News blog readers may be familiar with the famous ‘J curve’ relating alcohol consumption to health outcomes, including brain health. The J curve shows a negative correlation between alcohol consumption and cognitive functioning at a low level of alcohol consumption (< 7 units/week), turning to a positive association in quantities exceeding about 28 units/week. One large glass of wine per day should be safe according to this finding. However, the data from which these findings are derived is cross-sectional. The BMJ has recently published a longitudinal study of alcohol and its effect on both cognition and brain structure (as measured by functional MRI). The news is bad I am afraid. In the words of the editor, Fiona Godlee, ‘better’ research flattens the J curve. The study seems to show a linear increase in risk with increasing intake of alcohol. The result was statistically significant for people drinking more than about two small glasses of wine per day. Why was a harmful effect at low dose detected in this longitudinal study but not the cross-sectional studies? So here is the thing – people with higher cognitive functioning tend to have higher alcohol consumption at baseline. In fact, the ‘cleverer’ the person, the more they tend to drink. The result is a difference in the findings of cross-sectional and longitudinal studies. While cross-sectional studies show no difference in cognition with moderate alcohol intake, the longitudinal studies show that cognition and brain structure decline at relatively low levels of alcohol consumption. To put this another way, moderate alcohol intake abolishes the cognitive advantage that moderate alcohol consumers have at baseline. Interestingly, not all parts of the brain are equally affected on MRI. Likewise the effect on cognition is not global; it affects lexical more than semantic fluency, for example. This is an extremely well-written, detailed and interesting study. The cohort of people who participated in the study were civil servants followed up for 30 years. The results are of immense public health importance. Human happiness, wealth and prosperity all relate to brain function. A person’s intellectual endowment is a precious gift and should not be lightly squandered. I will take these findings too heart, both in my personal life and as a public health practitioner. It is really a question of long-term loss vs. short-term gain – alcohol is a pleasant social lubricant, much beloved of myself, and a small glass of wine has even been shown to improve creative problem-solving!
— Richard Lilford, CLAHRC WM Director
- Di Castelnuovo A, Costanzo S, Bagnardi V, Donati MB, Iacoviello L, de Gaetano Alcohol dosing and total mortality in men and women. Arch Intern Med. 2006; 166(22): 2437-45.
- Topiwala A, Allan C, Valkanova V, et al. Moderate alcohol consumption as risk factor for adverse brain outcomes and cognitive decline: longitudinal cohort study. BMJ. 2017; 357:j2353.
- Godlee F. Better research flattens the J shaped curve. 2017; 357: j2755.
- Benedek M, Panzierer L, Jauk E, Neubauer AC. Creativity on tap? Effects of alcohol intoxication on creative cognition. Consciousness Cognition. 2017. [ePub].