To identify relative risk of Parkinson’s disease-related death based on comprehensive family history.

There is an inherited component to risk for Parkinson’s disease (PD). Most studies estimating the risk to individuals in a family have focused on close relatives.

A unique Utah population resource, including a genealogy of Utah pioneers from the mid-1800s linked to Utah death certificates, was used to estimate the risk for PD-related death based on family history of PD death. The analysis included first- to third-degree relatives.

We first estimated the risk of PD-related death based on the number of affected first-degree relatives, rather than the typical estimate of risk based on presence or absence of any first-degree family history. The data showed increasing relative risk (RR) with one, two, and three first-degree relatives with PD-related death. Then we estimated the RR for PD-related death based on the number of affected second-degree relatives in two scenarios. With PD-related deaths in second-, but not in first- and third-degree relatives, RR was not significantly increased. In contrast, in the presence of exactly one PD-related death in a first-degree relative, the RR increased from 1.34 to 2.10 going from one to two PD-related deaths in second-degree relatives. Due to the small number of cases, the analysis could not be performed with three affected second-degree relatives. We then estimated the RR for PD-related death based on the number of affected third-degree relatives in the absence of any affected first- and second-degree relatives. The RR for PD-related death was not increased.