Does active leisure protect cognition? Evidence from a national birth cohort

Abstract

Social, physical and intellectual activities are thought to facilitate cognitive performance and slow the rate of age associated cognitive decline, but little is known about this association in younger adulthood. We used multiple regression to test the association between two kinds of activity at 36 years—physical exercise and spare-time activity—and verbal memory at 43 and 53 years in 1919 males and females enrolled in the MRC National Survey of Health and Development (the British 1946 birth cohort). Both kinds of activities were significantly and positively associated with memory performance at 43 years, after controlling for sex, education, occupational social class, IQ at 15 years, and recurrent ill health and significant mental distress. Furthermore, physical exercise at 36 years (but not spare-time activity) was associated with a significantly slower rate of decline in memory from 43 to 53 years, after controlling for the same factors, with evidence that continuing physical exercise after 36 years was important for protection. We conclude that physical exercise and spare-time activity are significantly associated with benefit to memory in midlife, although these two kinds of voluntary activity may exert their effects on cognition via different paths.

Introduction

The identification of controllable factors that modify rate of age-associated cognitive decline has major public health implications. The suggestion that engagement in challenging spare-time activities can diminish (Schaie, 1984), and perhaps even reverse (Schaie & Willis, 1986) the rate of this decline is therefore of considerable importance. There are, however, several theoretical and methodological problems in interpreting findings in this area.

First, it is unclear which activities are most important for cognitive maintenance. Significant effects have been reported for intellectual stimulation (Arbuckle, Gold, Andres, Schwartzman, & Chaikelson, 1992; Hultsch, Hertzog, Small, & Dixon, 1999), social engagement (Bassuk, Glass, & Berkman, 1999) and physical exercise (Albert et al., 1995; Carmelli, Swan, LaRue, & Eslinger, 1997; Kramer et al., 1999). Unfortunately these different components are not easy to isolate from each other. This is important, however, for understanding biological pathways to neural development, and for formulating possible intervention strategies for minimising cognitive decline.

Second, direction of causality is problematic. While it is possible that activity directly promotes cognitive growth and maintenance, those with high cognitive ability are also likely to engage in such activities. Similarly, decline in cognitive performance may lead to diminution of activity. This issue is difficult to resolve, even with longitudinal data (Hultsch et al., 1999).

Third, some studies do not control for factors that may account for the association between activity and cognition, particularly education and occupational social class (Schaie, 1984; Gold et al., 1995).

Fourth, it is unclear whether there is a sensitive period for activity engagement. Most studies have focused on later life, and little is known about the effects of activity on cognition in earlier adulthood. It is particularly important to determine if patterns of activity established early in life are more effective than activities begun later, and whether any benefit of this activity depends on the extent to which it is sustained.

The Medical Research Council National Survey of Health and Development (the British 1946 birth cohort) provides an opportunity to examine effects of activity on memory performance in a pre-retirement population. Participants were asked about physical exercise and spare-time activities at 36 years. Verbal memory was then measured at 43 and 53 years. We investigated the association between the above two types of activity and verbal memory at these ages, controlling for sex, educational attainment, socioeconomic status, and mental and physical health status. In addition, general intellectual ability was measured at 15 years in this cohort. Since this is highly correlated with adult IQ (Birren, Kinney, Schaie, & Woodruff, 1981; Deary, Whalley, Lemmon, Crawford, & Starr, 2000) we therefore had a rare opportunity to adjust these analyses for baseline IQ. This would reduce the likelihood that any apparent effect of activity on memory arose from those of high cognitive ability simply being more likely to engage in stimulating activities.