Maintaining Cognitive Function with Aging: What Helps?

Getting older can be challenging. Among other things, and of neurologic interest, cognitive function decreases with age. The rate and degree of this decrease, however, varies widely. In the last several years, improved quality of life in older years has become a goal. This has led to the concept of "successful aging," which delineates aging without undue functional or cognitive deterioration. However, most studies related to this idea have primarily evaluated functional decline, and have not incorporated clear cognitive measures. Other studies have evaluated various factors which may help predict the rate of cognitive decline, or the progression into dementia, but variations in definitions, duration, etc limit the application of the findings therein.

The Health ABC Study (Health, Aging and Body Composition) is a long term prospective evaluation of a large number (3,075) of community-dwelling persons in Memphis and Pittsburgh. The participants were 70-79 years old when recruited in 1997. A recent analysis of this cohort seeks to evaluate a variety of factors which may be associated with maintained cognitive function over a period of several years.

Many data points were obtained at enrollment, including age, race, gender, educational level, tobacco and ethanol use, exercise level, perceived health status, and a number of biologic markers. To evaluate cognition, the Modified Mini-Mental State Examination was given at baseline and at years 3, 5, and 8. This battery is a brief set of tests with components evaluating, at least to some degree, orientation, concentration, language, praxis, and immediate and delayed memory. Change over time in cognitive function was divided into 3 strata: maintainers, minor decliners, and major decliners.

2,509 patients had data suitable for this analysis. In this cohort, 758 (30%) were maintainers, 1,340 (53%) minor decliners, and 411 (16%) major decliners. Demographic factors associated with being in the "maintainer" group included younger age and white race. Associated psychosocial factors were at least high school education or at least a ninth grade literacy level, not living alone, working or volunteering, not being a caretaker, and receiving sufficient social support. Health factors predicting "maintainer" status included higher health self-rating, ingestion of > 1 alcoholic drink daily, refraining from tobacco use, moderate to vigorous weekly exercise, lower BMI, and the absence of hypertension, diabetes, and stroke. And, associated biologic factors were absence of the APO E4 allele, higher triglyceride levels, and lower levels of CRP, IL-6, and fasting glucose.

However, many of these factors dropped out in the multivariate analysis. The remaining factors predicting being in the maintainer, rather than the minor decliner group, were age, white race, at least a high school education and ninth grade literacy level, weekly moderate to vigorous exercise, and refraining from smoking. Major decline was predicted by age, educational level of less than high school, lower than a ninth grade literacy level, a lower level of social support, and presence of the APO E4 gene.

Most of this is not particularly surprising, although confirmation in a large cohort is reassuring. The issue is how these data can help effect change. Some factors, such as age and race, are not modifiable. It is difficult to readily craft a good social support system. However, regular exercise, maintaining activity, and refraining from smoking or other tobacco use all appear to be associated with maintenance of cognitive function, and are all factors which can be addressed. The authors were surprised that biologic factors were not more significant. They hypothesize that exercise and other modifiable factors overpower the effects of biologic characteristics in this large sample.

This study reinforces that straightforward life changes can be associated with improved aging. Exercise, staying active, and not smoking will serve us all well as we grow older.