LRRK2 and Parkinson disease: For LRRK2, we found that the brain-age gap was positively associated with rates of decline of HVLT total recall in asymptomatic cases, i.e. a larger brain-age gap was associated with more favourable cognitive trajectories, but negatively in LRKK2-PD cases, i.e. a larger brain-age gap was associated with faster cognitive decline (Fig. 5).