Background and purpose
Studies of high body mass index (BMI) and cognition in the elderly have shown conflicting results. While some studies have shown a detrimental effect of high BMI on cognitive function, others have observed beneficial effects on cognition. Our aim was to assess cognitive function in a large population-based sample of overweight (BMI 25–29.9 kg/m2) and obese (BMI ≥ 30 kg/m2) community-dwelling elderly participants compared with their counterparts with BMI < 25 kg/m2 (i.e. controls) living in the same population.
One-thousand nine-hundred and forty-nine population-dwelling participants aged ≥ 65 years in central Spain [the Neurological Diseases in Central Spain study (NEDICES)] underwent a neuropsychological assessment, including tests of global cognitive performance [measured with a 37-item version of the Mini-Mental State Examination (37-MMSE)], psychomotor speed, verbal fluency, memory and pre-morbid intelligence.
There were 507 with BMI < 25 kg/m2, 850 overweight and 592 obese participants. In regression analyses that adjusted for age, gender, educational category, intake of medications that potentially affect cognition function, diabetes mellitus, hypertension, dementia, ever smoker, ever drinker and waist circumference, we found that obese/overweight status was associated with the lowest quartiles of the 37-MMSE, Trail Making Test-A (number of errors; indeed more errors), verbal fluency, delayed free recall, immediate logical memory and pre-morbid intelligence.
In this large population sample, overweight and obese participants performed poorer on formal neuropsychological tests than their counterparts with BMI < 25 kg/m2. These results support the hypothesis of a detrimental effect of high BMI on impaired cognition in the elderly.