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

Occupational physical activity: the good, the bad, and the proinflammatory

Background

Physical activity (PA) is beneficial for preventing several conditions associated with underlying chronic inflammation, e. g., cardiovascular disease (CVD) and cancer. While an active lifestyle appears to have anti-inflammatory effects, high levels of occupational PA (OPA) were associated with inflammation and elevated mortality risks. We aimed to summarize the current knowledge (1) on the association between inflammation and OPA and (2) its implications for health and mortality.

Methods and results

This mini-review summarized relevant literature published before January 2023 using established scientific databases and sources. For the primary outcome, observational studies (S) reporting immunological effects (O) in subjects (P), with high (I) vs. low OPA (C), were included. For secondary outcomes, i.e., morbidity and mortality associated with inflammatory processes, (systematic) reviews were included. While "active" occupations and "moderate" OPA appear to have beneficial effects, low (particularly sedentary) and "high-intensity" OPA (particularly including heavy lifting tasks) were associated with inflammation and (CVD and cancer-related) mortality; higher leisure-time PA has been almost consistently associated with lower proinflammatory markers and all-cause mortality risks. Workplace interventions appear to counter some of the observed health effects of unfavorable work strain.

Conclusion

The few studies addressing OPA "intensity" and inflammatory markers are largely heterogeneous regarding OPA classification and confounder control. Sedentary and "heavy" OPA appear to promote proinflammatory effects. In addition to targeted management of work-related physical strain and hazardous environmental co-factors, occupational health providers should focus on employer-initiated exercise interventions and the promotion of leisure-time PA.

Voluntary physical activity counteracts the proliferative tumor growth microenvironment created by adipose tissue via high-fat diet feeding in female rats

The adipokine secretion profile created from adipose tissue may represent the molecular mechanism behind the obesity‐breast cancer association. Two adipokines, adiponectin (ADIPO), and leptin (LEP), are altered with obesity and exert antagonistic effects on breast cancer proliferation. We set out to determine whether the adipose‐dependent tumor promoting growth environment created by a high‐fat diet (HFD) in female Sprague‐Dawley rats is altered compared to established responses in male rats and whether voluntary physical activity (PA) ameliorates any HFD‐dependent effects. We found that conditioned media (CM) created from the adipose tissue of female HFD‐fed rats increased the proliferation of MCF7 cells compared to those cells grown in CM prepared from lean adipose tissue. HFD‐CM inhibited AMPK and activated Akt signaling, decreased p27 phosphorylation at T198, reduced total p27 and AdiporR1 protein levels and promoted cell‐cycle entry. PA reversed the proliferative effects of HFD‐CM on MCF7 cells by preventing the effects of HFD on AMPK, Akt, p27 and AdipoR1, ultimately resulting in cell‐cycle withdrawal. Overexpressing AdipoR1 abolished the proliferative effects of the HFD‐CM on MCF7 cells and enhanced the anti‐proliferative effects PA on the HFD‐CM. Thus, PA represents a means to prevent deleterious obesity‐related alterations in tumor growth environment which are brought about by changes in adipokine secretion profile from adipose tissue in the presence of estrogen. Furthermore, although adipose produces hundreds of adipokines, the ADIPO:LEP ratio may serve to indicate the contribution of adipose in creating a tumor growth microenvironment.

Adaptation of a counseling intervention to address multiple cancer risk factors among overweight/obese Latino smokers

More than 60% of cancer-related deaths in the United States are attributable to tobacco use, poor nutrition, and physical inactivity, and these risk factors tend to cluster together. Thus, strategies for cancer risk reduction would benefit from addressing multiple health risk behaviors. We adapted an evidence-based intervention grounded in social cognitive theory and principles of motivational interviewing originally developed for smoking cessation to also address physical activity and fruit/vegetable consumption among Latinos exhibiting multiple health risk behaviors. Literature reviews, focus groups, expert consultation, pretesting, and pilot testing were used to inform adaptation decisions. We identified common mechanisms underlying change in smoking, physical activity, and diet used as treatment targets; identified practical models of patient-centered cross-cultural service provision; and identified that family preferences and support as particularly strong concerns among the priority population. Adaptations made to the original intervention are described. The current study is a practical example of how an intervention can be adapted to maximize relevance and acceptability and also maintain the core elements of the original evidence-based intervention. The intervention has significant potential to influence cancer prevention efforts among Latinos in the United States and is being evaluated in a sample of 400 Latino overweight/obese smokers.

Scientific decision making, policy decisions, and the obesity pandemic

Rising and epidemic rates of obesity in many parts of the world are leading to increased suffering and economic stress from diverting health care resources to treating a variety of serious, but preventable, chronic diseases etiologically linked to obesity, particularly type 2 diabetes mellitus and cardiovascular diseases. Despite decades of research into the causes of the obesity pandemic, we seem to be no nearer to a solution now than when the rise in body weights was first chronicled decades ago. The case is made that impediments to a clear understanding of the nature of the problem occur at many levels. These obstacles begin with defining obesity and include lax application of scientific standards of review, tenuous assumption making, flawed measurement and other methods, constrained discourse limiting examination of alternative explanations of cause, and policies that determine funding priorities. These issues constrain creativity and stifle expansive thinking that could otherwise advance the field in preventing and treating obesity and its complications. Suggestions are made to create a climate of open exchange of ideas and redirection of policies that can remove the barriers that prevent us from making material progress in solving a pressing major public health problem of the early 21st century.

Design of a randomized controlled trial for multiple cancer risk behaviors among Spanish-speaking Mexican-origin smokers

BACKGROUND

Smoking, poor diet, and physical inactivity account for as much as 60% of cancer risk. Latinos experience profound disparities in health behaviors, as well as the cancers associated with them. Currently, there is a dearth of controlled trials addressing these health behaviors among Latinos. Further, to the best of our knowledge, no studies address all three behaviors simultaneously, are culturally sensitive, and are guided by formative work with the target population. Latinos represent 14% of the U.S. population and are the fastest growing minority group in the country. Efforts to intervene on these important lifestyle factors among Latinos may accelerate the elimination of cancer-related health disparities.

METHODS/DESIGN

The proposed study will evaluate the efficacy of an evidence-based and theoretically-driven Motivation And Problem Solving (MAPS) intervention, adapted and culturally-tailored for reducing cancer risk related to smoking, poor diet, and physical inactivity among high-risk Mexican-origin smokers who are overweight/obese (n = 400). Participants will be randomly assigned to one of two groups: Health Education (HE) or MAPS (HE + up to 18 MAPS counseling calls over 18 months). Primary outcomes are smoking status, servings of fruits and vegetables, and both self-reported and objectively measured physical activity. Outcome assessments will occur at baseline, 6 months, 12 months, and 18 months.

DISCUSSION

The current study will contribute to a very limited evidence base on multiple risk factor intervention studies on Mexican-origin individuals and has the potential to inform both future research and practice related to reducing cancer risk disparities. An effective program targeting multiple cancer risk behaviors modeled after chronic care programs has the potential to make a large public health impact because of the dearth of evidence-based interventions for Latinos and the extended period of support that is provided in such a program.

TRIAL REGISTRATION

National Institutes of Health Clinical Trials Registry # NCT01504919.

Study protocol to investigate the effect of a lifestyle intervention on body weight, psychological health status and risk factors associated with disease recurrence in women recovering from breast cancer treatment [ISRCTN08045231]

BACKGROUND

Breast cancer survivors often encounter physiological and psychological problems related to their diagnosis and treatment that can influence long-term prognosis. The aim of this research is to investigate the effects of a lifestyle intervention on body weight and psychological well-being in women recovering from breast cancer treatment, and to determine the relationship between changes in these variables and biomarkers associated with disease recurrence and survival.

METHODS/DESIGN

Following ethical approval, a total of 100 patients will be randomly assigned to a lifestyle intervention (incorporating dietary energy restriction in conjunction with aerobic exercise training) or normal care control group. Patients randomised to the dietary and exercise intervention will be given individualised healthy eating dietary advice and written information and attend moderate intensity aerobic exercise sessions on three to five days per week for a period of 24 weeks. The aim of this strategy is to induce a steady weight loss of up to 0.5 Kg each week. In addition, the overall quality of the diet will be examined with a view to (i) reducing the dietary intake of fat to approximately 25% of the total calories, (ii) eating at least 5 portions of fruit and vegetables a day, (iii) increasing the intake of fibre and reducing refined carbohydrates, and (iv) taking moderate amounts of alcohol. Outcome measures will include body weight and body composition, psychological health status (stress and depression), cardiorespiratory fitness and quality of life. In addition, biomarkers associated with disease recurrence, including stress hormones, estrogen status, inflammatory markers and indices of innate and adaptive immune function will be monitored.

DISCUSSION

This research will provide valuable information on the effectiveness of a practical, easily implemented lifestyle intervention for evoking positive effects on body weight and psychological well-being, two important factors that can influence long-term prognosis in breast cancer survivors. However, the added value of the study is that it will also evaluate the effects of the lifestyle intervention on a range of biomarkers associated with disease recurrence and survival. Considered together, the results should improve our understanding of the potential role that lifestyle-modifiable factors could play in saving or prolonging lives.

Development and evaluation of a breast cancer prevention decision aid for higher-risk women

OBJECTIVE

To develop and evaluate the effectiveness of a breast cancer prevention decision aid for women aged 50 and older at higher risk of breast cancer.

DESIGN

Pre-test-post-test study using decision aid alone and in combination with counselling.

SETTING

Breast Cancer Risk Assessment Clinic.

PARTICIPANTS

Twenty-seven women aged 50-69 with 1.66% or higher 5-year risk of breast cancer.

INTERVENTION

Self-administered breast cancer prevention decision aid.

MAIN OUTCOME MEASURES

Acceptability; decisional conflict; knowledge; realistic expectations; choice predisposition; intention to improve life-style practices; psychological distress; and satisfaction with preparation for consultation.

RESULTS

The decision aid alone, or in combination with counselling, decreased some dimensions of decisional conflict, increased knowledge (P < 0.01), and created more realistic expectations (P < 0.01). The aid in combination with counselling, significantly reduced decisional conflict (P < 0.01) and psychological distress (P < 0.02), helped the uncertain become certain (P < 0.02), and increased intentions to adopt healthier life-style practices (P < 0.03). Women rated the aid as acceptable, and both women and practitioners were satisfied with the effect it had on the counselling session.

CONCLUSION

The decision aid shows promise as a useful decision support tool. Further research should compare the effect of the decision aid in combination with counselling to counselling alone.

Exercise, cachexia, and cancer therapy: a molecular rationale

Evidence from recent publications indicates that repeated exercise may enhance the quality of life of cancer patients. The lack of reported negative effects and the consistency of the observed benefits lead one to conclude that physical exercise may provide a low-risk therapy that can improve patients' capacity to perform activities of daily living and improve their quality of life. Repeated physical activity may attenuate the adverse effects of cancer therapy, prevent or reverse cachexia, and reduce risk for a second cancer through suppression of inflammatory responses or enhancement of insulin sensitivity, rates of protein synthesis, and anti-oxidant and phase II enzyme activities. These results most likely come about through the ability of physical exercise to attenuate a chronic inflammatory signaling process and to transiently activate the mitogen-activated protein kinase, c-Jun NH2-terminal kinase, c-Jun NH2-terminal kinase-mitogen-activated protein kinase, and nuclear factor-kappa B pathways and through its ability to enhance insulin sensitivity. Expanded molecular-based research into these areas may provide new insights into the biological mechanisms associated with cancer rehabilitation and endogenous risk.

Physical activity in first-degree relatives of breast cancer patients

This study sought to evaluate physical activity in women at moderate risk for breast cancer, the correlates of engaging in regular physical activity, and whether physical activity relates to psychological well-being. The results revealed that 55% of women were regularly active. Logistic regression models indicated that positive affect was associated with increased and negative affect was associated with decreased overall and leisure activity. Older, married, and employed women were more likely to engage in household/occupational activity, whereas women who perceived their risk for breast cancer as high were less likely. More educated women and those with higher perceived risk were more likely to engage in leisure activity, and married women were less likely. These results suggest a need to increase activity levels in women at moderate risk for breast cancer, provide variables upon which interventions can be tailored to promote activity, and point to psychological benefits of activity in this population.

The effect of physical activity on breast cancer risk: a cohort study of 30,548 women

BACKGROUND

In epidemiological studies abundant physical activity has been related to decreased breast cancer risk, though the results have been inconsistent. The purpose of this paper was to study the association of physical activity at leisure and commuting to work and incidence of breast cancer.

METHODS

The study cohort consisted of 30,548 female participants of the Finnish adult health behaviour survey, based on annual random samples of Finns aged 15-64, collected in 1978-1993. By the end of 1995, 332 breast cancer cases had been diagnosed in the cohort. Relative risks of breast cancer were adjusted for age at survey, body mass index (BMI), education, length of follow-up, parity and age at first birth using Poisson regression models.

RESULTS

Compared to women exercising less than once a week, the adjusted relative risk of breast cancer for women exercising once a week was 0.80 (95% confidence interval (CI): 0.58-1.10), for women exercising 2-3 times per week 0.92 (95% CI: 0.78-1.22) and for women exercising daily 1.01 (95% CI: 0.72-1.42). Women who reported commuting, walking or bicycling to work 30 min or more daily had slightly lower adjusted risk of breast cancer (RR: 0.87, 95% CI: 0.62-1.24) than women working at home, being unemployed or driving a car to working place.

CONCLUSION

Although a small protective effect of regular physical activity for breast cancer incidence was found in physical activity when commuting to work, the role of the physical activity in breast cancer prevention is still an open question.

Lifetime physical activity and breast cancer risk in the Shanghai Breast Cancer Study

Overall physical activity in adolescence and adulthood, and changes in activity over the lifespan were analysed by in-person interviews among 1459 women newly diagnosed with breast cancer and 1556 age-matched controls in urban Shanghai. Physical activity from exercise and sports, household, and transportation (walking and cycling) was assessed in adolescence (13-19 y) and adulthood (last 10 y), as was lifetime occupational activity. Logistic regression was used to estimate odds ratios (OR) and 95% confidence limits (OR (95% CL)) while controlling for confounders. Risk was reduced for exercise only in adolescence (OR = 0.84 (0.70-1.00)); exercise only in adulthood (OR = 0.68 (0.53-0.88)), and was further reduced for exercise in both adolescence and adulthood (OR = 0.47 (0.36-0.62)). Graded reductions in risk were noted with increasing years of exercise participation (OR(1-5 yrs)= 0.81 (0.67-0.94); OR(6-10 yrs)= 0.74 (0.59-0.93); OR(11-15 yrs)= 0.55 (0.38-0.79); OR(16 + yrs)= 0.40 (0.27-0.60);P(trend,)< 0.01). Lifetime occupational activity also was inversely related to risk (P(trend)< 0.01). These findings demonstrate that consistently high activity levels throughout life reduce breast cancer risk. Furthermore, they suggest that women may reduce their risk by increasing their activity levels in adulthood.

Breast cancer among former college athletes compared to non-athletes: a 15-year follow-up

A growing body of evidence indicates that physical activity is protective against breast cancer. In 1996-97, we conducted a 15-year follow-up of 5398 college alumnae comprised of former college athletes with their non-athletic classmates. Participants completed a detailed mailed questionnaire on their health history from 1981-82 to the present. Excluding women who had died and non-deliverable questionnaires, 84.7% (n = 3940) of the participants in our earlier study responded to the questionnaire; the response rate for former athletes was 86.6% (n = 1945), for non-athletes, 83.0% (n = 1995). Results confirmed our earlier findings. Based on self-reports, former college athletes had a significantly lower risk of breast cancer than the non-athletes. The OR for the 15-year incidence of breast cancer is 0.605 with 95% confidence interval (CI) (0.438-0.835); the 15-year incident breast cancers were 64 among the athletes and 111 among the non-athletes. Among women under 45 the protective effect of physical activity on the risk of breast cancer is considerably greater; odds ratio (OR) = 0.164, 95% CI (0.042-0.636). Athletic activity during the college and pre-college years is protective against breast cancer throughout the life span, and more markedly among women under 45. These results confirm our earlier findings and the findings of other investigators.