Joanna Kruk

Physical Activity and its Relation to Cancer Risk: Updating the Evidence

Scientific evidence for the primary prevention of cancer caused by physical activity of regular moderate-intensity or greater is rapidly accumulating in this field. About 300 epidemiologic studies on the association between physical activity and cancer risk have been conducted worldwide. The objectives of this paper were three-fold: (i) to describe briefly the components of physical activity and its quantification; (ii) to summarize the most important conclusions available from comprehensive reports, and reviews of the epidemiologic individual and intervention studies on a role physical activity in cancer prevention; (iii) to present proposed biological mechanisms accounting for effects of activity on cancer risk. The evidence of causal linked physical activity and cancer risk is found to be strong for colon cancer - convincing; weaker for postmenopausal breast and endometrium cancers - probable; and limited suggestive for premenopausal breast, lung, prostate, ovary, gastric and pancreatic cancers. The average risk reductions were reported to be 20-30%. The protective effects of physical activity on cancer risk are hypothesized to be through multiple interrelated pathways: decrease in adiposity, decrease in sexual and metabolic hormones, changes in biomarkers and insulin resistance, improvement of immune function, and reduction of inflammation. As there are several gaps in the literature for associations between activity and cancer risk, additional studies are needed. Future research should include studies dealing with limitations in precise estimates of physical activity and of a lack of consensus on what defines sedentary behavior of individuals and those linked with the proposed biomarkers to cancer risk and controlled exercise intervention trials.

The Role Oxidative Stress in the Pathogenesis of Eye Diseases: Currnt Status and a Dual Role of Physical Activity

Extensive research during the past three decades has demonstrated the mechanisms by which an imbalance in the redox status of prooxidant/antioxidant reactions in cells with advantage of prooxidant reactions (oxidative stress, OS) can cause peroxidation of nucleic acids, bases, lipids, proteins and carbohydrates, thus resulting in their damage. These actions result in stimulation of signal transduction pathways and activation of transcription factors that can lead to chronic inflammation and cause tissue dysfunction. The most important oxidants are reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by various metabolic pathways, physical, chemical and biological factors, and pathological conditions. The eye is one of the major target of the ROS/RNS attack due to exposition on several environmental factors like high pressure of oxygen, light exposure, ultraviolet rays, ionizing radiation, chemical pollutants, irritant, and pathogenic microbes, which are able to shift the redox status of a cell towards oxidizing conditions. There is increasing evidence indicating that persistent OS contributes to the development of many ocular diseases. Increases in the accumulation of hydrogen peroxide and markers of the oxidative damage to DNA, lipids, proteins observed in several eye diseases and usage of antioxidants in their treatment and prevention emphasize the involvement of OS pathways. This paper summarizes the present state of knowledge in the involvement of OS in the etiology of non-cancer ocular diseases (dry eye syndrome; corneal and conjunctive diseases; cataract; glaucoma; age-related macular degeneration; retinitis pigmentosa; diabetic retinopathy, autoimmune and inflammatory uveitis) and cancer ocular diseases (melanoma; retinoblastoma; lymphoma). The paper also discusses the potential applications of antioxidants in the prevention of eye diseases and shows a duality of physical exercise actions: protection against the ROS/RNS damage by regular-moderate physical activity and damaging effect through mediation of OS by endurance exercise without adaptable physical training.

Oxidative stress and skin diseases: possible role of physical activity.

BACKGROUND The skin is the largest body organ that regulates excretion of metabolic waste products, temperature, and plays an important role in body protection against environmental physical and chemical, as well as biological factors. These include agents that may act as oxidants or catalysts of reactions producing reactive oxygen species (ROS), reactive nitrogen species (RNS), and other oxidants in skin cells. An increased amount of the oxidants, exceeding the antioxidant defense system capacity is called oxidative stress, leading to chronic inflammation, which, in turn, can cause collagen fragmentation and disorganization of collagen fibers and skin cell functions, and thus contribute to skin diseases including cancer. Moreover, research suggests that oxidative stress participates in all stages of carcinogenesis. We report here a summary of the present state of knowledge on the role of oxidative stress in pathogenesis of dermatologic diseases, defensive systems against ROS/RNS, and discuss how physical activity may modulate skin diseases through effects on oxidative stress. The data show duality of physical activity actions: regular moderate activity protects against ROS/RNS damage, and endurance exercise with a lack of training mediates oxidative stress. These findings indicate that the redox balance should be considered in the development of new antioxidant strategies linked to the prevention and therapy of skin diseases.

Lifestyle components and primary breast cancer prevention.

Breast cancer primary prevention is a high research priority due to the high psychological and economic costs. The disease is a multistep process and several risk factors have been recognized. Over the past three decades numerous studies have investigated the association of lifestyle with breast cancer, showing independent effects of various factors. We report here a summary of the present state of knowledge on the role of lifestyle patterns, such as physical activity, diet, smoking, hormone therapy, and experience of psychological stress in the modulation of breast cancer in women, and discuss commonly accepted biological mechanisms hypothesized as responsible for the associations. The findings indicate that regular physical activity of moderate to vigorous intensity is probably linked with the decreased breast cancer risk among postmenopausal females and suggestive for a decrease of the risk in premenopausal women. In contrast, the consumption of high-fat diet, alcohol intake, and use of combined estrogen and synthetic progestagen hormonal therapy may increase the risk. Epidemiological findings dealing with a role of smoking and experience of psychological stress are conflicting.

Occupational physical activity and the risk of breast cancer

The association between occupational and the risk of breast cancer was analyzed using data from a case-control study of 257 women with breast cancer and 565 control women. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for occupations having light and medium activity compared with sedentary ones. After adjusted for potential confounders, women in sedentary occupations had a 29% higher risk, compared to those with the physically medium demanding jobs. For women at age > or =55 years higher occupational physical levels were associated with 53-60% reduction in the risk. There was a significant decreasing trend in the ORs from sedentary to medium work (P=0.001); while no association emerged in younger women. These findings demonstrate that the protective effect of higher levels activity in occupations on breast cancer appears to be confined to older women.

Dietary Fat and Physical Activity in Relation to Breast Cancer among Polish Women

BACKGROUND Dietary fat has been inconsistently associated with the risk of breast cancer. The purpose of this study was to examine the relationship between meat and animal and plant fat intake and breast cancer risk in subgroups by total lifetime physical activity, using data from a case-control study conducted in the Region of Western Pomerania, Poland. MATERIALS AND METHODS The study included 858 women with histological confirmed breast cancer and 1,085 controls, free of any cancer diagnosis. The study was based on a self-administered questionnaire including questions about socio-demographic characteristics, current weight and height, reproductive factors, family history of breast cancer and lifestyle habits. Unconditional logistic regression was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS High animal fat intake significantly increased OR from 1.7 times (OR=1.66, 95%CI=1.07-3.59) to 2.9 times (OR=2.9, 95%CI=1.37- 6.14) independent of physical activity level, comparing the third versus the lowest quartile. Women with a high intake of red meat or processed meat and low physical activity showed increased risk of breast cancer: OR=2.70, 95%CI=1.21-6.03 and 1.78, 95%CI=1.04-3.59, respectively. The plant fat dietary pattern was negatively associated with breast cancer in sedentary women (OR=0.57, 95%CI=0.32-0.99). CONCLUSIONS These results indicated that a diet characterized by a high consumption of animal fat is associated with a higher breast cancer risk in sedentary women, while consumption of plant fat products may reduce risk in the same group.

Health and economic costs of physical inactivity.

Physical inactivity has reached epidemic levels in developed countries and is being recognized as a serious public health problem. Recent evidence shows a high percentages of individuals worldwide who are physically inactive, i.e. do not achieve the WHOs present recommendation of 150 minutes of moderate to vigorous intensity per week in addition to usual activities. Living in sedentary lifestyle is one of the leading causes of deaths and a high risk factor for several chronic diseases, like cancer, cardiovascular disease, diabetes type 2, and osteoporosis. This article summarizes evidence for relative risk of the civilization diseases attributable to physical inactivity and the most important conclusions available from the recent investigations computing the economic costs specific to physical inactivity. The findings provide health and economic arguments needed for people to understand the meaning of a sedentary lifestyle. This may be also useful for public health policy in the creation of programmes for prevention of physical inactivity.

Self-reported psychological stress and the risk of breast cancer: A case-control study

The aim of this study was to examine the relationship between severe life events and breast cancer risk. This study was based on a case–control examination of 858 Polish invasive breast cancer cases and 1085 controls matched for age and place of residence. Data on life events, sociodemographic characteristic, reproductive factors, family history of breast cancer, current weight and height, and lifestyle habits were collected between January 2003 and May 2007 using a self-administered questionnaire. Odds ratios with 95% confidence intervals were estimated as the measure of the relationship between life event stress and breast cancer risk using unconditional logistic regression analyses. After adjustment for potential breast cancer risk factors, women with four to six individual major life events had 5.33 times higher risk for breast cancer, compared with those in the lowest quartile. Similarly, women with a lifetime life change score greater than 210 had about 5 times higher risk compared to women with corresponding scores in the range 0–70. Several life events (death of a close family member, personal injury or illness, imprisonment/trouble with the law, retirement) were significantly associated with breast cancer risk. These findings suggest that major life events can play an important role in the etiology of breast cancer.

Association between Vegetable, Fruit and Carbohydrate Intake and Breast Cancer Risk in Relation to Physical Activity

BACKGROUND Although the nutritional may exert effect on the breast cancer risk, it is not clear whether the role diet is the same in sedentary and physically active women. The aim of this study was to evaluate the association between fruit, vegetable and carbohydrate intake and the risk of breast cancer among Polish women considering their physical activity level. MATERIALS AND METHODS A case-control study was conducted that included 858 women with histological confirmed breast cancer and 1,085 controls, free of any cancer diagnosis, aged 28-78 years. The study was based on a self-administered questionnaire to ascertain physical activity, dietary intake, sociodemographic characteristics, reproductive factors, family history of breast cancer, current weight and high, and other lifestyle factors. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated in unconditional logistic regression analyses including a broad range of potential confounders. RESULTS With comparison of the highest vs lowest quartile of intake, strong significant associations were observed for total vegetables (OR=0.37, 95%CI=0.20-0.69 P for trend <0.01 and OR=0.53, 95%CI=0.29-0.96, P for trend <0.02), and total fruits (OR=0.47, 95%CI=0.25-0.87, P for trend <0.05 and OR=0.47, 95%CI=0.24-0.90, P for trend <0.02) among women characterized by the lowest and the highest quartile of physical activity. No associations were observed for total carbohydrate intake. Additional analysis showed a positive association for sweets and desert intake among women in the lowest quartile of physical activity (OR=3.49, 95%CI=1.67-7.30, P for trend <0.009) for extreme quartiles of intake comparing to the referent group. CONCLUSIONS The results suggest that a higher consumption of vegetable and fruit may be associated with a decreased risk of breast cancer, especially among women who were low or most physically active throughout their lifetimes. These findings do not support an association between diet high in carbohydrate and breast cancer. However, a higher intake of sweets and deserts may by associated with an increased risk of breast cancer among women who were less physically active.

Intensity of lifetime physical activity and breast cancer risk among Polish women

Abstract Physical activity is associated with a lower risk of breast cancer, although research findings are inconsistent regarding the type, duration, intensity, and frequency of activities that are necessary to reduce the risk, as well as dependence on menopausal status. To address these issues, I examined the effect of physical activity on breast cancer risk among 858 Polish invasive breast cancer cases and 1085 controls. Data on components of lifetime household, occupational, and recreational activities were collected in 2003–2007, using a self-administered questionnaire. Odds ratios with 95% confidence intervals were estimated using unconditional logistic regression analyses and a full assessment of confounding variables. For all types of physical activity, odds ratios were calculated for self-reported and compendium-based assigned levels of activity. Moderate- and vigorous-intensity total and recreational activities, as well as moderate- and long-lasting low-intensity household activities, lowered the risk by at least 44% for the highest versus lowest quartiles of activity in both menopausal groups. The associations were linear (Ptrend≤ 0.009). There was a suggestion of a risk reduction for occupational activity among post-menopausal women. These findings show that a risk reduction can be achieved by vigorous-intensity activities or by longer-lasting activities of moderate-intensity.