Obesity and Alzheimer's

Beydoun et al (2008) found that relationships between obesity and Alzheimer's Disease (AD) risk may vary by gender. Their analysis of data from the Baltimore Longitudinal Study of Aging (BLSA) found that obesity (especially around the waist) was tied to increased AD risk for women. For men, being underweight seemed to increase risk. In California, Whitmer et al (2005) also found increased AD risk for obese women, but for men, the association was "non-significant". However, Whitmer et al suggested that there were too few underweight participants for analysis of risk (1.3%), while Beydoun et al included underweight status as a risk factor with a similar proportion (1.4 - 3.0%) in a smaller study population (2,322 vs 10,276).

A sex difference may begin to explain what Luchsinger and Mayeux (2007) called "conflicting results" in previous studies of adiposity and AD risk. Luchsinger and Mayeux suggest that obesity may increase AD risk by increasing diabetes risk, while Kivipelto et al (2005) suggest that vascular disorders may be the mediating factor.

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It's always hard for me to believe that all the significant confounds are being taken into account. When I saw that Whitmer's group felt the underweight sample was too small, I revisited Beydoun's population statistics, and was surprised to find they were working with an even smaller group. I'm dubious about their finding that underweight men are at increased risk. Previously on DBlog, we've seen that women may be at greater risk for diabetes and vascular problems (see 11/15/06), which are both theorized to mediate the relationship between weight and AD.

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