A study involving 130 HIV-positive people has found that memory impairment was associated with a significantly larger waistline.
Some 40% of participants (average age 46) had impaired cognition. This group had an average waist circumference of 39 inches, compared to 35 inches for those without such problems. Memory impairment was also linked to diabetes in those older than 55 (15% of those with memory problems had diabetes compared to only 3% of those without memory problems).
Waistline was more important than BMI. Unfortunately, some anti-HIV drugs cause weight gain in this area.
The finding is consistent with evidence that abdominal weight is more important than overall weight for cognitive impairment and dementia in the general population.
(2012). Role of Obesity, Metabolic Variables, and Diabetes in HIV-Associated Neurocognitive Disorder.
Neurology. 78(7), 485 - 492.