Exercise and physical health: cancer and immune function

Over the last decade, there has been accumulating epidemiological data suggesting that exercise may decrease the risk of cancer, particularly colon cancer. However, exercise appears unrelated to rectal cancer risk. With regard to other cancers, because physical activity can alter levels of reproductive hormones, investigators have hypothesized that active individuals should experience decreased incidence of breast or prostate cancer. The better conducted studies suggest that exercise may reduce the risk of developing breast cancer. However, the epidemiological data on prostate cancer have been inconsistent. Meanwhile, data on other site-specific cancers have been sparse. An exciting and emerging body of research has suggested that exercise, at least in moderate amounts, can enhance the human immune system. Theoretically, then, this provides a further biological basis for expecting an inverse relationship between physical activity and cancer risk. However, the changes seen in immune function tend to be transient in nature; thus, the physiological significance with respect to cancer development is uncertain. Preliminary data also suggest that exercise may be beneficial for cancer patients by improving the quality of life and enhancing immune function. Although promising, this needs more careful research. Again, it is unclear whether the enhanced immune function is of any clinical significance in retarding the spread of cancer that has already developed. Finally, with regard to URTIs, moderate exercise appears to decrease the risk of this infection, although high-endurance exercise may increase the risk. This finding parallels the changes seen in the immune system in response to exercise and comes as no surprise, as the immune system also regulates susceptibility to infections.     

Physical activity and colon cancer

Heart disease and cancer, the major causes of mortality and morbidity in Western countries, have common risk factors. Exercise appears to reduce the risk of cardiovascular disease, but its role with respect to primary prevention of cancer has not been emphasized. Here we evaluate the epidemiological studies dealing with exercise and colon cancer. Despite the fact that different methods of assessing the amount of typical exercise of individuals and the different types of physical activity measured (occupational and recreational), there is remarkably consistent evidence that people who are highly physically active could be at a reduced risk of cancer of the colon. An analysis of case-control and cohort studies suggests that exercise might reduce the risk, at least in men, by up to one-third. We conclude that exercise has been overlooked as a potentially useful, effective, and acceptable method for reducing the risk of colon cancer.     

The effect of over- and undernutrition on cancer

Overnutrition, as a factor in carcinogenesis, has been a matter of concern for over 80 years. Overnutrition relates to excess intake of calories, and fat is the major contributor to caloric burden. Thus, fat has been the focus of many epidemiological studies, but as long ago as 1975 some investigators were suggesting that excess energy intake might be the major factor relating to cancer incidence. Ecological studies support the idea that a high fat (high energy?) diet may represent a risk for cancer but case-control or follow-up studies generally do not. The effects of undernutrition have been studied experimentally. Mostly conducted in rats or mice, they show virtually uniformly that caloric (energy) restriction inhibits the growth of spontaneous, transplanted or induced tumours. The effect is observed even when the calorie-restricted animals ingest more fat than do the controls. Energy utilization via exercise reduces tumour growth in rats and a life history of physical labour reduces risk in man. The mechanism(s) by which caloric restriction exerts its effects are moot, but it has been shown to reduce insulin levels and to reduce oncogene expression. Energy restriction also increases activity of antioxidant enzymes and leads to enhanced DNA repair. Increased energy flux (by means of decreased intake or increased output) may provide a simple and inexpensive approach to reducing the risk of cancer in man.     

The "epidemic" of breast cancer in the U.S.--determining the factors

Breast cancer incidence rates in the United States rose by 24% between 1973 and 1991. Mortality during this period, however, remained stable. Both the 5-year relative survival rate and the rates of in situ and stage I breast cancers have been increasing, while the incidence of later-stage cancers has been decreasing. Increased mammography screening may explain the documented jump in breast cancer incidence rates during the mid-1980s. Differences in the distribution of breast cancer risk factors may account, in part, for the temporal trends in breast cancer incidence. In particular, breast cancer risk factors may vary by birth cohort, including age at menarche, age at first birth, physical activity, obesity, diet, alcohol intake, estrogen therapy, and exposure to environmental organochlorines. After decades of epidemiologic research, a preventive approach to breast cancer that focuses on the physiologic effects of the sex steroid hormones, and their potential interactions with family history, is being carefully formulated.     

Physical activity, physical fitness, and all-cause and cancer mortality: a prospective study of men and women

We studied physical fitness and physical activity in relation to all-cause and cancer mortality in a cohort of 7080 women and 25,341 men examined at the Cooper Clinic in Dallas, Texas, during 1970 to 1989. Physical fitness was assessed at baseline by a maximal treadmill exercise test, while physical activity was self-reported on the attendant health habits questionnaire. Both men and women averaged about 43 years of age at baseline (range, 20 to 88 years), and they were followed for approximately 8 years on average. Through the end of 1989, the women contributed 52,982 person-years of observation and incurred 89 deaths, including 44 deaths due to cancer. The men contributed 211,996 person-years and incurred 601 deaths, with 179 due to cancer. After adjustment for baseline differences in age, examination year, cigarette habit, chronic illnesses, and electrocardiogram abnormalities, we found a strong inverse association between risk of all-cause mortality and level of physical fitness in both men and women (P for trend < 0.001). Physically active men also were at lower risk of all-cause mortality than were sedentary ones (P for trend = 0.01). Among women, however, self-reported physical activity was not significantly related to risk of death from all causes. The risk of mortality from cancer declined sharply across increasing levels of fitness among men (P for trend < 0.001), whereas among women the gradient was suggestive but not significant (P for trend = 0.07). Physically active men also were at lower risk of death from cancer than were sedentary men (P for trend = 0.002), but among women physical activity was unrelated to cancer mortality.     

Physical activity and risk of breast cancer in the Framingham Heart Study

The authors analyzed data from the Framingham Heart Study to evaluate the association between physical activity and breast cancer risk. Physical activity was ascertained by a physician-administered questionnaire from 2,321 women at the fourth biennial examination conducted in 1954-1956. Breast cancers were identified by self-report, surveillance of admissions to Framingham Union Hospital, and review of death records; all but one were histologically confirmed. During 28 years of follow-up, 117 breast cancer cases were diagnosed among the 2,307 women with data on physical activity and reproductive history (a potential confounder). Analysis was performed using Cox proportional hazards models with age as the underlying time variable. Models were adjusted for age at physical activity assessment, menopausal status, age at first pregnancy, parity, education, occupation, and alcohol ingestion. We observed a gradient of increasing risk of breast cancer with increasing physical activity (trend p = 0.06). The relative risk for women in the highest versus lowest activity quartile was 1.6 (95% confidence interval 0.9-3.0; p = 0.13). Although both moderate-to-heavy leisure and occupational activities were associated with an increased risk, the association was marginally significant only for leisure activity (p = 0.06). Our findings do not support a protective effect of physical activity during adulthood for breast cancer, but suggest an increased risk among more active women.     

Physical activity and risk of colorectal cancer in men and women

We examined the association between self-reported occupational and recreational physical activity and the subsequent risk of colorectal cancer in a population-based cohort in Norway. During a mean follow-up time of 16.3 years for males and 15.5 years for females, 236 and 99 colon cancers and 170 and 58 rectal cancers were observed in males and females, respectively, among 53,242 males and 28,274 females who attended the screening between 1972 and 1978. Physical activity at a level equivalent to walking or bicycling for at least four hours a week during leisure-time was associated with decreased risk of colon cancer among females when compared with the sedentary group (RR = 0.62, 95% CI 0.40-0.97). Reduced risk of colon cancer was particularly marked in the proximal colon (RR = 0.51, 95% CI 0.28-0.93). This effect was not observed for occupational physical activity alone, probably due to a narrow range of self-reported physical activity at work among females. However, by combining occupational and recreational physical activity we observed an inverse dose-response effect as increasing total activity significantly reduced colon cancer risk (P for trend = 0.04). Among males 45 years or older at entry to the study, an inverse dose-response effect was observed between total physical activity and colon cancer risk (P for trend = 0.04). We also found in males a stronger preventive effect for physical activity in the proximal as compared to distal colon. In addition, we found a borderline significant decrease in colon cancer risk for occupational physical activity in males 45 years or older when compared to the sedentary group (RR = 0.74, 95% CI 0.53-1.04). All results were adjusted for age, body mass index, serum cholesterol and geographic region. No association between physical activity and rectal cancer was observed in males or females. The protective effect of physical activity on colon cancer risk is discussed in regard to energy balance, dietary factors, age, social class, body mass index and gastrointestinal transit time.     

Athletics and osteoarthritis

Athletes, and an increasing number of middle aged and older people who want to participate in athletics, may question whether regular vigorous physical activity increases their risk of developing osteoarthritis. To answer this, the clinical syndrome of osteoarthritis must be distinguished from periarticular soft tissue pain associated with activity and from the development of osteophytes. Sports that subject joints to repetitive high levels of impact and torsional loading increase the risk of articular cartilage degeneration and the resulting clinical syndrome of osteoarthritis. However, moderate habitual exercise does not increase the risk of osteoarthritis; selected sports improve strength and mobility in older people and people with mild and moderate osteoarthritis. People with abnormal joint anatomy or alignment, previous significant joint injury or surgery, joint instability, above-average body weight, disturbances of joint or muscle innervation or inadequate muscle strength probably have increased risk of osteoarthritis. These people and those with early osteoarthritis can benefit from regular physical activity, but they should have a careful evaluation of their joint structure and function before participation. They should consider measures that decrease the intensity and frequency of impact and torsional loading of joints, including use of sports equipment that decreases joint impact loading, maintaining or improving muscle strength, tone, and general conditioning so that muscle contractions help protect joints from injury and high impact, and decreasing body weight.     

Physical activity and women in the United States: an overview of health benefits, prevalence, and intervention opportunities

Despite decades of physical activity research and interventions conducted on men, very little is known about the patterns of physical activity among US women. Rates from several national surveys show much lower rates of physical activity for women than for men. Among women, rates may vary by socioeconomic status. Studies relating physical activity and experience with heart disease, cancer, osteoporosis, and mental health are discussed. Interventions in the workplace and the community may increase the level of physical activity among US women. A history of not participating in exercise and lack of time for this activity appear to be important constraints for many women. The Surgeon General's Report on physical activity sanctioned future research on specific groups, such as women. Applied research coupled with community and workplace policies that support women's efforts to be more physically active may decrease the rates of some chronic diseases in this population.     

3D CT of fractures: comparison of volume and surface reconstruction

Melatonin is a hormone primarily produced by the pineal gland at night and is suppressed by exposure to light. Experimental studies have indicated that melatonin may protect against cancer development. In the majority of totally blind people, melatonin is never suppressed by light exposure. The aim of this study was to test the hypothesis that blind people have a decreased cancer incidence, and that this effect is more pronounced in the totally blind than in the severely visually impaired. We identified a cohort of 1,567 totally blind and 13,292 severely visually impaired subjects and obtained information about cancer incidence from the Swedish Cancer Registry. We calculated standardized incidence ratios (SIRs) based on the number of person-years and incidence rates specific for national age, sex, and calendar year. Totally blind people had a lower incidence of all cancers combined [SIR = 0.69; 95% confidence interval (CI) = 0.59-0.82]. The risk reduction was observed in both men and women and was equally pronounced in hormone-dependent tumors as in other types of cancer. In the severely visually impaired, SIR was 0.95 (95% CI = 0.91-1.00). The findings support the hypothesis that blind people have a lower cancer incidence, although other explanations than the higher melatonin exposure must also be considered.     

A descriptive epidemiology of physical activity from a Northern Ireland perspective

The benefits of physical activity are well documented and exercise is included in most health promotion recommendations but, before adopting a population strategy, it is important to establish baseline patterns of physical activity so as to make regional and international comparisons and measure behaviour change. This review examines adult physical activity participation in a national and international context and highlights how difficult it is to draw meaningful conclusions and detect trends from studies that measure physical activity using different measuring instruments. Overall, about 4 in 5 people are active at least occasionally but the more rigorous the definition of habitual physical activity the lower the participation rates so that less than 1 in 5 people perform regular vigorous physical activity. Males are more active than females with a decrease in physical activity with increasing age. There is a social class gradient with those in social classes 1 and 2 being more active.     

Changes in the energy needs of the elderly: an often encountered cause of nutritional deficiencies and frailty

Changes in the body composition of elderly people and diminished physical activity reduce the energy requirement and the daily energy intake. It is especially frail elderly people who run an increased risk of a poor nutritional condition which further enhances fragility. Frailty is often defined as the state of reduced physiologic reserve associated with increased susceptibility to disability. In frail elderly people energy requirement is often reduced. Studies have shown that when energy intake falls below a level of about 6.3 MJ, it is hard to obtain a diet with a sufficient supply of minerals and water soluble vitamins. It is especially the daily intake of vitamins of the B complex and of vitamin C that then prove insufficient. In addition, immobile elderly and elderly of 75 years and older are at risk for an inadequate vitamin D status. An adequate diet is one of the factors that may prevent frail health. Screening lists have been developed to quickly obtain information about the nutritional status of older adults. However, these lists still have to be adapted to the Dutch dietary pattern. Currently, a change of the body weight is the best warning of insufficient nutrition.     

Exercise as stigma management for individuals with onset-controllable and onset-uncontrollable spinal cord injury.

Studies have suggested that individuals with physical disabilities are often stigmatized and are perceived to possess less favorable physical and psychological characteristics than individuals without disability. Purpose: To investigate whether able-bodied adults' perceptions of people with different causes of spinal cord injury (SCI) are influenced by physical activity status information. Method and Participants: Each participant (N = 198) read all five vignettes describing individuals with SCI who had varying levels of physical activity participation and cause of injury information (e.g., onset-uncontrollable [hit by impaired driver] and onset-controllable [caused by impaired driving]). After reading each vignette, participants completed a 12-item Warmth and Competence Questionnaire to evaluate each target. One-way repeated measures multivariate analyses of variance were conducted to examine the within-subjects differences. Results: Physically active individuals with onset-uncontrollable SCI were rated most favorably on warmth and competence. Physically active individuals with onset-controllable SCI also were rated more favorably on warmth and competence than physically inactive targets with onset-controllable SCI. Conclusion: A physically active lifestyle may be beneficial in managing the stigma experienced by individuals with both onset-controllable and onset-uncontrollable SCI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diet, lifestyle, and colorectal cancer: is hyperinsulinemia the missing link?

Several dietary and other lifestyle factors have been implicated in the development of colorectal cancer. However, the precise nature and actual magnitude of the relationship between individual nutrient intakes and other lifestyle factors and colorectal cancer risk are not clear. A unifying hypothesis has recently been proposed that explains why obesity, physical inactivity, alcohol, and consumption of a typical Western diet increase colorectal cancer risk. This hypothesis suggests that these dietary and other lifestyle factors are associated with insulin resistance and hyperinsulinemia and that hyperinsulinemia, in turn, may stimulate growth of colorectal tumors. Two recently published large prospective epidemiologic studies indicate a significant increase in colorectal cancer risk in subjects with diabetes mellitus, thereby supporting this hypothesis.     

Changes in physical activity, mortality, and incidence of coronary heart disease in older men

BACKGROUND: We studied the relations between physical activity and changes in physical activity, all-cause mortality, and incidence of major coronary-heart-disease events in older men. METHODS: In 1978-80 (Q1), 7735 men aged 40-59 were selected from general practices in 24 British towns, and enrolled in a prospective study of cardiovascular disease, which included physical activity data. In 1992 (Q92), 12-14 years later, 5934 of the men (91% of available survivors, mean age 63 years) gave further information on physical activity and were then followed up for a further 4 years. The main endpoints were all-cause mortality during 4 years of follow-up from Q92, and major fatal and non-fatal coronary-heart-disease events during 3 years of follow-up from Q92. FINDINGS: Among 4311 men with no history of coronary heart disease, stroke, or "other heart trouble" by Q92 and who did not report "poor health", there were 219 deaths. In the inactive/occasionally active, light, moderate, and moderately vigorous/vigorous activity groups there were 101 (18.5/1000 person-years) 48 (11.4), 23 (7.3), and 47 (9.1) deaths, respectively (adjusted risk ratios 1.00, 0.61 [95% CI 0.48-0.86], 0.50 [0.31-0.79], 0.65 [0.45-0.94]). Men who were sedentary at Q1 and who began at least light activity by Q92 had significantly lower all-cause mortality than those who remained sedentary, even after adjustment for potential confounders (risk ratio=0.55 [0.36-0.84]). Physical activity improved both cardiovascular mortality (0.66 [0.35-1.23]) and non-cardiovascular mortality (0.48 [0.27-0.85]). The relation between physical activity at Q92, changes in physical activity, and mortality were similar for men with pre-existing cardiovascular disease. INTERPRETATION: Maintaining or taking up light or moderate physical activity reduces mortality and heart attacks in older men with and without diagnosed cardiovascular disease. Our results support public-health recommendations for older sedentary people to increase physical activity, and for active middle-aged people to continue their activity into old age.     

Exercise and gall bladder function

Epidemiological research has demonstrated protective effects of varying strength from physical activity against the risk for several chronic diseases such as coronary heart disease, hypertension, non-insulin-dependent diabetes mellitus and osteoporosis. Epidemiological studies have been supported by experimental research showing that exercise training improves coronary heart disease risk factors and other health-related factors. In contrast, the association between physical activity, exercise and gall stone disease has not yet been firmly established. This paper presents the theoretical role of aerobic exercise: (i) in the primary prevention of gall stone disease; and (ii) as a potential prokinetic agent in high risk gall stone disease groups. Primary risk factors in the pathogenesis of gall stone formation include cholesterol supersaturation in the solutes that precipitate from bile, hypernucleation (measured as "crystal appearance time') and finally hypomotility of the gall bladder which allows bile stasis and crystal formation. While the results of epidemiological studies suggest that physical activity may be inversely associated with gall stone disease, the mechanisms by which exercise may influence gall stone disease pathogeneses are poorly understood. In this paper the association between physical activity and exercise to gall bladder function and gall stone disease will be examined. Recommendations for future research and the implications for the primary prevention of gall stone disease will also be discussed.     

Helicobacter pylori in 1997

In this review Helicobacter pylori (H. pylori) infection and its relation to different diseases is presented. H. pylori doesn't cause inconvenience to most infected people, though all infected persons have chronic active gastritis. The 10 year risk of peptic ulcer for people infected with H. pylori is about 10%. Randomized double-blinded trials have shown that eradication of H. pylori can cure most patients with peptic ulcer disease. Some people infected with H. pylori develop atrophic gastritis which is a risk factor for development of gastric cancer. It is not known if H. pylori screening and eradication would have a prophylactic effect against gastric cancer. It is also unknown if persons with non-organic dyspepsia and persons in long-term treatment with proton-pump-inhibitors would benefit from H. pylori eradication.     

Comparative study of expression of p21 and c-myc protein in hepatocellular carcinoma with pericarcinomatous liver tissue]

A new 2H/1H and 18O/16O equilibration device was tested, standardized and employed for the determination of total energy expenditure. It was shown that overweight men and women have increased resting metabolic rate as well as increased total energy expenditure when compared to their lean counterparts. The physical activity level (PAL)index was slightly decreased which possibly suggests a decreased physical activity in obese people.     

Environmental estrogens and reproductive health: a discussion of the human and environmental data

Estrogenic activity of certain xenobiotics is an established mechanism of toxicity that can impair reproductive function in adults of either sex, lead to irreversible abnormalities when administered during development, or cause cancer. The concern has been raised that exposure to ambient levels of estrogenic xenobiotics may be having widespread adverse effects on reproductive health of humans and wildlife. The purpose of this review is to evaluate (a) the nature of the evidence supporting this concern, and (b) the adequacy of toxicity screening to detect, and risk assessment procedures to establish safe levels for, agents acting by this mechanism. Observations such as adverse developmental effects after maternal exposure to therapeutic levels of the potent estrogen diethylstilbestrol or male fertility problems after exposure to high levels of the weak estrogen chlordecone clearly demonstrate that estrogenicity is active as a toxic mechanism in humans. High level exposures to estrogenic compounds have also been shown to affect specific wildlife populations. However, there is little direct evidence to indicate that exposures to ambient levels of estrogenic xenobiotics are affecting reproductive health. Reports of historical trends showing decreasing reproductive capacity (e.g., decreased sperm production over the last 50 years) are either inconsistent with other data or have significant methodologic inadequacies that hinder interpretation. More reliable historical trend data show an increase in breast cancer rate, but the most comprehensive epidemiology study to data failed to show an association between exposure to persistent, estrogenic organochlorine compounds and breast cancer. Clearly, more work needs to be done to characterize historical trends in humans and background incidence of abnormalities in wildlife populations, and to test hypotheses about ambient exposure to environmental contaminants and toxic effects, before conclusions can be reached about the extent or possible causes of adverse effects. It is unlikely that current lab animal testing protocols are failing to detect agents with estrogenic activity, as a wide array of estrogen-responsive endpoints are measured in standard testing batteries. Routine testing for aquatic and wildlife toxicity is more limited in this respect, and work should be done to assess the validity of applying mammalian toxicology data for submammalian hazard identification. Current risk assessment methods appear to be valid for estrogenic agents, although the database for evaluating this is limited. In conclusion, estrogenicity is an important mechanism of reproductive and developmental toxicity; however, there is little evidence at this point that low level exposures constitute a human or ecologic health risk. Given the potential consequences of an undetected risk, more research is needed to investigate associations between exposures and effects, both in people and animals, and a number of research questions are identified herein. The lack of evidence demonstrating widespread xenobiotic-induced estrogenic risk suggests that far-reaching policy decisions can await these research findings.     

Perceived environmental predictors of physical activity over 6 months in adults: Activity Counseling Trial.

[Correction Notice: An erratum for this article was reported in Vol 27(2) of Health Psychology (see record 2008-12766-001). One result in Table 2 was misinterpreted in the text. It was reported that men who responded "yes" to frequently seeing people being active in their neighborhoods did about 75 minutes more physical activity per week (pPurpose: In the present study, the authors extend previous cross-sectional findings by using a prospective design to determine whether physical and social environmental characteristics predict physical activity over 6 months. Design: Inactive adults were recruited to the Activity Counseling Trial, a multicenter, randomized, controlled trial of physical activity intervention in primary care. Participants were 387 women and 474 men aged 35-75 years in 3 regions; 1/3 were minorities; 56% had some college education. Baseline perceived environmental variables were used to predict physical activity at 6 months, adjusting for experimental condition and other potential moderators. Measures: The validated 7-day physical activity recall interview was used to estimate minutes of moderate to vigorous physical activity. A standardized survey was used to measure social and physical environmental variables around the home and neighborhood. Results: Women reporting no unattended dogs and low crime in their neighborhoods and men reporting frequently seeing people being active in their neighborhoods did 50-75 more minutes of physical activity per week than did those with different environmental characteristics. Interactions of environmental variables with age group suggested that older adults may be more affected by environmental variables than are younger adults. Conclusions: Self-reported social and physical environmental variables were significantly related to moderate to vigorous physical activity among a diverse sample of adults living in 3 regions of the United States. These prospective findings strengthen the conclusion from previous cross-sectional studies that environmental variables are important correlates of physical activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)