By having an intelligence measure from even earlier in life, the Lothian studies are helping distinguish glitter from gold in the vast literature on factors correlated with cognition. A good recent example is Deary's analysis of the potential benefits of drinking, Thompson says. A smattering of correlational studies suggest that drinking small amounts of wine has positive effects on cognition late in life—indeed, Deary initially found a similar result when he first looked for a relationship between alcohol consumption and cognitive performance in the Lothian cohort. When he accounted for the participants' IQ scores on the Scottish Mental Survey, however, the perceived benefit dissolved. Rather than gaining cognitive benefit from drinking wine when they were older, “people who drank more were already likely to be smart,” Deary says.
The Lothian cohort has similarly challenged other reported influences on cognition, such as diet, body mass index, and caffeine consumption. None of those factors seems to have any effect on cognitive skills in the Lothian cohort when childhood intelligence is accounted for, Deary says. Even the effects of social and intellectual activity disappeared when he took into account how bright children were at age 11, possibly because those children are more likely to end up being socially and intellectually engaged.And a final clip:
...the growing body of data from the Lothian Birth Cohort studies and other aging research supports a theory that some describe irreverently, and a little brutally, as the “water tank hypothesis”: The better put-together your brain is early on, thanks to good genes and, to some extent, a favorable early life environment, the more cognitive reserves you have to lose to neurodegeneration. In other words, Martin says, “the more you start out with in the tank, the longer it takes to draw down.”