Platelet indices and incident hypertension: effect modification by body mass index in a Chinese cohort

Background: Routine platelet indices have been linked to blood pressure and vascular risk. However, longitudinal evidence on the association between platelet count (PLT), mean platelet volume (MPV), plateletcrit (PCT), and platelet distribution width (PDW) and incident hypertension remains limited, and it is unclear whether these associations differ according to adiposity. We aimed to examine associations of PLT, MPV, PCT, and PDW with incident hypertension and assess whether these associations vary by body mass index (BMI). Methods: We analysed 51,191 hypertension-free adults aged ≥18 years from the 2006 baseline examination of the Kailuan Study, with follow-up through 31 December 2023. We measured PLT, MPV, PCT, and PDW from routine full blood counts. We used weighted Cox regression to estimate overall hazard ratios (HRs) and by Chinese BMI categories, adjusting for age, sex, fasting blood glucose, physical activity, and smoking. Restricted cubic splines assessed dose-response relationships. Results: During a median follow-up of 8.2 years, 29,491 participants developed hypertension (incidence rate = 70.67 per 1000 person-years). Higher PLT (HR = 1.07; 95% confidence interval (CI) = 1.05-1.09) and PDW (HR = 1.03; 95% CI = 1.01-1.04) were associated with greater hypertension risk, whereas MPV showed a modest inverse association (HR = 0.98; 95% CI = 0.96-1.00) and PCT was not significantly associated (HR = 0.99; 95% CI = 0.98-1.01). Absolute incidence rates increased across Chinese BMI categories from 33.59 to 105.13 per 1000 person-years. BMI-stratified analyses suggested heterogeneous patterns, particularly for MPV and PDW. Splines indicated approximately linear positive associations for PLT and PDW, a mild inverse/flat pattern for MPV, and nonlinear associations for PCT. Conclusions: Routine platelet indices showed modest associations with incident hypertension, with heterogeneous patterns across BMI categories. These findings suggest that platelet-related haematological traits may reflect BMI-dependent differences in hypertension risk, but external validation and formal prediction analyses are needed before clinical use.