title: Population-based prospective study of cigarette smoking and risk of incident essential tremor.
abstract: BACKGROUND
  Smoking cigarettes is associated with lower risk of Parkinson disease (PD). Despite the clinical links between PD and essential tremor (ET), there are few data on smoking in ET. One study showed an association between smoking and lower ET prevalence. We now study whether baseline smoking is associated with lower risk of incident ET.
  
  
  METHODS
  Using a population-based, cohort design, baseline cigarette smoking habits were assessed in 3,348 participants in an epidemiologic study in Spain, among whom 77 developed incident ET.
  
  
  RESULTS
  There were 3,348 participants, among whom 397 (11.9%) were smokers at baseline. Five (6.5%) of 77 incident ET cases had been smokers at baseline, compared with 392 (12.0%) of 3,271 controls (p = 0.14). Baseline pack-years were lower in incident ET cases than in controls (9.2 +/- 17.7 vs 15.7 +/- 28.4, p = 0.002). Participants were stratified into baseline pack-year tertiles, and few incident ET cases were in the highest tertile (4 [5.2%] cases vs 431 [13.2%] controls, p = 0.039). In Cox proportional hazards models, the highest baseline pack-year tertile was associated with lower risk of incident ET; those in the highest pack-year tertile were one-third as likely to develop ET when compared with nonsmokers (relative risk [RR] 0.37, 95% CI 0.14-1.03, p = 0.057 [unadjusted model] and RR 0.29, 95% CI 0.09-0.90, p = 0.03 [adjusted model]).
  
  
  CONCLUSIONS
  We demonstrated an association between baseline heavy cigarette smoking and lower risk of incident essential tremor. The biologic basis for this association requires future investigation.
authors.affiliation: G.H. Sergievsky Center, Department of Neurology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA. EDL2@columbia.edu
authors.forename: Elan D
authors.initials: ED
authors.lastname: Louis
authors.forename: Julián
authors.initials: J
authors.lastname: Benito-León
authors.forename: Félix
authors.initials: F
authors.lastname: Bermejo-Pareja
mesh_terms: D000368:Aged; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D015331:Cohort Studies; D015897:Comorbidity; D020329:Essential Tremor / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology*; D013995:Time
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine