Sex similarities and differences in cognition: A longitudinal study of healthy control participants from the Parkinson Progression Markers Initiative.

BACKGROUND

Despite sex-based differences in age-related diseases and life expectancy, limited research has explicitly examined sex differences in aging. Longitudinal study designs are particularly underutilized. The current study retrieved longitudinal data from the healthy control group of the Parkinson's Progression Markers Initiative to examine baseline differences and cognitive changes in males and females over time.

METHODS

Male (n = 125, mean age = 61.61) and female (n = 68, mean age = 59.44) participants completed neuropsychological measures annually for up to five years. Measures included the Montreal Cognitive Assessment (MoCA), Letter Number Sequencing (LNS), Semantic Fluency (SFT), Symbol Digit Modalities Test (SDMT), Benton Judgment of Line Orientation Test (BJLOT), Hopkins Verbal Learning Test-Revised Immediate and Delayed Recall (HVLT-R). Within-person changes in cognition and between-group differences longitudinal change trajectories as predicted by sex were examined in a hierarchical fashion. Effects of age and education were also examined.

RESULTS

At baseline, females had higher scores on the SFT, SDMT, and the HVLT-R Immediate and Delayed Recall, while males had higher scores on the BJLOT. However, rates of change in cognition over time did not significantly differ by sex. Higher baseline age predicted lower scores for all neuropsychological outcome measures, and higher education predicted higher scores for all neuropsychological outcome measures except for the MoCA.

CONCLUSIONS

Although there were sex differences in certain domains of cognitive function, rates of cognitive change over time did not significantly differ by sex. Intraindividual variability in cognitive trajectories of aging was observed. Future research should examine factors that predict individual trajectories of aging in healthy individuals.