The Relationship between Depression and Comorbid Conditions with Dementia in the 2021 National Health Interview Survey

ABSTRACT Background Dementia, including Alzheimer's Disease (AD), is characterized by memory loss and other cognitive impairment symptoms. Dementia etiology is complex and may potentially be associated with both neuropsychiatric and comorbid conditions. However, few studies have examined the role of depression and chronic comorbid conditions (diabetes, hypertension, and cancer) with dementia, particularly in a national sample. Methods We investigated retrospective cross-sectional data from the 2021 National Health Interview Survey (NHIS) among US adults (n = 14,965) aged ≥ 50 years. Bivariate and multivariate logistic regression analyses were conducted to examine the association between depression and comorbid conditions (in separate models) with dementia, adjusting for sex, age, race/ethnicity, and education. We further studied the interaction/joint effect of depression and each respective comorbid condition on dementia odds. Results We found that those with depression had a significantly higher odds of dementia compared to those without depression (AOR = 3.33; 95% CI = 2.49-4.45). In addition, we found a significant interaction between depression and each respective comorbid condition significantly increased the odds of dementia as follows: diabetes (AOR = 3.24; 95% CI = 2.16-4.85), hypertension (AOR = 3.33; 95% CI = 2.53-4.37), and cancer (AOR = 1.90; 95% CI = 1.21-2.99). Conclusion We found that depression alone and the interaction/joint effects of depression with comorbid conditions, including diabetes, hypertension, and cancer, increased the odds of dementia. Therefore, intervention strategies targeting depression, as well as depression jointly with a chronic condition, may potentially reduce and/or slow dementia development.