Age-specific population attributable fractions for frailty, functional disability, and hospitalisation in Chinese older people: an ICOPE-based prospective cohort study

Declines in intrinsic capacity have been associated with increased risks of frailty, disability, and hospitalisation. We estimated population attributable fractions (PAFs) for these outcomes with respect to intrinsic capacity-related conditions and traditional modifiable risk factors in different age groups. We analysed data from a territory-wide, multicentre, community-based, prospective cohort study (2023-24) in Hong Kong. Among 22 237 Chinese adults aged 60 years and older with follow-up data, we calculated age-specific PAFs for incident frailty, instrumental activities of daily living (IADL) disability, and hospitalisation associated with 13 modifiable risk factors. These risk factors included intrinsic capacity conditions, cardiometabolic conditions, and socioeconomic and lifestyle factors, and combinations of these. Between March 21, 2023, and Dec 31, 2024, 47 776 participants were recruited to the study. 41 226 (86·3%) had complete baseline data for all intrinsic capacity conditions, cardiometabolic conditions, socioeconomic and lifestyle factors, demographic covariates, and outcome variables and were therefore included in our study sample. 22 237 (53·9%) of 41 226 participants completed follow-up assessments at least 6 months after baseline with a mean follow-up of 360·4 days (SD 71·6, median 348·0, IQR 307·0-399·0), 1398 (7·1%) of 19 777 participants had incident frailty, 1152 (6·0%) of 19 171 participants had incident IADL disability, and 2068 (11·1%) of 18 622 participants were hospitalised. Limited mobility was the leading risk factor associated across all outcomes (PAFs 9·8-25·3%). Depressive symptoms were a strong risk factor associated with frailty (PAF 19·1%). Age-stratified analyses revealed that limited mobility had the highest PAFs in adults aged 80 years and older, whereas depressive symptoms showed peak PAFs in those aged 60-69 years in most cases. Hypertension contributed to all outcomes (PAFs 8·4-19·6%) only in adults younger than 80 years. In adults aged 60-69 years physical activity was the predominant risk factor associated with frailty (PAF 21·9%) and disability (PAF 22·3%). The attributable risk of lower education with frailty increased with age, reaching its peak in adults aged 80 years and older (PAF 20·2%). Regarding the joint effects of the risk factors, intrinsic capacity decline was the factor associated with the highest overall attributable risk for all outcomes, exceeding the impact of cardiometabolic diseases and socioeconomic and lifestyle risk. Our findings provide insights into age-specific risk factors for frailty, disability, and hospitalisation in older people, underlining the importance of targeted prevention strategies across age groups. Our findings further support a shift towards prioritising intrinsic capacity to better support healthy ageing at the population level. The Hong Kong Jockey Club Charities Trust.