High Blood Pressure Linked to Parkinson’s in Han Chinese
Hypertension, or high blood pressure, almost doubles the risk of developing Parkinson’s disease in people of Han Chinese descent living in Singapore, a case-controlled study found.
In contrast, a comparison of similar studies conducted in the U.S. and the U.K. found that hypertension was associated with a reduced risk of the condition, the scientists noted.
“Our study … suggests that early diagnosis and treatment of hypertension may potentially reduce the risk of [Parkinson’s disease], at least in our population,” the researchers wrote.
The study, “Case-control study of hypertension and Parkinson’s disease,” was published in the journal Nature NPJ Parkinson’s.
The underlying biology of Parkinson’s disease is complex and thought to be influenced by both genetic and environmental factors.
Hypertension, or high blood pressure, is a common chronic condition associated with an increased risk of cardiovascular disease and is a leading factor in disorders of the small blood vessels in the brain.
Studies suggest that blood vessel disease may affect and damage nerve cells (neurons) that produce the signaling molecule dopamine. These neurons are damaged and lost in people with Parkinson’s, leading to characteristic symptoms. Furthermore, blood vessel disease-causing stroke is more likely in people of Asian descent compared to Caucasians with a European background.
However, few studies have examined an association between hypertension and Parkinson’s in Asian populations.
Using a matched case-controlled approach, researchers based at the National Neuroscience Institute in Singapore investigated the association between hypertension and Parkinson’s risk. They performed an analysis of similar matched case-control studies found in the medical literature.
The study included 671 Parkinson’s patients (mean age 63.9 years) and the same number of sex-matched healthy controls (mean age 63.5) without neurodegenerative diseases. The study included only Han Chinese, which is the predominant ethnic group in the Singapore population. The number of smokers and non-smokers was the same between patients and controls.
The case-controlled analysis revealed that the prevalence of hypertension in those with Parkinson’s was 46.1%, which was significantly higher than that of 31.9% in the control group.
The presence of hypertension was associated with a 1.9-fold higher risk of Parkinson’s, even after adjusting for age and sex. The results remained significant with further adjustments for hypertension-associated conditions such as diabetes, higher fat levels in the bloodstream (hyperlipidemia), and smoking status.
Next, the team conducted a literature search covering the past 20 years to find other case-control studies as a comparison. After screening content and duplicates, three eligible matched case-controlled studies that fit their inclusion criteria were selected for further analysis. Two of these studies were conducted in the U.S. by questionnaire, and the other in the U.K., based on medical records.
Conversely, the pooled analysis of these matched case-control studies showed a protective effect of hypertension on the risk of Parkinson’s disease. After adjustments, there was a significant 20% lower risk among these other studies. There was, however, considerable variation between these studies.
The opposing increased risk of hypertension in the Singapore population may be “explained by a variance in prevalence of [Parkinson’s disease] and hypertension in different populations, ethnic-specific genetic factors, or exposure to environmental agents or lifestyle habits, or a combination of these factors,” the team wrote.
”Some studies, which did not satisfy our meta-analysis inclusion criteria showed that hypertension was significantly associated with increased risk of [Parkinson’s disease] among Asians, corroborating our observation,” the authors noted. “If we have included studies with non-matched samples in our meta-analysis, there is a shift in trend towards higher odds of [Parkinson’s disease] risk in the presence of hypertension.”
“Future longitudinal studies to evaluate the role of ethnic-specific gene variants in mediating the interaction between hypertension and [Parkinson’s disease] will be of interest,” the authors wrote.