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1.  Recreational physical activity and risk of papillary thyroid cancer among women in the California Teachers Study 
Cancer epidemiology  2012;37(1):46-53.
Purpose
Little is known about the relationship between physical activity and thyroid cancer risk, and few cohort data on this association exist. Thus, the present study aimed to prospectively examine long-term activity and risk of papillary thyroid cancer among women.
Methods
116,939 women in the California Teachers Study, aged 22 to 79 years with no history of thyroid cancer at cohort entry, were followed from 1995-1996 through 2009; 275 were diagnosed with invasive papillary thyroid cancer. Cox proportional-hazards regression provided relative risk (RR) estimates and 95% confidence intervals (CI) for associations between thyroid cancer and combined strenuous and moderate recreational physical activity both in the long-term (high school through age 54 years or current age if younger than 54 years) and recently (during the three years prior to joining the cohort).
Results
Overall, women whose long-term recreational physical activity averaged at least 5.5 MET-hours/week (i.e. were active) had a non-significant 23% lower risk of papillary thyroid cancer than inactive women (RR=0.77, 95% CI: 0.57, 1.04). RR estimates were stronger among normal weight or underweight women (body mass index, BMI<25.0 kg/m2, trend p=0.03) than among overweight or obese women (trend p=0.35; homogeneity-of-trends p=0.03). A similar pattern of risk was observed for recent activity (BMI<25 kg/m2, trend p=0.11; BMI≥25 kg/m2, trend p=0.16; homogeneity-of-trends p=0.04). Associations for long-term activity did not appear to be driven by activity in any particular life period (e.g. youth, adulthood).
Conclusions
Long-term physical activity may reduce papillary thyroid cancer risk among normal weight and underweight women.
doi:10.1016/j.canep.2012.09.003
PMCID: PMC3543486  PMID: 23116823
Physical activity; thyroid cancer; cancer prevention; women; overweight/obesity; Body Mass Index
2.  Alcohol consumption and breast cancer risk among postmenopausal women following the cessation of hormone therapy use: the California Teachers Study 
Background
Alcohol consumption increases breast cancer risk, but its effect may be modified by hormone therapy (HT) use, such that exposure to both may be synergistic. Because many women stopped taking HT after mid-2002, it is important to quantify risks associated with alcohol consumption in the context of HT cessation, as these risks may be more relevant to cancer prevention efforts today.
Methods
Among 40,680 eligible postmenopausal California Teachers Study cohort participants, 660 were diagnosed with invasive breast cancer before 2010. Multivariate Cox proportional hazards regression models were used to estimate relative risks (RR) and 95% confidence intervals (CI).
Results
Increased breast cancer risk associated with alcohol consumption was observed among postmenopausal women who were current HT users (RR=1.60, 95% CI: 1.13–2.26 and RR=2.11, 95% CI: 1.41–3.15 for <20 and ≥20 g/d of alcohol), with risks being similar by HT preparation. Alcohol did not increase risk among women who had stopped using HT within 3 years or 3–4 years before completing the follow-up questionnaire or in the more distant past. Results were similar for ER+ and ER+PR+ tumors; while power was limited, no increase in risk was observed for ER- tumors.
Conclusions
Following the cessation of HT use, alcohol consumption is not significantly associated with breast cancer risk, although a non-significant increased risk was observed among women who never used HT.
Impact
Our findings confirm that concurrent exposure to HT and alcohol has a substantial adverse impact on breast cancer risk. However, after HT cessation, this risk is reduced.
doi:10.1158/1055-9965.EPI-12-0418
PMCID: PMC3721729  PMID: 22832206
breast cancer; alcohol; hormone therapy; cessation; epidemiology
3.  Body Size and the Risk of Postmenopausal Breast Cancer Subtypes in the California Teachers Study Cohort 
Cancer causes & control : CCC  2012;10.1007/s10552-012-9897-x.
Purpose
To evaluate how the association between body size and breast cancer risk varies by tumor receptor subtype, host factors and other exposures among women in the California Teacher Study cohort.
Methods
Among 52,642 postmenopausal women, 2,321 developed invasive breast cancer with known estrogen- and progesterone-receptor status (1,652 ER+PR+, 338 ER+PR−, 312 ER−PR−) between 1995 and 2007. In a subset of 35,529 with waist circumference data, 1,377 developed invasive breast cancer with known ERPR status (991 ER+PR+, 208 ER+PR−, 169 ER−PR−) between 1997 and 2007. Multivariate Cox regression was performed to estimate relative risks (RR) and 95% confidence intervals (CI).
Results
Obesity, adult weight gain of ≥40 pounds, greater abdominal adiposity and greater height increased risk of ER+PR+ breast cancer. The increased risk associated with postmenopausal obesity was limited to those who did not use hormone therapy (HT) at cohort entry (RR=1.37, 95% CI: 1.05–1.78 for BMI ≥30 vs. <25 kg/m2; P-interaction=0.14) and those who were not overweight or obese at age 18 (P-interaction=0.06). The increased risk associated with greater abdominal adiposity was limited to those who were not also overweight or obese (P-interaction=0.01). Neither obesity, abdominal adiposity nor height were associated with the risk of ER−PR− tumors.
Conclusions
The effects of body size on postmenopausal breast cancer risk differed by hormone receptor subtype, and among women with ER+PR+ tumors, by HT use and early adult body size.
doi:10.1007/s10552-012-9897-x
PMCID: PMC3366039  PMID: 22286371
breast cancer; obesity; hormone receptor status; abdominal adiposity; hormone therapy
4.  Determinants and Within-Person Variability of Urinary Cadmium Concentrations among Women in Northern California 
Environmental Health Perspectives  2013;121(6):643-649.
Background: Cadmium (Cd) is a toxic metal associated with increased morbidity and mortality. Urinary Cd (U-Cd) concentration is considered a biomarker of long-term exposure.
Objectives: Our objectives were to evaluate the within-person correlation among repeat samples and to identify predictors of U-Cd concentrations.
Methods: U-Cd concentrations (micrograms per liter) were measured in 24-hr urine samples collected from 296 women enrolled in the California Teachers Study in 2000 and a second 24-hr sample collected 3–9 months later from 141 of the participants. Lifestyle and sociodemographic characteristics were obtained via questionnaires. The Total Diet Study database was used to quantify dietary cadmium intake based on a food frequency questionnaire. We estimated environmental cadmium emissions near participants’ residences using a geographic information system.
Results: The geometric mean U-Cd concentration was 0.27 µg/L and the range was 0.1–3.6 µg/L. The intraclass correlation among repeat samples from an individual was 0.50. The use of a single 24-hr urine specimen to characterize Cd exposure in a case–control study would result in an observed odds ratio of 1.4 for a true odds ratio of 2.0. U-Cd concentration increased with creatinine, age, and lifetime pack-years of smoking among ever smokers or lifetime intensity-years of passive smoking among nonsmokers, whereas it decreased with greater alcohol consumption and number of previous pregnancies. These factors explained 42–44% of the variability in U-Cd concentrations.
Conclusion: U-Cd levels varied with several individual characteristics, and a single measurement of U-Cd in a 24-hr sample did not accurately reflect medium- to long-term body burden.
doi:10.1289/ehp.1205524
PMCID: PMC3672909  PMID: 23552363
cadmium; biomarkers; diet; exposure science; GIS
5.  Hormonal Factors and the Risk of Papillary Thyroid Cancer in the California Teachers Study Cohort 
Background
Despite the increasing incidence of thyroid cancer, there is limited information on its etiology. The strikingly higher rates in young women, compared to men, suggest that sex steroid hormones may be involved in the development of this disease.
Methods
We investigated the effects of menstrual, reproductive, and other hormonal factors on papillary thyroid cancer risk in the prospective California Teachers Study (CTS) cohort. Among 117,646 women, 233 were diagnosed with invasive histologically-confirmed papillary thyroid cancer after cohort enrollment and before January 1, 2008. Relative risks (RR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards regression models.
Results
Among younger women (age <45 years at baseline; approximately one-third of the cohort), but not older women, later age at menarche (age ≥14 years) was associated with increased risk (RR=1.88, 95% CI: 1.13–3.13; pinteraction by age=0.06). Risk was also increased among young women who had longer (>30 days) adolescent menstrual cycles (RR=1.78, 95% CI: 1.01–3.14) and whose last pregnancy had ended within five years of cohort enrollment (RR=2.21, 95% CI: 1.13–4.34). Among older women (age ≥45 years at baseline), ever use of estrogen-only therapy was associated with a statistically non-significant increase in risk (RR=1.69, 95% CI: 0.95–2.98).
Conclusions
The findings from this prospective analysis suggest that several factors related to delayed pubertal development and the transient effects of pregnancy may be particularly important in influencing risk in young women.
Impact
These results suggest the importance of future research into the role of progesterone and the estrogen-to-progesterone ratio.
doi:10.1158/1055-9965.EPI-11-0381
PMCID: PMC3288117  PMID: 21791618
papillary thyroid cancer; menstrual factors; reproductive factors; exogenous hormone use; epidemiology
6.  Dietary phytocompounds and risk of lymphoid malignancies in the California Teachers Study cohort 
Cancer causes & control : CCC  2010;22(2):237-249.
Objective
We examined whether dietary intake of isoflavones, lignans, isothiocyanates, antioxidants, or specific foods rich in these compounds is associated with reduced risk of B-cell non-Hodgkin lymphoma (NHL), multiple myeloma (MM), or Hodgkin lymphoma (HL) in a large, prospective cohort of women.
Methods
Between 1995-1996 and December 31, 2007, among 110,215 eligible members of the California Teachers Study cohort, 536 women developed incident B-cell NHL, 104 developed MM, and 34 developed HL. Cox proportional hazards regression, with age as the time-scale, was used to estimate adjusted rate ratios (RRs) with 95% confidence intervals (CIs) for risk of lymphoid malignancies.
Results
Weak inverse associations with risk of diffuse large B-cell lymphoma were observed for isothiocyanates (RR for ≥12.1 vs. <2.7 mcM/day=0.67, 95% CI: 0.43-1.05) and an antioxidant index measuring hydroxyl radical absorbance capacity (RR for ≥2.2 vs. <0.9 μM Trolox equiv/g/day=0.68, 95% CI: 0.42-1.10; ptrend=0.08). Risk of other NHL subtypes, overall B-cell NHL, MM, or HL was not generally associated with dietary intake of isoflavones, lignans, isothiocyanates, antioxidants, or major food sources of these compounds.
Conclusions
Isoflavones, lignans, isothiocyanates, and antioxidant compounds are not associated with risk of most B-cell malignancies, but some phytocompounds may decrease risk of selected subtypes.
doi:10.1007/s10552-010-9692-5
PMCID: PMC3074494  PMID: 21107674
lymphoma; diet; isothiocyanates; antioxidants; cohort studies
7.  Dietary Assessment in the California Teachers Study: Reproducibility and Validity 
Cancer causes & control : CCC  2008;19(6):595-603.
Objective
To evaluate the reproducibility and validity of the food-frequency questionnaire (FFQ) used in the California Teachers Study (CTS) cohort and to use this data to quantify the effects of correcting nutrient-breast cancer relative risks for measurement error.
Methods
195 CTS cohort members participated in a 10-month dietary validation study that included four 24-hour dietary recalls and pre- and post-study FFQs. Shrout-Fleiss intraclass correlations for reproducibility were computed. Under several standard assumptions concerning the correlations of errors in the FFQs and 24-hour recalls, we calculated energy-adjusted deattenuated Pearson correlations for validity and tested for differences in validity according to a number of demographic and other risk factors. For each nutrient, we compared ot performance of the FFQ versus the 24-hour recalls, estimating the number of days of recalls that give equivalent information about true intake as does a single FFQ.. Finally, the effects of adjustment for measurement error on risk estimates were evaluated in 44,423 postmenopausal cohort members, 1,544 of whom developed breast cancer during seven years of follow-up. Relative risks (RR) and confidence intervals (CI) were calculated using Cox proportional hazards with and without correction for measurement error.
Results
Reproducibility correlations for the nutrients ranged from 0.60 to 0.87. With a few exceptions, validity correlations were reasonably high (range: 0.55–0.85), including r=0.74 for alcohol. Performance of the FFQ differed by age for percent of calories from fat and by body mass index and hormone therapy use for alcohol consumption. For most nutrients examined, our FFQ is comparable to two to six recalls for each subject in capturing true intake. In the measurement error-adjusted risk analyses, corrected RRs were within 13% of uncorrected values for all nutrients examined except for linoleic acid. For alcohol consumption the corrected RR (per 20g/1000kcal/d) was 1.36 (95% CI: 1.03–1.51) compared to the uncorrected estimate of 1.25 (95% CI: 1.10–1.42).
Conclusion
The FFQ dietary assessment used in the CTS is reproducible and valid for all nutrients except the unsaturated fatty acids. Correcting relative risk estimates for measurement error resulted in relatively small changes in the associations between the majority of nutrients and the risk of postmenopausal breast cancer.
doi:10.1007/s10552-008-9124-y
PMCID: PMC2751594  PMID: 18256894
dietary assessment; reproducibility; validity; calibration; breast cancer; alcohol
8.  Dietary patterns and risk of ovarian cancer in the California Teachers Study cohort 
Nutrition and cancer  2008;60(3):285-291.
Previous studies have examined the association between individual foods or nutrients, but not overall diet, and ovarian cancer risk. To account for the clustering of foods in the diet, we investigated the association between dietary patterns and risk of ovarian cancer in the prospective California Teachers Study cohort. Of 97,292 eligible women who completed the baseline dietary assessment in 1995–1996, 311 women developed epithelial ovarian cancer on or before December 31, 2004. Based on principal components analysis, five major dietary patterns were identified and termed “plant-based,” “high-protein/high-fat,” “high-carbohydrate,” “ethnic,” and “salad-and-wine.” Multivariable Cox proportional hazards regression analysis was used to estimate associations between these dietary patterns and risk of incident ovarian cancer. Most of the dietary patterns were not significantly associated with ovarian cancer risk. However, women who followed a plant-based diet had higher risk; comparing those in the top quintile of plant-based food intake with those in the lowest quintile, the relative risk of ovarian cancer was 1.65 (95% confidence interval: 1.07–2.54; Ptrend=0.03). Associations with the five dietary patterns did not vary by known ovarian cancer risk factors or other behavioral or sociodemographic characteristics. Overall, our results show no convincing associations between dietary patterns and ovarian cancer risk.
doi:10.1080/01635580701733091
PMCID: PMC2365491  PMID: 18444162
9.  Diet and Risk of Ovarian Cancer in the California Teachers Study Cohort 
American journal of epidemiology  2007;165(7):802-813.
Dietary phytochemical compounds, including isoflavones and isothiocyanates, may inhibit cancer development but have not yet been examined in prospective epidemiologic studies of ovarian cancer. The authors have investigated the association between consumption of these and other nutrients and ovarian cancer risk in a prospective cohort study. Among 97,275 eligible women in the California Teachers Study cohort who completed the baseline dietary assessment in 1995–1996, 280 women developed invasive or borderline ovarian cancer by December 31, 2003. Multivariable Cox proportional hazards regression, with age as the timescale, was used to estimate relative risks and 95% confidence intervals; all statistical tests were two sided. Intake of isoflavones was associated with lower risk of ovarian cancer. Compared with the risk for women who consumed less than 1 mg of total isoflavones per day, the relative risk of ovarian cancer associated with consumption of more than 3 mg/day was 0.56 (95% confidence interval: 0.33, 0.96). Intake of isothiocyanates or foods high in isothiocyanates was not associated with ovarian cancer risk, nor was intake of macronutrients, antioxidant vitamins, or other micronutrients. Although dietary consumption of isoflavones may be associated with decreased ovarian cancer risk, most dietary factors are unlikely to play a major role in ovarian cancer development.
doi:10.1093/aje/kwk065
PMCID: PMC2093945  PMID: 17210953
antioxidants; cohort studies; diet; isoflavones; isothiocyanates; nutrition; ovarian neoplasms; women's health
10.  Wine and other alcohol consumption and risk of ovarian cancer in the California Teachers Study cohort 
Cancer Causes & Control  2007;18(1):91-103.
Objective
Whether alcohol consumption influences ovarian cancer risk is unclear. Therefore, we investigated the association between alcohol intake at various ages and risk of ovarian cancer.
Methods
Among 90,371 eligible members of the California Teachers Study cohort who completed a baseline alcohol assessment in 1995–1996, 253 women were diagnosed with epithelial ovarian cancer by the end of 2003. Multivariate Cox proportional hazards regression analysis was performed to estimate relative risks (RRs) and 95% confidence intervals (CIs).
Results
Consumption of total alcohol, beer, or liquor in the year prior to baseline, at ages 30–35 years, or at ages 18–22 years was not associated with risk of ovarian cancer. Consumption of at least one glass per day of wine, compared to no wine, in the year before baseline was associated with increased risk of developing ovarian cancer: RR = 1.57 (95% CI 1.11–2.22), Ptrend = 0.01. The association with wine intake at baseline was particularly strong among peri-/post-menopausal women who used estrogen-only hormone therapy and women of high socioeconomic status.
Conclusions
Alcohol intake does not appear to affect ovarian cancer risk. Constituents of wine other than alcohol or, more likely, unmeasured determinants of wine drinking were associated with increased risk of ovarian cancer.
doi:10.1007/s10552-006-0083-x
PMCID: PMC1764867  PMID: 17186425
Ovarian cancer; Alcoholic beverages; Cohort studies; Women’s health

Results 1-10 (10)