Monday, 15 January 2018

Alcohol and dementia

The front page of yesterday's Sunday Times carried the news that Public Health England intends to use its bizarre new calorie limits to bully restaurants and food manufacturers into downsizing and degrading their products.

Public Health England (PHE) has told fast-food chains and supermarket ready-meal makers to “calorie cap” their foods, cutting down lunches and dinners to 600 calories and breakfast to 400.

The plan, to put the whole of the UK on a diet, is due out in March.

This is as I predicted when the new guidelines of 400 calories for breakfast and 600 calories for lunch and dinner were announced a few weeks ago:

I suspect that there is an agenda at work here. The 400-600-600 'rule' will allow PHE and its army of scolds to name and shame every restaurant portion, takeaway and ready meal that contains more than the government-approved quantity of calories. Individual meals will be portrayed as hazardous per se and will become targets for advertising bans, taxes and reformulation. A whole Pandora's Box is being quite deliberately opened. 

The same Sunday Times article also suggested that the alcohol guidelines might be lowered yet again:

To add to the agony, it coincides with research showing that the UK’s alcohol rules are too lax, with even drinking one pint or glass of wine a day poisoning the brain and raising the risk of dementia.

It's unclear whether Public Health England tipped off the press about this study or whether the Sunday Times decided to combine two 'public health' stories. The idea that the government would change the drinking guidelines on the back of a single study that looks at single outcome is absurd, but you never know these days.

The study itself involved a group of people being given sort of online quiz to test their reaction times (details are not provided) and asked how much they drank. Non-drinkers were excluded. The authors report that 'cognitive performance declined as alcohol consumption increased beyond 10 g/day' (a UK unit is 8 grams) and their conclusion reads as follows:

Current advice from the UK Department of Health is for men and women to not consume more than 16 g of pure alcohol per day (two units) on average. Findings reported here suggest that daily alcohol consumption above one unit is may have an adverse cognitive impact. Recommendations should be sensitive to this, especially among middle-aged and older members of the population.

But, as David Spiegelhalter points out in this blog post, the data do not support the conclusion. Here is the graph showing response times in milliseconds (y-axis) and daily alcohol consumption (x-axis).

The first thing to note is that this is not a study of dementia and the differences in response times are pretty small. The second thing to note is that the scale of the x-axis is insane! The third thing to note is, as Spiegelhalter says, response times are not quickest at around 10 grams of alcohol a day. They are quickest at around 18 grams a day, ie. more than two units. Moreover, response times remain relatively low even for very heavy drinkers.

In reality, the main finding seems to be that light drinkers don't have very good cognitive skills (and therefore, in the world of newspapers, are more likely to suffer from dementia). This is clearly not what the researchers wanted to find.

The usual excuse given by those who don't want to admit that there are any benefits from drinking alcohol is the hoary old 'sick quitter' chestnut, but the authors can't use that here because they excluded non-drinkers from their analysis. And so they resort to a 'sick light drinker' hypothesis that they seem to have invented for convenience:

The ‘J’ shaped association reported here should be considered critically. To reduce the ‘sick quitter’ effect abstainers were omitted. However, participants who may have only reduced alcohol intake for health reasons rather than quit, remain in the analysis.

No evidence for this little theory is presented. As usual, negative effects of drinking are reported uncritically while positive effects are met with a wall of speculation, doubt and hypotheses that are unevidenced but unfalsifiable.

The reality is that this study supports previous studies (such as this) that find a U or J-curved relationship between alcohol consumption and cognitive ability, with abstainers and light drinkers doing worse than heavier consumers. Its authors were evidently displeased with their findings and so they misrepresented them, created a misleading graph and called for a change to government guidelines.

The media then covered the study with such headlines as Just ONE pint a day ‘poisons your brain and increases your risk of dementia’ and another lie from 'public health' had travelled the world before the truth could get its shoes on.

1 comment:

Dr Evil said...

If that scale was reduced re RT you would very nearly get a straight line. What about age being factored in too plus other things like coffee/caffeine, energy drinks etc all of which can affect reaction times. This is just a way to try to propose a 2 unit limit. Well, my 2 unit limit is 39.5 grammes as I use Japanese units.