Background: Motor neuron disease (MND), Parkinson’s disease (PD), and Alzheimer’s disease (AD) are three incurable neurodegenerative diseases that affect individuals of all sexes and ethnicities. They contribute substantially to mortality and disability worldwide and pose significant and growing public health challenges. Concussion as a potential risk factor for MND, PD, and AD remains underexplored in population-based studies.

Objectives: To examine the association between concussion and MND, PD, and AD in population-based case–control studies in New Zealand.

Methods: Three nationwide case–control studies were conducted using Statistics New Zealand’s Integrated Data Infrastructure (IDI), a longitudinal dataset of routinely collected social, health, and census data for all New Zealand residents. Cases of MND, PD, and AD, along with matched population controls, were identified from national mortality data from 1988 to 2020. Concussion histories were obtained from Accident Compensation Corporation (ACC) and hospital discharge data. Odds ratios (ORs) were estimated using logistic regression, adjusting for age, sex, ethnicity, and socioeconomic status.

Results: A history of concussion was associated with increased odds of PD (OR 1.68, 95% CI: 1.43–1.98) and AD (OR 1.77, 95% CI: 1.62–1.92), with similar associations observed in both sexes. Repeated concussions were associated with higher risks of PD and AD, with the strongest associations observed among individuals with two concussions (PD: OR 2.25, 95% CI: 1.41–3.59; AD: OR 2.17, 95% CI: 1.73–2.73) and three or more concussions (PD: OR 2.63, 95% CI: 1.11–6.23; AD: OR 2.31, 95% CI: 1.39–3.84). No association was observed between concussion and MND (OR 1.02, 95% CI: 0.79–1.29).

Conclusions: This study adds to the evidence that concussion, particularly repeated concussion, is associated with an increased risk of PD and AD, but not MND.