Body Mass Index and Decline of Cognitive Function

Background The association between body mass index (BMI) and cognitive function is a public health issue. This study investigated the relationship between obesity and cognitive impairment which was assessed by the Korean version of the Mini-mental state examination (K-MMSE) among mid- and old-aged people in South Korea. Methods A cohort of 5,125 adults, age 45 or older with normal cognitive function (K-MMSE >= 24) at baseline (2006), was derived from the Korean Longitudinal Study of Aging (KLoSA) 2006 similar to 2012. The association between baseline BMI and risk of cognitive impairment was assessed using multiple logistic regression models. We also assessed baseline BMI and change of cognitive function over the 6-year follow-up using multiple linear regressions. Results During the follow-up, 358 cases of severe cognitive impairment were identified. Those with baseline BMI >= 25 kg/m(2) than normal-weight (18.5 >= BMI<23 kg/m(2)) were marginally less likely to experience the development of severe cognitive impairment (adjusted odds ratio [aOR] = 0.73, 95% CI = 0.52 to 1.03; P-trend = 0.03). This relationship was stronger among female (aOR = 0.63, 95% CI = 0.40 to 1.00; P-trend = 0.01) and participants with low-normal K-MMSE score (MMSE: 24-26) at baseline (aOR = 0.59, 95% CI = 0.35 to 0.98; P-trend<0.01). In addition, a slower decline of cognitive function was observed in obese individuals than those with normal weight, especially among women and those with low-normal K-MMSE score at baseline. Conclusion In this nationally representative study, we found that obesity was associated with lower risk of cognitive decline among mid- and old-age population.