Clinical polysomnography may contain markers of cognitive decline years before diagnosis, while heterogeneous montages and acquisition conditions complicate cross-site prediction. Team CAU_KU developed a compact late-fusion system for predicting cognitive impairment one to six years after polysomnography. Using 6,600 multicenter recordings, our pipeline standardizes six EEG derivations from variable PSG configurations and samples quality-controlled windows across the night. Time-domain and time-frequency branches are trained separately, calibrated at the subject level, and fused by probability averaging. The final system achieves an age-conditioned AUROC of 0.746 on the official Challenge validation set. These results support the value of complementary sleep EEG representations within routine polysomnography for cross-site prediction of future cognitive impairment.