Sensitivity analyses restricted to participants with 2-wave data and adjusted with inverse probability of censoring weighting confirmed these findings.<h4>Conclusions and relevance</h4>In this cohort study of middle-aged and older adults in Taiwan, APOE ε4 carriage, particularly homozygosity, was associated with accelerated age-related cognitive decline detectable after age 70 years, whereas non-APOE polygenic risk was not associated with cognitive decline over the current follow-up. The gene discussed is APOE; the disease is Mental deterioration.