Association between control status of blood pressure and frailty among middle-aged and older adults with hypertension in China: a longitudinal study

Objective To assess the association between blood pressure (BP) control and frailty among middle-aged and older populations with hypertension in China from 2013 to 2018. Design Prospective longitudinal study. Setting This study analysed data from the China Health and Retirement Longitudinal Study, a nationally representative survey administered in 28 provinces of China. Participants A total of 3254 participants diagnosed with hypertension previous to 2013 were taken into analysis. 1932 participants who were not frail in 2013 were enrolled to calculate relative risk. Outcome measures The frailty score was constructed following Rookwood's Cumulative deficit frailty index, with a score >0.25 defined as frailty (outcome variable). The self-reported status of BP control (exposure variable) represented the general status of the participant's BP level. A fixed-effects model was used to analyse the association between BP control and frailty. A Cox proportional hazard model was further used to further calculate the relative risk of frailty for different BP control levels. Results The fixed-effects model showed that compared with well-controlled BP, poorly controlled BP exhibited a positive association with frailty score (beta=0.015; 95% CI 0.011 to 0.019; p<0.001). The Cox proportional hazard model also revealed a higher risk of frailty in the poorly controlled group (HR=1.96; 95% CI 1.49 to 2.56; p<0.001). Based on subgroup analyses, poorly controlled BP was positively associated with frailty in respondents aged <60 years old (fix-effects model: beta=0.015, p=0.021; Cox model: HR=2.25, p<0.001), but not significant among those aged >= 75 years old. Conclusions We provide new evidence of a negative association between BP control and frailty risk, but the findings differ among different age groups. Individualised strategies for BP management should be developed, especially for older hypertension patients.