Predicting future cognitive impairment from polysomnography (PSG) is challenging because sleep physiology varies strongly with age and across clinical centers. We integrated pretrained SleepFM representations with compact and extended digital sleep biomarkers, demographic information, and age-matched pairwise ranking in a unified prediction framework. The submitted system achieved an official validation age-conditioned AUROC of 0.626. Among candidate sleep biomarkers, transition instability showed consistent associations with cognitive impairment across all three development centers and a positive adjusted association after accounting for age, sex, BMI, and site, whereas the respiratory effort-related arousal (RERA) index showed marked center dependence. These results support combining foundation-model representations with robust digital biomarkers for age-aware multicenter cognitive-risk prediction.