Friday, August 6, 2010

The J-curve: science versus politics

Stanton Peele in the LA Times:
But in 1995, based on the results of studies identifying subjects who drank and did not drink and then following their health outcomes over time, the guidelines modestly declared - amid a sea of information about the dangers of drinking - that "alcoholic beverages have been used to enhance the enjoyment of meals by many societies throughout human history" and that "current evidence suggests that moderate drinking ... is associated with a lower risk for coronary heart disease in some individuals."

A firestorm resulted over these words, led by the late Sen. Strom Thurmond, R-S.C., a notorious teetotaler. Somehow, the section came through intact, to the amazement of a member of the committee writing the guidelines, Marion Nestle, then-chairwoman of the Department of Nutrition, Food Studies and Public Health at New York University. "It's a miracle, a miracle," she told The New York Times. "It is a triumph of science and reason over politics. The committee process was very contentious, but the outcome makes the fuss seem worthwhile." (emphasis added)
Peele goes on to note that it's no longer the religious right that's providing the anti-science opposition; rather, it's the public healthists who've taken arms against the 2010 guidelines' noting of additional benefits of moderate drinking.

And so it's fun to have a flip through the Kiwi equivalent. The New Zealand Food and Nutrition Guidelines for Older People [Updated: see here] talks a whole lot about the risks and very very little about the benefits. Recall that the J-curve is strongest for middle aged and older people.
Alcohol causes a range of adverse effects on health, including cirrhosis of the liver, pancreatitis, endocrine disorders, cardiomyopathy, gastritis, high blood pressure, haemorrhagic stroke, and cancers of the mouth, pharynx, larynx, oesophagus, breast and liver. It also contributes to death and injury on the roads, drowning, suicide, assaults and domestic violence, other non-traffic related mortality and morbidity, and some mental health disorders and sexual health problems. High levels of alcohol use are also associated with alcohol dependence and abuse (Ministry of Health 2008a). Moderate alcohol consumption may have some benefits for older people, but further research is needed to fully understand the potential benefits.
Every risk is conclusively proven; every benefit needs further study. Interesting. Recall that the J-curve is defined over all-source mortality. So as nasty as all the bad stuff is, it has to be dominated by the good stuff for folks drinking moderately.
The relationship between alcohol consumption and cardiovascular health has been investigated for many years. Despite the apparent benefits of regular, light to moderate alcohol consumption for cardiovascular mortality in older people, the risks and benefits of alcohol consumption are still not well understood. It is now thought that the cardiovascular benefits of alcohol consumption have been overstated. Methodological issues and uncontrolled confounding have called previous evidence into question (Jackson et al 2005; Rimm and Moats 2007) (see also Part 9: Chronic Disease and Nutrition for Older People).
That last line is terrible, shoddy work. Here's what Rimm and Moats 2007 actually said:
An inverse association between alcohol consumption and coronary heart disease (CHD) has been shown in epidemiologic studies for more than 30 years; beneficial changes in high-density lipoprotein (HDL) cholesterol, clotting factors, insulin sensitivity, and inflammation provide biological plausibility. Recently, the importance of including drinking patterns in defining “moderate drinking” has been appreciated. A recent meta-analysis raised questions about systematic misclassification error in observational studies because of inclusion among “nondrinkers” of ex-drinkers and/or occasional drinkers. However, misclassification among a small percentage of nondrinkers cannot fully explain the inverse relation, and there is substantial evidence to refute the “sick quitter” hypothesis. Furthermore, it has been shown that moderate alcohol consumption reduces CHD and mortality in individuals with hypertension, diabetes, and existing CHD. To address the issue of residual confounding by healthy lifestyle in drinkers, in a large prospective study we restricted analysis to only “healthy” men (who did not smoke, exercised, ate a good diet, and were not obese). Within this group, men who drank moderately had a relative risk for CHD of 0.38 (95% CI, 0.16–0.89) compared with abstainers, providing further evidence to support the hypothesis that the inverse association of alcohol to CHD is causal, and not confounded by healthy lifestyle behaviors.(emphasis added)
The article proves THE EXACT OPPOSITE of what the Kiwi nutritional guidelines claim. The article's conclusion:
The evidence discussed above provides substantial support for the hypothesis that moderate drinking reduces the risk of CHD. Beer, wine, and spirits all have demonstrated significant benefits. These benefits are likely mediated through strong and lasting effects of alcohol on HDL cholesterol, fibrinogen, and glycemic control. The “sick-quitter” hypothesis and the concern that moderate drinkers lead a healthier lifestyle may explain a small proportion of the benefit attributed to alcohol in some studies, but recent studies which have removed sick quitters, updated alcohol and covariate information on diet and lifestyle factors, and separately documented benefits of alcohol among healthy and unhealthy populations further add to the evidence that moderate alcohol consumption is causally related to a lower risk of CHD.
Is the Ministry of Health outsourcing its alcohol analysis to the New Zealand Drug Foundation, who seem to have stopped reading the literature after questions were raised but before they were answered?

Even when they admit there are benefits, every benefit gets couched in uncertainty; none of the scaremongering gets a confidence interval attached:
Due to the possible benefits of alcohol consumption and vascular health, there is an increasing amount of research being done on the effects of alcohol consumption on cognitive decline, dementia and Alzheimer’s disease – conditions that are related to vascular health. In a systematic review of largely epidemiological population cohort studies, low to moderate alcohol intake in subjects aged 65 years and over was associated with a significantly reduced risk of incident dementia and Alzheimer’s disease, and a reduced risk of vascular dementia and cognitive decline (Peters et al 2008). In an analysis of two large-scale prospective studies of older people, moderate alcohol consumption showed no increase in risk for physical disability or cognitive function measures (Lang, Guralnik et al 2007). In one of these studies, moderate alcohol consumption was associated with better subjective wellbeing and fewer depressive symptoms than with never having drunk any alcohol (Lang, Wallace et al 2007). The authors noted that the results should be interpreted with caution, however, and these studies are subject to the same methodological concerns regarding the validity of the findings on the cardiovascular benefits of alcohol consumption.
They further recommend:
It should be noted that these guidelines for responsible drinking are not recommendations to consume alcohol. A recommendation for older people to increase their alcohol consumption to achieve any health benefit is not warranted. Current evidence does not suggest that non-drinking older people should be encouraged to take up regular moderate drinking to see potential cardiovascular benefits (Gulbransen and McCormick 2007).
What do you find if you check Gulbransen and McCormick? Basically, worries about the kinds of confounds thoroughly answered by Rimm and Moats, above, and others.

Science has started beating politics in US nutritional guidelines on alcohol. It'll take extensive personnel changes at New Zealand's Ministry of Health for that to happen here. A good start would be recognizing that the modern literature (ie the last 4 years) seems to have thoroughly answered the critiques raised in the early 2000s about potential confounds in the J-curve. The worries about potential confounds were plausible: if "never drinkers" and "people who quit drinking because their health was terrible" were coded similarly in the data, that could produce a J-curve without any health benefits from moderate drinking. But that just wasn't what was going on in the data. It's been resolved. Continuing to cite Jackson's 2005 op-ed as somehow devastating for the J-curve shows the triumph of politics over science at the Ministry of Health.

2 comments:

  1. Does the evidence for the J-curve include nailing the direction of causality? i.e. can we rule out that the people who drink moderately are more likely to be healthier for some other reason?

    ReplyDelete
  2. Things point towards causality:
    1) Correcting for all the health-related behaviours we can does little to attenuate the J-curve; it would be surprising then if other unmeasured health behaviours were really driving things.
    2) Earlier worries that "sick quitters" made teetotallers appear less healthy have been entirely answered; the J-curve is robust to excluding former drinkers.

    ReplyDelete

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