Relationship between changes of body mass index and cognitive decline in Parkinson's disease

Abstract

Although the relation between body mass index (BMI) changes and risk of dementia is not always associated linearly, decreased BMI has been reported that it may be associated with increased risk of cognitive decline in the elderly. Weight loss is very common in patients with Parkinson's disease (PD) because of changes in appetite due to medication or chewing and swallowing difficulty related with muscular rigidity or higher energy expenditure due to involuntary movement. However, studies comparing BMI changes with cognitive function in PD have not been done yet. We performed this study to evaluate association between BMI changes and rate of cognitive decline and to know whether co-morbid conditions occur more frequently in BMI reduction group of PD. PD patients who measured their height and weight to calculate BMI and evaluated cognitive function regularly at the movement clinic of CNUH were recruited retrospectively. The patients (n = 78) were divided into two groups according to BMI changes during initial 6 months: decreased vs. stable BMI groups. Cognitive functions were evaluated by the Korean versions of Mini-Mental State Examination (MMSE) and the modified Mini-Mental State (3MS) test. Clinical examination, MMSE and 3MS were done at 6-, 12-, 24- and 36-month of follow-up. The rate of cognitive decline (MMSE and 3MS score changes/months) was compared in both groups from the baseline to each follow up. The co-morbid conditions such as pneumonia or bone fracture were evaluated through detailed chart review. The decreased BMI group showed more rapid decline of cognitive function than that of stable BMI group in PD. The rate of cognitive decline measured by both MMSE and 3MS tests was significantly faster especially at the 24- and 36- month of the follow-ups compared with the initial 1-year period of the follow-up in the decreased BMI group. No significant difference in the frequency of co-morbid diseases was found between the two groups. This study suggests that decreased BMI might be a useful indicator for future risk of dementia and let clinicians predict faster rate of cognitive decline in patients with PD.