The synergic effects of frailty on disability associated with urbanization, multimorbidity, and mental health: implications for public health and medical care.

Frailty is garnering increasing interest as a potential target in disability prevention. Since it is uncertain how frailty interacts with multimorbidity, urbanization, and mental health to affect disability, we investigated the epidemiology of frailty and its synergies with these factors. The study enrolled 20,898 participants aged 65 and older living in New Taipei city. All participants received face to face interview to assess frailty, multimorbidity, urban or rural residence, and mental health. Individual versus combined effects of risk factors were evaluated using the Rothman synergy index. Prevalence of frailty was 5.2% overall, 7.2% in multimorbid participants, 9.6% in rural residents, and 20.8% in those with mental disorders. Logistic regression, adjusted for age and sex, showed significant associations between disability and frailty (OR 8.5, 95% CI 6.4-11.2), multimorbidity (OR 1.3, 95% CI 1.0-1.6), urbanization (OR 1.3, 95% CI 1.0-1.7), and mental disorders (OR 7.3, 95% CI 5.6-9.5); these factors had a significant synergic effect on disability. Frailty is common in older adults and associated with disability, and was synergetic with multimorbidity, mental disorders, and residing rurally. Targeting frailty prevention and intervention needs a special attention on those vulnerable groups.