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Christine M Friedenreich

Publications and source records attributed to Christine M Friedenreich.

17 recordsLinked to original sources
PubMed2007

Physical activity and endometrial cancer risk: a review of the current evidence, biologic mechanisms and the quality of physical activity assessment methods.

OBJECTIVES: To (1) determine the nature of the association between physical activity and endometrial cancer risk; (2) assess the contribution of variation in the quality of physical activity measurement to inconsistencies in study results; and (3) review the biologic mechanisms that might mediate possible effects of physical activity on risk. METHODS: We reviewed and summarized all published epidemiologic studies examining physical activity and endometrial cancer risk, and evidence relating to possible biologic mechanisms. We assigned each study a quality score for physical activity measurement. RESULTS: Fourteen of the 18 studies showed a convincing or possible protective effect of physical activity on endometrial cancer risk, with an average relative risk reduction of around 30%. A dose-response relation was observed in 7 of 13 studies. The quality score was not related to the observed strength of association or the presence of a dose-response relation. There was epidemiologic and biologic evidence that vigorous activity, as well as light and moderate intensity activities, such as housework, gardening or walking for transportation, may reduce risk. CONCLUSIONS: Physical activity probably has a protective role in endometrial cancer development. More epidemiologic and biologic evidence is needed to make conclusive recommendations on optimal types, characteristics or time periods of physical activity.

Endometrial Neoplasms↗
PubMed2007

Adaptation and evaluation of the National Cancer Institute's Diet History Questionnaire and nutrient database for Canadian populations.

BACKGROUND AND OBJECTIVE: Despite assumed similarities in Canadian and US dietary habits, some differences in food availability and nutrient fortification exist. Food-frequency questionnaires designed for the USA may therefore not provide the most accurate estimates of dietary intake in Canadian populations. Hence, we undertook to evaluate and modify the National Cancer Institute's Diet History Questionnaire (DHQ) and nutrient database. METHODS: Of the foods queried on the DHQ, those most likely to differ in nutrient composition were identified. Where possible these foods were matched to comparable foods in the Canadian Nutrient File. Nutrient values were examined and modified to reflect the Canadian content of minerals (calcium, iron, zinc) and vitamins (A, C, D, thiamin, riboflavin, niacin, B6, folate and B12). DHQs completed by 13 181 Alberta Cohort Study participants aged 35-69 years were analysed to estimate nutrient intakes using the original US and modified versions of the DHQ databases. Misclassification of intake for meeting the Dietary Reference Intake (DRI) was determined following analysis with the US nutrient database. RESULTS: Twenty-five per cent of 2411 foods deemed most likely to differ in nutrient profile were subsequently modified for folate, 11% for vitamin D, 10% for calcium and riboflavin, and between 7 and 10% for the remaining nutrients of interest. Misclassification with respect to meeting the DRI varied but was highest for folate (7%) and vitamin A (7%) among men, and for vitamin D (7%) among women over 50 years of age. CONCLUSION: Errors in nutrient intake estimates owing to differences in food fortification between the USA and Canada can be reduced in Canadian populations by using nutrient databases that reflect Canadian fortification practices.

Adult↗
PubMed2006

Reliability and validity of the Past Year Total Physical Activity Questionnaire.

The authors determined the validity and reliability of their Past Year Total Physical Activity Questionnaire (PYTPAQ), which assesses the frequency, duration, and intensity of occupational, household, and recreational activities performed over the past year. The PYTPAQ was completed twice at baseline, 9 weeks apart (on average), by 154 healthy Canadian men and women aged 35-65 years for assessment of reliability. The PYTPAQ was completed again 1 year later as a self-administered questionnaire. Four times during the year, participants wore an accelerometer for 7 days and completed 7-day physical activity logs. The authors assessed validity by comparing PYTPAQ summary values with 1-year averages of the physical activity logs and accelerometer data and with physical fitness and anthropometric data measured at baseline and 1 year. Spearman correlations for reliability (metabolic equivalent-hours/week) were 0.64 for total activity, 0.70 for occupational activity, 0.73 for recreational activity, and 0.65 for household activity. For total activity, the intraclass correlation coefficient for correlation between the PYTPAQ and the 7-day physical activity logs was 0.42 (95% confidence interval: 0.28, 0.54), and for the accelerometer data it was 0.18 (95% confidence interval: 0.03, 0.32). Spearman correlations between PYTPAQ hours/week of vigorous activity and maximal oxygen uptake were 0.37 and 0.32 at baseline and follow-up, respectively. In general, the PYTPAQ has acceptable reliability and validity for measurement of past-year physical activity that is comparable to that of similar questionnaires.

Adult↗
PubMed2006

Physical activity in relation to mammographic density in the dutch prospect-European prospective investigation into cancer and nutrition cohort.

BACKGROUND: Evidence accumulates that physical inactivity is one of the few modifiable risk factors for breast cancer. The mechanism through which physical inactivity affects breast cancer risk is not clear. The study aim was to investigate the association between physical activity and breast density because mammographic density is strongly associated with breast cancer risk. METHODS: We did a cross-sectional study in 620 women, of ages 49 to 68 years and participants of the Dutch Prospect-European Prospective Investigation into Cancer and Nutrition cohort. A self-administered questionnaire was used to obtain information on duration and intensity of physical activity (recreational, household, and occupational) during the year preceding study recruitment. A total activity index (inactive, moderately inactive, moderately active, and active) was estimated by combining all activity types. Percent and absolute breast density were determined on screening mammograms using a computer-aided method. Multivariate linear regression was used to examine the association between physical activity and breast density. RESULTS: Mean percent density was 35.3% [95% confidence interval (95% CI), 31.8-38.8] for the inactive category compared with 36.1% (95% CI, 33.0-39.2) for the active category. Mean absolute density values for the inactive and active category were 45.8 cm(2) (95% CI, 40.9-50.7) and 42.6 cm(2) (95% CI, 38.3-47.0), respectively. Subgroup analysis for postmenopausal women showed similar results, as did separate analyses for recreational and household activity. CONCLUSIONS: The result does not support a relation between current physical activity and mammographic density in postmenopausal women.

Adult↗
PubMed2006

Effect of physical activity on women at increased risk of breast cancer: results from the E3N cohort study.

PURPOSE: There is a need to investigate the type, duration, frequency, and intensity of physical activity that are critical to reduce the risk of breast cancer, and if this relation differs among subgroups of women. METHODS: We analyzed the relation between physical activity and breast cancer incidence between 1990 and 2002 (n=3,424 cases), among 90,509 women of the French E3N cohort, ages between 40 and 65 years in 1990. We gave special attention to effect modification by body mass index (BMI), family history of breast cancer, parity, and hormone replacement therapy (HRT). RESULTS: A linear decrease in risk of breast cancer was observed with increasing amounts of moderate (P(trend)<0.01) and vigorous (P(trend)<0.0001) recreational activities. Compared with women who reported no recreational activities, those with more than five weekly hours of vigorous recreational activity had a relative risk of 0.62 (0.49-0.78). This decrease was still observed among women who were overweight, nulliparous, had a family history of breast cancer, or used HRT. Compared with the whole cohort, among nulliparous women, the reduction of risk observed was of a higher magnitude, although the test for heterogeneity did not reach statistical significance. CONCLUSION: A risk reduction of breast cancer was particularly observed with vigorous recreational activity. Further investigations are needed to confirm that intensity is an important variable to consider in risk reduction and to identify the precise biological mechanisms involved in such a risk reduction.

Adult↗
PubMed2005

A longitudinal study of exercise barriers in colorectal cancer survivors participating in a randomized controlled trial.

BACKGROUND: The Colorectal Cancer and Home-Based Physical Exercise (CAN-HOPE) trial compared the effects of a 16-week home-based exercise program to usual care on quality of life in colorectal cancer survivors. PURPOSE: In this study, we report the weekly exercise barriers from the exercise group. METHODS: Participants randomized to the exercise group (N = 69) were asked to report their exercise on a weekly basis by telephone. Those participants not achieving the minimum weekly exercise prescription (3 times per week of 30 min of moderate intensity exercise) were asked for a primary exercise barrier. RESULTS: We obtained 1,073 (97.2%) weeks of adherence data out of a possible 1,104 (i.e., 69 x 16). Participants did not meet the minimum exercise prescription in 39.2% (421/1,073) of the weeks. We obtained an exercise barrier in 83.8% (353/421) of these cases. Overall, participants reported 37 different exercise barriers; the three most common were lack of time/too busy, nonspecific treatment side effects, and fatigue. The top 7 to 10 barriers accounted for 70% to 80% of all missed exercise weeks. CONCLUSIONS: These findings may have utility for promoting exercise in this population both inside and outside of clinical trials.

Colorectal Neoplasms↗
PubMed2005

Associations between aerobic fitness and estrogen metabolites in premenopausal women.

UNLABELLED: Chronic physical activity may alter estrogen metabolism, a proposed biomarker of breast cancer risk, by causing a shift toward higher 2-OHE1 and lower 16alpha-OHE1 levels. PURPOSE: To investigate the association between an objective indicator of chronic exercise, aerobic fitness, and 2-OHE1 and 16alpha-OHE1 in premenopausal women. METHODS: Women with high aerobic fitness (N=17; VO2max>or=48 mL.kg.min-1) were compared with women with average aerobic fitness (N=13; VO2max<or=40 mL.kg.min-1) in terms of 2-OHE1 and 16alpha-OHE1 profiles. Participants were healthy, regularly menstruating, Caucasian women, aged 20-42 yr, with a normal body mass index (BMI) of 18-24, not using pharmacologic contraceptives. We measured height, weight, sum of four skinfolds, and maximal aerobic fitness (VO2max), using an incremental cycle ergometer test. Urine samples were collected during the follicular and luteal phase of the menstrual cycle. RESULTS: There were no statistically significant differences between average and highly fit women for 2-OHE1, 16alpha-OHE1, or the 2:16alpha-OHE1 ratio in either the follicular or luteal phase. However, the high-fitness group showed a trend toward a higher luteal 2:16alpha-OHE1 (P=0.20). In ancillary analyses, a higher sum of skinfolds was associated with significantly higher luteal 16-OHE1 levels (r=0.39, P=0.03) and lower luteal phase 2:16 OHE ratio (r=-0.41, P=0.02). Higher BMI was associated with lower follicular phase 2-OHE1 (r=-0.37, P=0.04) and lower follicular 2:16 OHE1 ratio (r=-40, P=0.03). CONCLUSION: This exploratory study is the first to investigate the association between aerobic fitness and estrogen metabolites in premenopausal women using metabolic parameters. We observed no statistically significant association between aerobic fitness and 2-OHE1 and 16alpha-OHE1, but found that body composition was associated with 2-OHE1 and 16alpha-OHE1 levels.

Adult↗
PubMed2004

Case-control study of anthropometric measures and prostate cancer risk.

A population-based case-control study of 988 stage T2 or greater prostate cancer cases and 1063 controls was conducted in Alberta from November 1997 to December 2000 to examine the influence of anthropometric risk factors on the risk of prostate cancer using several different measures. An in-person interview was conducted, and all anthropometric measurements were taken using standardized methods. Respondents also recalled their body weight at each decade from age 20 to the referent year. Several anthropometric variables were derived, and unconditional logistic regression analyses were performed. The multivariable odds ratios, when comparing the highest to the lowest quartile were: for body mass index, OR = 1.12 (95% CI 0.85-1.47); for waist-hip ratio, OR = 1.07 (0.83-1.38); for height, OR = 0.78 (0.60-1.02); for weight, OR = 0.91 (0.70-1.18); for weight gain since age 20, OR = 0.91 (0.70-1.19); and for difference between minimum and maximum adult weight, OR = 0.89 (0.69-1.16). Our study provides evidence for no association between any measures of anthropometry including several derived measures of changes in weight over lifetime and prostate cancer risk.

Adult↗
PubMed2004

Predictors of adherence and contamination in a randomized trial of exercise in colorectal cancer survivors.

The purpose of this study was to examine predictors of exercise adherence (i.e. exercise in the intervention group) and exercise contamination (i.e. exercise in the control group) in a randomized controlled trial of home-based exercise in colorectal cancer survivors. At baseline, 102 participants completed measures of the theory of planned behavior, personality, past exercise, exercise stage of change, physical fitness, and medical/demographics and then were randomly assigned in a 2:1 ratio to an exercise (n=69) or control (n=33) group. Exercise was monitored weekly for 16 weeks using self-reports by telephone. Ninety-three (91%) participants completed the trial. Adherence was 76% in the exercise group and contamination was 52% in the control group. Hierarchical stepwise regression analyses indicated that baseline exercise stage of change (beta=0.35; p=0.001), employment status (beta=-0.28; p=0.010), treatment protocol (beta=-0.26; p=0.018), and perceived behavioral control (beta=0.20; p=0.055) explained 39.6% of the variance in exercise adherence. Intentions (beta=0.36; p=0.049) and baseline exercise stage of change (beta=0.30; p=0.095) explained 29.9% of the variance in exercise contamination. These findings may have implications for conducting clinical trials of exercise in colorectal cancer survivors and for promoting exercise to colorectal cancer survivors outside of clinical trials.

Colorectal Neoplasms↗
PubMed2004

Physical activity and breast cancer risk: the effect of menopausal status.

Convincing epidemiologic evidence exists that physical activity reduces breast cancer risk. The association may differ by menopausal status, because stronger evidence for a risk reduction exists for postmenopausal than for premenopausal women. This review examines potential reasons for the differences in effect by menopausal status, including possible underlying biologic mechanisms.

Age Factors↗
PubMed2004

Exercise motivation and adherence in cancer survivors after participation in a randomized controlled trial: an attribution theory perspective.

The purpose of this study was to examine postprogram exercise motivation and adherence in cancer survivors who participated in the Group Psychotherapy and Home-Based Physical Exercise (GROUP-HOPE; Courneya, Friedenreich, Sela, Quinney, & Rhodes, 2002) trial. At the completion of the GROUP-HOPE trial, 46 of 51 (90%) participants in the exercise group completed measures of attribution theory constructs. A 5-week follow-up self-report of exercise was then completed by 30 (65%) participants. Correlational analyses indicated that program exercise, perceived success, expected success, and affective reactions were strong predictors of postprogram exercise. In multivariate stepwise regression analyses, program exercise and perceived success were the strongest predictors of postprogram exercise. Additionally, perceived success was more important than objective success in understanding the attribution process, and it interacted with personal control to influence expected success and negative affect. Finally, postprogram quality of life and changes in physical fitness were correlates of perceived success. We concluded that attribution theory may have utility for understanding postprogram exercise motivation and adherence in cancer survivors.

Adult↗
PubMed2003

The group psychotherapy and home-based physical exercise (group-hope) trial in cancer survivors: physical fitness and quality of life outcomes.

Physical exercise has been shown to enhance quality of life (QOL) in cancer survivors using pretest-posttest designs and compared to usual care (i.e. no intervention). In the present study, we conducted a randomized controlled trial to determine if exercise could improve QOL in cancer survivors beyond the known benefits of group psychotherapy (GP). We matched 22 GP classes (N=108) on content and then randomly assigned 11 (n=48) to GP alone and 11 (n=60) to GP plus home-based, moderate-intensity exercise (GP+EX). Participants completed a physical fitness test and QOL measures (e.g. Functional Assessment of Cancer Therapy scales) at the beginning and end of GP classes (about 10 weeks). We had excellent recruitment (81%), retention (89%), and adherence (84%) rates and a modest contamination (22%) rate. Using intention-to-treat repeated measures analyses of variance, we found significant Time by Condition interactions for functional well-being, fatigue, and sum of skinfolds. We also found borderline significant interactions for physical well-being, satisfaction with life, and flexibility. All interactions favored the GP+EX condition. We conclude that a home-based, moderate intensity exercise program may im-prove QOL in cancer survivors beyond the benefits of GP, particularly in relation to physical and functional well-being.

Adult↗
PubMed2002

Case-control study of anthropometric measures and breast cancer risk.

A population-based case-control study of 1,233 incident breast cancer cases and 1,241 controls was conducted in Alberta between 1995 and 1997 to examine the influence of anthropometric factors on the risk of breast cancer using several newly derived variables. Data on current height, weight and waist and hip circumference were collected by interviewers using standardized methods. Respondents recalled their body weight at each decade from age 20 to the referent year. Several variables were estimated, and unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations for any of the estimated variables with breast cancer risk for premenopausal women (462 cases, 475 controls) were found. The results for postmenopausal women (771 cases, 762 controls) in the highest vs. lowest quartiles were, for waist circumference, OR = 1.30 (95% CI 0.97-1.73); waist-hip ratio, OR = 1.43 (95% CI 1.07-1.93); weight gain since age 20, OR = 1.35 (05% CI 1.01-1.81); difference between maximum and minimum weights over adult lifetime, OR = 1.56 (95% CI 1.16-2.08); and the reference weight minus the minimum weight since age 20, OR = 1.47 (95% CI 1.10-1.97). Statistically significant trends in risk were observed for these variables. Effect modification with hormone replacement therapy use was found for most variables assessed for postmenopausal women, with much stronger associations found among never-users compared to ever-users. We found strong evidence that waist-hip ratio and weight gained over lifetime, as assessed by different variables, are postmenopausal breast cancer risk factors. These effects were independent of dietary intake and lifetime total physical activity.

Adult↗
PubMed2002

Physical activity and cancer prevention: etiologic evidence and biological mechanisms.

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

Breast Neoplasms↗
PubMed2002

Correlates of adherence and contamination in a randomized controlled trial of exercise in cancer survivors: an application of the theory of planned behavior and the five factor model of personality.

In this study, we examined correlates of adherence and contamination in a randomized controlled trial (RCT) of exercise in cancer survivors using the theory of planned behavior and the Five Factor Model of personality (FFM). We randomly assigned cancer survivors in group psychotherapy classes to either a waiting-list control group (n = 45) or a home-based, moderate intensity exercise program (n = 51). At baseline, participants completed measures of the theory of planned behavior, the FFM, past exercise, physical fitness, medical variables, and demographics. We then monitored exercise over a 10-week period by weekly self-reports. Hierarchical multiple regression analyses indicated that the independent predictors of overall RCT exercise across both conditions were past exercise (beta = .36, p < .001), assignment to experimental condition (beta = .34, p < .001), sex (beta = .30, p < .001), and intention (beta = .14, p < .10). For exercise adherence in the exercise condition, the independent predictors were sex (beta = .38, p < .01), extraversion (beta = .30, p < .05), normative beliefs (beta = -.27, p < .05), and perceived behavioral control (beta = .23, p < .10). Finally, the independent predictors of exercise contamination in the control condition were past exercise (beta = .70, p < .001), sex (beta = .20, p < .05), and intention (beta = .17, p < .10). We conclude that the correlates of exercise adherence and contamination differ in kind as well as in degree. Explanations for these findings and practical implications for conducting exercise RCTs in this population are offered.

Adult↗
PubMedDate not supplied

An analysis of the effect of selection bias on the association of hormone replacement therapy and breast cancer risk.

A sensitivity analysis was conducted to determine the impact on measures of effect of a suspected differential participation response rate between hormone replacement therapy (HRT) users and nonusers, among controls recruited to a population-based case-control study of breast cancer. The age-specific prevalence of current HRT use among controls was compared to data from the 1996 Canadian National Population Health Survey (NPHS). Control women identified as current HRT users were randomly re-sampled to replicate the prevalence of HRT use reported by the NPHS. Unconditional logistic regression was conducted to estimate odds ratios (OR) and 95 percent confidence intervals (CI) for the use of HRT and breast cancer risk before and after re-sampling. Multivariate adjusted ORs for breast cancer and estrogen-only and estrogen-progestin formulations were 0.76 (0.53-1.10) and 0.94 (95% CI: 0.64 - 1.38), respectively, using the original case-control controls and 0.99 (0.77-1.27) and 1.57 (95% CI: 1.02 - 2.40), respectively, following re-sampling of the controls. This sensitivity analysis illustrates the extent to which differential participation rates between HRT users and nonusers may affect estimates of measures of effect.

Aged↗