Cognitive decline and mortality in a community-based cohort: the Monongahela Valley Independent Elders Survey

OBJECTIVES

To compare, in a longitudinal cohort study, declines in specific cognitive domains on their ability to predict time to death, in the presence and absence of dementia, and to explore an explanatory role for vascular disease.

DESIGN

Prospective population-based epidemiological study.

SETTING

The mid-Monongahela valley of southwestern Pennsylvania from 1987 to 2002.

PARTICIPANTS

Nine hundred eighty-nine community-dwelling adults aged 65 and older enrolled in the Monongahela Valley Independent Elders Survey.

MEASUREMENTS

Biennial assessments of a range of cognitive domains for up to 12 years. Mortality was modeled as a function of decline in each domain, adjusting for vascular diseases and stratified according to age (< or =75 (younger-old) and >75 (older-old)) using Cox proportional hazards modeling.

RESULTS

Average annual declines in almost all cognitive domains were significant predictors of mortality in the cohort as a whole. However, after adjustment for dementia, only general cognition, processing speed, the language composite, and the executive function composite remained significant. Adjustment for vascular diseases did not alter the results. In the younger-old group, decline in memory (hazard ratio (HR)=21.4) and executive function (HR=25.5) remained strong predictors after adjustment for dementia and vascular disease. In the older-old group, decline in processing speed was a strong predictor of mortality before (HR=7.4) and after (HR=5.3) controlling for dementia and vascular diseases.

CONCLUSION

Decline in most cognitive domains predicted mortality across the cohort, but declines in memory and learning were not independent of dementia. Different domains predicted mortality in the younger and older subgroups.

Cognitive assessment of older primary care patients with and without memory complaints

BACKGROUND

Dementia screening is currently recommended only for symptomatic patients.

OBJECTIVE

To evaluate memory complaints, a mental status test, and several cognitive tests as dementia screens in primary care.

DESIGN

Cross-sectional clinical epidemiologic study.

PARTICIPANTS

Three hundred thirty-nine comprehensively assessed, primary care patients aged > or = 65 years.

MEASUREMENTS

Memory complaints were abstracted from chart review. Scores on Mini-Mental State Examination (MMSE) and domain-specific cognitive testing were compared to a dementia diagnosis based on Clinical Dementia Rating score > or = 1, and areas under the receiver operating characteristic curves (AUC) were calculated. Classification and regression tree analyses were performed on memory complaints and tests with the highest AUCs.

RESULTS

Of 33 patients with dementia, only 5 had documented memory complaints. In 25 patients with documented memory complaints, no cognitive tests further improved identification of the 5 with dementia. In 28 patients with dementia but without memory complaints, an MMSE score < 20 identified 8 cases; among those with MMSE scores 20-21, a visual memory test identified a further 11 cases. Further cognitive testing could not detect 9 dementia cases without memory complaints and with MMSE scores > or = 22.

CONCLUSIONS

In older primary care patients with memory complaints, cognitive screening does not help identify those who require further examination for dementia. Most patients with dementia do not report memory complaints. In these asymptomatic individuals, general mental status testing, supplemented by a memory test when the mental status score is equivocal, will identify lower-scoring patients who need dementia assessment. However, high-scoring asymptomatic dementia cases will remain undetected.

The Clock Drawing Test Is an Independent Predictor of Incident Use of 24-Hour Care in a Retirement Community

BACKGROUND

It is unclear how early cognitive impairment affects future care needs. Furthermore, the Mini-Mental State Examination (MMSE), a commonly used screening tool in the clinical setting, tends to have a ceiling effect for early cognitive decline. One of the earliest changes in cognitive function is executive impairment. We examined the relationship between executive function, measured with a clock drawing protocol (CLOX1) designed to capture executive impairment, and incident need for increased level of care and total mortality.

METHODS

Residents (n = 230) in independent living at a continuing care retirement community were followed for incident need for 24-hour care (mean 2.5 years). Baseline assessment included health status and physical and cognitive function. Time to event analysis was performed to determine the association of the CLOX1 score with the outcomes.

RESULTS

Forty percent of residents had a CLOX1 score <12, and 10% had an MMSE score <26. The event rate for a CLOX1 score <12 was 30 per 100 person-years (p-y) and 13 per 100 p-y for a score > or =12. Similarly, the event rate was 34 per 100 p-y versus 17 per 100 p-y for MMSE <26 and MMSE > or =26, respectively. A CLOX1 score <12 was associated with a twofold higher risk of incident use of 24-hour care (hazard ratio 2.2; 95% confidence interval: 1.5-3.4) and death (hazard ratio 2.3; 95% confidence interval: 1.1-4.8) even after controlling for age, sex, comorbidity, and MMSE scores. The MMSE score was not an independent predictor of incident use of 24-hour care or mortality.

CONCLUSION

The clock drawing test, scored for executive impairment, but not the MMSE, predicted incident use of 24-hour care and mortality in this cohort of independent older adults.