The long and short term effects of alcohol consumption on cognitive decline

Abstract

In an ageing population, cognitive decline represents a major cause of concern. Alcohol has been shown to have a differential impact on cognitive decline according to the level of consumption, but less is known on the longitudinal effects. The aim of this study was to examine the influence of alcohol consumption at age 36 and 43 yr on cognitive decline between 43 and 53 yr. The study examined 735 men and 778 women from the Medical Research Council (MRC) National Survey of Health and Development, who were followed up since their birth in March 1946. Decline in verbal memory and visual search speed was measured. Alcohol data was obtained over 7 days using 5 days diet diary and 2 days interview recall at age 36 and 43 yr. The confounding variables included were father's social class, childhood cognition, education, adult social class and depression. Cognition at 53 yr was regressed on cognition at 43 yr, alcohol consumption, and confounders, separately for men and women. Results showed that alcohol consumption at 36 yr was associated with decline in verbal memory performance in men. Light drinkers (0-3 units/day) and moderate drinkers (2-5 units/day) had 1.80 (95% CI: 0.73 to 2.88) and 1.72 (0.57-2.86) slower decline than non-drinkers, while heavy drinkers (3-8 units/day) showed a more rapid decline with 1.28 (0.11-2.45). These associations become non-significant after controlling for the confounders (in particular when controlling for education). No associations were found in women. There was non-significant association between alcohol at 36 yr and decline in visual search performance. Alcohol consumption at 43 yr had a stronger impact on verbal memory decline in men, which was maintained after adjusting for all the confounders. The regression coeff. for light, moderate and heavy drinkers were 1.18, 1.34, and 1.32 (0.21-2.15; 0.24-2.44; 0.25-2.40) in reference to non-drinkers, highlighting a protection for moderate drinkers. No associations were found for verbal memory decline in women. For the visual search speed test no associations were found in men. However, for women, there was a significant association between alcohol behaviour at 43 yr and decline in visual search performance. Results indicate that the short-term effect of alcohol consumption on cognitive decline is stronger than the long-term effect, which was explained by educational attainment at 26 yr. It is concluded that future policies on drinking behaviour should not only highlight the debilitating effects of different levels of drinking, but also take into account the beneficial influence of education.