Being overweight is associated with hippocampal atrophy: the PATH Through Life Study

Background: The prevalence of obesity has increased dramatically in the past two decades, with major implications for individual well-being, population health and the economy. Of particular concern is the risk obesity presents for brain health and its consequences in an ageing population. These associations and their time course are not well understood, particularly after middle age. The aim of this study was to investigate whether being overweight/obese or having an increasing body weight is associated with hippocampal atrophy in early old age. Methods: Participants were 420 unimpaired (Mini-Mental State Examination >26) individuals aged 60–64 years, living in the community and taking part in a large prospective study of ageing over an 8 year follow-up. Magnetic resonance imaging scans were collected at three assessments and the hippocampus was manually traced by expert neuroscientists. Multi-level analyses assessing the relationship between body mass index (BMI) and hippocampal atrophy over 8 years while controlling for important covariates were conducted. Results: Analyses showed that BMI was negatively associated with left (coefficient: −10.65 mm 3 ; s.e. 4.81; P =0.027) and right (coefficient: −8.18 mm 3 ; s.e. 4.91; P =0.097) hippocampal volume at the first assessment. Over the follow-up period, those with a higher BMI experienced greater hippocampal atrophy and more so in the left ( P =0.001) than in the right ( P =0.058) hippocampus. Conclusions: The findings from this study provide important evidence indicating that being overweight or obese is associated with poorer brain health. These results are consistent with those of previous animal and human studies and further stress the importance of reducing the rate of obesity through education, population health interventions and policy.