Age-Dependent Association Between Body Mass Index and All-Cause Mortality Among Patients with Hypertension: A Longitudinal Population-Based Cohort Study in China

Abstract

Purpose

The association between body mass index (BMI) and all-cause mortality may vary among hypertensive patients of different ages. This study aimed to investigate the age-dependent association between BMI and all-cause mortality among patients with hypertension.

Patients and Methods

A total of 212,394 participants with hypertension aged 20–85 years from Minhang Hypertension Standardization Management System in Shanghai of China were included. Follow-up began at the time when individuals were first recorded and ended at death, loss to follow-up, or December 31, 2018, whichever came first. Additive Cox proportional hazards models with thin plate smoothing functions and conventional Cox proportional hazards models were adopted to examine the relationship between BMI, age, and mortality. The joint effect of BMI and age on mortality was assessed using a bivariate response model.

Results

We found that the BMI–mortality relationship followed a U-shaped pattern, with a trough at 26–27 kg/m². Compared with normal weight, underweight was associated with a 50% increased risk of premature mortality (hazard ratio 1.50, 95% confidence interval 1.43 to 1.57). Whereas among those aged 45–59 and 60–85 years, overweight was associated with 13% (0.87, 0.80 to 0.94) and 18% (0.82, 0.80 to 0.84) reduction in risk of death, respectively. Bivariate response model indicated a significant interaction between BMI and age (P < 0.05). Among younger and older patients, we found a descending trend for mortality risk, with BMI increasing at different age levels, whereas a reverse J-shaped relation pattern was observed among middle-aged patients.

Conclusion

The impact of BMI on all-cause mortality in hypertensive patients varies with age, and moderate weight gain may benefit longevity in middle-aged and older patients.

Keywords:

• body mass index
• age
• all-cause mortality
• hypertension
• generalized additive model

Abbreviations

BMI, Body mass index; CVD, Cardiovascular diseases; HER, Electronic health record; SBP, systolic blood pressure; DBP, diastolic blood pressure; WHO, World Health Organization; CDC, Center for Disease Control and Prevention; DAG, Directed acyclic graph; ICD-10, International Statistical Classification of Diseases and Related Health Problems, 10th revision; SD, standard deviation; HRs, hazard ratios; CIs, confidence intervals; df, degrees of freedom.

Ethics Approval and Informed Consent

The study was approved by the Institutional Review Board of Minhang District Center for Disease Control and Prevention (NO: EC-P 2019-009). Informed consent from participants was not required, as anonymized data was collected from electronic medical records in this study.

Acknowledgments

The investigators are grateful to the dedicated participants and all research staff of the study.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis, and interpretation, or in all areas; took part in drafting, revising, or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This study was funded by the National Natural Science Foundation of China (grants 82173612 and 82273730); Shanghai Rising-Star Program (21QA1401300); Shanghai Municipal Natural Science Foundation (22ZR1414900); Shanghai Municipal Science and Technology Major Project (ZD2021CY001).