One in five people with Parkinson's has a family history of the disease

A large-scale study conducted in Italy has shown that approximately 1 in 5 people with Parkinson’s disease have a family history of the disorder when the analysis includes not only first-degree relatives but also second- and third-degree relatives. First-degree relatives consist of parents, siblings, and children, while second-degree relatives include aunts, uncles, grandparents, grandchildren, nieces, and nephews. Third-degree relatives extend to first cousins, great-grandparents, great-aunts, great-uncles, and great-grandchildren. The researchers highlighted that individuals with Parkinson’s tend to have a higher prevalence of family members affected by the disease than earlier studies indicated. They emphasized that gathering family history data beyond immediate relatives is crucial for identifying clusters of the disease and uncovering novel risk factors for Parkinson’s. The study, titled “Family History in Parkinson’s Disease: A National Cross-Sectional Study,” was published in Movement Disorders Clinical Practice. Parkinson’s is a neurodegenerative disorder influenced by both genetic and environmental factors, characterized by motor symptoms such as slowed movements, muscle rigidity, tremors, and problems with balance. In addition to these motor symptoms, nonmotor issues such as sleep disturbances, emotional challenges, memory problems, and cognitive impairment are also common. A family history, particularly among first-degree relatives, is a well-established risk factor for the disease, with research estimating that approximately 15% of Parkinson’s patients have such a history. To better understand family history beyond immediate relatives, researchers across 14 regions in Italy enrolled 2,035 adults with Parkinson’s. Data were collected through structured interviews, covering family history, tremors, cognitive issues, and major psychiatric disorders such as depression and bipolar disorder. Clinical and genetic data were gathered through neurological exams and regional databases. The patients had an average age of 68.9, with motor symptoms typically appearing around the age of 60.2. On average, patients had been living with the disease for 8.7 years, and three out of every five patients were male. In this study, 34.5% of the patients reported a family history extending to third-degree relatives, and 21.9% of them had a formal Parkinson’s diagnosis in their family. Among those with either confirmed or possible family history, 67.9% reported an affected first-degree relative, while 32.1% had affected second- or third-degree relatives. For nonmotor symptoms, 11.9% of patients reported a family history of cognitive impairment, 2% for tremors, 6.2% for depression, and 1.2% for bipolar disorder. When considering possible cases, these rates rose to 21.6% for cognitive impairment, 8.2% for tremors, 12.1% for depression, and 2% for bipolar disorder. The researchers also compared patients with familial Parkinson’s to those without any family history of the disease, referred to as sporadic cases. Patients with a family history of Parkinson’s had a significantly younger age of onset (58.5 vs. 60.8 years) and a longer disease duration (9.6 vs. 8.4 years) compared to those with sporadic Parkinson’s. Depression was more common in the familial group (9.8% vs. 5.7%), and while there was a trend toward more tremors in familial cases (3.7% vs. 2.0%), cognitive and bipolar disorders were equally distributed between both groups. After adjusting for disease duration, there were no significant differences between the two groups in terms of disease stage, as measured by the Hoehn and Yahr scale. Motor and nonmotor symptoms were similarly distributed, except for a decreased sense of smell (hyposmia), which was more prevalent in familial cases. Genetic testing was conducted on 443 patients (21.8%) to identify variants in genes associated with Parkinson’s, including SNCA, LRRK2, GBA1, PRKN, and PINK1. Among those with confirmed family history, positive genetic results were more frequent than in the sporadic group (36.4% vs. 25.8%). However, the prevalence of common Parkinson’s-related gene variants, such as GBA1, LRRK2, and PRKN, was similar between both groups. The researchers concluded that their findings should encourage further studies to assess Parkinson’s risk in family members, thereby enhancing counseling for patients and their families.