Predictive value of life’s crucial 9 for all-cause mortality and cardiovascular disease: an analysis of the PURE-China cohort study

Background Cardiovascular health (CVH) metrics have progressed from Life’s Simple 7 to Life’s Essential 8 (LE8). Life’s Crucial 9 (LC9) extends LE8 by incorporating mental health, yet whether LC9 offers incremental prognostic value for mortality and cardiovascular disease (CVD) remains unclear, particularly in Chinese populations. Purpose To evaluate the association of LE8 and LC9 with all-cause mortality and major CVD in the PURE-China cohort, and to assess whether adding depressive symptoms meaningfully improves risk prediction beyond LE8. Methods PURE–China is a population-based prospective cohort enrolling adults aged 35–70 years from 12 provinces (2005–2009). We analyzed 36,859 participants (mean age 50.5 years) followed for a median of 12.0 years. LE8 (0–100) was calculated as the unweighted mean of eight components (nicotine exposure, diet, physical activity, sleep, BMI, blood lipids, blood glucose, and blood pressure). Depressive symptoms were measured using the short-form Composite International Diagnostic Interview (CIDI-SF; 0–7) and mapped to a 0–100 depression score; LC9 was defined as the mean of LE8 and the depression score. LE8/LC9 were categorized as low (0–49), moderate (50–79), and high (80–100). The primary outcome was a composite of all-cause mortality and major cardiovascular events. Cox frailty models with community-level random intercepts were fitted with multivariable adjustment. Incremental predictive performance of LC9 vs LE8 was assessed using Harrell’s C-statistic, Akaike Information Criterion (AIC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Results During follow-up, 1,914 deaths and 2,881 major CVD events occurred (4,085 composite events). Age- and sex-standardized incidence rates (per 1,000 person-years) declined monotonically across LC9 categories: composite endpoint 16.95 (low), 10.07 (moderate), and 6.40 (high); major CVD 13.10, 7.57, and 4.20; all-cause mortality 7.80, 3.93, and 2.76. In fully adjusted models, each 10-point higher LC9 was associated with lower risk of the composite endpoint (HR 0.78), major CVD (HR 0.74), and all-cause mortality (HR 0.80). Compared with low LC9, high LC9 was associated with substantially lower risks of the composite endpoint (HR 0.40), major CVD (HR 0.34), and all-cause mortality (HR 0.40) (all P for trend <0.001). However, adding depressive symptoms yielded negligible improvement in discrimination and no meaningful enhancement in reclassification (NRI/IDI). Conclusions In PURE-China, higher LE8 and LC9 was strongly and dose-dependently associated with lower all-cause mortality and major CVD risk. However, incorporating depressive symptoms into LE8 to form LC9 provided minimal incremental predictive performance, suggesting LC9 may be valuable for etiologic risk stratification but offers limited added benefit for outcome prediction beyond LE8 in this population.