Outdoor work and risk for Parkinson's disease: a population-based case–control study

Abstract

Objectives Sunlight is the main contributor to vitamin D in humans. Since inadequate levels of vitamin D have been linked to increased risks for neurodegenerative diseases, we examined whether outdoor work is associated with a reduced risk for Parkinson’s disease in a population-based case–control study of Danish men. Methods We identified 3819 men with a primary diagnosis of Parkinson’s disease in the period 1995–2006 in the Danish National Hospital Register and selected 19 282 age- and sex-matched population controls at random from the Central Population Register. Information on work history was ascertained from the Danish Supplementary Pension Fund and the Central Population Register. Based on trade grouping codes and job titles, we evaluated the extent of outdoor work of study subjects as a proxy of exposure to sunlight. Results Relying on trade grouping codes, we estimated ORs for study subjects with moderate, frequent and maximal outdoor work compared with exclusive indoor work of 0.90 (95% CI 0.78 to 1.02), 0.86 (95% CI 0.75 to 0.99) and 0.72 (95% CI 0.63 to 0.82), respectively, for Parkinson’s disease. Reduced risks were also found for Parkinson’s disease among outdoor workers based on study subjects’ job titles. Conclusions Our findings suggest that men working outdoors have a lower risk for Parkinson’s disease. Further studies of measured vitamin D levels in outdoor workers are warranted to clarify a potential inverse association between vitamin D and the risk for Parkinson’s disease.

Inverse associations of outdoor activity and vitamin D intake with the risk of Parkinson’s disease

“…As for the outdoor activity, Kenborg et al (2011) recently reported that men working outdoors have a lower risk of PD, which is in line with our results. The mechanism of this finding was still unclear.…”

“…Outdoor activities were also reported to be linked to PD (Kenborg et al, 2011). Additionally, the dynamic changes of serum vitamin D are determined by dietary and sun avoidance factors, as 20% vitamin D is obtained from food (eggs, fish, animal liver, and dairy products), while 80% is from skin synthesis as a product of skin 7-dehydrocholesterol transformations induced by ultraviolet radiation (American Diabetes Association, 2007;Marcinowska-Suchowierska et al, 2010).…”

An estimate of the global reduction in mortality rates through doubling vitamin D levels

“…Perhaps the strongest evidence is from a study of outdoor work and risk of Parkinson's disease in Denmark. The odds ratio decreased consistently with respect to the amount of outdoor work, reaching a low of 0.72 (95% confidence interval 0.63-0.82) for maximal outdoor work (Kenborg et al, 2011).…”

Clinical Features in a Danish Population-Based Cohort of Probable Multiple System Atrophy Patients

“…Acknowledging that the diagnosis of MSA is challenging and that MSA patients frequently are misdiagnosed as suffering from IPD (ICD-10, G20.9), the author group initiated cooperation with the Danish Parkinson's Disease in Denmark (PASIDA) study [13] . Of the 45 potential MSA patients in the PASIDA cohort, 15 patients fulfilled the diagnostic criteria for probable MSA and were included.…”

“…), we expanded our diagnostic definition to include G23.8 and G28.9. In addition, we incorporated 15 probable MSA patients from the ongoing PASIDA study of Parkinson's disease in Denmark [13,26] . We may have missed MSA-C patients who were classified under codes for ataxia-associated disease.…”