Intraindividual variability of reaction time predicts all-cause mortality in elderly
Higher intraindividual variability of reaction time (IIVRT) predicts all-cause mortality independent of lower global cognition and prodromal dementia, a new study has found.
Over an 8-year follow-up period, the mortality rate in the cohort of 861 elderly adults was 22.2 percent (n=191). The mean survival time was 4.3±2.2 years.
Mean reaction time and median IIVRT were significantly lower in those who died (778.69±238.77 ms and 6.70, respectively) than in survivors (743.19±184.16 ms and 5.85, respectively; p<0.001 and p=0.001, respectively).
Moreover, general cognitive ability (-0.98±1.49 vs -0.43±1.20; p<0.001) was significantly lower in those who died, while cardiovascular disease (CVD) risk score (17.82±3.47 vs 16.97±3.37; p=0.003) was significantly higher.
While both IIVRT (hazard ratio [HR], 1.35; 95 percent CI, 1.15 to 1.59; p<0.001) and mean reaction time (HR, 1.36; 1.20 to 1.54; p<0.001) were significantly associated with all-cause mortality in unadjusted Cox models, only IIVRT remained a significantly predictor of all-cause mortality after adjusting for covariates in multivariate Cox regression models (HR, 1.22; 1.01 to 1.48; p=0.04).
Backward elimination from the fully adjusted model to obtain the best set of all-cause mortality predictors yielded a final model that showed IIVRT (HR, 1.22; 1.00 to 1.47; p=0.045), sex (HR, 1.78; 1.32 to 2.42; p<0.001) and age (HR, 1.13; 1.10 to 1.17; p<0.001) as the best set of predictors.
Notably, cognition scores were not significant predictors of all-cause mortality (HR, 0.88; 0.77 to 1.01; p=0.06).
Participants were recruited from the Sydney Memory and Ageing Study. Those with Mini-Mental State Scores ≤24, with baseline dementia or other neurological conditions and malignancy were excluded.