Electronic Theses and Dissertations

Date

2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Epidemiology

Committee Chair

Fawaz Mzayek

Committee Member

Debra Bartelli

Committee Member

Maryam Karimi

Committee Member

Yu Jiang

Abstract

The weight-adjusted waist index (WWI), calculated as waist circumference (cm)/√weight (kg) is positively associated with arthritis and all-cause mortality. However, its longitudinal association with arthritis and all-cause mortality among older population, where excess abdominal fat plays a key role in disease development and death, remains underexplored. Thus, the aim of this dissertation was to investigate the longitudinal association between WWI and the risk of arthritis and mortality among U.S aging population. We analyzed data from 3,765 participants aged 51+ in the Health and Retirement Study (2006–2022). Group-based trajectory modeling was used to create WWI trajectories. The relationship between WWI trajectories and arthritis risk was assessed using weighted logistic regression, while the effect of WWI on mortality was evaluated using weighted Cox regression. The pandemic's effect on WWI was analyzed using linear mixed-effects regression. We reported odds ratios (ORs), hazard ratios (HRs), mean difference, 95% CIs, and P-values. Three distinct WWI trajectories were identified: low (30.0%), intermediate (59.4%), and high (10.6%). Over 12 years, the incidence of arthritis was 57.7%. Subgroup analysis showed that alcohol drinkers in the high-WWI trajectory [AOR = 1.87; 95% CI: 1.21, 2.88] had a higher risk of arthritis compared to the low-WWI trajectory. Similarly, among those engaging in high physical activity, the high-WWI trajectory had a higher risk of arthritis [AOR = 3.85; 95% CI: 1.63, 9.13]. The overall incidence of death was 95 deaths per 1000 person-years. For each 1 cm/√kg increase in WWI, the risk of death increased by 9% [AHR = 1.09; 95% CI: 1.04, 1.14]. This association was significant in men [AHR = 1.16; 95% CI: 1.05, 1.29], but not in women [AHR = 1.06; 95% CI: 0.99, 1.12]. Finally, WWI increased from pre- to post-pandemic [β = 0.18; 95% CI: 0.10, 0.27]. We identified three distinct WWI trajectories: low, intermediate and high. Individuals in the high-WWI trajectory who consumed alcohol or engaged in high physical activity levels had a greater risk of arthritis than those in the low-WWI trajectory. WWI was positively associated with mortality risk. Gender modified the effect of WWI on mortality. Abdominal obesity increased during COVID-19 pandemic.

Comments

Data is provided by the student.”

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open Access

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