title: Olfactory dysfunction in Parkinson's disease: Positive effect of cigarette smoking.
abstract: BACKGROUND
  There is compelling evidence from over 60 epidemiological studies that smoking significantly reduces the risk of Parkinson's disease (PD). In general, those who currently smoke cigarettes, as well as those with a past history of such smoking, have a reduced risk of PD compared to those who have never smoked. Recently it has been suggested that a cardinal nonmotor sensory symptom of PD, olfactory dysfunction, may be less severe in PD patients who smoke than in PD patients who do not, in contrast to the negative effect of smoking on olfaction described in the general population.
  
  
  METHODS
  We evaluated University of Pennsylvania Smell Identification Test (UPSIT) scores from 323 PD patients and 323 controls closely matched individually on age, sex, and smoking history (never, past, or current).
  
  
  RESULTS
  Patients exhibited much lower UPSIT scores than did the controls (P < 0.0001). The relative decline in dysfunction of the current PD smokers was less than that of the never- and past-PD smokers (respective Ps = 0.0005 and 0.0019). Female PD patients outperformed their male counterparts by a larger margin than did the female controls (3.66 vs. 1.07 UPSIT points; respective Ps < 0.0001 and 0.06). Age-related declines in UPSIT scores were generally present (P < 0.0001). No association between the olfactory measure and smoking dose, as indexed by pack-years, was evident.
  
  
  CONCLUSIONS
  PD patients who currently smoke do not exhibit the smoking-related decline in olfaction observed in non-PD control subjects who currently smoke. The physiological basis of this phenomenon is yet to be defined.
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology:, Head and Neck Surgery Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Sharer
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology:, Head and Neck Surgery Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Fidias E
authors.initials: FE
authors.lastname: Leon-Sarmiento
authors.affiliation: Parkinson's Disease Research, Education and Clinical Center, Philadelphia Veterans Administration Medical Center, Philadelphia, Pennsylvania, USA.|Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Morley
authors.affiliation: Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Weintraub
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology:, Head and Neck Surgery Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Doty
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D000857:Olfaction Disorders / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology*; D055696:Olfactory Perception / Q000502:physiology*; D010300:Parkinson Disease / Q000503:physiopathology*; D012307:Risk Factors; D012737:Sex Factors; D012903:Smell / Q000502:physiology*; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D013997:Time Factors
keywords: Parkinson's disease; UPSIT; cigarette smoking; l-dopa; olfaction; psychophysics