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Biomedical subjects

C M Friedenreich

Publications and source records attributed to C M Friedenreich.

At least 19 recordsLinked to original sources
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↗
PubMed1994

Influence of methodologic factors in a pooled analysis of 13 case-control studies of colorectal cancer and dietary fiber.

We examined the study design features and data collection methods from 13 case-control studies of colorectal cancer and diet, which had been previously combined and analyzed, to determine whether they influenced the results obtained from a pooled analysis. We assessed the methods used in each study, estimated a quality score, and used random effects models to re-estimate the pooled odds ratio for the association between dietary fiber and colorectal cancer for these data. Key features of the methods used in each study and the quality score were examined in random effects models to determine whether the heterogeneity found between study-specific risk estimates could be explained by these variables. The odds ratio for dietary fiber and colorectal cancer was 0.46 (95% confidence interval = 0.34-0.64) for the 13 case-control studies as estimated with a random effects model. Two factors, whether the diet questionnaire had been validated before use in the case-control study and whether qualitative data on dietary habits and cooking methods had been incorporated into the nutrient estimation, explained some of the heterogeneity found between studies. Risk estimates for dietary fiber and colorectal cancer were closer to the null for the studies that had these two characteristics. Quality score did not explain any between-study heterogeneity. Random effects models, which included fixed effects covariates, explained some between-study heterogeneity in these data and would be useful for future pooled analyses.

Case-Control Studies↗
PubMed1994

Recreational physical activity and risk of benign proliferative epithelial disorders of the breast in women.

The association between recreational physical activity and the risk of benign proliferative epithelial disorders (BPED) of the breast was examined in a case-control study conducted in Adelaide, Australia, between 1983 and 1985. The study included 383 incident, histologically confirmed cases of BPED identified through the major private pathology laboratory, 383 unbiopsied community controls matched to the cases for age and area of residence, and 192 controls whose biopsies did not show any signs of epithelial proliferation. Subjects reported their level of usual weekly physical activity in a self-administered questionnaire. When cases were compared with community controls, there was some evidence for a negative association between risk of BPED and total recreational physical activity. However, the reverse was observed when the cases were compared with biopsy controls. These patterns were essentially the same when examined by intensity of activity and by menopausal status. Despite the lack of an association between physical activity and risk BPED in this study, further investigation is warranted because of the potential benefits for the primary prevention of breast disease.

Adult↗
PubMed1993

A cohort study of alcohol consumption and risk of breast cancer.

The association between alcohol consumption and breast cancer risk was examined in 519 newly incident, histologically confirmed cases of breast cancer diagnosed between 1982 and 1987 within a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. These women had completed a self-administered food frequency questionnaire including alcohol consumption at enrollment into the study prior to their breast cancer diagnosis. For the total cohort, only a weak association between total alcohol consumption and breast cancer risk is observed, the adjusted relative risk for those drinking 30 or more g/day being 1.22 (95% confidence interval (CI) 0.78-1.90) compared with nondrinkers. There is some evidence for a positive association in women who were premenopausal at the time of enrollment for whom there was a monotonic increase in risk with increasing alcohol intake. Compared with nondrinkers, the adjusted relative risk for alcohol consumption of between 0 and < 10 g of alcohol daily was 1.11 (95% CI 0.71-1.71), between 10 and < 20 g was 1.37 (95% CI 0.79-2.36), between 20 and < 30 g was 1.51 (95% CI 0.80-2.86), and > or = 30 g was 1.86 (95% CI 0.96-3.66; p (trend) = 0.07). These findings contrasted with the results for postmenopausal women where there appeared to be no evidence of any relation. The association in premenopausal women is generally reasonably consistent with that of other studies that have found positive associations with alcohol intake.

Adult↗
PubMed1993

Dietary fiber, vitamins A, C, and E, and risk of breast cancer: a cohort study.

Risk of breast cancer was examined in relation to intake of dietary fiber and vitamins A, C, and E, and food groups which are sources of these dietary constituents, in a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. Between 1982 and 1987, 519 incident, histologically confirmed cases of breast cancer were identified among women who previously had completed self-administered dietary questionnaires. Their nutrient and food intake was compared with that of 1,182 women who had not developed breast cancer during the follow-up period. Women at the uppermost quintile level of dietary fiber intake had a 30 percent reduction in risk of breast cancer relative to that for women at the lowest quintile level (adjusted odds ratio = 0.68, 95 percent confidence interval = 0.46-1.00), and the reduction in risk persisted after adjustment (separately) for total vitamin A, beta-carotene, vitamin C, and alpha-tocopherol. Inverse associations of similar magnitude were observed in association with consumption of pasta, cereals (the trend for which was statistically significant), and vegetables rich in vitamins A and C. Smaller, statistically nonsignificant reductions in risk were observed with increasing intake of dietary retinol, beta-carotene, and vitamin C, but the magnitude of these associations was reduced after adjustment for other dietary factors. Vitamin E intake was not associated with altered risk of breast cancer.

Ascorbic Acid↗
PubMed1993

Recall bias in the association of micronutrient intake and breast cancer.

A nested case-control study within the Canadian National Breast Screening Study was conducted to examine whether there was evidence for recall bias in the reporting of past micronutrient intake. Dietary data collected upon enrollment between 1982 and 1985 from 325 breast cancer cases and 628 matched controls were compared with data collected in 1988 after disease diagnosis. The retrospective estimates of mean micronutrient intakes from food sources were found to be very similar to the prospective estimates for cases and controls. Errors of omission and commission for the reporting of previous supplementary vitamin use were identical for both subject groups. The odds ratios estimated for the association of micronutrient intake and breast cancer for the prospective and retrospective data were similar in magnitude and the 95% confidence intervals overlapped considerably. There was no evidence for recall bias in the estimation of past micronutrient intake by breast cancer cases as compared to controls.

Bias↗
PubMed1993

Methods for pooled analyses of epidemiologic studies.

This paper presents a systematic methodology for the pooling and analysis of previously conducted epidemiologic studies. It discusses the methodologic issues to consider and the procedures to follow when conducting a pooled analysis of individual subject level data. I review random and fixed effects models to estimate pooled risks and the methods to examine whether heterogeneity in study-specific effect estimates exists. Analytic strategies presented here can be used to assess sources of heterogeneity, particularly those originating from different study designs and methods. I describe methods for incorporating a qualitative assessment of the study design and data collection methods into the quantitative estimation of the overall effect. Finally, I make recommendations for future pooled analyses of epidemiologic studies.

Epidemiologic Methods↗
PubMed1991

A cohort study of fat intake and risk of breast cancer.

Between 1982 and 1987, 519 newly incident, histologically confirmed cases of breast cancer were identified in a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. These women had completed a dietary questionnaire before the occurrence of their breast cancer, and this has been used to estimate their intake of dietary fat and several other nutrients. There is evidence of a positive association between breast cancer and total fat intake, with a relative risk of 1.35 (95% confidence interval, 1.00-1.82) per 77 g per day, and some evidence of a dose-response relationship (P = .052).

Adult↗