Although educational and occupational attainments have been extensively studied, there are very few reports examining the influence of socially and intellectually engaged lifestyle to dementia. One case control study of AD in Japan (Kondo, Niino, & Shido, 1994
; 60 cases), reported that cases were significantly less active in various use of leisure time, hobbies and psychosocial behaviors. Another case-control study examined the presence of nonoccupational activities during midlife in 193 subjects with possible and probable AD (Friedland et al., 2001
). When activity patterns were classified into intellectual, passive and physical, cases were less likely to have participated in intellectual activities.
There have been only few prospective longitudinal studies examining the influence of socially and intellectually engaged lifestyle to incident dementia. In a survey sample of 422 elderly subjects the relation of various indicators of socio-economic status to incident dementia was investigated (Bickel & Cooper, 1994
). Only poor quality living accommodations were associated with increased risk of incident dementia, while indicators of social isolation such as low frequency of social contacts within and outside the family circle, low standard of social support and living in single person household did not prove to be significant.
In another cohort, the average minute per day participation in cognitively challenging “complex” (i.e., playing a musical instrument, handicrafts) and basic “simple” (dressing, eating) activities was assessed for 1877 subjects (Zabar, Corrada, Fozard, Costa, & Kawas, 1996
). Regular participation in complex (relative to simple) activities did reduce the risk of developing dementia within 2 years but not within 5, 10 or 15 years, suggesting that the effect near the time of diagnosis may reflect changes in activities due to early dementia. Unfortunately, this study has been published only in an abstract form and no details are available.
Another study evaluated social and leisure activity data in 2040 nondemented elderly community residents from Gironde (France) and recorded incident dementia on follow-up visits (Fabrigoule et al., 1995
). Traveling, doing odd jobs and knitting were associated with lower risk of incident dementia when occupational status was controlled for. However, the analyses were not controlled for either ethnic group, gender, educational attainment, cerebrovascular risk factors or depressive symptomatology. In addition, for doing odd jobs and knitting, the effect was significant only when subjects who did the activities without difficulty were compared to subjects who did not do them because of deficiencies or disabilities. When the comparison group was subjects who were not engaged in these two activities for other reasons, no significant influence was noted. Therefore, the reasons for engaging in leisure activities, rather than the leisure activities per se, seemed to affect incident dementia in this study.
There have been at least three large prospective studies that demonstrated a clear association between engaged lifestyle and incident dementia. In one of them, social ties (spouse, living arrangements, contacts with friends and relatives, confidant reciprocity and group membership) and participation in productive activities (helping others with daily tasks, paid work and volunteer work) were assessed for 2486 community-dwelling Japanese-American men (free of dementia at baseline) who were followed for 3 years (Balfour, Masaki, White, & Launer, 2001
). Both social engagement and productive activities were significantly and inversely associated with risk of incident dementia. With each additional social tie, the OR for dementia decreased by 16% and with each additional productive activity, the OR for dementia decreased by 72% and the effect of the two scales was synergistic. This study is available only in an abstract form.
We recently reported the results of a study involving a total of 1772 nondemented individuals aged 65 years or older, living in Northern Manhattan New York who were identified and followed longitudinally in a community based cohort incidence study for up to 7 years (mean 2.9 years; Scarmeas, Levy, Tang, Manly, & Stern, 2001
). In the initial visit, an interview elicited self-reported participation in a variety of leisure activities of intellectual (reading magazines or newspapers or books, playing cards or games or bingo, going to classes etc.), social (visiting or being visited by friends or relatives, etc.) and even physical (walking for pleasure or excursion, physical conditioning, etc.) nature. presents the cumulative risk for developing dementia in the high and low leisure activity groups, as calculated from survival analysis models. Even when factors like ethnic group, education and occupation were controlled for, subjects with high leisure activity had 38% less risk of developing dementia. The risk of incident dementia was reduced by approximately 12% for each additional leisure activity adopted. The effect of leisure activities on incident dementia was still present even when baseline cognitive performance, health limitations interfering with social activities, cerebrovascular disease and depression were considered.
Fig. 1 Survival curve based on Cox analysis comparing cumulative dementia incidence in subjects with high and low leisure activities in three age groups of the cohort (Scarmeas et al., 2001).
In another prospective study, frequency of participation in common cognitive activities (i.e., reading a newspaper, magazine, books) was assessed at baseline for 801 elderly Catholic nuns, priests and brothers without dementia (Wilson et al., 2002
). During a mean follow-up of 4.5 years, 1-point increase in the cognitive activity score was associated with a 33% reduction in the risk for AD. Additionally, engagement in cognitive activities was also associated with slower rates of cognitive decline. The results held even when many potential confounders were controlled for and even when subjects with memory impairment at baseline evaluation were excluded from the analyses.
In contrast to previous studies that were investigating risk for incident dementia, another study by the same group has explored the rate of cognitive decline in relation to premorbid reading activity in subjects who had already manifested the disease. In a cohort of 410 persons with AD followed for a 4-year period higher levels of premorbid reading activity was associated with more rapid decline in the global cognitive and verbal measures (Wilson et al., 2000
). Although counterintuitive at first glance, the results are consistent with the hypothesis that intellectual activities may enhance brain’s reserve capacity and that at any level of clinical severity, the underlying AD pathology is more advanced in patients with more CR. Therefore, although subjects with higher CR (compared to ones with lower CR) may manifest dementia symptomatology later in life, they may decline faster after dementia onset. These results for reading activity parallel previous similar ones for education and occupation (Stern, Tang et al., 1995