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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Public Health

Year Degree Awarded

2018

Month Degree Awarded

May

First Advisor

Brian Whitcomb

Subject Categories

Epidemiology | Hormones, Hormone Substitutes, and Hormone Antagonists | Musculoskeletal Diseases | Women's Health

Abstract

Almost 40% of servicewomen use hormonal contraception every year, and 60% will use a contraceptive method in their military career. Rates of contraceptive use and musculoskeletal injury are higher among servicewomen as compared to civilians. Gender differences in rates of musculoskeletal injury have led investigators to question the role of sex hormones, including contraception. Recent studies suggest that hormonal contraceptives may decreased risk of anterior cruciate ligament (ACL) injury, potentially decreasing early onset osteoarthritis (OA). We utilized the Total Army Injury and Health Outcome Database, which prospectively captured demographics, clinical and pharmacy records on over 5.6 million Army soldiers since 1994. Hormonal contraceptive use was identified in the Pharmacy Data Transaction Service. The first project described changes in covariates and contraceptive use overtime. Over the ten years of follow-up, there were increases in age, education, and rank of servicewomen at entry. Among contraceptive users, rates of pill use decreased from 79.71% in 2002 to 51.67% in 2011 with increased use of the ring, implant and IUD. Contraceptive users were young, higher ranking and more likely to be nulliparous. Education varied widely by contraceptive method with injection and patch users having the lowest and ring users the highest level of education. The second and third projects examined the association of hormonal contraceptive and ACL injury or OA by survival analysis using multivariate Cox proportional hazards models. In project two, a total of 2,253 incident ACL tears were identified from medical billing codes. In our final model, current users were 15% less likely to have incident ACL injury. Project 3 identified a total of 3,943 OA cases. In the final model, ever use of contraceptive was associated with a 19% reduced risk of OA compared to never users. Strengths of our study include the evaluation of all types of contraceptive use in a large, diverse, population-based cohort. Information gathered from this study informs future studies considering hormonal contraceptives a modifiable risk factor for ACL injury and OA, informing contraceptive decision making, clinical recommendations, and injury prevention strategies for servicewomen particularly around key career events including basic training and deployment.

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