Body mass index in essential tremor

Background: The pathogenesis of essential tremor (ET) is unknown, but it could be neurodegenerative. Weight loss has been observed in patients with neurodegenerative diseases. Objectives: To compare body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) in ET cases and controls and to determine whether BMI is correlated with tremor severity and duration. Methods: Patients with ET were ascertained from the Neurological Institute of New York, New York, NY. Control subjects were recruited from 2 studies at the same institution. Height and weight were measured and BMI was calculated. Dietary data were collected using a Willett Semi-Quantitative Food-Frequency Questionnaire. Tremor severity was assessed using a clinical scale and the Klove Matthews Motor Steadiness Battery. Results: The 78 cases and 242 controls were of similar age. Mean (SD) BMI in cases vs controls was 26.5 (5.0) vs 28.2 (4.8) (P=.008). This difference remained significant in an unconditional linear regression analysis that adjusted for age, sex, ethnicity, and years of education (P=.02). Mean daily caloric intake was similar in cases and controls. In cases, BMI was negatively correlated with both measures of tremor severity (r=-0.22; P=.05 and r=-0.24; P=.03) and with tremor duration (r=-0.22; P=.05). Conclusions: The BMI was lower in ET cases than in controls, and lower BMI was associated with disease of greater severity and longer duration. Caloric intake did not differ between groups, suggesting that lower BMI is not due to a reduction in calories. Lower BMI may be due to increased energy expenditure in ET.