Date of Award

January 2015

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Shiyi Wang

Abstract

Objective: The associations of smoking and body mass index (BMI) with health-related quality of life (QoL) are not well understood among breast cancer survivors. We examined the QoL of breast cancer patients by smoking status and BMI (1) to determine if there are differences in physical and mental component summary (PCS and MCS) scores, (2) to evaluate whether there is an interaction between smoking and BMI on QoL, (3) to assess smoking pattern changes pre- and post-cancer diagnosis, and (4) to measure changes of physical and mental health by smoking status.

Methods: In this study, we included 6,756 breast cancer patients from the SEER-MHOS linkage database (1998-2011) who were 65 to 95 years old (inclusive) and did not present with any other types of cancer. A multivariate linear regression model was used to measure differences in PCS and MCS scores in different smoking statuses and BMI categories. A subgroup analysis was performed among 604 patients who responded to surveys pre- and post-diagnosis. We evaluated the patients' smoking behavior changes and assessed their mean PCS and MCS score changes by their smoking status.

Results: After adjusting for patient demographics, cancer characteristics, and comorbidities, smoking was significantly associated with reduced PCS and MCS scores in breast cancer patients. Being underweight, overweight or obese was negatively correlated with physical health, while being underweight was significantly associated with a lower mental health score. There was no significant interaction between smoking and BMI on QoL. In our subgroup population, only about 26.2% of the smokers quit after breast cancer diagnosis. In the unadjusted analysis, patients who quit smoking after cancer diagnosis showed greater physical health deterioration but less mental health decline compared to patients who continued smoking after diagnosis, or who never smoked.

Conclusions: Smoking and non-normal BMI were associated with poorer QoL, indicating the need to support breast cancer patients who wish to quit smoking and pursue a healthy BMI. The results also suggest that achieving a normal BMI may have greater impact on the mental health of underweight individuals than on those who are overweight or obese. Almost 73.8% of cancer patients did not quit smoking after their cancer diagnosis, indicating a need for encouraging smoking cessation among breast cancer survivors.

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This is an Open Access Thesis.

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