First-degree relatives of Parkinson’s patients are more likely to develop the disease and are at a higher risk for other neuropsychiatric disorders, a study shows.
Most Parkinson’s cases are considered to be sporadic, but several studies have suggested that the disease results from a combination of genetic and environmental factors.
Several genes have been pinpointed as the cause of 6 to 7 percent of the clinical variability observed in Parkinson’s disease.
To better understand the impact of genetic and environmental factors on the development of Parkinson’s, researchers reviewed potential risk factors that could be linked to familial aggregation of the disease.
Clinical records of all individuals registered in the Taiwan National Health Insurance Research Database in 2015 were analyzed. Of the total registered population of 24,349,599 individuals, 112,037 were diagnosed with Parkinson’s disease.
This included 149,187 individuals who had a parent affected by Parkinson’s, 3,698 with an affected offspring, 3,495 with an affected sibling, and 15 individuals with an affected twin.
Researchers found that individuals who had a first-degree relative with Parkinson’s disease had a 1.69 times increased chance of also developing the disease. This risk was similar for both male and female relatives and was greater for twins, who were 63.12 times more likely to develop Parkinson’s.
The risk of developing Parkinson’s was 2.2 times higher for siblings, 1.86 times higher for offspring, 1.59 times higher for parents, and 1.46 times higher for spouses.
These results suggest that the clinical variability of Parkinson’s prevalence observed in the Taiwanese population is accounted for by genetic factors (heritability) at 11%, shared environmental factors at 9.1%, and non-shared environmental factors at 79.9%.
Additional analysis further showed that first-degree relatives of Parkinson’s patients are also at an increased risk for some other neuropsychiatric disorders than the general population. These include major depression, anxiety, multiple sclerosis, Alzheimer’s disease, and amyotrophic lateral sclerosis, among others.
Researchers believe that Parkinson’s disease “should be considered an age-related multifactorial syndrome with mainly genetic and environmental components.”
“First-degree relatives of PD patients are more likely to develop PD and other neuropsychiatric diseases. Environmental factors account for a high proportion of the pheno- typic variance of PD,” they wrote.
“Our findings provide information useful for counseling families of Parkinson’s patients,” they also said.
Additional studies are still needed to identify the environmental causes responsible for Parkinson’s susceptibility, and the genetic contribution for disease variability remains to be determined in other populations.