The effect of obesity on cognitive decline - A systematic review

Abstract

Background – Obesity is suggested to be associated with accelerated cognitive decline, however, research into this association is not yet conclusive. This review examines studies investigating the association between obesity and changes in weight with cognitive decline in the general population. Methods – PubMed was searched for relevant cohort studies investigating obesity (defined by BMI, waist circumference, or waist-to-hip ratio) and cognition assessed at least twice over time. Search terms were related to obesity, cognitive decline, and cohort studies. Screening and data extraction were performed by one researcher. Results – The search returned 1021 articles, of which 72 were eligible for full text screening. In total 33 articles were included. The literature revealed that there are indications for a role of obesity in accelerated decline in cognition in middle aged adults. Obesity seemed to have a protective effect on cognition in older persons. Importantly, a large part of the studies did not report significant associations. A high waist-to-hip ratio was associated with accelerated cognitive decline in adults. Higher waist circumference in older persons was in most studies associated with slower decline, but results were inconsistent. Studies that assessed weight changes over time concluded that both increases and decreases in BMI over time were associated with accelerated cognitive decline. Conclusion - Obesity in mid-life, and changes in BMI over time seem to accelerate cognitive decline. A stable, normal weight should be encouraged to protect cognition over time. Further research is needed to confirm and explore the association between obesity and cognition.