Association of olfactory dysfunction with risk for future Parkinson's disease

Although olfactory dysfunction is commonly associated with Parkinson's disease (PD), it is not known whether such dysfunction can predate the onset of clinical PD in a community-based population. This study examines the association of olfactory dysfunction with future development of PD in Honolulu-Asia Aging Study cohort members

Olfaction was assessed from 1991 to 1996 in 2,267 men in the Honolulu-Asia Aging Study aged 71 to 95 years who were free of clinical PD and dementia at the time of olfaction testing. Participants were followed for up to 8 years for incident PD RESULTS: In the course of follow-up, 35 men were diagnosed with PD (24.6/10,000 person-years). The average age at the time of diagnosis was 82.9 +/- 3.8 (range, 76-93) years, and the average time to a diagnosis was 4.0 +/- 1.9 (range, 1-8) years. During the first 4 years of follow-up, age-adjusted incidence of PD declined from 54.5/10,000 person-years in the lowest quartile of odor identification to 26.6, 8.2, and 8.4/10,000 person-years in the second, third, and fourth quartiles, respectively (p < 0.001 for trend). After adjustment for age and other potential confounders, the odds ratios for PD in the lowest quartile was 5.2 (95% confidence interval, 1.5-25.6) compared with the top two quartiles. This relation was not evident beyond 4 years of follow-up.

Impaired olfaction can predate clinical PD in men by at least 4 years and may be a useful screening tool to detect those at high risk for development of PD in later life.