Search PubMed⌕ Search

Biomedical subjects

C M Friedenreich

Publications and source records attributed to C M Friedenreich.

At least 19 recordsLinked to original sources
PubMed2001

Case-control study of lifetime physical activity and breast cancer risk.

A population-based case-control study of 1,233 incident breast cancer cases and 1,237 controls was conducted in Alberta, Canada, in 1995-1997 to examine the effect of lifetime physical activity patterns on breast cancer risk. No associations between physical activity and breast cancer were found for premenopausal women. For postmenopausal women in the highest quartile (> or =161 metabolic equivalent (MET)-hours/week per year) versus the lowest quartile (<104.8 MET-hours/week per year) of lifetime total physical activity, the adjusted odds ratio was 0.70 (95% confidence interval (CI): 0.52, 0.94). When the risks associated with each type of activity were examined for postmenopausal women, household and occupational activity conferred the largest risk reductions (odds ratio (OR) = 0.57, 95% CI: 0.41, 0.79 and OR = 0.59, 95% CI: 0.44, 0.81, respectively, for highest vs. lowest quartiles of activity), while recreational activity was not associated with any risk reductions. For postmenopausal women, the authors found stronger risk reductions for those who were also nonsmokers (OR = 0.64, 95% CI: 0.46, 0.88), non-alcohol-drinkers (OR = 0.39, 95% CI: 0.11, 0.77), or nulliparous (OR = 0.22, 95% CI: 0.07, 0.70) when they compared the highest with the lowest quartile of lifetime total physical activity. This study provides evidence that lifetime total activity reduces risk of postmenopausal breast cancer.

Adult↗
PubMed2001

A review of physical activity and prostate cancer risk.

OBJECTIVES: The purpose was to review the etiologic role and the possible biologic mechanisms for physical activity in the primary prevention of prostate cancer and to identify future research priorities. METHODS: We conducted literature searches and systematically reviewed all the epidemiologic studies of physical activity and prostate cancer and the literature on the underlying biologic mechanisms. RESULTS: Among 24 previously conducted studies, 14 studies suggested an inverse association of physical activity on prostate cancer; however, no overall association was found in six studies and an increased risk of prostate cancer was observed amongst the most physically active men in four other studies. The methodologic limitations in these studies include variations in detection of latent disease and possible outcome misclassification, crude assessments of physical activity, inadequate control for confounding, and incomplete examination of effect modification. CONCLUSIONS: Physical activity may have an inverse association with prostate cancer risk; however, the epidemiologic evidence is currently inconsistent and the magnitude of the risk reduction observed is small. These inconsistent results could be attributable, in part, to methodologic limitations of previous studies. Hence, further investigation of the etiologic role of physical activity is needed before more definitive conclusions can be made. Specifically, research studies should be designed to measure all types and parameters of physical activity throughout lifetimes. Furthermore, a better understanding of the biologic mechanisms and etiologically relevant time periods in prostate carcinogenesis when physical activity may be operative is needed, so that these studies can be properly designed.

Exercise↗
PubMed2001

Influence of physical activity in different age and life periods on the risk of breast cancer.

We conducted a population-based case-control study of 1,237 incident breast cancer cases and 1,241 controls in Alberta between 1995 and 1997 to examine the effect of physical activity performed at different ages and life periods on breast cancer risk. In this study, we measured all types of physical activity done throughout life with a questionnaire developed and tested specifically for this study. We found that breast cancer risk was most associated with a risk reduction for activity done later in life, particularly between menopause and the reference year, for which we observed an odds ratio of 0.70 (95% confidence interval = 0.52-0.95). We also stratified the study participants into four categories according to their patterns of physical activity performed before and after menopause. For the women who sustained physical activity throughout life vs those who were never active, we found an odds ratio of 0.58 (95% confidence interval = 0.41-0.83). This study suggests that sustained activity throughout life and particularly activity done later in life may have the most benefit in reducing breast cancer risk.

Adolescent↗
PubMed2001

Relation between intensity of physical activity and breast cancer risk reduction.

PURPOSE: To examine the influence of frequency, duration, and intensity of physical activity on risk of breast cancer and to compare breast cancer risks associated with self-reported versus assigned intensity levels of activity. METHODS: A population-based case-control study of 1233 incident breast cancer cases and 1241 controls was conducted in Alberta between 1995 and 1997. The frequency, duration and intensity of occupational, household, and recreational activities were measured throughout lifetime using the Lifetime Total Physical Activity Questionnaire and cognitive interviewing methods. Unconditional logistic regression analyses were used to estimate odds ratios and a full assessment of confounding and effect modification was undertaken. Odds ratios for self-reported and compendium-based assigned levels of activity were compared for lifetime total activity and by type of activity. RESULTS: Breast cancer risk reductions were comparable when self-reported and assigned intensity values were used, although the results and trends were more evident with the assigned intensity data. Moderate-intensity occupational and household activities decreased breast cancer risk, whereas recreational activity, at any intensity level, did not contribute to a breast cancer risk reduction. CONCLUSION: This study found that moderate-intensity activities were the major contributors to the decrease in breast cancer risk found in this study and that risk reductions were more evident when the frequency and duration of activity alone were modeled. Of the three types of activity considered, the greatest risk reductions observed were for occupational and household activities.

Activities of Daily Living↗
PubMed2001

Review of anthropometric factors and breast cancer risk.

Epidemiological evidence implicating anthropometric risk factors in breast cancer aetiology is accumulating. For premenopausal women, breast cancer risk increases with increasing height, but decreases with higher weight or body mass index, and no association with increased central adiposity exists. For postmenopausal women, an increased risk of breast cancer is found with increasing levels of all the anthropometric variables including height, weight, body mass index, waist-hip ratio, waist circumference and weight gain. Weight loss appears to decrease risk, particularly if it occurs later in life. Breast size may be a risk factor for breast cancer, however, the current evidence is inconclusive. Several hypothesized biologic mechanisms exist to explain how anthropometric factors influence breast cancer risk. Obesity may increase levels of circulating endogenous sex hormones, insulin and insulin-like growth factors that all, in turn, increase breast cancer risk. Genetic predisposition to obesity and to specific body fat distributions are also implicated. With obesity, there are increased levels of fat tissue that can store toxins and can serve as a continuous source of carcinogens. Recommendations for future research on anthropometric factors and breast cancer are provided. Sufficient evidence exists to support strategies to avoid weight gain throughout life as a means of reducing postmenopausal breast cancer risk.

Anthropometry↗
PubMed2001

Physical activity and cancer: lessons learned from nutritional epidemiology.

Convincing epidemiologic evidence currently exists for an association between physical activity and the prevention of colon and breast cancer Physical activity may also reduce the risk of cancer at several other sites. With increasing research on this topic, it is apparent that studies of physical activity and cancer have numerous methodological similarities with studies of nutrition and cancer Lessons learned from nutritional epidemiology that can be applied to studies of physical activity and cancer prevention and recommendations for future research are discussed in this review.

Diet↗
PubMed2001

Framework PEACE: an organizational model for examining physical exercise across the cancer experience.

The primary purpose of this article is to provide a framework for organizing research on physical exercise and cancer control. A secondary purpose is to use this framework to provide an overview of the extant literature and to offer directions forr future research. The proposed framework, entitled Physical Exercise Across the Cancer Experience (PEACE), divides the cancer experience into 6 time periods: 2 prediagnosis (i.e., prescreening and screening/diagnosis) and 4 postdiagnosis (i.e., pretreatment, treatment, posttreatment, and resumption). Based on these time periods, 8 general cancer control outcomes are highlighted. Two cancer control outcomes occur prediagnosis (i.e., prevention and detection), and 6 occur postdiagnosis (i.e., buffering, coping, rehabilitation, health promotion, palliation, and survival). An overview of the physical exercise literature indicates that only I time period (i.e., prescreening) and cancer control outcome (i.e., prevention) has received significant research attention. Some time periods (i.e., treatment and resumption) and cancer control outcomes (i.e., coping and health promotion) have received modest research attention, whereas other time periods (i.e., screening/diagnosis, pretreatment, and posttreatment) and cancer control outcomes (i.e., detection, buffering, rehabilitation, palliation, and survival) have received only minimal attention. It is hoped that Framework PEACE will stimulate a more comprehensive and in-depth inquiry into the role of physical exercise in cancer control.

Exercise↗
PubMed2001

Physical activity and cancer prevention: from observational to intervention research.

The purpose of this review is to articulate how progress in epidemiological research on physical activity and cancer prevention can be made. This report briefly reviews the accumulated evidence for an etiological role of physical activity in the prevention of cancer of the colon, breast, prostate, testes, lung, endometrium, and ovary and summarizes the evidence for a causal association for each of these sites. The evidence for a causal association between physical activity and colon and breast cancers is found to be "convincing," for prostate cancer to be "probable," for lung and endometrial cancers to be "possible," and for testicular and ovarian cancers to be currently "insufficient" to make any definitive conclusions. The emerging literature on physical activity and cancer prevention intervention studies is presented, and an overview of the literature on physical activity intervention is also provided. Given the level of evidence that is currently available for the associations between physical activity and cancer, it is argued that for additional progress to be made in this field, there need to be intervention studies on physical activity and cancers of the colon and breast. For the remaining cancer sites, better designed observational epidemiological studies are needed that address the identified methodological limitations found in previous studies. These limitations include crude and incomplete physical activity assessment, lack of adequate control for confounding and effect modification, as well as a lack of consideration of the underlying biological mechanisms that are operative. This review concludes with detailed recommendations for future research in this field.

Activities of Daily Living↗
PubMed2001

Risk factors for benign breast biopsies: a nested case-control study in the Alberta breast screening program.

A nested case-control study was conducted to identify risk factors for benign breast biopsies in 382 cases (women with a benign biopsy result) and 399 controls (women who had not undergone a biopsy) who were sampled from the Alberta breast cancer screening program. The breast biopsy specimens of the cases were reviewed by a panel of pathologists, and percent fibroglandular tissue density was assessed. The multivariable odds ratios for the risk of open benign breast biopsy associated with current cigarette smoking was 2.04 (95% CI 1.32-3.13), for ever regular smoking was 1.61 (1.20-2.16), and for passive smoking was 1.41 (0.99-2.02). A risk reduction was found for ever alcohol consumption (0.61 [0.44-0.85]). Some risk reductions were found when the highest and the lowest quintiles of total aerobic recreational activity were compared (0.71 [0.42-1.20]), stair climbing (0.61 [0.37-1.01]) and walking pace (0.13 [0.02-0.741). Lifestyle risk factors may be implicated in the continuum between detection of an abnormality on a screening mammogram and a breast biopsy specimen. By considering these risk factors, breast screening programs may be better able to identify those women who require a breast biopsy and reduce the number of benign breast biopsies.

Aged↗
PubMed1999

Physical exercise and quality of life following cancer diagnosis: a literature review.

With almost 8 million Americans alive today who have been through the cancer experience, it is important to develop interventions to maintain quality of life (QOL) following cancer diagnosis. Physical exercise is an intervention that may address the broad range of QOL issues following cancer diagnosis including physical, functional, psychological, emotional, and social well-being. The purpose of the present article was to provide a comprehensive and critical review of the topic and to offer suggestions for future research. The review located 24 empirical studies published between 1980 and 1997. Eighteen of the studies were interventions (i.e. quasi-experimental or experimental) but most of these were preliminary efficacy studies that suffered from the common limitations of such designs. Overall, however, the studies have consistently demonstrated that physical exercise has a positive effect on QOL following cancer diagnosis, including physical and functional well-being (e.g. functional capacity, muscular strength, body composition, nausea, fatigue) and psychological and emotional well-being (e.g. personality functioning, mood states, self-esteem, and QOL). Besides overcoming the limitations of past research, recommendations for future research included: (a) extending the research beyond breast and early-stage cancers; (b) comparing and integrating physical exercise with other QOL interventions; (c) examining resistance exercises, the timing of the intervention, and contextual factors; (d) expanding the breadth of the QOL indicators examined; and (e) investigating the rates and determinants of recruitment and adherence to an exercise program following cancer diagnosis.

Chronic Disease↗
PubMed1998

Epidemiologic issues related to the association between physical activity and breast cancer.

A workshop on physical activity and breast cancer was held in November 1997 to review previous epidemiologic research on this topic and to identify new areas for research. This article is the first of three summaries of the workshop's activities. The material reviewed included 21 studies that reported a measure of physical activity in relation to breast cancer outcomes and were published by December 1997. They were identified in a computerized literature search and a "by-hand" review of journals. The study designs, populations, data collection methods, and results were examined and the strengths and limitations of the studies identified. The strengths and limitations are discussed herein, as are recommendations for future research. Fifteen of the 21 studies suggested that physical activity reduces the risk of breast cancer, whereas four studies found no association and two studies found an increased risk of breast cancer associated with physical activity. Specific subgroups of the population may experience a greater decrease in breast cancer with increased levels of physical activity. These include women who are lean, parous, and premenopausal. Some examination of confounding and effect modification was undertaken. Hypothesized biologic mechanisms for this putative association include an effect of physical activity on endogenous hormones, energy balance, and the immune system. The overall evidence supports a reduction in breast cancer risk with increased physical activity. However, numerous questions remain regarding this putative association. These include the underlying biologic model and the parameters of physical activity that are associated with risk, such as the types of activity (occupational, recreational, and household), the components of activity (frequency, intensity, and duration), the time periods in life that are associated with risk reduction, and the important confounders and effect modifiers of this association. Use of intermediate endpoints for breast cancer may be useful in such investigations.

Breast Neoplasms↗
PubMed1998

The lifetime total physical activity questionnaire: development and reliability.

OBJECTIVE: To develop and test the intra-rater reliability of an interview-administered questionnaire that assesses lifetime patterns of total physical activity including occupational, household, and exercise/sports activities. METHODS: The questionnaire was developed and pretested using cognitive interviewing techniques on a sample of women with and without previous breast cancer diagnoses. A pilot study was conducted with 115 women who were interviewed twice, 6 to 8 wk apart by interviewers trained in cognitive interviewing methods. Respondents used recall calendars to record their education, occupations, life events, and physical activity patterns before the interviews. Interviewers helped respondents recall their lifetime exposures, including their occupational, household, and exercise/sports activities, using these calendars and memory-probing strategies. Activity levels were estimated as the average number of hours of activity per week over different time periods. Means and correlation coefficients were estimated and compared for the two time periods. RESULTS: The questionnaire was found to be highly reliable. The test-retest correlations for hours per week spent in total lifetime physical activity was 0.74, for lifetime occupational activity was 0.87, for household activity was 0.77, and for exercise/sports activities was 0.72. CONCLUSIONS: This is the first questionnaire to measure lifetime physical activity by collecting data on each type of physical activity separately over lifetime and by measuring frequency, intensity, and duration of each activity. It is also the first physical activity questionnaire to be developed, refined, and administered using cognitive-based methods employed in survey research. Respondents were able to reliably recall their lifetime physical activity patterns. This instrument can be used for any disease outcome for which physical activity may be a risk factor.

Breast Neoplasms↗
PubMed1997

Relationship between exercise pattern across the cancer experience and current quality of life in colorectal cancer survivors.

The purpose of this study was to identify the main exercise patterns of colorectal cancer survivors across the cancer experience and determine their relationship with current quality of life (QOL). Participants were 130 colorectal cancer survivors who were diagnosed within the previous 4 years and had received adjuvant treatment. Each participant completed a mailed, self-administered questionnaire that assessed exercise behavior at three time points (prediagnosis, active treatment, posttreatment), current QOL (physical, functional, emotional, social), and overall satisfaction with life (SWL). Colorectal cancer survivors exhibited four main exercise patterns across the cancer experience which were labeled maintainers (active at all three time points), temporary relapsers (active prediagnosis, inactive during treatment, active posttreatment), permanent relapsers (active prediagnosis, inactive during treatment, inactive posttreatment), and nonexercisers (inactive at all three time points). Statistical analyses showed that: (a) functional QOL was the least possessed but most important QOL dimension underlying overall SWL, (b) exercise levels decreased from prediagnosis to active treatment and then increased from active treatment to posttreatment but not back to prediagnosis levels, and (c) permanent relapsers reported the lowest QOL of the four main exercise patterns. It was concluded that cancer treatment has a negative impact on exercise levels and that those previously active individuals who fail to reinitiate exercise after cancer treatment experience the lowest QOL 1 to 4 years later. Findings are discussed in reference to previous research along with suggestions for future research, practical implications, and limitations of the study.

Activities of Daily Living↗
PubMed1995

A review of physical activity and breast cancer.

Breast cancer risk is influenced by endogenous hormones. Physical activity may offer one means for the primary prevention of breast cancer through its influence on ovarian hormones. This influence is manifested by changes in age at menarche and the number and nature of ovulatory menstrual cycles, factors that themselves are related to breast cancer risk. Animal experimental studies show that breast cancer risk is decreased by exercise at the time of tumor initiation but not necessarily by exercise during tumor promotion. Epidemiologic studies indicate, overall, a decreased risk of breast cancer among those women who are more physically active, whereas experimental studies of the effects of exercise in women have shown that exercise can influence characteristics of the menstrual cycle. Nevertheless, the experimental studies in women and epidemiologic studies of physical activity and breast cancer risk have been hampered by a number of methodologic limitations. The major problems in the epidemiologic studies include crude and incomplete measurements of physical activity over a woman's lifetime and inadequate control for potential confounding factors. Experimental studies of the effects of physical activity on menstrual activity in women have not adequately quantified the intensity of activity and the resultant effects on menstrual cycle changes.

Animals↗
PubMed1995

Physical activity and risk of breast cancer.

The association between recreational physical activity and breast cancer risk was examined in a population-based case-control study in Adelaide, Australia between 1982 and 1984. There were 451 incident, histologically confirmed cases of breast cancer, identified through the South Australian Central Cancer Registry, which were each age-matched to one control selected at random from the electoral register. These women, aged 20-74 years at diagnosis, reported their level of weekly recreational physical activity in a self-administered questionnaire. The questionnaire reports of light, moderate and vigorous physical activity were converted into total kilocalories per week of energy expenditure. A decrease in risk of breast cancer was found with increasing levels of total recreational physical activity (P (trend) = 0.09). The adjusted odds ratio for those women who expended more than 4,000 kcal/week was 0.73 (95% confidence interval (CI) 0.51-1.05) compared with women who undertook no physical activity. The reduction in risk with recreational physical activity was most evident for women who undertook any vigorous activity. These results provide some support for the hypothesis that physical activity may decrease the risk of developing breast cancer.

Adult↗
PubMed1994

Methodologic issues for pooling dietary data.

This paper presents the methodologic issues to consider when conducting a pooled analysis of data from nutritional epidemiologic studies. Because a wide variety of dietary assessment methods have been used in nutritional epidemiology, pooled analyses often combine data collected under very different circumstances. Whether these different methods influence the results obtained in a pooled analysis has not yet been examined. One of the main concerns in a pooled analysis is whether the data to be pooled are comparable. Questions to consider regarding data comparability and methods to address these questions in a pooled analysis are discussed.

Diet Surveys↗