OBJECTIVES: This review aimed to assess the clinical efficacy and tolerability of statins in the treatment of dementia.
METHODS: We searched the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS, as well as many trials registries and grey literature sources (27 October 2008). Double-blind, randomized controlled trials of statins given for at least 6 months in people with a diagnosis of dementia were included. Two independent authors extracted and assessed data independently against the inclusion criteria. Data were pooled where appropriate and entered into a meta-analysis.
RESULTS: Three studies were identified (748 participants, age range 50-90 years). All patients had a diagnosis of probable or possible Alzheimer's disease according to standard criteria, and most patients were established on a cholinesterase inhibitor. Change in Alzheimer's Disease Assessment Scale cognitive subscale from baseline was a primary outcome in three studies; when data were pooled, statins did not provide any beneficial effect in this cognitive measure (mean difference -1.12; 95% confidence interval -3.99, 1.75; p = 0.44). All studies provided a change in Mini-Mental State Examination from baseline; there was no significant benefit from statins in this cognitive measure when the data were pooled (mean difference -1.53; 95% confidence interval -3.28; 0.21, p = 0.08). There were no studies identified assessing the role of statins in treatment of vascular dementia. There was no evidence that statins were detrimental to cognition.
CONCLUSIONS: There is insufficient evidence to recommend statins for the treatment of dementia.
AIMS: The effect of statin treatment on ventricular arrhythmic complications is uncertain. We sought to test whether statins reduce the risk of ventricular tachyarrhythmia, cardiac arrest, and sudden cardiac death.
METHODS AND RESULTS: We searched MEDLINE, EMBASE, and CENTRAL up to October 2010. Randomized controlled trials comparing statin with no statin or comparing intensive vs. standard dose statin, with more than 100 participants and at least 6-month follow-up were considered for inclusion and relevant unpublished data obtained from the investigators. Twenty-nine trials of statin vs. control (113 568 participants) were included in the main analyses. In these trials, statin therapy did not significantly reduce the risk of ventricular tachyarrhythmia [212 vs. 209; odds ratio (OR) = 1.02, 95% confidence interval (CI) 0.84-1.25, P = 0.87] or of cardiac arrest (82 vs. 78; OR = 1.05, 95% CI 0.76-1.45, P = 0.84), but was associated with a significant 10% reduction in sudden cardiac death (1131 vs. 1252; OR = 0.90; 95% CI 0.82-0.97, P = 0.01). This compared with a 22% reduction in the risk of other 'non-sudden' (mostly atherosclerotic) cardiac deaths (1235 vs. 1553; OR = 0.78, 95% CI 0.71-0.87, P < 0.001). Results were not materially altered by inclusion of eight trials (involving 41 452 participants) of intensive vs. standard dose statin regimens.
CONCLUSION: Statins have a modest beneficial effect on sudden cardiac death. However, previous suggestions of a substantial protective effect on ventricular arrhythmic events could not be supported.
<b>BACKGROUND: </b>It has been suggested that statins substantially reduce the risk of venous thromboembolic events. We sought to test this hypothesis by performing a meta-analysis of both published and unpublished results from randomised trials of statins.<b>Methods and FINDINGS: </b>We searched MEDLINE, EMBASE, and Cochrane CENTRAL up to March 2012 for randomised controlled trials comparing statin with no statin, or comparing high dose versus standard dose statin, with 100 or more randomised participants and at least 6 months' follow-up. Investigators were contacted for unpublished information about venous thromboembolic events during follow-up. Twenty-two trials of statin versus control (105,759 participants) and seven trials of an intensive versus a standard dose statin regimen (40,594 participants) were included. In trials of statin versus control, allocation to statin therapy did not significantly reduce the risk of venous thromboembolic events (465 [0.9%] statin versus 521 [1.0%] control, odds ratio [OR] = 0.89, 95% CI 0.78-1.01, p = 0.08) with no evidence of heterogeneity between effects on deep vein thrombosis (266 versus 311, OR 0.85, 95% CI 0.72-1.01) and effects on pulmonary embolism (205 versus 222, OR 0.92, 95% CI 0.76-1.12). Exclusion of the trial result that provided the motivation for our meta-analysis (JUPITER) had little impact on the findings for venous thromboembolic events (431 [0.9%] versus 461 [1.0%], OR = 0.93 [95% CI 0.82-1.07], p = 0.32 among the other 21 trials). There was no evidence that higher dose statin therapy reduced the risk of venous thromboembolic events compared with standard dose statin therapy (198 [1.0%] versus 202 [1.0%], OR = 0.98, 95% CI 0.80-1.20, p = 0.87). Risk of bias overall was small but a certain degree of effect underestimation due to random error cannot be ruled out. Please see later in the article for the Editors' Summary.<b>CONCLUSIONS: </b>The findings from this meta-analysis do not support the previous suggestion of a large protective effect of statins (or higher dose statins) on venous thromboembolic events. However, a more moderate reduction in risk up to about one-fifth cannot be ruled out.
OBJECTIVE: To assess the clinical efficacy and safety of atorvastatin in the treatment of Alz-heimer's disease.DATA SOURCES: Medline (1948/2011-04), Embase (1966/2011-04), Cochrane Library (Issue 3, 2011), Chinese National Knowledge Infrastructure (1989/2011-04), and the Chinese Biomedical Literature Database (1979/2011-04) were searched for randomized clinical trials regardless of lan-guage. Abstracts of conference papers were manually searched. Furthermore, Current Controlled Trials (http://controlled-trials.com), Clinical Trials.gov (http://clinicaltrials.gov), and Chinese Clinical Trial Registry (http://www.chictr.org) were also searched.Key words included Alzheimer disease, dementia, cognition, affection, memory dysfunction, hydroxymethylglutaryl-CoA reductase inhibitors, atorvastatin and statins.DATA SELECTION: Randomized controlled trials of grade A or B according to quality evaluation criteria of the Cochrane Collaboration were selected, in which atorvastatin and placebo were used to evaluate the effects of atorvastatin in the treatment of Alzheimer's disease. Study methodological quality was evaluated based on criteria described in Cochrane Reviewer's Handbook 5.0.1. Revman 5.1 software was used for data analysis.MAIN OUTCOME MEASURES: Clinical efficacy, safety, withdrawal from the studies, and withdrawal due to adverse effects.CONCLUSION: There is insufficient evidence to recommend atorvastatin for the treatment of mild to moderate Alzheimer's disease, because there was no benefit on general function, cognitive function or mental/behavior abnormality outcome measures. Efficacy and safety need to be confirmed by larger and higher quality randomized controlled trials, especially for moderate to severe Alzheimer's disease, because results of this systematic review may be limited by selection bias, implementation bias, as well as measurement bias.
We conducted this systematic review to support the U.S. Preventive Services Task Force in updating its 2014 recommendation on screening for cognitive impairment in older adults. Our review addressed the direct evidence on the benefits and harms of screening for cognitive impairment versus no screening, the test accuracy of screening instruments to detect mild cognitive impairment (MCI) and dementia, and the benefits and harms of treatment for MCI and mild to moderate dementia among community-dwelling older adults age 65 years and older.
DATA SOURCES:
We performed an updated search of MEDLINE, PubMed Publisher-Supplied, PsycINFO, and the Cochrane Central Register of Controlled Trials for studies published through January 2019. We supplemented searches by examining reference lists from related articles and expert recommendations and searched federal and international trial registries for ongoing trials.
STUDY SELECTION:
Two researchers reviewed 11,644 titles and abstracts and 966 full-text articles against prespecified inclusion criteria. We included test accuracy studies that included screening instruments that could be delivered in primary care in 10 minutes or less by a clinician or self-administered in 20 minutes or less compared with a reference standard. We included trials of major pharmacologic and nonpharmacologic interventions in persons with MCI or mild to moderate dementia and large, observational studies examining adverse effects of these interventions. We conducted dual, independent critical appraisal of all provisionally included studies and abstracted all important study details and results from all studies rated fair or good quality. Data were abstracted by one reviewer and confirmed by another.
DATA ANALYSIS:
We synthesized data separately for each key question and within subcategories of screening instruments and treatments. For diagnostic accuracy studies, we focused on sensitivity and specificity of instruments that were evaluated in more than one study. We conducted a qualitative synthesis of results using summary tables and figures to capture key study characteristics, sources of clinical heterogeneity, and overall results of each study. Quantitative synthesis was limited to test performance of the Mini Mental State Examination (MMSE) (due to insufficient number of homogeneous studies for other instruments) and U.S. Food and Drug Administration (FDA)–approved medications to treat Alzheimer’s Disease on global cognitive outcomes, global function, and harms; nonpharmacologic interventions aimed at the patient on global cognitive outcomes; and caregiver and caregiver-patient dyad interventions on caregiver burden and depression outcomes. We ran random-effects meta-analyses using the DerSimonian and Laird method and sensitivity analyses using a Restricted Likelihood Estimation Model with the Knapp-Hartung correction to calculate the pooled differences in mean changes (for continuous data) and pooled risk ratio (for binary data). We used meta-regression to explore potential effect modification by various study, population, and intervention characteristics in cases where 10 or more studies were pooled. We generated funnel plots and conducted tests for small-study effects for all pooled analyses. Using established methods, we assessed the strength of evidence for each question.
RESULTS:
Screening (Key Questions 1–3): Only one trial was identified that examined the direct effect of screening for cognitive impairment on important patient outcomes, including potential harms. In that trial, at 12 months, there was no difference in health-related quality of life between those who were screened vs. not screened. Symptoms of depression and anxiety were also similar between groups at 1, 6, and 12 months as was health care utilization and advance care planning. We identified 59 studies that addressed the diagnostic accuracy of 49 screening instruments to detect cognitive impairment. Most instruments were only studied in a handful of well-designed diagnostic accuracy studies in primary care–relevant populations. The MMSE, a brief test taking 7 to 10 minutes to complete, remains the most thoroughly studied instrument. The pooled estimate across 15 studies (n=12,796) resulted in 89 percent sensitivity (95% CI, 0.85 to 0.92) and 89 percent specificity (95% CI, 0.85 to 0.93) to detect dementia at a cutoff of 23 or less or 24 or less. Other screening instruments evaluated in more than one study included the very brief instruments (≤5 minutes) of the CDT, MIS, MSQ, Mini-Cog, Lawton IADL, VF, AD8, and FAQ and the brief instruments (6 to 10 minutes) of the 7MS, AMT, MoCA, SLUMS, and TICS with sensitivity to detect dementia usually at 0.75 or higher and specificity at 0.80 or higher for all instruments. For self-administered, longer tests (>10 minutes), only the IQCODE was assessed in more than one study, with sensitivity to detect dementia ranging from 0.80 to 0.88 and specificity ranging from 0.51 to 0.91. Across all instruments, test performance was generally higher in the detection of dementia vs. mild cognitive impairment, although confidence intervals overlapped. No studies directly addressed the adverse psychological effects of screening or adverse effects from false-positive or false-negative testing. Treatment (Key Questions 4 and 5): We identified 224 trials and 3 observational studies representing more than 240,000 patients and/or caregivers that addressed the treatment or management of MCI or mild to moderate dementia. None of the treatment trials were linked with a screening program; in all cases, trial participants were persons with known MCI or dementia. Pharmacologic Interventions: Based on 45 trials (n=22,431) and three observational studies (n=190,076) that evaluated acetylcholinesterase inhibitors (AChEIs) (i.e., donepezil, galantamine, rivastigmine) and memantine, these medications may improve measures of global cognitive function in the short term, but the magnitude of change is small. In meta-analyses, the differences in changes between those on AChEIs or memantine compared with those on placebo ranged from approximately 1 to 2.5 points on the ADAS-Cog-11 and 0.5 to 1 point on the MMSE over 3 months to 3 years of followup. AChEIs and memantine appeared to increase the likelihood of improving or maintaining patients’ global function by 15 percent (for memantine) to 50 percent (for rivastigmine) in the short term (pooled 95% confidence interval range, 0.49 to 2.69). Other outcome measures were inconsistently reported. Total adverse events and discontinuation due to adverse events were more common with AChEIs, but not memantine, compared with placebo. Rates of serious adverse events overall were not higher among those taking medications vs. placebo, but individual studies noted increased rates of serious adverse events. Trials evaluating other medications or dietary supplements (k=29; n=6,489), including discontinuing antihypertensives, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (atorvastatin and simvastatin), nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen, indomethacin, and celecoxib), gonadal steroids (estrogen [plus or minus progesterone] and testosterone), and dietary supplements and vitamins (multivitamins, B vitamins, vitamin E, and omega-3 fatty acids) showed no benefit on global cognitive or physical function in persons with mild to moderate dementia or MCI. Nonpharmacologic Interventions: We identified 61 trials (n=7,847) that evaluated nonpharmacologic patient-level interventions, including cognitive-focused, exercise, and multicomponent and other interventions. Among all interventions, there was no clear benefit on global or domain-specific measures of cognitive function compared with control conditions at 3 months to 2 years followup. Effect estimates generally favored the intervention groups over control groups, but the magnitude of effect was inconsistent across trials and represented very wide confidence intervals (ranging from no effect to a large effect). Physical function outcomes, including change in activities of daily living and independent activities of daily living, as well as quality of life and mental and neuropsychiatric symptoms, were inconsistently reported. There was, however, a pattern of effect for exercise interventions, with small improvements seen in measures of physical function and symptoms for intervention groups, whereas control groups reported worsening function. Caregiver and caregiver-patient dyad interventions including psychoeducation for the caregiver and care and case management interventions, reported in 88 trials (n=14,880), resulted in a consistent benefit on caregiver burden and depression outcomes. Effect sizes were mostly small, however, and were of unclear clinical significance. Little harm was evident in the few nonpharmacologic intervention trials that reported harms.
LIMITATIONS:
There is a lack of evidence around how screening for and treating MCI and early-stage dementia affects decision making outcomes. Furthermore, there has been little reproducibility in testing specific screening instruments in primary care populations. The treatment literature is limited by a lack of consistency in the specific outcomes reported and short followup duration. It is difficult to interpret the clinical importance of the small average effects seen among treatment trials, and many measures likely have limited responsiveness for patients with less pronounced cognitive impairment. Consistent and standardized reporting of results according to meaningful thresholds of clinical significance would be helpful in interpreting the small average effects on continuous outcome measures. Other important measures such as quality of life, physical function, and institutionalization, were inconsistently reported.
CONCLUSIONS:
Several brief screening instruments can adequately detect cognitive impairment, especially in populations with a higher prevalence of underlying dementia. There is no empiric evidence, however, that screening for cognitive impairment or early diagnosis of cognitive impairment improves patient, caregiver, family, or clinician decision making or other important outcomes nor causes harm. In general, there is support that AChEIs and memantine and interventions that support caregivers, including those that help coordinate care for patients and caregivers, can result in small improvements in the short term. Unfortunately, the average effects of these benefits are quite small and likely not of clinical significance. Any benefits are further limited by the commonly experienced side effects of medications and the limited availability of complex caregiver interventions. Cognitive stimulation and training, exercise interventions, and other medications and supplements showed some favorable effects on patients’ cognitive and physical function, but trial evidence lacked consistency and the estimates of benefit were imprecise. There is less evidence related to screening for and treating MCI. The test performance of the few instruments evaluated to detect MCI was lower than the sensitivity and specificity to detect dementia and there is little evidence for any pharmacologic or nonpharmacologic interventions to preserve or improve patient functioning in persons with MCI.
