• epidemiology;
  • nested case−control study;
  • Parkinson's disease;
  • telomere length

Background and purpose

Telomere shortening has been implicated in neurodegenerative disorders. However, available data on the association between telomere length and Parkinson's disease (PD) are inconclusive.


A nested case−control design was used amongst men participating in the prospective Physicians’ Health Study. A large proportion of participants provided blood samples in 1997 and they were followed through 2010. Men with self-reported PD were age-matched to controls in a 1:2 ratio. Quantitative PCR was used to determine the telomere repeat copy number to single gene copy number ratio (TSR) in genomic DNA extracted from peripheral blood leukocytes. TSR was used as a measure for relative telomere length (RTL) in our analyses. Conditional logistic regression was used to determine the risk of PD associated with RTL.


Data on RTL were available from 408 cases and 809 controls. Median TSR was shorter in controls than in cases (47.7 vs. 50.2; P = 0.02). The age-adjusted odds ratio (OR) for PD was 0.66 [95% confidence interval (CI) 0.46–0.95; Ptrend over quartiles 0.02] comparing the lowest to the highest quartile. The pattern of association was unchanged when comparing RTL below versus above the median (age-adjusted OR 0.75; 95% CI 0.59–0.96). Associations were similar after additional adjustment for many covariates.


Contrary to what was expected, in this large nested case−control study amongst men shorter telomeres were associated with reduced PD risk. Future research on the nature of this counterintuitive association is warranted.