The Longitudinal Effects of Low Body Mass Index on Unfavorable Physical Health Outcomes Among Older Adults Receiving Homecare Nursing: A Prospective Cohort Study

Body mass index (BMI) is an inexpensive, easy-to-calculate, and noninvasive marker of malnutrition. Few studies have examined the longitudinal effects of BMI on the incidence of unfavorable physical health outcomes (UPHOs) among older adults receiving homecare nursing. Therefore, this prospective cohort study examined the longitudinal effects of low BMI on the occurrence of UPHOs at multiple time points (i.e., 1-, 3-, and 6-months) among older adults (≥ 75 years) receiving homecare nursing across Japan. Using an online questionnaire, homecare nurses reported clients' height and weight, as well as socio-demographic characteristics (e.g., age and gender) and health conditions (e.g., diagnosis and dependency level). The occurrence of seven UPHOs (urinary tract infection, respiratory infection, pressure ulcer or skin tear, dehydration, poor dyspnea control, poor pain control, and traumatic fall) was also reported. The longitudinal effects of low BMI on the total number of UPHOs at 1-, 3-, and 6-months follow-ups were examined using a Restricted Moment Model (RMM) with a log link function. Among 660 participants included in the analysis, 42.12% were males, 36.96% had dementia, and 44.09% had low BMI. Adjusting for client's characteristics and the number of UPHOs at the baseline, low BMI at the baseline could increase the incidence of UPHOs at 1-, 3- and 6-month follow-ups (incidence rate ratio [95% confidence interval]:1.59 [1.21, 2.07], 1.57 [1.18, 2.07], 1.35 [1.02, 1.79], respectively). Adequate management of low BMI among older adults receiving homecare nursing would have a favorable effect on reducing the occurrence of UPHOs, thereby reducing the deterioration of overall physical conditions.