Parkinson's belongs to a group of conditions called motor system disorders, which occur when the brain loses dopamine-producing cells. It affects more than one percent of people aged 60 years and above.
Symptoms include trembling in the arms, hands, legs, jaw, and face, stiffness of arms and legs and trunk, slowness of movement, and impaired balance and coordination. Eventually, walking, talking, and everyday tasks become more challenging.
Parkinson's disease is the fourteenth leading cause of death among Americans, according to the Centers for Disease Control and Prevention (CDC).
The team behind the new study was led by Dr. Karin Wirdefeldt of the Karolinska Institutet in Stockholm. They used questionnaires to determine levels of physical activity of many types including housework, commuting, occupational work, leisure time exercise, and total daily physical activity.
Overall activity was converted into "metabolic equivalent" (MET) hours per day, using estimated oxygen consumption associated with each type of activity.
Participants were all healthy at the start of the study in 1997. By 2010, 286 individuals had developed Parkinson's disease. Those who spent more than six hours per week on housework and commuting had a 43 percent lower risk than those who spent fewer than two hours per week on these activities.
Among men only, a "medium amount" of overall activity (judged as an average of 39 MET hours per day) was found to carry the lowest risk, a 45 percent lower risk, of Parkinson's disease, compared with a low level of total physical activity. The risk was not lowered by leisure time exercise or job-related physical activity alone, among either men or women.
Full details appear in Brain: A Journal of Neurology.
Wirdefeldt believes the study has a number of strengths. It included both men and women, and it was a prospective study, because all information on physical activity was assessed in advance of Parkinson's disease developing. A prospective study follows individuals over a period of time, looking for particular outcomes such as the development of a disease.
The team's findings are also backed up by a further analysis in which they pooled the data from the current study with that of five earlier prospective studies. This analysis supported the finding that more physical activity is linked to a lower risk of Parkinson's disease.
"Another major strength of this study is that we considered the entire spectrum of daily energy output, rather than purely focusing on dedicated exercising," she said. "Further, we conducted a rich set of sensitivity analyses to test the robustness of our findings.
"The protective effect of physical activity was further supported when we summarized all available evidence from published prospective cohort studies. These findings are important for both the general population and for the health care of patients with Parkinson's disease."
The team believes that their measurement of total physical activity (via an extensive questionnaire) "captures a comprehensive picture of daily physical activities and may be a better representation of a modulating factor for Parkinson's disease risk compared to a specific type of physical activity."
Previous research has shown that only a few risk factors are consistently linked to Parkinson's disease. These include family history of the condition, and the protective effects of smoking and consuming caffeine. But intensive physical exercise has been linked with neuroprotective effects in earlier animal experiments.
Comment: Studies have shown that nicotine is helpful for Alzheimer's disease, Parkinson's disease, attention deficit/hyperactivity disorder and schizophrenia. See:
Study finds smoking wards off Parkinson's disease
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The mechanism behind the impact of exercise is not yet fully understood, but it likely involves benefits to brain cells whose primary neurotransmitter is dopamine. A 2003 study indicated that exercise may alter these neurons to make them less vulnerable to toxins.
A further 2007 study suggested that exercise may boost dopamine release in the striatum, part of the forebrain that is crucial for a range of cognitive processes.
Future work must focus on understanding this mechanism, but for now the experts concluded, "The available evidence from animal and human studies suggests favorable biological effects of exercise with regard to Parkinson's disease risk."
References
Yang, F. et al. "Physical activity and risk of Parkinson's disease in the Swedish National March Cohort." Brain, 19 November 2014. DOI.
Comment: In addition to exercise, one of the best ways to prevent or ameliorate Parkinson's disease is to adopt a gluten-free ketogenic diet.
Dramatic recovery In Parkinson's patient with gluten free diet
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