Suppose you were at a fashionable cocktail party talking to well-educated liberal-minded people. How would they evaluate the following three statements?
1. Carbon emissions are leading to global warming.
2. Second hand smoke is a significant health risk.
3. It’s healthier to be normal weight than overweight or modestly obese.
I think most people would say all three are true. But why? One answer is that these people are rational, and scientific studies show these statements to be true. But I’m not sure that’s the case. I believe science does show the first statement is very likely true. But the second statement is far less obvious, and the third really doesn’t have much scientific support at all.
Many years ago I discussed second hand smoke with another economist. I pointed out that studies hadn’t found much health risk. He said that common sense suggests it’s a risk. After all, first hand smoke is very risky, so you’d expect second hand to be somewhat risky. I actually like that reasoning, but I’m not sure it’s right. Suppose non-smokers only spend 10% of their time close to smokers, and suppose smoke gets diluted rapidly in the air (isn’t there a formula involving the square or cube of the distance?) The effects might then be trivial.
Update: Wikipedia reports that there is a scientific consensus that second hand smoke is harmful. Oddly, they also report the following, without comment on its accuracy:
Gio Batta Gori, a tobacco industry spokesman and consultant and an expert on risk utility and scientific research, wrote in the libertarianCato Institute‘s journalRegulation that “…of the 75 published studies of ETS and lung cancer, some 70 percent did not report statistically significant differences of risk and are moot. Roughly 17 percent claim an increased risk and 13 percent imply a reduction of risk.”
That was the sort of article that I recall reading. Perhaps that information is inaccurate, given the apparent scientific consensus. I would appreciate if someone could educate me on this question. We all know about the major problem of confirmation bias in empirical scientific studies. Just to be clear I find it very likely that second hand smoke produces some risks; my question was whether the effects of a colleague smoking down the hall from you are statistically significant. Maybe, but I’m still not convinced.
Higher levels of obesity associated with increased risk of death
Being overweight associated with lower risk of death
CHICAGO – In an analysis of nearly 100 studies that included approximately 3 million adults, relative to normal weight, overall obesity (combining all grades) and higher levels of obesity were both associated with a significantly higher all-cause risk of death, while overweight was associated with significantly lower all-cause mortality, according to a study in the January 2 issue of JAMA.
“Estimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting,” according to background information in the article.
Katherine M. Flegal, Ph.D., of the National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Md., and colleagues conducted a study to compile and summarize published analyses of body mass index (BMI) and all-cause mortality that provide hazard ratios (HRs) for standard BMI categories. For the review and meta-analysis, the researchers identified 97 studies that met inclusion criteria, which provided a combined sample size of more than 2.88 million individuals and more than 270,000 deaths. Regions of origin of participants included the United States or Canada (n = 41 studies), Europe (n = 37), Australia (n = 7), China or Taiwan (n = 4), Japan (n = 2), Brazil (n = 2), Israel (n = 2), India (n = l), and Mexico (n = l).
All-cause mortality HRs for overweight (BMI of 25-<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30-<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5-<25).
The researchers found that the summary HRs indicated a 6 percent lower risk of death for overweight; a 18 percent higher risk of death for obesity (all grades); a 5 percent lower risk of death for grade 1 obesity; and a 29 percent increased risk of death for grades 2 and 3 obesity.
The authors note that the finding that grade 1 obesity was not associated with higher mortality suggests that that the excess mortality in obesity may predominantly be due to elevated mortality at higher BMI levels.
The researchers add that their findings are consistent with observations of lower mortality among overweight and moderately obese patients. “Possible explanations have included earlier presentation of heavier patients, greater likelihood of receiving optimal medical treatment, cardioprotective metabolic effects of increased body fat, and benefits of higher metabolic reserves.”
The use of predefined standard BMI groupings can facilitate between-study comparisons, the authors conclude.
That’s pretty powerful. I can imagine alternative explanations; maybe people with alcohol, drug, or mental illness issues tend to be thinner. But that would have to be shown. Is there actually any evidence that the overweight or mildly obese are less healthy? And is the distribution of people’s weight bell-shaped, implying most overweight people are in the “healthier” two categories, not the very obese?
What unites all three beliefs described above? Coal plants putting pollution into the air are ugly. Common sense suggests you don’t want to mess with beautiful Mother Nature. Many consider smoking to be an ugly habit. And normal weight people often look better than the obese. You’d think that people who look better are in fact healthier. I suppose people subconsciously think Keats was right, and link truth and beauty.
I was recently criticized in the comment section for suggesting that unemployment insurance might cause a very small number of Americans to remain unemployed longer than otherwise. This is certainly not an attractive idea, given the very real suffering being endured by millions of unemployed people. But scientific studies show that it happens to be true.
Studies also suggest that there are behavioral differences between boys and girls at age one day. Or even one hour. That fact doesn’t particularly bother me, but I suppose if I were a very strong feminist I might find reality to be more attractive if this were not so.
Then there is the whole issue of “natural” foods, “local” foods, and all that.
Among conservatives, global warming and evolution seem to cause discomfort.
As a libertarian, I’d prefer it were the case that we’d be better off with a government that did not regulate the environment, force people to save, redistribute income, provide school vouchers, target NGDP, etc. And maybe we would. But I’m not convinced, which is why I remain a moderate or pragmatic libertarian.
Mayor Bloomberg should be overjoyed if he read the JAMA study quoted above. But I’m pretty sure he’d actually be really annoyed.
Of course there’s nothing new in this post, but it’s worth considering these biases every once and a while.
PS. All you commenters about to say “how dare you call yourself a libertarian” should take a deep breath, and consider the length of the list of things the government is doing that I don’t think they should be doing
PPS. Here it is . . . pig out folks!!