Occupational physical activity and risk for prostate cancer in a nationwide cohort study in Sweden

Physical activity in relation to risk of prostate cancer: a systematic review and meta-analysis

Background

Prostate cancer (PCa) is one of the most common cancers among men, yet little is known about its modifiable risk and protective factors. This study aims to quantitatively summarize observational studies relating physical activity (PA) to PCa incidence and mortality.

Materials and methods

Published articles pertaining to PA and PCa incidence and mortality were retrieved in July 2017 using the Medline and EMBASE databases. The literature review yielded 48 cohort studies and 24 case-control studies with a total of 151 748 PCa cases. The mean age of the study participants at baseline was 61 years.

Results

In random-effects models, comparing the highest versus the lowest level of overall PA showed a summary relative risk (RR) estimate for total PCa incidence close to the null [RR = 0.99, 95% confidence interval (CI) = 0.94-1.04]. The corresponding RRs for advanced and non-advanced PCa were 0.92 (95% CI = 0.80-1.06) and 0.95 (95% CI = 0.85-1.07), respectively. We noted a statistically significant inverse association between long-term occupational activity and total PCa (RR = 0.83, 95% CI = 0.71-0.98, n studies = 13), although that finding became statistically non-significant when individual studies were removed from the analysis. When evaluated by cancer subtype, an inverse association with long-term occupational activity was noted for non-advanced/non-aggressive PCa (RR = 0.51, 95% CI = 0.37-0.71, n studies = 2) and regular recreational activity was inversely related to advanced/aggressive PCa (RR = 0.75, 95% CI = 0.60-0.95, n studies = 2), although these observations are based on a low number of studies. Moreover, PA after diagnosis was related to reduced risk of PCa mortality among survivors of PCa (summary RR based on four studies = 0.69, 95% CI = 0.55-0.85).

Conclusions

Whether PA protects against PCa remains elusive. Further investigation taking into account the complex clinical and pathologic nature of PCa is needed to clarify the PA and PCa incidence relation. Moreover, future studies are needed to confirm whether PA after diagnosis reduces risk of PCa mortality.

Physical Activity and Prostate Cancer: An Updated Review

Prostate cancer affects a major proportion of older men, and effective preventive measures are few. Earlier suggestions of 10-30% risk reduction from vigorous physical activity thus merit further analysis. This narrative review updates information on associations between physical activity and prostate cancer, seeking activity patterns associated with maximal risk reduction. Systematic searches of Ovid/MEDLINE and PubMed databases from 1996 to June 2016 have linked the terms prostate neoplasms/prostate cancer with occupation, occupational title, sedentary job or heavy work, exercise, physical activity, sports, athletes, physical education/training or aerobic fitness. Combining these searches with findings from earlier reviews, 85 analyses were captured, although three were repeat analyses of the same data set. Seven analyses reported increased risk, and a further 31 showed no clear relationship. However, 24 analyses found a trend to diminished risk, and 21 a significant decrease (10-30% or more) in at least some subject subsets. Benefit was seen more consistently in occupational than in leisure studies, usually with adolescence or the early 20 s as the optimal age for preventive activity. In general, benefit showed a dose-response relationship, with vigorous activity required for maximal effect. Furthermore, several recent observational studies have indicated that physical activity is beneficial in preventing disease recurrence and improving survival following the diagnosis and treatment of prostate cancer. Despite continued research, conclusive proof of an association between regular physical activity and a low risk of prostate cancer remains elusive. However, reports that exercise exacerbates risk are few, and despite issues around controls, covariates, and co-morbidities, an impressive number of studies have now found significant benefit, suggesting that regular physical activity is important in terms of disease development, progression, and therapy. Given also the many other health benefits of an active lifestyle, it can be recommended as a potentially useful measure in the prevention of prostate cancer.

Prostate cancer surveillance by occupation and industry: the Canadian Census Health and Environment Cohort (CanCHEC)

As there are no well-established modifiable risk factors for prostate cancer, further evidence is needed on possible factors such as occupation. Our study uses one of the largest Canadian worker cohorts to examine occupation, industry, and prostate cancer and to assess patterns of prostate cancer rates. The Canadian Census Health and Environment Cohort (CanCHEC) was established by linking the 1991 Canadian Census Cohort to the Canadian Cancer Database (1969-2010), Canadian Mortality Database (1991-2011), and Tax Summary Files (1981-2011). A total of 37,695 prostate cancer cases were identified in men aged 25-74 based on age at diagnosis. Cox proportional hazards models were used to estimate hazards ratios and 95% confidence intervals. In men aged 25-74 years, elevated risks were observed in the following occupations: senior management (HR = 1.12, 95% CI: 1.04-1.20); office and administration (HR = 1.19, 95% CI: 1.11-1.27); finance services (HR = 1.09, 95% CI: 1.04-1.14); education (HR = 1.05, 95% CI: 1.00-1.11); agriculture and farm management (HR = 1.12, 95% CI: 1.06-1.17); farm work (HR = 1.11, 95% CI: 1.01-1.21); construction managers (HR = 1.07, 95% CI: 1.01-1.14); firefighting (HR = 1.17, 95% CI: 1.01-1.36); and police work (HR = 1.22, 95% CI: 1.09-1.36). Decreased risks were observed across other construction and transportation occupations. Results by industry were consistent with occupation results. Associations were identified for white-collar, agriculture, protective services, construction, and transportation occupations. These findings emphasize the need for further study of job-related exposures and the potential influence of nonoccupational factors such as screening practices.

Inflammation polymorphisms and prostate cancer risk in Jamaican men: Role of obesity/body size

African ancestry and obesity are associated with higher risk of prostate cancer (PC). In a pilot study, we explored interactions between obesity (as measured by waist to hip ratio (WHR)) and inflammatory SNPs in relation to PC risk among Jamaican men. This study evaluated 87 chemokine and cytokine associated SNPs in obese and normal weight cases (N=109) and controls (N=102) using a stepwise penalized logistic regression approach in multivariable analyses. Upon stratification by WHR (normal weight (WHR<0.90) or obese (WHR≥0.90)), inheritance of CCR6 rs2023305 AG+GG (OR=1.75, p=0.007), CCR9 rs7613548 AG+GG (OR=1.71, p=0.012) and IL10ra rs2229113 AG+GG (OR=1.45, p=0.01) genotypes was associated with increase in overall or low grade (Gleason score<7) PC risk among normal weight men. These odds were elevated among obese men who possessed the CCR5 rs1799987 AG+GG (OR=1.95, p=0.003) and RNASEL rs12135247 CT+TT genotypes (OR=1.59, p=0.05). CCR7 rs3136685 AG+GG (p=0.032) was associated with a 1.52-1.70 fold increase in the risk of high grade cancer (Gleason score≥7) among obese men. CCR7 variant emerged as an important factor associated with high grade PC risk among obese men in our analyses. Overall, genetic loci found significant in normal weight men were not significant in obese men and vice-versa, partially explaining the role of obesity on PC risk among black men. Also, older age was an important risk factor both in normal weight and obese men but only with regard to low grade PC. Associations of inflammatory SNPs with obesity are suggestive and require further validation in larger cohorts to help develop an understanding of PC risk among obese and non-obese men of African descent.

Physical activity as a risk factor for prostate cancer diagnosis: a prospective biopsy cohort analysis

OBJECTIVES

To assess the association between physical activity, evaluated by the Physical Activity Scale for the Elderly (PASE) questionnaire, and prostate cancer risk in a consecutive series of men undergoing prostate biopsy.

PATIENTS AND METHOD

From 2011 onwards, consecutive men undergoing 12-core prostate biopsy were enrolled into a prospective database. Indications for a prostatic biopsy were a prostate-specific antigen (PSA) value of ≥4 ng/mL and/or a positive digital rectal examination. Body mass index (BMI) and waist circumferences were measured before the biopsy. Fasting blood samples were collected before biopsy and tested for: total PSA, glucose, high-density lipoprotein cholesterol, and trygliceride levels. Blood pressure was recorded. Metabolic syndrome (MetS) was defined according to the Adult Treatment panel III. The PASE questionnaire was completed before the biopsy.

RESULTS

In all, 286 patients were enrolled with a median (interquartile range, IQR) age and PSA level of 68 (62-74) years and 6.1 (5-8.8) ng/mL, respectively. The median (IQR) BMI was 26.4 (24.6-29) kg/m(2) and waist circumference was 102 (97-108) cm, with 75 patients (26%) presenting with MetS. In all, 106 patients (37%) had prostate cancer at biopsy. Patients with prostate cancer had higher PSA levels (median [IQR] 6.7 [5-10] vs 5.6 [4.8-8] ng/mL; P = 0.007) and lower LogPASE scores (median [IQR] 2.03 [1.82-2.18] vs 2.10 [1.92-2.29]; P = 0.005). On multivariate analysis, in addition to well-recognised risk factors such as age, PSA level and prostate volume, LogPASE score was an independent risk factor for prostate cancer diagnosis (odds ratio [OR] 0.146, 95% confidence interval [CI] 0.037-0.577; P = 0.006]. LogPASE score was also an independent predictor of high-grade cancer (OR 0.07, 95% CI 0.006-0.764; P = 0.029).

CONCLUSION

In our single-centre study, increased physical activity, evaluated by the PASE questionnaire, is associated with a reduced risk of prostate cancer and of high-grade prostate cancer at biopsy. Further studies should clarify the molecular pathways behind this association.

Bipolar disorder and leadership--a total population study

OBJECTIVE

To investigate whether persons with bipolar disorder and their siblings have leadership traits and are overrepresented in executive professions.

METHOD

A nested case-control study based on longitudinal Swedish total population registries. Data from officer suitability interviews (n=1,126,519), and information on occupations were collected. Bipolar patients (n=68,915) and their healthy siblings were compared with controls.

RESULTS

Bipolar patients without comorbidity (pure; n=22,980) were overrepresented in both the highest and lowest strata of officer suitability; their healthy siblings in the highest strata only. Patients with pure bipolar disorder were underrepresented in executive professions, whereas their siblings were overrepresented in these professions (particularly political professions). Patients with general bipolar disorder (including those with comorbidities) and their healthy siblings were overrepresented only in the lowest strata of officer suitability ratings. General bipolar patients were underrepresented in executive professions, whereas their siblings had similar rates of executive professions as controls. Adjusting results for IQ slightly attenuated point estimates, but resulted in pure bipolar patients and their siblings no longer being significantly overrepresented in superior strata of officer suitability, and siblings no longer being overrepresented in executive professions.

CONCLUSION

Results support that traits associated with bipolar disorder are linked to superior leadership qualities.

Prostate cancer and physical activity: adaptive response to oxidative stress

Prostate cancer is the most common form of cancer affecting men in the Western world. Its relative incidence increases exponentially with age and a steady increase is observed with extended life span. A sedentary lifestyle represents an important risk factor and a decrease in prostate cancer prevalence is associated with exercise. However, the molecular mechanisms involved in this process remain unknown. We hypothesize that reactive oxygen species generated by physical exercise are a key regulatory factor in prostate cancer prevention. Aging is correlated with increased oxidative stress (OS), which in turn provides a favorable environment for tumorigenesis. Running training is known to enhance the antioxidant defense system, reducing oxidative stress. In this context, the decrease in OS induced by exercise may delay the development of prostate cancer. This review focuses on oxidative stress-based mechanisms leading to prostate cancer sensitization to exercise, which could have some impact on the development of novel cancer therapeutic strategies.

Mental illness, suicide and creativity: 40-year prospective total population study

We previously demonstrated that patients with schizophrenia or bipolar disorder and their relatives are overrepresented in creative occupations. Here, we use a new dataset with a considerably larger sample of patients (n = 1,173,763) to survey other psychiatric diagnoses and to validate previous findings. The specific aims of this study were to i) investigate if creativity is associated with all psychiatric disorders or restricted to those with psychotic features, and ii) to specifically investigate authors in relationship to psychopathology. We conducted a nested case-control study using longitudinal Swedish total population registries, where the occurrence of creative occupations in patients and their non-diagnosed relatives was compared to that of matched population controls. Diagnoses included were schizophrenia, schizoaffective disorder, bipolar disorder, unipolar depression, anxiety disorders, alcohol abuse, drug abuse, autism, ADHD, anorexia nervosa, and completed suicide. Creative professions were defined as scientific and artistic occupations. Data were analyzed using conditional logistic regression. Except for bipolar disorder, individuals with overall creative professions were not more likely to suffer from investigated psychiatric disorders than controls. However, being an author was specifically associated with increased likelihood of schizophrenia, bipolar disorder, unipolar depression, anxiety disorders, substance abuse, and suicide. In addition, we found an association between creative professions and first-degree relatives of patients with schizophrenia, bipolar disorder, anorexia nervosa, and for siblings of patients with autism. We discuss the findings in relationship to some of the major components of creativity.

Obesity trends and determinants in Indonesia

Obesity is becoming a serious issue in many developing countries, with negative implications for economic growth and human wellbeing. While previous micro level studies on obesity have mostly used cross-section data, we analyze trends and determinants with panel data from Indonesia. Over the past 20 years, obesity has increased remarkably in Indonesia across all population groups, including rural and low income strata. The problem is particularly severe among women. Panel regressions confirm that changing food consumption patterns, coupled with decreasing physical activity, directly contribute to this trend. From a policy perspective, nutrition awareness and education campaigns, combined with programs to support leisure time exercise especially for women, seem to be most promising to contain the obesity pandemic.

Creativity and mental disorder: family study of 300,000 people with severe mental disorder

BACKGROUND

There is a long-standing belief that creativity is coupled with psychopathology.

AIMS

To test this alleged association and to investigate whether any such association is the result of environmental or genetic factors.

METHOD

We performed a nested case-control study based on Swedish registries. The likelihood of holding a creative occupation in individuals who had received in-patient treatment for schizophrenia, bipolar disorder or unipolar depression between 1973 and 2003 and their relatives without such a diagnosis was compared with that of controls.

RESULTS

Individuals with bipolar disorder and healthy siblings of people with schizophrenia or bipolar disorder were overrepresented in creative professions. People with schizophrenia had no increased rate of overall creative professions compared with controls, but an increased rate in the subgroup of artistic occupations. Neither individuals with unipolar depression nor their siblings differed from controls regarding creative professions.

CONCLUSIONS

A familial cosegregation of both schizophrenia and bipolar disorder with creativity is suggested.

Does physical activity reduce the risk of prostate cancer? A systematic review and meta-analysis

CONTEXT

Numerous observational epidemiologic studies have evaluated the association between physical activity and prostate cancer (PCa); however, the existing results are inconsistent.

OBJECTIVE

To determine the association between physical activity and risk of PCa.

EVIDENCE ACQUISITION

A systematic search was performed using the Medline, Embase, and Web of Science databases through 15 May 2011 to identify all English-language articles that examined the effect of physical activity on the risk of PCa. This meta-analysis was conducted according to the guidelines for the meta-analysis of observational studies in epidemiology.

EVIDENCE SYNTHESIS

This meta-analysis consisted of 88,294 cases from 19 eligible cohort studies and 24 eligible case-control studies. When data from both types of studies were combined, total physical activity (TPA) was significantly associated with a decreased risk of PCa (pooled relative risk [RR]: 0.90; 95% confidence interval [CI], 0.84-0.95). The pooled RR for occupational physical activity (OPA) and recreational physical activity (RPA) were 0.81 (95% CI, 0.73-0.91) and 0.95 (95% CI, 0.89-1.00), respectively. Notably, for TPA, we observed a significant PCa risk reduction for individuals between 20 and 45 yr of age (RR: 0.93; 95% CI, 0.89-0.97) and between 45 and 65 yr of age (RR: 0.91; 95% CI, 0.86-0.97) who performed activities but not for individuals <20 yr of age or >65 yr of age.

CONCLUSIONS

There appears to be an inverse association between physical activity and PCa risk, albeit a small one. Given that increasing physical activity has numerous other health benefits, men should be encouraged to increase their physical activity in both occupational and recreational time to improve their overall health and potentially decrease their risk of PCa.

Does leisure time physical activity protect against shoulder pain at work?

BACKGROUND

Shoulder pain is a common problem that can impact on work. Leisure time physical activity (LTPA) has the potential to reduce the impact of shoulder pain through its physiological, psychological and social benefits.

AIMS

To determine whether LTPA reduces the prevalence of shoulder pain in a working population.

METHODS

Participants were selected from a longitudinal population-based cohort study, the North West Adelaide Health Study. Information was gathered by questionnaire on LTPA, smoking, depression and socio-economic factors. Body mass index was measured in a clinic setting. Occupational physical activity (OPA) estimated by job title and shoulder pain was measured using the Shoulder Pain and Disability Index. Workers with and without shoulder pain were compared using logistic regression analysis.

RESULTS

Of the 1502 working participants, 16% reported having current shoulder pain. Shoulder pain was associated with older age (OR 1.98, 95% CI: 1.31-2.99) (age >50 years), smoking (OR 1.44, CI: 1.02-2.04), secondary-level educational attainment (OR 1.68, 95% CI: 1.07-2.65), high body mass index (BMI) (OR 1.54, 95% CI: 1.14-2.08) and depression (OR 2.42, 95% CI: 1.60-3.64). There was no effect of LTPA on shoulder pain.

CONCLUSIONS

In this community-based cohort, there was no statistically significant association seen between LTPA, OPA and shoulder pain. There was, however, an association between smoking, BMI, secondary-level education, depression and shoulder pain. These modifiable factors may be better targets for preventive efforts than LTPA to reduce the risk of shoulder pain.

Physical activity and genitourinary cancer prevention

The present review of epidemiologic studies of physical activity and genitourinary cancers (prostate, bladder, renal cell, and testicular cancers) suggests a weak inverse relation of physical activity to risk of prostate and renal cell cancer, with average risk decreases of less than 10% comparing high versus low levels of physical activity. For prostate cancer, studies that assessed activity intensity or those that considered fatal prostate cancer as a study endpoint produced the strongest inverse association. For renal cell cancer, the inverse relation with physical activity was more apparent among women than men, among normal weight than overweight or obese individuals, and among older than younger individuals. In contrast to prostate and renal cell cancer, available data show that physical activity is not associated with bladder or testicular cancer. Future research should include improvements in self-reported activity measures and incorporation of objective assessments of physical activity over the life course in order to more precisely characterize types, parameters, and timing of physical activity in relation to genitourinary cancers. Also, data are lacking regarding whether fitness potentially influences genitourinary cancer risk. The relation of physical activity and fitness to genitourinary cancer prognosis and survival requires specific attention. Mechanistic research should identify the underlying biologic pathways potentially linking physical activity to genitourinary cancers.

Exercise in cancer

Physical exercise has attracted increased interest in rehabilitation of oncological patients. The purpose of this paper is to review the literature and summarize the evidence of physical exercise in preventing cancer, its ability in attenuating the effect of cancer and its treatments and to provide guidelines for exercise prescription Review of recent literature by electronic search of MEDline (Pub Med), Cancer lit, Cochrane libraries, CINAHL were done using Keywords and the variables were identified and systematically evaluated. There is strong evidence for reduced risk of colorectal and breast cancer with possible association for prostate, endometrial and lung cancer with increasing physical activity. Exercise helps cancer survivors cope with and recover from treatment; exercise may improve the health of long term cancer survivors and extend survival. Physical exercise will benefit throughout the spectrum of cancer. However, an understanding of the amount, type and intensity of exercise needed has not been fully elucidated. There is sufficient evidence to promote exercise in cancer survivors following careful assessment and tailoring on exercise prescription.

Exercise therapy across the prostate cancer continuum

Exercise has been increasingly investigated as an adjunct therapy for cancer patients. The purpose of this paper is to comprehensively review the literature regarding exercise as a therapeutic adjunct for prostate cancer (PC). Several studies in patients with PC have shown quality of life improvements associated with exercise. Although no study has established the effect of exercise as a monotherapy for PC, the molecular mechanisms responsible for the potential association between exercise and PC are being elucidated. Given the low-risk, high-reward nature of these studies, further investigations are needed to better define the function of exercise along the PC continuum.

Energy intake, physical activity, energy balance, and cancer: epidemiologic evidence

Energy intake, physical activity, and obesity are modifiable lifestyle factors. This chapter reviews and summarizes the epidemiologic evidence on the relation of energy intake, physical activity, and obesity to cancer. High energy intake may increase the risk of cancers of colon-rectum, prostate (especially advanced prostate cancer), and breast. However, because physical activity, body size, and metabolic efficiency are highly related to total energy intake and expenditure, it is difficult to assess the independent effect of energy intake on cancer risk. There are sufficient evidences to support a role of physical activity in preventing cancers of the colon and breast, whereas the association is stronger in men than in women for colon cancer and in postmenopausal than in premenopausal women for breast cancer. The evidence also suggests that physical activity likely reduces the risk of cancers of endometrium, lung, and prostate (to a lesser extent). On the other hand, there is little or no evidence that the risk of rectal cancer is related to physical activity, whereas the results have been inconsistent regarding the association between physical activity and the risks of cancers of pancreas, ovary and kidney. Epidemiologic studies provide sufficient evidence that obesity is a risk factor for both cancer incidence and mortality. The evidence supports strong links of obesity with the risk of cancers of the colon, rectum, breast (in postmenopausal women), endometrium, kidney (renal cell), and adenocarcinoma of the esophagus. Epidemiologic evidence also indicates that obesity is probably related to cancers of the pancreas, liver, and gallbladder, and aggressive prostate cancer, while it seems that obesity is not associated with lung cancer. The role of obesity in other cancer risks is unclear.

Prostate cancer in Mexican-Americans: identification of risk factors

BACKGROUND

There is a paucity of information regarding prostate cancer (PCa) risk factors among Hispanics, the fastest-growing ethnic group in the United States.

METHODS

This population-based case-control study included 176 Texas men of Mexican descent with PCa and 174 age- and ethnicity-matched controls. Demographic, lifetime occupational history, family history of cancer, lifestyle (e.g., smoking, alcohol, diet, and recreational physical activity) and anthropometric information were collected by personal interviews. Chemical exposure and physical activity were determined using job-exposure matrices for each reported job.

RESULTS

Logistic regression models adjusted for relevant covariates were used to evaluate their independent effects. Compared to controls, cases were three times more likely to work in jobs with high agrichemical exposure (OR = 3.44, 95% CI 1.84-6.44), and 54% less likely to work in jobs with moderate/high occupational physical activity (OR = 0.46, 95% CI 0.28-0.77). In analyses stratified by stage, cases with organ-confined PCa were three times more likely to have high agrichemical exposure (OR = 3.39, 9%CI 1.68-6.84), and 56% less likely to have moderate/high levels of occupational physical activity (OR = 0.44, 95% CI 0.26-0.76). Increased risk of being diagnosed with advanced PCa was associated with obesity at time of diagnosis (OR = 2.50, 95% CI 1.20-5.20) and high levels of agrichemical exposure (OR = 4.65, 95% CI 1.97-10.97), but not with occupational physical activity.

CONCLUSIONS

This case-control study, the first conducted in a homogeneous Hispanic population, identified modifiable PCa risk factors, such as physical activity and agrichemical exposure, which may be useful in developing interventions for this understudied population.

Prevention of prostate cancer: more questions than data

Established risk factors for prostatic adenocarcinoma include increasing age, ethnical origin (race), and familial/hereditary factors. Moreover, the epidemiology of the disease gives some indications that its etiology is probably not only genetic but also environmental. Pathological studies support the fact that geographic differences in incidence and prevalence do not stem from genetic variations as men with the same genetic background raised in different environments present the risk of prostate cancer associated with their country of residency. Prostate cancer is basically an ideal candidate for exogenous preventive measures, such as dietary and pharmacological prevention, due to some specific features: high prevalence, long latency, endocrine dependency, availability of serum markers (prostate-specific antigen) and histological precursor lesions (prostatic intraepithelial neoplasia). Dietary/nutritional factors that may influence disease development include total energy intake (as reflected by body mass index), dietary fat, cooked meat, micronutrients and vitamins (carotenoids, retinoids, vitamins C, D, and E), fruit and vegetable intake, minerals (calcium, selenium), and phytoestrogens (isoflavonoids, flavonoids, lignans). Pharmacological prevention may use drugs that act on intraprostatic testosterone metabolism (finasteride, dutasteride) or induce apoptosis and inhibit tumor growth and metastasis (statins). Since most studies reported to date are case-control analyses, there remain more questions than evidence-based data. However, several large randomized trials are ongoing to clarify the potential for successful prostate cancer prevention. Until we have the results, lifestyle changes could be recommended to men at risk for developing clinical prostate cancer and 5-alpha-reductase inhibitors need to be discussed with men who are concerned about prostate cancer.

Nested case-control study of occupational chemical exposures and prostate cancer in aerospace and radiation workers

BACKGROUND

To date, little is known about the potential contributions of occupational exposure to chemicals to the etiology of prostate cancer. Previous studies examining associations suffered from limitations including the reliance on mortality data and inadequate exposure assessment.

METHODS

We conducted a nested case-control study of 362 cases and 1,805 matched controls to examine the association between occupational chemical exposures and prostate cancer incidence. Workers were employed between 1950 and 1992 at a nuclear energy and rocket engine-testing facility in Southern California. We obtained cancer-incidence data from the California Cancer Registry and seven other state cancer registries. Data from company records were used to construct a job exposure matrix (JEM) for occupational exposures to hydrazine, trichloroethylene (TCE), polycyclic aromatic hydrocarbons (PAHs), benzene and mineral oil. Associations between chemical exposures and prostate cancer incidence were assessed in conditional logistic regression models.

RESULTS

With adjustment for occupational confounders, including socioeconomic status, occupational physical activity, and exposure to the other chemicals evaluated, the odds ratio for low/moderate TCE exposure was 1.3; 95%CI = 0.8 to 2.1, and for high TCE exposure was 2.1; 95%CI = 1.2 to 3.9. Furthermore, we noted a positive trend between increasing levels of TCE exposure and prostate cancer (P-value for trend = 0.02).

CONCLUSION

Our results suggest that high levels of TCE exposure are associated with prostate cancer among workers in our study population.

Knowledge, beliefs and barriers associated with prostate cancer prevention and screening behaviors among African-American men

African-American men have the highest prostate cancer rates worldwide, and innovative efforts are needed to increase cancer prevention and screening behaviors among this population. Formative research was conducted to assess attitudes and behaviors linked to prostate cancer prevention activities that could be used to develop a culturally relevant intervention for an African-American church-based population. Four gender-specific focus groups were conducted with 29 men and women at two African-American churches in central North Carolina. Three primary themes emerged from the focus group discussions: culturally and gender-influenced beliefs and barriers about cancer prevention and screening; barriers related to the healthcare system: and religious influences, including the importance of spiritual beliefs and church support. These discussions revealed the importance of the black family, the positive influence of spouses/partners on promoting cancer screening and healthy behaviors, the roles of faith and church leadership, and beliefs about God's will for good health. These findings also revealed that there are still major barriers and challenges to cancer prevention among African Americans, including continued mistrust of the medical community and negative attitudes toward specific screening tests. Findings provide important insights to consider in implementing successful prostate cancer prevention interventions designed for church-based audiences.

Lifetime physical activity and prostate cancer risk

The purpose of our study was to investigate the relation in between physical activity in different periods of life at work and in leisure-time and prostate cancer risk. We conducted a case-control study on prostate cancer in Italy between 1991 and 2002, which included 1,294 incident cases of histologically confirmed prostate cancer below 75 years of age and 1,451 controls, who were admitted to hospital for acute nonneoplastic conditions. Odds ratios (OR) of prostate cancer according to physical activity in different periods of life were obtained by unconditional multiple logistic regression models, including terms for age, study centre, education, social class, body mass index, energy intake, family history and other selected covariates. Compared to the lowest level of occupational physical activity, the multivariate ORs for prostate cancer for the highest level were 0.94 (95% confidence interval, CI, 0.75-1.17) at age 15-19, 0.78 (95% CI, 0.63-0.97) at age 30-39 and 0.75 (95% CI, 0.61-0.93) at age 50-59. A significant inverse trend in risk was found for activity at work at ages 30-39 and 50-59. The inverse associations were consistent in strata of age at diagnosis, body mass index, education and social class. No significant association was found for leisure-time physical activity. The inverse association between occupational physical activity and prostate cancer risk may reflect favorable hormonal correlates of physical activity, but residual confounding by socioeconomic covariates cannot be excluded.

A Prospective Study of Occupation and Prostate Cancer Risk

A wide variety of occupations has been associated with prostate cancer in previous retrospective studies. Most attention has been paid to farming, metal working, and the rubber industry. Today, these results cannot be affirmed with confidence, because many associations could be influenced by recall bias, have been inconsistent, or have not been confirmed satisfactory in subsequent studies. This study was conducted to investigate and confirm these important associations in a large prospective cohort study. The authors conducted a prospective cohort study among 58,279 men. In September 1986, the cohort members (55-69 years) completed a self-administered questionnaire on potential cancer risk factors, including job history. Related job codes were clustered in professional groups. These predefined clusters were investigated in 3 time windows: 1) profession ever performed, 2) longest profession ever held, and 3) last profession held at baseline. Follow up for incident prostate cancer was established by linkage to cancer registries until December 1993. A case-cohort approach was used based on 830 cases and 1525 subcohort members. To minimize false-positive results, 99% confidence intervals (99% CI) were calculated. Although moderately decreased prostate cancer risks were found for electricians, farmers, firefighters, woodworkers, textile workers, butchers, salesmen, teachers, and clerical workers, none of the relative risks (RR) were found to be statistically significant. For road transporters, metal workers, and managers, no association with prostate cancer risk was found. Although the RR for railway workers, mechanics, welders, chemists, painters, and cooks was moderately increased, these estimates were not statistically significant. For men who reported to have ever worked in the rubber industry, we found a substantially increased prostate cancer risk, but not statistically significant (RR, 4.18; 99% CI = 0.22-80.45). For policemen, we found a substantial and marginally statistically significant increased prostate cancer risk, especially for those who reported working as a policeman for most of their occupational life (RR, 3.91; 99% CI = 1.14-13.42) or as the last profession held at baseline (RR, 4.00; 99% CI = 1.19-13.37). Most of the previously investigated associations between occupation and prostate cancer risk could not be confirmed with confidence in this prospective study. The lack of statistical significance for rubber workers could be caused by the scarcity of rubber workers in this cohort and subsequent lack of power. The results for policemen were substantial and statistically significant, although a conservative value for significance level was used.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Age and temporal trends of total physical activity in Swedish men

INTRODUCTION/PURPOSE

Despite a large public health interest in physical activity and its role in obesity and other chronic diseases, only few reports to date have addressed total levels and trends of physical activity. We have studied in a cross-sectional setting with a retrospective recall of physical activity an association of levels of total physical activity and different types of activities with age and with calendar-time.

METHODS

In a population-based study of 33,466 men aged 45-79 yr in central Sweden, information on physical activity and other lifestyle factors was collected through a self-administered questionnaire. Level of total activity at ages 15, 30, and 50 yr was assessed quantitatively, based on six questions on different activities: work/occupation, housework, walking/bicycling, exercise, inactive leisure time, and sleeping. The physical activity levels were measured as metabolic equivalents, MET-hours per days.

RESULTS

Total daily physical activity decreased at age 30 yr (-1.6%, 95% CI: -1.7, -1.4) and at age 50 yr (-3.9%, 95% CI: -4.0, -3.7) compared with age 15 yr. Total physical activity decreased over a period of 60 yr in all three separate age groups (-9.1% among 15-yr-olds, 95% CI: -9.8, -8.5; -2.3% among 30-yr-olds 95% CI: -3.0, -1.6; and -2.9% among 50-yr-olds, 95% CI: -3.4, -2.5).

CONCLUSION

These negative trends in physical activity observed by age and with time might explain the trends in increasing prevalence of obesity.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.