In this population-matched and sibling cohort study, researchers compared 61,748 individuals diagnosed with stress-related disorders (PTSD, acute stress reaction, adjustment disorder, and other stress reactions) between January 1987 and December 2008 with 595,335 unexposed people in the general population. They also compared 44,839 of those exposed individuals with 78,482 of their unaffected full siblings. The researchers began follow-up from the age of 40 or five years subsequent to diagnosis, whichever came later, until the initial diagnosis of a neurodegenerative disease, death, emigration, or the end of follow-up, whichever occurred first.
All neurodegenerative diseases were identified through the National Patient Register and categorized as either primary or vascular. Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis were evaluated separately. The researchers used Cox proportional hazards regression models to estimate hazard ratios (HRs) with 95% CIs after controlling for multiple confounders. They performed data analysis from November 2018 to April 2019.
The results of the study showed that individuals with a stress-related disorder were at an increased risk of developing neurodegenerative diseases juxtaposed to unexposed individuals (HR=1.57; 95% CI, 1.43 to 1.73). The researchers observed that the increased risk was greater for vascular neurodegenerative diseases (HR=1.80; 95% CI, 1.40 to 2.31) than for primary neurodegenerative diseases (HR=1.31; 95% CI, 1.15 to 1.48). They also found a statistically significant link between stress-related disorders and Alzheimer disease (HR=1.36; 95% CI, 1.12 to 1.67) but not Parkinson disease (HR=1.20; 95% CI, 0.98 to 1.47) or amyotrophic lateral sclerosis (HR=1.20; 95% CI, 0.74 to 1.96). The researchers noted that the results of the sibling cohort supported the results of the population-matched cohort.