Midlife level and 15-year changes in general cognitive ability in a sample of men: The role of education, early adult ability, BMI, and pulse pressure

Abstract

The objective of the study was to examine determinants of midlife level and long-term changes in a general cognitive ability (g) factor. The data were from a Swedish sample of men (n=262; M=49.9years, SD=4.0) for which cognitive (conscript) test scores at age 18 were retrieved. In midlife the men completed a battery of cognitive tests that was re-administered at five-year intervals up to 15years after the baseline assessment. Second-order latent growth curve models were used to examine predictors of midlife level and longitudinal changes in a g factor reflecting four cognitive measures (WAIS-R Block Design, vocabulary, action recall, and word fluency). The results showed education (years of schooling) to be related to ability level (intercept) before (β=0.71), but not after (β=0.09), adjustment of an early adult (age 18) g factor (reflecting three different cognitive measures) that was highly predictive of midlife g level (adjusted β=0.89). Neither education nor g at age 18 (or midlife g level) was related to long-term changes in g, though. Conversely, baseline age, BMI, and pulse pressure were unrelated to midlife ability level, but higher baseline age, higher BMI and higher pulse pressure in midlife were predictive of cognitive decline. Thus, whereas higher levels of initial ability or educational attainment do not appear to buffer against onset of age-related decline in g in midlife and young-old age, maintenance of lower levels of pulse pressure and body weight could possibly have such an effect. However, further research is required to evaluate the mechanisms behind the observed relationships of the targeted variables and cognitive decline.