Predictors of successful ageing: findings from the longitudinal follow-up of the Lothian Birth Cohort 1921

The progressive ageing of the world's population implies that any age-associated deterioration will become ever more prevalent. Some individuals can be identified as ageing more 'successfully' than their peers; the maintenance of mental abilities in old age is one marker of this. Isolating modifiable determinants of cognitive ageing is therefore a research priority. Factors from the domains of work, social support networks and activity participation were examined in an ageing group retrospectively and contemporaneously. Aged 11, these individuals had taken a test of mental ability (the Moray House Test: MHT) as part of the 1932 Scottish Mental Survey. Some 550 survivors were recruited -79 years old into a longitudinal study of cognitive ageingthe Lothian Birth Cohort 1921-when they again took the MHT, plus a battery of tests (Raven's Progressive Matrices, Verbal Fluency and Logical Memory). A 2nd wave of testing was completed at -83 years old. Over the 4 years of follow-up, significant decline was observed in cognitive ability (composite of the 3 tests) and separately for Raven's and Verbal Fluency, but not for Logical Memory. In regression analyses, higher cognitive ability at age 79 assessed by the MHT (expressed as age-79 IQ) was predicted by less hazardous working conditions, a quieter working environment and receiving more supervisor support; living with a spouse/partner for a fewer number of years in young adulthood and having fewer close friends/relatives in old age; and increased activity in midlife and old age. Each factor explained about 1% to 3% of the variance, independent of age-11 IQ and sex. Less cognitive decline from 79 to 83 years old (on the general ability composite) was associated with increased support from coworkers and walking (versus not) at age 80, each accounting for about 2% of the variance (independent of age-11 IQ and sex). When the analyses were pooled across lifestyle domains and further potential confounders (including education, social class, depression and disease history) were controlled, measures of the hazards encountered at work and lifetime activity participation each accounted for 1% to 3% of the variance in age-79 IQ, whilst walking accounted for about 2% of the variance in later life cognitive change. Inactivity in midlife and a lack of exercise in old age are plausible risk factors for cognitive decline. They are, fortunately, potentially malleable; promoting activity may offer pathways to improved cognitive ageing