Defining at-risk populations for Parkinson's disease: lessons from ongoing studies.

It is currently widely acknowledged that the natural history of PD includes a preclinical phase, and there are increasing efforts to identify markers that would allow the identification of individuals at risk for PD. Here, we discuss the issues related to defining at-risk populations for PD and review findings of current population-based cohorts that have reported potential biomarkers for PD, such as the Honolulu-Asia Aging Study (HAAS) and the PRIPS (Prospective Validation of Risk factors for the development of Parkinson Syndromes) study. We also discuss enriched risk cohorts designed to evaluate specificity and predictive value of markers exemplified by the PARS (Parkinson Associated Risk Study) and the TREND (Tübinger evaluation of Risk factors for the Early detection of NeuroDegeneration) study. Although there is still a long way to go, studies designed according to these concepts might eventually provide sufficient data to form the basis for future screening programs for PD risk to be applied at a population level.

Meeting report: consensus statement-Parkinson's disease and the environment: collaborative on health and the environment and Parkinson's Action Network (CHE PAN) conference 26-28 June 2007.

BACKGROUND: Parkinson's disease (PD) is the second most common neurodegenerative disorder. People with PD, their families, scientists, health care providers, and the general public are increasingly interested in identifying environmental contributors to PD risk. METHODS: In June 2007, a multidisciplinary group of experts gathered in Sunnyvale, California, USA, to assess what is known about the contribution of environmental factors to PD. RESULTS: We describe the conclusions around which they came to consensus with respect to environmental contributors to PD risk. We conclude with a brief summary of research needs. CONCLUSIONS: PD is a complex disorder, and multiple different pathogenic pathways and mechanisms can ultimately lead to PD. Within the individual there are many determinants of PD risk, and within populations, the causes of PD are heterogeneous. Although rare recognized genetic mutations are sufficient to cause PD, these account for < 10% of PD in the U.S. population, and incomplete penetrance suggests that environmental factors may be involved. Indeed, interplay among environmental factors and genetic makeup likely influences the risk of developing PD. There is a need for further understanding of how risk factors interact, and studying PD is likely to increase understanding of other neurodegenerative disorders.

Effect of walking distance on 8-year incident depressive symptoms in elderly men with and without chronic disease: the Honolulu-Asia Aging Study.

OBJECTIVES: To determine the effect of walking on incident depressive symptoms in elderly Japanese-American men with and without chronic disease. DESIGN: Prospective cohort study. SETTING: The Honolulu-Asia Aging Study. PARTICIPANTS: Japanese-American men aged 71 to 93 at baseline. MEASUREMENTS: Physical activity was assessed according to self-reported distance walked per day. Depressive symptoms were measured using an 11-question version of the Centers for Epidemiologic Studies Depression Scale (CES-D 11) at the fourth examination (n=3,196) and at the seventh examination 8 years later (1999/00, n=1,417). Presence of incident depressive symptoms was defined as a CES-D 11 score of 9 or greater or taking antidepressants at Examination 7. Subjects with prevalent depressive symptoms at baseline were excluded. RESULTS: Age-adjusted 8-year incident depressive symptoms were 13.6%, 7.6%, and 8.5% for low (<0.25 miles/day), intermediate (0.25-1.5 miles/day), and high (>1.5 miles/day) walking groups at baseline (P=0.008). Multiple logistic regression analyses, adjusted for age, education, marital status, cardiovascular risk factors, prevalent diseases, and functional impairment, showed that those in the intermediate and highest walking groups had significantly lower odds of developing 8-year incident depressive symptoms (odds ratio (OR)=0.52, 95% confidence interval (CI)=0.32-0.83, P=.006 and OR=0.61, 95% CI= 0.39-0.97, P=.04, respectively). Analysis found that this association was significant only in participants without chronic diseases (coronary heart disease, cerebrovascular accident, cancer, Parkinson's disease, dementia, or cognitive impairment) at baseline. CONCLUSION: Daily physical activity (≥0.25 mile/day) is significantly associated with lower risk of 8-year incident depressive symptoms in elderly Japanese-American men without chronic disease at baseline.