Monday, 11 February 2013

A global phenomenon

So it isn't just New Zealand's Ministry of Health who seem to apply different standards of evidence on the health effects of alcohol depending on whether, for any particular disorder, alcohol consumption seems to ameliorate or worsen the condition. I'd written:
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.
There's an interesting letter in the latest issue of The Lancet. Michael Roerecke and Jurgen Rehm recently put out another metastudy on the cardioprotective benefits of low to moderate alcohol consumption. They don't recommend that people start drinking for heart health, but they find the cardioprotective benefits awfully hard to deny.

Well, Tim Stockwell tries to deny it. He's the one who recently suggested that minimum pricing for alcohol in British Columbia strongly reduced alcohol-related mortality rates despite that the aggregate B.C. time trend showed no particular decline in mortality; I suppose the counterfactual had to have been a stronger worsening.* Anyway, in a letter to Addiction, he keeps wondering if it's possible ever to derive any evidence of protective benefits from population epidemiological studies because of potential uncontrolled confounding. Except, as you'll recall, that most of the evidence we have of the harms of heavy alcohol use hardly come from experimental studies where we tell the treatment group to drink a fifth of whisky a day while telling the controls to abstain; it's the same kind of epidemiological evidence which is also subject to potential confounding from that heavy drinkers would not be like moderate drinkers even if they didn't drink: the things that predispose you to alcoholism seem likely to predispose you to all kinds of other negative outcomes. Confounding is everywhere.

And so I just loved Roerecke and Rehm's reply to Stockwell in the latest issue. They write, in a beautiful glove slap:
Given the above points and further points made in [1], it seems that some researchers in the field may be using different standards in assessing the cardioprotective effect of alcohol vs. its detrimental effect. Consider two examples. One is the effects of alcohol on colon cancer [12]. Would the same arguments used to judge the relationship between alcohol and ischaemic heart disease not hold for this relation as well? The other example is the more than 200 other risk relations between alcohol and disease and injury outcomes [13]. Of course, this is not a good argument against scrutinizing the cardioprotective effect of alcohol, but we sense a desire by some in the field to apply tough standards on protective effects and more lenient standards on other effects, where sometimes the responses to very simple survey questions such as ‘Did your partner’s alcohol consumption contribute to your marriage problems?’ are accepted as causal evidence.
 It seems that I'm not the only one frustrated by non-truth-seekers.

* The study is here; I've not had a chance to assess it in much depth. I'd be curious whether running the CPI in place of minimum prices in their series would yield similar effects to those found - there isn't that much change in the minimum price over the period, and they use CPI adjusted prices. That has to be most of their price variation over the interval. I'd also be a bit nervous about using a panel estimator where my main regressor of interest had no panel variation. And, I'm not sure that I've ever before seen this line in an empirical paper, or anything like it:
Estimates for acute AA deaths prevented are not provided due to both counter-intuitiveness and the lack of stability in the lagged associations for these short-term outcomes.
I'm also not quite sure what to think about their using lengthy lags of prices where most of the time series price variation is just CPI. Surely lagged consumption would have a better basis in theory for predicting current acute injury than would lagged prices where most price variation is CPI. I also note that while Chris Auld, an applied econometrician whose work I trust, had worked with this group on price elasticity estimates a while ago, his name isn't associated with the group's more recent adventures. So I'd have to check the group's new work in reasonable detail before I'd believe it.

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