Carmen Jochem

Physical activity in relation to risk of hematologic cancers: a systematic review and meta-analysis

Background: Despite the existence of numerous biologic pathways potentially linking increased physical activity to decreased risk of hematologic cancers, the associations between physical activity and subtype-specific hematologic cancers have not been comprehensively quantified. Methods: We conducted a systematic review and meta-analysis of physical activity in relation to subtype-specific hematologic cancers. We summarized the data from 23 eligible studies (15 cohort and eight case–control studies) and estimated summary relative risks (RR) and 95% confidence intervals (CI) using random-effects models. Results: When comparing high versus low physical activity levels, the RR for non-Hodgkin lymphoma was 0.91 (95% CI, 0.82–1.00), for Hodgkin lymphoma it was 0.86 (95% CI, 0.58–1.26), for leukemia it was 0.97 (95% CI, 0.84–1.13), and for multiple myeloma it was 0.86 (95% CI, 0.68–1.09). When focusing on subtypes of non-Hodgkin lymphoma, the RR for diffuse large B-cell lymphoma was 0.95 (95% CI, 0.80–1.14) and for follicular lymphoma it was 1.01 (95% CI, 0.83–1.22). In an exploratory analysis combining all hematologic cancers, high versus low physical activity levels yielded a statistically significant RR of 0.93 (95% CI, 0.88–0.99). Conclusions: Physical activity showed statistically nonsignificant associations with risks of non-Hodgkin lymphoma, Hodgkin lymphoma, multiple myeloma, and leukemia. These findings may not represent a true lack of associations given the variation in high versus low physical activity definitions, the quality of physical activity assessments, and the variability in hematologic cancer classification schemes in individual studies. Impact: Physical activity is unrelated to risks of subtype-specific hematologic cancers. Cancer Epidemiol Biomarkers Prev; 23(5); 833–46. ©2014 AACR.

Obesity and Colorectal Cancer

There is strong evidence that modifiable lifestyle factors such as obesity play a key role in colorectal carcinogenesis. Epidemiologic data have consistently reported a positive association between obesity and colorectal cancer. The relative risk associated with general obesity (as assessed by BMI) is higher in men than in women and for cancer of the colon than for cancer of the rectum. Abdominal obesity (as assessed by waist circumference (WC) or waist-to-hip ratio) is associated with an increased risk of colorectal cancer in both sexes, with stronger associations for cancer of the colon than for cancer of the rectum. Plausible biological mechanisms include insulin resistance, hyperinsulinemia, chronic inflammation, altered levels of growth factors, adipocytokines and steroid hormones. In addition to its effect on colorectal cancer incidence, obesity may play a role in colorectal cancer recurrence, treatment outcomes and survival. Understanding the effects of childhood and adolescent obesity and weight change over the life course in relation to future risk of colorectal cancer is incomplete but essential for targeted preventive recommendations. This chapter summarizes the current evidence on the relationship between obesity and colorectal cancer and colorectal adenoma, a common precursor lesion.

Domains of physical activity and brain volumes: A population-based study

&NA; Observational studies and intervention trials suggest that physical activity (PA) is beneficial for human brain morphology, especially in older individuals. Few population‐based studies examined whether domain‐specific PA is associated with brain volumes. Accordingly, we studied putative associations of PA during leisure time, sports and work with volumes of the hippocampus, the prefrontal cortex, the temporal lobe, gray matter (GM), white matter (WM) and total brain (TBV) after 5.9 years by applying volumetric analysis and voxel‐based morphometry (VBM) with SPM 8/VBM 8 to brain magnetic resonance imaging data of 834 participants (447 women) aged 25 to 83 years from the population‐based Study of Health in Pomerania. The Baecke questionnaire was used to assess domain‐specific PA (Leisure time, Sport, and Work Index) at baseline. After correcting for multiple testing, volumetric analyses did not show any significant association of domain‐specific PA and volumes of the hippocampus, the prefrontal cortex, the temporal lobe, GM, WM and TBV. Multivariable‐adjusted VBM analyses of the associations between PA domains with GM and WM volumes did not reveal any statistically significant results. Region of interest analyses revealed a statistically significant cluster of increased GM volume in the bilateral anterior cingulate cortex in association with PA during sports. In conclusion, the overall results contrast with the findings from previous studies that found significant associations between PA and brain volumes. In addition, it remains unclear whether a differential association exists between domains of PA and brain volumes. Thus, future studies with larger sample size and prospective design are needed to investigate potential domain‐specific associations of PA with brain volumes.

Pre- and post-diagnosis physical activity, television viewing, and mortality among hematologic cancer survivors

Purpose The associations of physical activity and television (TV) viewing with mortality risk among individuals with hematologic malignancies remain unclear. Methods We examined the relations of physical activity and TV viewing time before and after diagnosis with mortality among 5182 U.S. adults aged 50–71 years from the NIH-AARP Diet and Health Study cohort who survived a first primary hematologic cancer between 1995–1996 and 2011. Results For the pre- and post-diagnosis analyses, we confirmed 2606 and 613 deaths respectively. In multivariable-adjusted Cox proportional hazard regression models, comparing high (≥4 hrs/wk) versus low (<1 hr/wk) activity levels, pre-diagnosis physical activity was associated with 18%-22% reduced risks of all-cause mortality among all hematologic cancer survivors, and survivors of non-Hodgkin lymphoma, myeloma, and leukemia, respectively. Additional control for BMI had little impact on the results, expect for myeloma survivors, for whom the association was no longer significant. Post-diagnosis physical activity was related to risk reductions in mortality ranging from 36%-47%. The associations for TV viewing did not show a clear pattern. Conclusion Our study suggests that pre- and post-diagnosis physical activity is associated with lower risk of all-cause mortality among hematologic cancer survivors. Further research is required to confirm this observation.

Limitations in Sedentary Behaviour Research and Future Research Needs

This section discusses limitations and uncertainties in sedentary behaviour research and briefly presents future research needs in the field. These include but are not limited to better understanding the association between sedentary behaviour and health, increasing the validity and reliability of measuring sedentary behaviour, more clearly identifying the determinants and correlates of sedentary behaviour, devising appropriate interventions to reduce sedentary behaviour, and effectively translating research findings aimed at decreasing extended periods of sitting into practice. Specifically, there is a need for prospective studies using objective measures of sedentary behaviour to determine how long people should maximal sit per day and how often they should interrupt their daily sitting to prevent the harmful effects of prolonged sitting. The combined use of self-report and accelerometer-derived measures is needed to enhance the validity and comprehensiveness of existing sedentary behaviour assessments. Future studies should also expand their exposure assessments to include sedentary behaviours in the transportation and household domains. To formulate personalized disease prevention strategies, enhanced research efforts are needed for certain population subgroups, such as persons with chronic diseases or disabilities, overweight/obese individuals, the elderly, socially disadvantaged individuals, and ethnic/racial minorities. In addition, additional future mechanistic and experimental work is required to identify the aetiologic pathways through which sedentary behaviour impacts upon the aetiology of chronic diseases.

Introduction to Sedentary Behaviour Epidemiology

Sedentary behaviour epidemiology is the study of the distribution, determinants, and health consequences of sedentary behaviours in the population. It seeks to identify biological, psychosocial, environmental, and genetic factors that affect sedentary behaviour. The term sedentary behaviour describes any waking behaviour characterized by an energy expenditure ≤1.5 metabolic equivalents (METs) while in a sitting or reclining posture. From an evolutionary perspective, sedentary behaviour is a relatively new phenomenon in human history, and it is strongly linked to the technical advances of the Industrial Revolution. In addition, sociocultural aspects fundamentally influence our understanding and perception of sedentary behaviours. Understanding these influences on modern sitting behaviour is crucial for successfully developing and implementing sedentary behaviour recommendations. Several countries have provided guidelines on sedentary behaviour for health. However, existing recommendations target mostly children and young people and do not provide specific information for adults and the elderly. Strengthening the evidence base regarding the relation between sedentary behaviour and health is critical for successfully developing and implementing comprehensive sedentary behaviour recommendations that include provisions for specific population subgroups, such as persons with pre-existing diseases or the elderly.

Sedentary Behaviour Epidemiology

Sedentary behaviour epidemiology is the study of the distribution, determinants, and health consequences of sedentary behaviours in the population. It seeks to identify biological, psychosocial, environmental, and genetic factors that affect sedentary behaviour. The term sedentary behaviour describes any waking behaviour characterized by an energy expenditure 1.5 metabolic equivalents (METs) while in a sitting or reclining posture. From an evolutionary perspective, sedentary behaviour is a relatively new phenomenon in human history, and it is strongly linked to the technical advances of the Industrial Revolution. In addition, sociocultural aspects fundamentally influence our understanding and perception of sedentary behaviours. Understanding these influences on modern sitting behaviour is crucial for successfully developing and implementing sedentary behaviour recommendations. Several countries have provided guidelines on sedentary behaviour for health. However, existing recommendations target mostly children and young people and do not provide specific information for adults and the elderly. Strengthening the evidence base regarding the relation between sedentary behaviour and health is critical for successfully developing and implementing comprehensive sedentary behaviour recommendations that include provisions for specific population subgroups, such as persons with pre-existing diseases or the elderly. 1.1 Definition of Sedentary Behaviour 1.1.

Epidemiologic Relationship Between Obesity and Ovarian Cancer

Ovarian cancer is the seventh most common cancer in women worldwide. Several systematic reviews and meta-analyses have shown a positive association between obesity and ovarian cancer, and the American Institute for Cancer Research and World Cancer Research Fund recently concluded that body fatness (marked by body mass index) is a probable risk factor for ovarian cancer. The positive relation of body fatness to ovarian cancer appears to be more evident among non-users of hormone therapy. Furthermore, compared to normal weight, obesity is associated with poorer ovarian cancer survival. Possible biological mechanisms linking obesity with ovarian cancer risk and progression include insulin resistance and hyperinsulinaemia, increased levels of circulating growth factors, chronic inflammation, and altered levels of sex hormones. Thus, obesity, as a modifiable risk factor, should be targeted for preventing ovarian cancer and for improving ovarian cancer survival.

Sedentary Behaviour and Adiposity

Obesity is thought to represent an intermediate variable in the pathway linking sedentary behaviour to the development of chronic disease, yet its role in the sedentary behaviour context has not been resolved. Numerous cross-sectional studies, prospective studies, and randomized controlled trials have examined the potential obesogenic effect of prolonged sedentary behaviour in children and adolescents, where television viewing has been the focus of the majority of studies. Results suggest that prolonged time spent sedentary is positively associated with adiposity in children and adolescents. The association may be partly explained by unhealthy eating behaviour associated with television viewing. By comparison, the current literature provides insufficient evidence for a positive relation between sedentary behaviour and adiposity among adults. Future prospective studies and randomized controlled trials using objective measures to monitor sedentary behaviour are needed to clarify the role of obesity in the sedentary behaviour context.