Daily coffee intake in midlife and enhanced late life cognition in twins

Background Coffee drinking has shown mixed results in its association with cognitive function in later life, likely due in part to influence from unmeasured genetic and environmental factors, leading to inconsistent findings between studies. Given that members of twin pairs share at least some of their genes and many early‐life experiences, twin studies have advantages in providing control for confounding factors, many unidentified, that affect late‐life cognition. We aimed to explore if coffee intake in midlife maintains cognitive function in late‐life. Method A total of 7,438 members of the NAS‐NRC Twin Registry of Male World War II Veterans born from 1917–1927 were included in this study. Number of cups of coffee consumed daily was collected via mailed questionnaire in 1967. Cognitive status was measured every 3 years from 1990‐2002 using the modified Telephone Interview for Cognitive Status (TICS‐m) (range 0‐50). Daily coffee intake was categorized as tertiles (T):(T1)=1‐2 cups, (T2)=3‐4 cups, (T3) > 5 cups, with reference=0 cups. Linear‐mixed‐effect regression models, controlling for age at time of initial TICS‐m, education, smoking and alcohol status and twin pair, were used to assess the association between daily intake of coffee in midlife and performance on the TICS‐m over a period of up to 12 years in later life. Result Participants’ mean age was 41.7 years (standard deviation (SD)=2.8) when information on coffee intake was collected and 66.9(SD=2.8) at the time of their first TICS‐m. A total of 6,665 males reported drinking coffee, and the mean number of cups was 3.6(SD=2.4) daily. Twins who consumed more than 2 cups of coffee obtained higher TICS‐m scores (T2:b=0.53; 95%CI=0.22,0.85) and (T3:b=0.50;95%CI=0.18,0.82) than non‐coffee drinkers. This equates to an average of 2.4‐2.6 TICS‐m points more for those in T2 and T3 compared to non‐coffee drinkers. However, the amount of coffee intake was not associated with the rate of cognitive decline (T1:p=0.84,T2:p=0.28,T3:p=0.09). Conclusion We found that higher amounts of midlife coffee drinking are associated with better cognitive performance, but not reduced rate of cognitive decline in late‐life even after accounting for shared genetic and early‐life environmental factors. Future research should investigate potential mechanisms linking coffee and cognition.