Short sleep duration heralds essential tremor: a prospective, population-based study.

Lewy bodies have been described in the locus coeruleus of some patients with essential tremor (ET), and this brainstem nucleus plays an important role in sleep cycle regulation. Despite this, no studies have investigated the relationship between daily sleep duration and the risk of ET. We determined whether baseline daily sleep duration was associated with an increased risk of incident ET. In this prospective, population-based study of individuals  >  65 years of age (the Neurological Disorders in Central Spain [NEDICES] cohort), participants were evaluated at baseline and 3 years later. At baseline, participants indicated their daily sleep duration as the sum of nighttime sleep and daytime napping. The average daily total sleep duration was grouped into four categories: ≤  5 hours (short sleepers), 6 hours, 7 to 8 hours (reference), and  ≥  9 hours (long sleepers) hours. In total, 3,303 participants had a median duration of follow-up of 3.3 years. There were 76 incident ET cases at follow-up. The relative risks for short sleepers and for long sleepers were 2.25 (95% confidence interval [CI], 1.21-4.16; P = 0.01) and 0.74 (95% CI, 0.41-1.32; P = 0.31), respectively. After adjustment for potential confounders, including age, sex, educational level, current smoker, current drinker, and depressive symptoms or antidepressant use, the risk remained significantly increased for short sleepers (relative risk, 1.95; 95% CI, 1.03-3.70; P = 0.04]). The results indicated that short daily sleep duration may be a pre-motor marker for ET. Additional prospective studies are needed to confirm these results, and the biological basis for this association merits additional investigation.