For the ``Screening for Cognitive Impairment During Sleep Studies: The George B. Moody PhysioNet Challenge 2026,'' Team CAU_KU develops a compact late-fusion system to predict cognitive impairment one to six years after clinical polysomnography (PSG). Heterogeneous montages and acquisition conditions complicate cross-site prediction, so we focus on electroencephalography (EEG), which can be consistently harmonized across sites and captures neural activity relevant to cognitive decline. Our pipeline standardizes six EEG derivations from variable PSG configurations and samples quality-controlled nighttime windows. Time-domain and time-frequency branches are trained separately, calibrated at the participant level, and fused by probability averaging. Both branches are trained from scratch, yielding a compact solution without pretrained models. These results suggest that complementary time-domain and time-frequency sleep EEG representations support cross-site prediction of future cognitive impairment.