Working in night shift may lower Parkinson's disease risk

A study published by researchers from National Institute of Health, Research Triangle Park, North Carolina, indicate that people who work rotating night shifts appear to have a lower risk of Parkinson's disease. On the other hand, an increased risk of developing this condition is linked to a longer average duration of sleep. The researchers found that working rotating night shifts disrupts circadian rhythms and may have a wide range of physiologic, psychological and social effects on shift workers. Previous studies link shift work to higher risk of some chronic diseases, including cardiovascular disease and certain types of cancers but any effect on the risk of developing Parkinson's disease has not been investigated. The researchers therefore evaluated data from the U.S. Nurses' Health Study, which enrolled 84,794 female nurses, to see if there was an association between working rotating night shifts and Parkinson's disease risk. Nurses who reported at least 15 years of night shift work were older and more likely to be current smokers and users of nonsteroidal antiinflammatory drugs (NSAID), such as ibuprofen or naproxen, compared with those who never worked rotating night shifts. Night shift workers also tended to drink more coffee but less alcohol and to have a higher body mass index. Women who worked night shifts slept slightly less than non-night shift workers. A total of 181 cases of Parkinson's disease were reported between1988 and 2000. The risk of Parkinson's disease was 50-percent lower among women who had at least 15 years of night shift work compared with those who never worked rotating night shifts. After accounting for differences in age and smoking status, the investigators found that longer sleep duration was associated with a higher risk of Parkinson's disease. Compared with nurses who slept no more than 6 hours per day, those who slept 9 or more hours per day had 84 percent increased risk. Plausible biologic explanations for these results are lacking, researcher points out. The study also notes that shift work has been associated with modest increases in blood levels of estradiol and uric acid, both of which may be protective against Parkinson's disease.