T G Ton

Publications (2)4.61 Total impact

• Article: The Risk of Parkinson Disease Associated with Urate in a Community-Based Cohort of Older Adults.

  S Jain, T G Ton, R M Boudreau, M Yang, E L Thacker, S Studenski, W T Longstreth, E S Strotmeyer, A B Newman
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  ABSTRACT: Background/Aims: Studies suggest an inverse association between urate concentration and the risk of Parkinson disease (PD). We investigated this in the Cardiovascular Health Study in an elderly community-based cohort of adults. Methods: The association of baseline urate (μmol/l) and incident PD over 14 years was assessed with locally weighted scatterplot smoothing (LOESS) regression from which categories of low (<300 μmol/l), middle (300-500 μmol/l), and high (>500 μmol/l) urate ranges were derived. Multivariate logistic regression models assessed the risk of PD for each urate range. Linear and quadratic terms were tested when modeling the association between urate and the risk of PD. Results: Women had significantly lower urate concentrations than did men [316.8 μmol/l (SD 88.0) vs. 367.4 μmol/l (SD 87.7), p < 0.0001] and in women no associations between urate and PD risk were observed. In men, LOESS curves suggested a U-shaped or threshold effect between urate and PD risk. With the middle range as reference, the risk of developing PD was significantly increased for urate <300 μmol/l (OR 1.69, 95% CI 1.03-2.78) but not for urate >500 μmol/l (OR 1.55, 95% CI 0.72-3.32) in men. A negative linear term was significant for urate <500 μmol/l, and across the entire range a convex quadratic term was significant. Conclusions: Results suggest a more complex relationship than previously reported between urate levels and the risk of PD in men. Low urate concentrations were associated with a higher PD risk and high urate concentrations were not associated with a further decrease in PD risk.
  Neuroepidemiology 06/2011; 36(4):223-229. · 2.31 Impact Factor
• Article: Post hoc Parkinson's disease: identifying an uncommon disease in the Cardiovascular Health Study.

  T G Ton, S Jain, R Boudreau, E L Thacker, E S Strotmeyer, A B Newman, W T Longstreth, H Checkoway
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  ABSTRACT: Although ongoing cohort studies offer a unique opportunity to apply existing information collected prospectively to further the scientific understanding of Parkinson's disease (PD), they typically have limited information for clinical diagnosis. We used combinations of self-report, International Classification of Diseases - 9th edition codes and antiparkinsonian medications to identify PD in the Cardiovascular Health Study. To determine whether the expected inverse association between smoking and PD is evident using our outcome definitions, we assessed baseline smoking characteristics for various definitions of PD. We identified 60 cases with prevalent PD (1.0%; 95% confidence interval, CI = 0.8-1.3%) and 154 with incident PD by year 14. Clear associations were observed for current smokers (odds ratio, OR = 0.50; 95% CI = 0.26-0.95) and for those who smoked ≥50 pack-years (OR = 0.53; 95% CI = 0.29-0.96). Estimates for smoking were similar when ≥2 data sources were required. Estimates for self-report alone were attenuated towards null. Using multiple data sources to identify PD represents an alternative method of outcome identification in a cohort that would otherwise not be possible for PD research. Ongoing cohort studies can provide settings in which rapid replication and explorations of new hypotheses for PD are possible.
  Neuroepidemiology 09/2010; 35(4):241-9. · 2.31 Impact Factor