Examining factors that could delay or prevent cognitive impairment in older adults is crucial. This study investigates the factors recommended by the biopsychosocial model, including physical activity, quality of life, early signs of dementia (mild behavioral impairment and subjective cognitive decline), and cognition in individuals with preclinical dementia. A structural equation model was employed with a cohort of 410 participants to analyze these relationships. The findings indicate that perceived stress and social support contribute to increased mild behavioral impairment, which subsequently affects cognition directly. Quality of life shows an association with subjective cognitive decline but not with mild behavioral impairment. Mediation analysis reveals that the relationship between perceived stress (indirect effect = -0.244) and moderate-to-vigorous physical activity (indirect effect = 0.08) with cognition is mediated by mild behavioral impairment. Furthermore, a statistically significant influence (∆χ2 = 4.236; p = 0.025) suggests a stronger relationship between perceived stress and mild behavioral impairment in the chronic disease group compared to those without chronic diseases.