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Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2019)

Occupational Cancer Risk in California Teachers and Risk Modification by Medication Use

By

Vikram Haridass

Doctor of Philosophy in Epidemiology

University of California, Irvine 2019

Professor Hoda Anton-Culver, Chair

Introduction: Teachers, as an occupational group, have been previously shown to have an elevated risk of breast, and endometrial cancers relative to the general population. However, no conclusive evidence regarding teacher-specific occupational risk factors driving this higher risk in cancer incidence have been established. Previous studies have found occupational physical activity levels to be inversely associated with risk of incident cancers, yet the conclusions regarding this association are not definitive.

The purpose of this dissertation is to assess cancer risk in participants of the California Teachers Study according to occupational characteristics and medication intake of school employees. The study will examine the association between various occupational characteristics and medication intakes among female school employees and cancer incidence of breast, endometrial, and malignant melanoma.

Methods: A prospective analysis of 133,479 female teachers and school administrators, aged 22-104 years, in the California Teachers Study cohort between 1995 and 2013 was conducted. Occupational characteristics and medication intakes were determined using participants’ responses to the comprehensive questionnaire administered at baseline. Age-standardized incidence rates were calculated according to participants’ occupational characteristics and compared to the incidence rates of California women, obtained from the California Cancer Registry. Multivariable Cox proportional hazard regression models were constructed to provide hazard ratios and corresponding 95% confidence intervals for estimates of cancer risk for breast, endometrial, and malignant melanoma according to occupational characteristics and medication intake of female teachers and school administrators.

Results: Throughout the eighteen years of follow-up in the California Teachers Study, there were 7,173, 1,351, and 1,919 teachers who developed breast cancer, endometrial cancer and malignant melanoma, respectively. There was an excess cancer incidence among California Teacher Study participants overall, and according to several occupational characteristics for breast, endometrial and malignant melanoma. Of note, lower levels of occupational physical activity was associated with an elevated risk across the three cancer types when compared to general female population of California and teachers with higher levels of occupational physical activity. Moreover, the elevated risk associated with minimal occupational physical activity levels was not mitigated by higher levels of recreational physical activity among participants of the study. Additionally, regular anti-inflammatory medication intake among study participants was associated with risk for breast cancer and malignant melanoma compared to non-regular users; there was no evidence for the difference in risk across the three cancer types according to statin use.

Conclusion: This study showed that female teachers and school administrators are at an elevated risk of breast cancer, endometrial cancer, and malignant melanoma which was largely driven by a lack of occupational physical activity and regular anti-inflammatory medication intake.

    Cover page: Occupational Cancer Risk in California Teachers and Risk Modification by Medication Use
    • Thesis
    • Peer Reviewed
    UC Irvine Electronic Theses and Dissertations (2015)

    Introduction: Diet has been implicated as a significant risk factor in terms of breast cancer progression and manifestation, but results are shaky when assessing the specific role played by diet. The Healthful Diet Score was developed using a-priori based methods that assessed the existing nutritional epidemiology evidence regarding breast cancer risk along with findings from widely-accepted standardized dietary indices: Alternate Mediterranean Diet Index, Alternative Healthy Eating Index-2010, Dietary Approach to Stop Hypertension (aMED, AHEI-2010, DASH). An increased diet quality score is indicative of greater adherence to healthy dietary patterns, which encompass all beneficial aspects of dietary consumption ranging from vitamins to polyunsaturated fat consumption. Breast cancer is the most common cancer observed amongst women in which many risk factors have been identified, including some modifiable factors such as diet. We assessed the role of overall diet quality, through our own a-priori index and standardized indices, on the risk of incident breast cancer (BRCA). Methods: California Teacher Study participants were women age 22-104 years old at baseline (1995-1996) who are members of California State Teachers Retirement System. Overall diet quality scores were computed for the eligible study population (n=94,404) through participants’ responses to the validated-FFQ. Descriptive statistics across the various measures of overall diet quality were generated. Multivariate Cox proportional hazard regression models were constructed to provide hazard ratios and corresponding 95% confidence intervals. Results: In terms of overall breast cancer risk, overall diet quality as defined by AHEI-2010 exhibited the greatest reduction of risk 13% for the highest adherers vs. lowest adherers (HRQ5vsQ1 0.87, 95% CI: 0.79-0.97). Similar reductions in overall breast cancer risk were also exhibited in the highest adherers of a DASH diet plan (HRQ5vsQ1 0.88, 95% CI: 0.79-0.97). In terms of pre-menopausal breast cancer risk, overall diet quality was not significantly associated with breast cancer risk across all measure of diet quality. When assessing the post-menopausal subgroup in this study, the role of overall diet quality became increasingly apparent in terms of breast cancer risk in which the highest risk reduction observed was 25% for highest adherers of the AHEI-2010 diet pattern (HRQ5vsQ1 0.75, 95% CI:0.70-0.91). Conclusion: Findings from this large prospective cohort study suggest that overall diet quality is significantly associated with invasive breast cancer risk amongst post-menopausal women, and the AHEI-2010 score displayed the strongest inverse association with breast cancer.

      Cover page: Diet Quality Scores and Risk of Incident Breast Cancer in the California Teachers Study
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2018)

      Background

      Evidence for the association between diet and breast cancer risk is inconsistent Thus, research that compares indexes of overall diet quality may provide new insight.

      Objective

      We examined the association between diet quality indexes and pre- and postmenopausal breast cancer risk in a large prospective cohort.

      Methods

      This was a prospective analysis of 96,959 women, aged 22-104 y, in the California Teachers Study cohort (1995-2011). Diet quality was characterized by 4 different indexes. Specifically, we examined Alternate Mediterranean Diet (aMED), Alternative Healthy Eating Index-2010 (AHEI-2010), Dietary Approaches to Stop Hypertension (DASH), and Paleolithic index (PALEO) scores with the risk of developing breast cancer. We used multivariable Cox proportional hazards regression models to derive HRs and 95% CIs for breast cancer risk.

      Results

      In the analysis of 42,517 women at risk of premenopausal breast cancer, there was no association between any of the indexes and incident breast cancer (346 cases). In the analysis of 54,442 women at risk of postmenopausal breast cancer at baseline, higher AHEI-2010, aMED, and DASH scores were inversely associated with incident breast cancer (3523 incident cases). Respectively, HRs (95% CIs) comparing quintile 5 to quintile 1 (reference) for AHEI-2010, aMED, and DASH indexes were 0.87 (0.78, 0.97; P-trend = 0.004), 0.91 (0.82, 1.02; P-trend = 0.03), and 0.89 (0.80, 1.00; P-trend = 0.03). The PALEO score was not associated with postmenopausal breast cancer (HR for quintile 5 compared with quintile 1: 1.05; 95% CI: 0.94, 1.17).

      Conclusions

      Diet quality indexes that emphasize intake of whole grains, vegetables, fruits, legumes, and nuts and seeds and de-emphasize red and processed meats and sugar-sweetened beverages were modestly associated with a lower risk of incident postmenopausal breast cancer risk. However, they were not associated with premenopausal breast cancer, and the PALEO score was not associated with cancer risk regardless of menopausal status.
      • 1 supplemental PDF
      Cover page: Diet Quality Scores Inversely Associated with Postmenopausal Breast Cancer Risk Are Not Associated with Premenopausal Breast Cancer Risk in the California Teachers Study.Creative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2021)

      Background

      The debate continues among medical professionals regarding the frequency, starting age, and stopping age for mammography screening. Some experts suggest tailoring recommendations based on individuals' personal breast cancer risk. Previous studies have not compared the impact of annual versus biennial mammography stratified by age group and risk category. The purpose of this study was to examine the relationship between mammography frequency and mortality by age group and risk category in the California Teachers Study.

      Methods

      Using data from study questionnaires from 93,438 women between the ages of 40 and 85 and linkages to the California Cancer Registry and other indices, overall and breast cancer-specific mortality by mammography frequency were estimated using multivariable Cox proportional hazards models, stratified by age group and risk category at baseline as determined by the Gail breast cancer risk model.

      Results

      During the follow-up period of 20 years, overall mortality risk was lower in women who had annual or biennial mammography compared to less frequent or no mammography in all age groups. Annual mammography was associated with lower overall mortality risk compared to biennial mammography among women age 50-85. This difference was especially apparent in women age 60-74, regardless of estimated Gail risk category at baseline. Breast cancer-specific mortality was lower among women who had annual mammography compared to biennial or less frequent mammography among women age 60-74, regardless of their baseline risk.

      Conclusions

      Our findings suggest that at least biennial mammography is beneficial to most women age 40-85 and that annual mammography is more beneficial than biennial mammography to most women age 50-85 in terms of overall mortality.
        Cover page: Mammography screening and mortality by risk status in the California teachers study
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