Molecular Epidemiology of Physical Activity and Cancer

The association between Life's Essential 8 and all-cause, cancer and non-cancer mortality in US Cancer Survivors: A retrospective cohort study of NHANES

OBJECTIVE

To investigate Life's Essential 8 (LE8), a measure of cardiovascular health (CVH), associations with mortality outcomes in cancer survivors.

METHODS

A prospective cohort study included 1818 cancer survivors aged ≥20 years (weighted population: 13,204,583) from National Health and Nutrition Examination Survey (NHANES) 2005-2018. Linked to mortality data through 2019, LE8 data were gathered through self-reports and lab tests. An LE8 score of 80-100 is considered high CVH, 60-79 is moderate CVH, and 0-59 is low CVH. Multivariable Cox proportional hazards regression models were employed to evaluate the associations between LE8 and all-cause, cancer-specific and non-cancer mortality. Subsequently, subgroup analyses were conducted to assess the relationship between LE8 and mortality rates across various subgroups.

RESULTS

At baseline, there were 1818 cancer survivors. In a 15-year follow-up, 2548 deaths occurred: 601 from cancer, 647 from heart disease, and 1300 from other causes. Multivariable models showed high CVH associated with lower hazard ratios for all-cause, cancer-specific and non-cancer mortality vs. low CVH. Cumulative mortality rates increased during follow-up, more so in the low CVH group. Subgroup analysis revealed significant LE8 interactions with age or Poverty Income Ratio (PIR) for all-cause mortality. Additionally, significant interactions between LE8 and PIR were identified for cancer-specific and non-cancer mortality risks (P for interaction <0.05).

CONCLUSION

Among U.S. cancer survivors, higher CVH is independently linked to lower all-cause, cancer-specific, and non-cancer mortality risks. The new CVH definition shows promise as a primary prevention strategy to reduce mortality rates in U.S. cancer survivors.

Physical activity: associations with health and summary of guidelines

The understanding of how physical activity and insufficient physical activity are associated with health outcomes has increased considerably over the past decades. Along with physical activity, the evidence on the associations between sedentary behavior and health has increased, which has resulted in the introduction of recommendations of sedentary behavior. In this article, we 1) present terminology for physical activity and sedentary behavior epidemiology, 2) show the relevant scientific evidence on associations of physical activity and sedentary behavior with selected health-related outcomes and 3) introduce the global guidelines for physical activity and sedentary behavior by the World Health Organization (WHO). Health-related outcomes include cardiovascular morbidity and mortality, total mortality, glucose regulation and type 2 diabetes, adiposity, overweight, obesity, cancer, musculoskeletal and bone health, brain health, and quality of life. These health-related outcomes are reflected across age groups and some population groups, such as pregnant and postpartum women. Furthermore, we discuss physical activity levels across Nordic countries and over time. For the Nordic Nutrition Recommendations, shared common physical activity guidelines were not developed. Instead, each country has created their own guidelines that are being referenced in the article, along with the global WHO guidelines.

Influence of physical activity at a young age and lifetime physical activity on the risks of 3 obesity-related cancers: systematic review and meta-analysis of observational studies

CONTEXT

Excess weight has been linked to increased risks of 13 types of cancers. Physical activity is a non-nutritional modifiable lifestyle factor that is not only crucial for weight control but is also known to regulate hormones and metabolic pathways that may contribute to carcinogenesis. There is solid evidence that being physically active during middle and late adulthood lowers the risks of 3 obesity-related cancers, namely breast cancer, colon cancer, and endometrial cancer. However, the associations between physical activity at a young age (childhood, adolescence, and young adulthood; age 5 to ≤30 yr) and lifetime physical activity and the risks of breast cancer, colon cancer, and endometrial cancer are less defined.

OBJECTIVE

The present systematic review and meta-analysis of observational studies was performed in accordance with the MOOSE guidelines to determine whether physical activity at a young age and lifetime physical activity may lower the risks of breast cancer, colon cancer, and endometrial cancer.

DATA SOURCES

The PubMed and Web of Science databases were searched for relevant observational studies published from inception to July 2018.

STUDY SELECTION

Observational studies (prospective cohort, case-cohort, nested case-control, historical cohort, and case-control) were considered relevant if they investigated the association between physical activity at a young age or lifetime physical activity and the risks of developing selected cancers.

DATA EXTRACTION

A random-effects meta-analysis was performed to generate the summary relative risk (RR) with 95%CI for the highest vs the lowest category of physical activity of any type.

RESULTS

Eighty publications were included in the present meta-analysis. Higher physical activity at a young age was associated with lower risks of breast cancer (RR 0.81, 95%CI 0.76, 0.87) and colon cancer (RR 0.67, 95%CI 0.50, 0.88). Similarly, lifetime physical activity was inversely associated with the risks of breast cancer (RR 0.79, 95%CI 0.72, 0.86) and colon cancer (RR 0.75, 95%CI 0.69, 0.82). For breast cancer, menopausal status did not appear to modify the observed inverse association. The benefit with respect to endometrial cancer risk reduction was only observed with higher lifetime physical activity (RR 0.77, 95%CI 0.67, 0.88), not with higher physical activity at a young age (RR 0.89, 95%CI 0.73, 1.07).

CONCLUSIONS

Being physically active over a lifetime, starting from early childhood, may lower the risks of developing breast cancer, colon cancer, and endometrial cancer.

Cardiorespiratory Fitness, Lung Cancer Incidence, and Cancer Mortality in Male Smokers

INTRODUCTION

The preventive role of cardiorespiratory fitness in lung cancer among smokers is unknown. This study aims to evaluate the association between cardiorespiratory fitness and lung cancer incidence and cancer mortality in former and current male smokers.

METHODS

From 1987 to 2014, cardiorespiratory fitness (quantified from treadmill exercise testing) was assessed in 2,979 men (former smokers, n=1,602; current smokers, n=1,377) aged 59.1 (SD=17.4) years and prospectively followed up for 11.6 (SD=7) years. Multivariable Cox hazard models and population attributable fraction of low cardiorespiratory fitness (<5 METs) for cancer outcomes were analyzed during 2018.

RESULTS

Of the 99 case patients diagnosed with lung cancer, 79 died of cancer 3.6 (SD=4.6) years after diagnosis. Among former smokers, 1-MET increase and categories of moderate and high cardiorespiratory fitness were associated with 13% (p=0.016), 51%, and 77% (p-trend=0.015) reductions in lung cancer incidence, respectively. Among current smokers who were later diagnosed with lung cancer, 1-MET increase and categories of moderate and high cardiorespiratory fitness were associated with 18% (p=0.008), 84%, and 85% (p-trend<0.001) reductions in cancer mortality, respectively. The population attributable fraction for lung cancer incidence was 10.8% among former smokers and 22.3% for cancer mortality among current smokers.

CONCLUSIONS

Higher cardiorespiratory fitness is associated with lower risk of lung cancer incidence in former smokers and reduced risk of cancer mortality in current smokers who were diagnosed with lung cancer. Screening for low cardiorespiratory fitness and achieving at least moderate cardiorespiratory fitness could potentially reduce lung cancer morbidity and mortality, providing a preventive strategy for smokers.

Cardiorespiratory fitness, incidence and mortality of lung cancer in men: A prospective cohort study

OBJECTIVES

To evaluate the association between cardiorespiratory fitness (CRF), lung cancer incidence and cancer mortality in men.

DESIGN

Prospective cohort study.

METHODS

Maximal exercise testing was performed in 4920 men (59.2±11.4years) free from malignancy at baseline. Multivariate Cox hazard models adjusted for established cancer risk factors including smoking were analyzed for lung cancer incidence and cancer mortality among those who were diagnosed with lung cancer. Population attributable risks (PAR) of low CRF (<5 METs) were determined.

RESULTS

During 12.7±7.5years follow-up, 105 (2.1%) participants were diagnosed with lung cancer and 83 (79%) of those died from cancer after 3.6±4.6 years from diagnosis. CRF was inversely and independently associated with cancer outcomes. A 1-MET increase and categories of moderate and high CRF were associated with 10%, 47% and 65% reduction in lung cancer incidence (p=0.002), and 13%, 58% and 76% reduction in cancer mortality (p=0.002), respectively. Also, individuals who were diagnosed with lung cancer and were at moderate or high CRF categories at baseline exhibited longer survival time (p<0.001). The PARs% for lung cancer incidence and cancer mortality were 8.7% and 18.5%, respectively.

CONCLUSIONS

Higher CRF is associated with lower lung cancer incidence in men. Among individuals who were diagnosed with lung cancer, higher CRF was associated with reduced cancer mortality and longer survival time. These results support the protective benefits of higher CRF in the prevention of lung cancer outcomes. Eliminating low CRF as a risk factor would potentially prevent considerable lung cancer morbidity and mortality.

How the growth rate of host cells affects cancer risk in a deterministic way

It is well known that cancers are significantly more often encountered in some tissues than in other ones. In this paper, by using a deterministic model describing the interactions between host, effector immune and tumor cells at the tissue level, we show that this can be explained by the dependency of tumor growth on parameter values characterizing the type as well as the state of the tissue considered due to the "way of life" (environmental factors, food consumption, drinking or smoking habits, etc.). Our approach is purely deterministic and, consequently, the strong correlation (r = 0.99) between the number of detectable growing tumors and the growth rate of cells from the nesting tissue can be explained without evoking random mutation arising during DNA replications in nonmalignant cells or "bad luck". Strategies to limit the mortality induced by cancer could therefore be well based on improving the way of life, that is, by better preserving the tissue where mutant cells randomly arise.

Physical activity and postmenopausal breast cancer: proposed biologic mechanisms and areas for future research

Convincing evidence now supports a probable preventive role for physical activity in postmenopausal breast cancer. The mechanisms by which long-term physical activity affect risk, however, remain unclear. The aims of this review were to propose a biological model whereby long-term physical activity lowers postmenopausal breast cancer risk and to highlight gaps in the epidemiologic literature. To address the second aim, we summarized epidemiologic literature on 10 proposed biomarkers, namely, body mass index (BMI), estrogens, androgens, sex hormone binding globulin, leptin, adiponectin, markers of insulin resistance, tumor necrosis factor-alpha, interleukin-6, and C-reactive protein, in relation to postmenopausal breast cancer risk and physical activity, respectively. Associations were deemed "convincing," "probable," "possible," or "hypothesized" using set criteria. Our proposed biological model illustrated the co-occurrence of overweight/obesity, insulin resistance, and chronic inflammation influencing cancer risk through interrelated mechanisms. The most convincing epidemiologic evidence supported associations between postmenopausal breast cancer risk and BMI, estrogens, and androgens, respectively. In relation to physical activity, associations were most convincing for BMI, estrone, insulin resistance, and C-reactive protein. Only BMI and estrone were convincingly (or probably) associated with both postmenopausal breast cancer risk and physical activity. There is a need for prospective cohort studies relating the proposed biomarkers to cancer risk and for long-term exercise randomized controlled trials comparing biomarker changes over time, specifically in postmenopausal women. Future etiologic studies should consider interactions among biomarkers, whereas exercise trials should explore exercise effects independently of weight loss, different exercise prescriptions, and effects on central adiposity.

Exercise and biomarkers for cancer prevention studies

The International Agency for Research on Cancer estimates that 25% of cancer cases worldwide are caused by overweight or obesity and a sedentary lifestyle. These lifestyle patterns may increase cancer risk by several mechanisms including increased estrogens and testosterone, hyperinsulinemia and insulin resistance, increased inflammation, and depressed immune function. Several randomized clinical trials have shown that physical activity and diet interventions can change biomarkers of cancer risk. In a controlled physical activity trial, we found decreases in serum estrogen, testosterone, and insulin in overweight, sedentary postmenopausal women with a 1-y exercise program consisting of moderate-intensity aerobic exercise, 45 min/d, 5 d/wk. In another controlled trial in middle-aged to older persons, we found that a 1-y exercise intervention of 60 min/d, 6 d/wk, reduced colon crypt cell proliferation in men who adhered closely to the program. Only 1 trial, the Women's Health Initiative Dietary Modification Trial, has published results of a dietary intervention on breast cancer incidence and reported a statistically nonsignificant 9% reduction in invasive breast cancer incidence in postmenopausal women following a low-fat dietary pattern for 8-12 y. Other trials under way are testing effects of weight loss, physical activity, and dietary patterns on other cancer biomarkers. The NCI-funded Transdisciplinary Research on Energetics and Cancer centers are exploring novel research into mechanisms linking energy balance with cancer risk and prevention. The worldwide trends toward increasing overweight and obesity and decreasing physical activity may lead to an increased incidence of several cancers unless other means of risk reduction counteract these effects. Thus, adoption of lifestyle changes by individuals and populations may have a large impact on the future incidence of cancer.