The Association Between Multimorbidity Patterns, Frailty Transitions, and 2-Year Mortality in Hospitalized Older Adults in China: A Prospective Cohort Study

Background Previous studies have mostly defined frailty using single time-point data, and it remains unclear how frailty transitions affect short-term mortality risk. Furthermore, little is known about the clinical outcomes of frailty in specific multimorbidity patterns. This study aims to investigate the interaction between multimorbidity and frailty transitions in the short-term mortality risk among older hospitalized adults in China. Methods This was a large-scale multicenter cohort study conducted from October 2018 to February 2021. We studied 8,270 hospitalized patients aged 65 and older. The FRAIL scale was used to assess frailty status. Frailty transitions were derived by considering frailty status at baseline and at the 3-month follow-up, encompassing five patterns: persistent non-frailty, persistent pre-frailty, persistent frailty, improvement, and deterioration. Five multimorbidity patterns identified via principal component analysis were used, and subjects were divided into two groups based on the median( M ) of their factor loadings. For each multimorbidity pattern, all possible combinations of tertiles and frailty transitions were evaluated. Cox regression models were used to test their association with mortality. Results The prevalence of multimorbidity in this cohort was 56.77%. Among the participants, 30.05% were persistently non-frail, 18.20% were persistently pre-frail, 6.29% were persistently frail, 29.56% showed improvement, and 15.90% showed deterioration. Compared with patients with a CCI = 0 and persistent non-frailty, those with a CCI \(\:\ge\:\)2 and persistent frailty had a 14.27-fold increased risk of 2 years mortality ( HR  = 14.27, 95% CI : 9.65–21.10). The severity of chronic disease comorbidity was proportional to the mortality risk across all groups experiencing frailty transitions. The cardiometabolic multimorbidity pattern ( HR M ₂ vs. M ₁  = 3.40, 95% CI :2.54–4.57) and the sensory-psychiatric disorders and cancer pattern ( HR M ₂ vs. M ₁ = 3.26, 95% CI :2.43–4.37) both increased the mortality risk for individuals with deterioration. The kidney and hematologic diseases pattern ( HR M ₂ vs. M ₁ = 4.71, 95% CI : 3.34–6.63) and the respiratory and musculoskeletal diseases pattern ( HR M ₂ vs. M ₁ = 5.33, 95% CI :3.78–7.51) both increased the mortality risk for individuals with persistent frailty. Conclusions Early detection and intervention of frailty and multimorbidity risk factors are essential for preventing or delaying their progression, which is crucial for elderly health. Trial registration: Chinese Clinical Trial Registry, ChiCTR1800017682, registered 09 August 2018.