BMI loss linked to Alzheimer’s disease risk

A decline in body mass index (BMI) over time seems to worsen the risk of Alzheimer’s disease (AD), particularly among women, in whom a dose-response effect is apparent, a recent study has found.

The study included 45,076 participants (23,298 men; 21,778 women) who had their BMI measured across three time periods: phase 1 (2002–2003), phase 2 (2004–2005), and phase 3 (2006–2007). The outcome was AD, as defined by prescriptions and clinician diagnoses; change in BMI and variability were set as independent variables.

Over an average follow-up of 2.7 years, 4,055 cases of AD were detected. The mean cumulative incidence rates were 16.3 and 23.9 cases per 1,000 person-years in men and women, respectively. Around 73.3 percent of men and 68.6 percent of women were able to maintain stable BMI over 2 years; the same stability over 4 years was reported in 66.1 percent and 62.6 percent, respectively.

Multivariate analysis found that a BMI decrease of 10.1–15.0 percent over 4 years increased the risk of AD in men by at least 30 percent (hazard ratio, 1.33, 95 percent confidence interval [CI], 1.02–1.72). Two-year changes showed no impact on AD risk.

Women, on the other hand, were more susceptible to the effect of changing BMI. Those who showed a 2-year drop of >15.0 percent (HR, 1.64, 95 percent CI, 1.19–2.26), 10.1–15.0 percent (HR, 1.54, 95 percent CI, 1.25–1.91), and 5.1–10.0 percent (HR, 1.17, 95 percent CI, 1.04–1.32) were all at greater risk of AD relative to women who maintained their BMI over the same time span.

Notably, a BMI increase of 10.1–15.0 percent (HR, 1.37, 95 percent CI, 1.09–1.72) and >15.0 percent (HR, 1.49, 95 percent CI, 1.10–2.02) also led to excess AD risk. Similar effects were observed at 4 years. For both BMI gain and loss, the magnitude of effect seemed to strengthen with increasing degree of BMI change.