IQ and health
I've blogger previously about the paradox that class seems to matter more than absolute income in determining health. For example
blacks in the United States have about 4 times the income of men in Costa Rica or Cuba, but about 9 years’ shorter life expectancy.Part of the answer may be that IQ, not income is a key predictor of health.
A recent study in the BMJ showed that correction for IQ attenuated but didn't eliminate much of the trend toward better health in higher socioeconomic classes (also see commentary here). Of course the two aren't independent as income and IQ are strongly and positively correlated.
This makes intuitive sense as two people with similar IQs but vastly different incomes (say a professor at a small liberal arts school and a manangement consultant) should both be able to follow similar lifestyles from a health perspective. While one makes more than the other, both should recieve good health care and be able to afford things like quality food and gym membership. As we move down the socioeconomic ladder, however, effects of deprivation might become more pronounced even with similar IQs, although in Scotland, access to health care should not differ.