Interactive Effect of Hypertension and Obesity on Disability among Older People: A Observational Study

Background: Both hypertension and obesity are strongly associated with disability, but these associations are in debate among older people. In this context, our study aimed to examine the interactive effect of hypertension and obesity with disability, especially including the control of blood pressure. Methods A cross-sectional study was conducted from August to October 2018 in Shanghai, 8648 community-dwelling individuals with a mean age of 70.39 years. Obesity was measured using the body mass index (BMI) in World Health Organization (WHO) Asia criteria. Hypertension control was defined as treatment with antihypertensive medication and a measured blood pressure of less than 140/90 mm Hg. Disability was measured using the self-reported physical self-maintenance scale (PSMS) and the instrumental activities of daily living (IADL) scale developed by Lawton and Brody. Logistic regression with 95% confidence intervals (CI) was used to explore the interactive effect of hypertension and obesity on disability. Results A total of 33.60% of participants reported hypertension control, 6.54% for poor hypertension control, 9.27% for ADL disability, and 32.47% for IADL disability. After adjusting social demographics and chronic conditions, versus without hypertension: in independent analyses, poor hypertension control was a risk factor (OR for ADL disability = 1.47, 95% CI = 1.10–1.96; OR for IADL disability = 1.55, 95% CI = 1.27–1.91); in interactive analyses, poor hypertension control was a risk factor in obese subset (OR for ADL disability = 1.73, 95% CI = 1.09–2.74; OR for IADL disability = 1.80, 95% CI = 1.31–2.47), but a protective factor in underweight subset (OR for ADL disability = 0.33, 95% CI = 0.18–0.62; OR for IADL disability = 0.32, 95% CI = 0.20–0.51). Conclusions Poor hypertension control, independent of its consequences, is a risk factor for disability among older people. In addition, hypertension and BMI status have interactive effect on disability among older people. Poor hypertension control is a risk factor among obese individuals, but a protective factor among underweight individuals.