Cognitive impairment is common in heart failure. Obesity is a known risk factor for cognitive dysfunction in heart failure, though the mechanisms remain unclear. Obesity increases risk for conditions like hypertension and type 2 diabetes mellitus (T2DM) as well as poor fitness levels, and this may serve as one possible pathway accounting for association between obesity and cognitive dysfunction.

We used structural equation modeling to test whether the combination of hypertension, T2DM, and reduced fitness mediate the association between obesity and cognitive dysfunction.

Two hundred heart failure patients completed neuropsychological testing and a physical fitness assessment. Hypertension and T2DM were ascertained via self-report and medical records. Body mass index (BMI) was calculated.

Forty-three percent of the sample was obese. Hypertension (70%) and T2DM (36%) were common, and fitness levels were reduced. The structural equation model with these factors as mediators between BMI and cognitive function demonstrated excellent fit (comparative fit index = 0.98; root mean-square error of approximations = 0.03). Higher BMI correlated with hypertension, T2DM, and poorer fitness. Each of these factors predicted worse cognition. Models that isolated medical comorbidities and physical fitness as the mediator were weaker than the full model.

Increased risk for medical comorbidities and reduced fitness levels helped to explain the negative effects of obesity on cognitive dysfunction in heart failure. Prospective studies should confirm this pattern and examine how weight loss benefits cognitive function in heart failure.