Body Mass Index Trajectories During Young Adulthood and Incident Hypertension: A Longitudinal Cohort in Chinese Population

BACKGROUND: This longitudinal study aims to characterize longitudinal body mass index (BMI) trajectories during young adulthood (20–40 years) and examine the impact of level‐independent BMI trajectories on hypertension risk. METHODS AND RESULTS: The cohort consisted of 3271 participants (1712 males and 1559 females) who had BMI and blood pressure (BP) repeatedly measured 4 to 11 times during 2004 to 2015 and information on incident hypertension. Four distinct trajectory groups were identified using latent class growth mixture model: low‐stable (n=1497), medium‐increasing (n=1421), high‐increasing (n=291), sharp‐increasing (n=62). Model‐estimated levels and linear slopes of BMI at each age point between ages 20 and 40 were calculated in 1‐year intervals using the latent class growth mixture model parameters and their first derivatives, respectively. Compared with the low‐stable group, the hazard ratios and 95% CI were 2.42 (1.88, 3.11), 4.25 (3.08, 5.87), 11.17 (7.60, 16.41) for the 3 increasing groups, respectively. After adjusting for covariates, the standardized odds ratios and 95% CI of model‐estimated BMI level for incident hypertension increased in 20 to 35 years, ranging from 0.80 (0.72–0.90) to 1.59 (1.44–1.75); then decreased gradually to 1.54 (1.42–1.68). The standardized odds ratios of level‐adjusted linear slopes increased from 1.22 (1.09–1.37) to 1.79 (1.59–2.01) at 20 to 24 years; then decreased rapidly to 1.12 (0.95–1.32). CONCLUSIONS: These results indicate that the level‐independent BMI trajectories during young adulthood have significant impact on hypertension risk. Age between 20 and 30 years is a crucial period for incident hypertension, which has implications for early prevention.