Two pints of lager and, er…I’ve forgotten
We’re far enough into 2014 that most of those New Year’s resolutions are either firmly embedded lifestyle changes, or, more likely, blissfully disregarded. Of the things that people give up at the start of a new year, alcohol is among the most common, and there are usually associated reports of the benefits of reducing your alcohol intake, as highlighted by the BBC in January, for example. Drinking is one of those interesting behaviours; interesting in terms of the complexity of the association with various health outcomes. For those drinking at the very high end of the spectrum, it is usually quite clear that this has a negative impact on their health. However, advice is often that moderate drinking needn’t be detrimental, and in fact, some types of alcohol are promoted for their health benefits (here’s a good commentary discussing some of those beliefs in relation to the heart, for example). Given the potential complexity of the association, people often find it hard to know how much drinking is too much, at least in terms of the possible effects on their health. A study published in the journal Neurology at the start of the year sought to examine that question, specifically focussing on how alcohol intake affects changes in cognitive function over time in middle-aged adults. Given the topic, the study was widely reported in the media, with articles in the Telegraph, Guardian and Daily Mail, for example.
What did the media say?
In the media reporting of the study, the Daily Mail led with “Just two pints of beer a day ‘speeds up memory loss in middle-aged men’”. The article highlighted that men in their forties were at risk of greater memory decline if they drank more than 4.5 units of alcohol per day, the equivalent of “less than two pints or two large glasses of wine”. The article noted that this excess decline was equivalent to 6 years of ageing in those drinking the most, compared to the light or moderate drinkers. There was also greater decline on the other attention and reasoning tests included. For those tests, the excess decline equated to about one and half years.
The article did a good job of summarising the design of the study, three assessments of alcohol consumption over 10 years, followed by three assessments of cognitive functions over the next 10 years, and helpfully quoted the lead author and referenced the journal the study was published in.
What about the actual research?
The study, led by Dr Severine Sabia from the Department of Epidemiology and Public Health at University College London, used data from the Whitehall II study, a large, well-known epidemiological study of civil servants established in the 1980s. For the current study, alcohol data were averaged from three assessment periods over 10 years. The participants could be classified as abstainers on all occasions, those having given up alcohol at the most recent assessment, occasional drinkers, or if they were more than occasional drinkers, their average daily consumption was calculated. Cognitive ability was assessed by a range of tests over the next 10 years, again on up to three occasions. The analytical sample numbered 7,153 individuals.
As noted in the media report above, the men drinking more alcohol (here described as more than 36 grams of alcohol per day – for reference, 8 g of alcohol is one unit, further details here), showed faster cognitive declines than those drinking up to 20 g/d. For women, the results were a little more complex, with both abstainers and those consuming the most (greater than 19 g/d) showing the fastest declines, though not all of those effects were statistically significant. Interestingly, the researchers did look at the associations in men separately by type of alcohol (beer, wine or spirits), and though the consumption of higher levels of spirits appeared to be particularly detrimental, further analyses suggested that the overall effect wasn’t driven by one type of alcohol.
The study had a number of strengths, including the long-term nature of the follow-up, 20 years in total, the large sample size, and the detailed consideration of alcohol consumption. The researchers pointed out that a lot of our knowledge of how alcohol affects cognitive abilities comes from studies with older people. Although intuitive, that approach might also miss effects that are built up across midlife, for example.
The bottom line.
Coming back to where we started this piece, the Daily Mail article ended with a quote from Dr Simon Ridley at Alzheimer’s Research UK, suggesting research like this might be “one more reason to stick to any New Year’s resolutions to cut back on alcohol”. While the association is often complex, in the current study, the association between alcohol consumption and excess cognitive decline was particularly well-illustrated, and this translated to a really thoughtful piece of coverage in much of the media follow-up. At Research the Headlines, while we often point out the bad and the ugly in the reporting of research (here’s a recent example from our back catalogue), we do also like to champion good reporting when we see it.
Sabia, S., Elbaz, A., Britton, A., Bell, S., Dugravot, A., Shipley, M., Kivimaki, M., & Singh-Manoux, A. (2014). Alcohol consumption and cognitive decline in early old age. Neurology, 82, 332-339. doi: 10.1212/WNL.0000000000000063