This is a significant discovery because the Han constitute the majority ethnic group in China. That amounts to ninety-two percent of the population on the mainland. To take it a step further, the Han not only is the world’s largest ethnic group but represents a total of eighteen percent of the entire world population. According to the case-controlled study, which appears in Nature NPJ Parkinson’s, the risk to people of Han descent doubles when hypertension (high blood pressure) is present.
It appears that in the U.K. and the U.S. similar studies have found just the opposite. U.S. scientists noted that chronic hypertension was linked to a reduced risk of Parkinson’s.
Yet Parkinson’s is a complex disease and may be affected by either genetic or environmental issues.
Hypertension is a chronic disorder related to cardiovascular disease. It is one of the primary factors of the brain that involves small blood vessels. Damage to these blood vessels leads to the characteristic Parkinson’s symptoms.
A stroke is another factor resulting from damage to blood vessels. It is found to be more common in the Asian population than in people of European descent.
About the Asian Study
Researchers at the Singapore Neuroscience Institute used a matched case approach to investigate the relationship between Parkinson’s risk and hypertension. The matched case studies used were similar to the studies they were able to locate in the medical literature.
Parkinson’s patients, all of Han descent, median 63.9 years (n671) were joined by an equal number of healthy participants median age 63.5 years. These participants included a like number of smokers and non-smokers in each group.
An analysis found that hypertension associated with Parkinson’s patients was 46.1% while the control group was lower at 31.9%.
The next step took the team back twenty years in order to find additional comparison studies. They were able to find three eligible cases for analysis. Two U.S. studies using questionnaires and one conducted in the U.K. using medical records. The results of the new analysis showed hypertension’s protective effect on Parkinson’s disease. Note that the researchers emphasized that there was considerable variation within these studies.
Possible explanations of the variance in different populations are suggested such as ethnic genetic factors, environmental agents, and simply different lifestyles.
The researchers worked with a meta-analysis using data from many independent studies on the subject. The results showed that there was a significant increase in the risk of Parkinson’s disease in the Asian population.
The authors stated that longitudinal studies (over a long period of time) conducted in the future will shed more light on the relationship between Parkinson’s disease and hypertension.