Socio-economic class differences in cancer incidence in Cali, Colombia

Considering the Role of Stress in Populations of High-Risk, Underserved Community Networks Program Centers

BACKGROUND

Cancer disparities are associated with a broad range of sociocultural determinants of health that operate in community contexts. High-risk populations may be more vulnerable to social and environmental factors that lead to chronic stress. Theoretical and empirical research indicates that exposure to contextual and sociocultural stress alters biological systems, thereby influencing cancer risk, progression, and, ultimately, mortality.

OBJECTIVE

We sought to describe contextual pathways through which stress likely increases cancer risk in high-risk, underserved populations.

METHODS

This review presents a description of the link between contextual stressors and disease risk disparities within underserved communities, with a focus on 1) stress as a proximal link between biological processes, such as cytokine responses, inflammation, and cancer and 2) stress as a distal link to cancer through biobehavioral risk factors such as poor diet, physical inactivity, circadian rhythm or sleep disruption, and substance abuse. These concepts are illustrated through application to populations served by three National Cancer Institute-funded Community Networks Program Centers (CNPCs): African Americans in the Deep South (the South Carolina Cancer Disparities Community Network [SCCDCN]), Native Hawaiians ('Imi Hale-Native Hawaiian Cancer Network), and Latinos in the Lower Yakima Valley of Washington State (The Center for Hispanic Health Promotion: Reducing Cancer Disparities).

CONCLUSIONS

Stress experienced by the underserved communities represented in the CNPCs is marked by social, biological, and behavioral pathways that increase cancer risk. A case is presented to increase research on sociocultural determinants of health, stress, and cancer risk among racial/ethnic minorities in underserved communities.

The association between cancer incidence and family income: analysis of Korean National Health Insurance cancer registration data

BACKGROUND

Economic status is known to be directly or indirectly related to cancer incidence since it affects accessibility to health-related social resources, preventive medical checkups, and lifestyle. This study investigates the relationship between cancer incidence and family income in Korea.

METHODS

Using the Korean National Health Insurance cancer registration data in 2009, the relationship between their family income class and cancer risk was analyzed. The age-standardized incidence rates of the major cancers were calculated for men and women separately. After adjusting for age, residential area, and number of family members, cancer risks for major cancers according to family income class were estimated using a logistic regression model.

RESULTS

In men, the risk of stomach cancer for Income Class 5 (lowest) was 1.12 times (95% CI 1.02-1.23) higher than that of Income Class 1 (highest), for lung cancer 1.61 times (95% CI 1.43- 1.81) higher, for liver cancer 1.22 times (95% CI 1.08-1.37) higher, and for rectal cancer 1.37 times higher (95% CI 1.18-1.59). In women, the risk of stomach cancer for Income Class 5 was 1.22 times higher (95% CI 1.08-1.37) than that for Income Class 1, while for cervical cancer it was 2.47 times higher (95% CI 2.08- 2.94). In contrast, in men, Income Class 1 showed a higher risk of thyroid cancer and prostate cancer than that of Income Class 5, while, in women the same was the case for thyroid cancer.

CONCLUSIONS

The results show the relationship between family income and cancer risk differs according to type of cancer.

The enduring and evolving relationship between social class and breast cancer burden: a review of the literature

INTRODUCTION

Breast cancer in women has historically been seen as a "cancer of affluence" and there is a well-documented higher incidence among women of higher social class, as well as in societies with higher resources. However, the relationship between social class and breast cancer disease characteristics, especially those associated with poorer prognosis, is less well documented, and the overall relationship between breast cancer mortality and social class has been shown to vary. Furthermore, rapid changes in women's health and health-related behaviors in societies around the world may have an impact on both incidence and mortality patterns for breast cancer in the future.

METHODS

A PUBMED search on breast cancer and social class (incorporating the MeSH-nested concept of SES) yielded 403 possible studies published between 1978 and 2009, of which 90 met criteria for review. Our review discusses conceptualization and measurement of women's social class in each study, as well as findings related to breast cancer incidence, tumor biology or mortality, associated with social class.

FINDINGS

We found mostly consistent evidence that breast cancer incidence continues to be higher in higher social class groups, with some modification of risk with adjustment for known risk factors, including physical activity and reproductive history. However, biologic characteristics associated with poorer prognosis were negatively associated with social class (i.e., greater occurrence among disadvantaged women), and mortality from breast cancer showed inconsistent relationship to social class.

CONCLUSIONS

We discuss these studies in relation to the growing burden of breast cancer among low resource groups and countries, and the need for cancer control strategies reflecting the emerging demographics of breast cancer risk.

Time trends in socioeconomic differences in incidence rates of cancers of gastro-intestinal tract in Finland

BACKGROUND

The magnitude of socioeconomic differences in health varies between societies, and over time within a given society. We studied the association between social class and incidence of cancers of the gastro-intestinal tract over time in a large cohort in Finland.

METHODS

We studied social class variation among 45-69 year-old Finns during 1971-95 in incidence of cancers of the gastro-intestinal tract by means of a computerized record linkage of the Finnish Cancer Registry and the 1970 Population Census, which included social class data.

RESULTS

There were 2.3 million individuals in the cohort under follow-up, with 1622 cases of cancer of the esophagus, 8069 stomach (non-cardia), 1116 cardia, 408 small intestine, 6361 colon, 5274 rectum, 1616 liver, 1756 gallbladder, and 5084 pancreas during 1971-1995. Cancers of the esophagus, stomach, cardia, gallbladder and pancreas were most common among persons belonging to a low social class. Cancers of the small intestine in males only, colon in both genders, and rectum in females were most common in the higher social classes. Incidence of stomach cancer decreased and incidence of colon cancer increased over time in both genders in all social classes, and the large differences between social classes remained unchanged over time. Incidence rates of cardia cancer did not change substantially over time.

CONCLUSION

There is a large variation in incidence of cancer of the gastrointestinal tract by social class in Finland. Although much of the observed social class differences probably could be explained by known etiological factors such as diet, physical exercise, alcohol consumption, smoking and exogenous hormone use, part of the variation is apparently attributable to largely unknown factors.

Explaining the Socioeconomic Variation in Cancer Risk in the Norwegian Women and Cancer Study

Associations between level of education and cancer risk is well supported by scientific evidence, but previous studies could only partly adjust for relevant confounding factors. In this article, we examined how risk of cancer varies with level of education and identified factors that explain this variation using data from a prospective cohort study, including 93,638 Norwegian women who responded to an extensive questionnaire in 1991/1992 or 1996/1997. A total of 3,259 incident primary invasive cancer cases were diagnosed during follow-up, which ended in December 2001. We used Cox proportional hazards model to calculate relative risks (RR) with 95% confidence intervals (95% CI). Besides a similar overall risk of female cancers by level of education, we observed differing risks between educational groups for cancers of the lung, breast, cervix, kidney, and skin melanoma. Women with >16 years of education had an increased risk of breast cancer (RR, 1.46; 95% CI, 1.19-1.79) and a decreased risk of lung cancer (RR, 0.30; 95% CI, 0.13-0.70) and cervical cancer (RR, 0.38; 95% CI, 0.17-0.85) compared with the lowest educated women (7-9 years). The middle educated (13-16 years) had the lowest risk of kidney cancer (RR, 0.24; 95% CI, 0.08-0.71), whereas the risk of skin melanoma was highest among women with 10 to 12 years of education (RR, 1.53; 95% CI, 1.05-2.24) compared with the lowest educated women. After multivariate adjustment for potential confounders related to level of education, the variation in cancer risk according to educational levels declined into nonsignificance for all these sites.

Behaviour partly explains educational differences in cancer incidence in the south-eastern Netherlands: the longitudinal GLOBE study

Cancer morbidity and mortality vary among socio-economic groups. We investigated whether educational differences in behaviour could explain the variation in cancer incidence. In 1991, a postal questionnaire on socio-economic status, exposure variables, health and health-related behaviour was filled out by 18,973 participants (response rate 70.1%) of the longitudinal GLOBE study. Participants were followed and linked with the regional population-based Eindhoven Cancer Registry. Between 1991 and 1998 a total of 760 new tumours were found. The risk of cancer (all sites combined) was higher in the three quartiles of lower educational level compared with the highest educational level, odds ratios (ORs) varying from 1.25, 1.34, 1.27 to 1.00 from the lowest to the highest category, respectively (P=0.14). The relative risk (RR) for lung cancer for low versus high education was 2.7 [95% confidence interval (CI) 1.3-5.3]; adjustment for smoking, alcohol intake and physical activity decreased the risk to 1.6 (95% CI 0.8-3.3). Smoking alone explained 39% of the association, when alcohol intake and physical exercise were added to the model 61% of the effect was explained. In conclusion, a lower education is associated with increased cancer risks, which can be explained partly by behavioural factors.

Prospective study of educational background and stomach cancer in Japan

BACKGROUND

Different lifestyle choices are commonly regarded as a reflection of socioeconomic status, and the latter is inversely correlated with the risk of developing stomach cancer. However, the details of this association are still unclear in terms of the degree to which lifestyle factors are having impact. To explain the correlation between socioeconomic status and stomach cancer, we therefore examined the roles played by different lifestyle factors.

METHODS

A prospective cohort study of diet and cancer was initiated in Japan during 1988. Data were collected by means of a self-administered questionnaire. A follow-up survey was conducted annually, and the cause of death was recorded from the death certificate. The total of 127,477 study participants resided in 45 areas of Japan, and we retrieved data for 18,746 men and 26,184 women for the present analysis. After 328,030 person-years of follow-up, 379 deaths from stomach cancer were detected: 261 in men and 118 in women.

RESULTS

For men, the age-adjusted relative risk was lowest in the highly educated group (relative risk = 0.72, 95% CI: 0.50-1.04). Relative risk after adjustment for age and dietary choices (including pickles, vegetables, fruit, green tea, and preference for salty foods) was the same as the age-adjusted relative risk (relative risk = 0.72, 95% CI: 0.50-1.04).

CONCLUSION

The expected inverse correlation between education level and death from stomach cancer was observed in men. However, this association could not be explained by differences in dietary habits, smoking, or alcohol consumption associated with socioeconomic status.

Socioeconomic status and stomach cancer incidence in men: results from The Netherlands Cohort Study

STUDY OBJECTIVE

To study the association between socioeconomic status (SES) and stomach cancer incidence (cardia and non-cardia) and the role of lifestyle factors in explaining this association.

DESIGN

Prospective cohort study on diet and cancer that started in 1986. Data were collected by means of a self administered questionnaire.

SETTING

Population originating from 204 municipalities in the Netherlands.

PARTICIPANTS

58,279 men aged 55-69 years. After 4.3 years of follow up, 162 incident stomach cancer cases were detected (49 cardia and 113 non-cardia cases).

MAIN RESULTS AND CONCLUSIONS

After adjustment for age, a lower overall stomach cancer risk was found for men with the highest attained level of education (RR highest/lowest level = 0.54, 95% CI 0.33, 0.89, trend, p = 0.02). This association became less strong after additional adjustment for smoking, intake of vitamin C, beta carotene, alcohol and coffee, family history of stomach cancer, and history of stomach disorders (RR = 0.61, 95% CI 0.34, 1.07, trend, p = 0.11). No clear association was found between occupation based SES indicators and stomach cancer risk. Analyses per subsite of stomach cancer revealed that for people with the highest level of education the age adjusted rate ratio for cardia cancer changed from 0.37 (95% CI = 0.13, 1.00) to 0.60 (95% CI = 0.19, 1.87) after additional adjustment for lifestyle variables, whereas the rate ratio for non-cardia cancer (RR = 0.59, 95% CI 0.33, 1.05) did not change after additional adjustment.

Socioeconomic differences in cervical cancer: two case-control studies in Colombia and Spain

OBJECTIVES

This study examined the causes of socioeconomic differences in invasive cervical cancer in two countries that differ substantially in cervical cancer incidence and economic development.

METHODS

Data were derived from two case-control studies carried out in Spain and Colombia; there were 373 case subjects, 387 control subjects, and 425 husbands interviewed with a structured questionnaire. Exfoliated cells were obtained from cervical or penile scrapes and tested for human papillomavirus (HPV) DNA.

RESULTS

Relative to better educated women, women with low educational levels in both countries reported fewer Pap smears and had a higher prevalence of HPV DNA. The prevalence ratio of HPV DNA across educational strata was twofold in Spain and fourfold in Colombia. In both countries, husbands of poorly educated women reported higher use of prostitutes than husbands of better educated women. In Colombia, 30% of husbands of poorly educated women harbored HPV DNA, compared with 10% of husbands of better educated women.

CONCLUSIONS

Socioeconomic differences in invasive cervical cancer could be partly explained by differences in the prevalence of HPV DNA and by a lower use of preventive care.

Cancer mortality by educational level in Italy

Social differences in health concern both ethics and science. From a public health point-of-view, one must assess actual differences and then try to find explanations. This was made possible for the first time for cancer in Italy via nationwide record-linkage between the 1981 census and the national death index. Over the subsequent six months after census, the study-base included 31,000 deaths for cancer and 18 million person-years at risk. Rate ratio (RR) were estimated through a Poisson regression model adjusted by age and geographic area of residence. Educational level was used as social level indicator. Profound social differences were evident for buccal cavity (RR = 3.10 for lowest cf highest educational level), esophagus (RR = 3.00), stomach (RR = 3.43), and larynx (RR = 3.30) among men, and for stomach (RR = 2.25) and uterus (RR = 1.76) among women. Colon (RR = 0.62) and pancreas cancers (RR = 0.65) presented an inverse relationship among men, as did colon (RR = 0.37), breast (RR = 0.56), ovary (RR = 0.45), and melanoma (RR = 0.62) among women. In conclusion, the Italian population at the beginning of the 1980s had large social differences in the risk of dying from cancer, confirming the patterns commonly found in such other countries as Great Britain, France, and New Zealand. Some dissimilarities, useful for hypothesis generation on the mechanisms of inequality, were evident, such as the generally highest social differences found among northern Italian men and among southern Italian women.

Education and mortality from cancer in São Paulo, Brazil

This study investigated social class differentials in cancer mortality in São Paulo county, Brazil, for the period 1978 to 1982. A measure of socioeconomic status based on education was used, and cancer risk by level of education was estimated by a case-control approach in which other cancers were considered as controls. For most cancers, the socioeconomic differences in risk were similar to those found in western Europe and North America. For lung cancer, however, the highest risk was observed in men and women with the most education. Other cancers related to tobacco--cancer of the larynx, pharynx, and esophagus--showed a negative association with education. The differences between social classes in consumption habits of alcohol and maté and the use of black tobacco are probably responsible for these contrasting patterns. For breast and cervix uteri cancer the social class patterns were similar to those found in developed countries--a positive relationship for breast and a negative one for cervix uteri cancer. The magnitude of the differences observed between social classes for these cancers was frequently greater in South America than in the United States or western Europe.

Diet and stomach cancer incidence. A case-control study in Turkey

A case-control study of diet and stomach cancer was conducted in Ankara, Turkey, between December 1987 and March 1988. One hundred patients with adenocarcinoma of the stomach were matched with 100 control subjects according to age, sex, and residential area. A dietary questionnaire was administered to all subjects by one of the authors. Gastric cancer patients consumed less fresh fruit and yellow-green vegetables (P less than 0.0001) and meats (P less than 0.001), and more salted food (P less than 0.001), condiments (P less than 0.0001), and salt (P less than 0.001) compared with the control group. Twenty-four percent of the gastric cancer patients and 4% of the groups with regard to the consumption of starches, fried foods, cereals, milk, dairy products, tea, alcohol, and tobacco. Stomach cancer patients brushed their teeth less frequently (P less than 0.0001) and had more deficient teeth (P less than 0.0001) compared with the control group.

Correlation patterns of cancer relative frequencies with some socioeconomic and demographic indicators in Brazil: an ecologic study

Sex-specific relative frequencies (RF) of oral, esophageal, stomach, colon, rectal, laryngeal, lung, female breast, cervical and penile cancers obtained from a government-sponsored, nation-wide data base of histopathological diagnoses were evaluated with respect to all possible inter-site correlations and with 12 socioeconomic and demographic variables for 23 States in Brazil. Use of bivariate and multivariate methods detected a high positive intercorrelation among RFs of lung, laryngeal and colon cancers regardless of sex. RFs for these 3 sites were also positively correlated with many markers of State development and affluence. Cervical and penile cancers emerged as a distinct subset with respect to their correlation patterns. RFs for these neoplasms were highly (positively) correlated (r = 0.8606, p less than 0.001) with each other and exhibited intense negative associations with many of the affluence markers and the former cancer sites. Bivariate correlations generally exhibited a better fit with female-specific RFs than with data from males which was reflected in the number of strong correlations detected by sex.

Genetic predisposition to breast cancer

Breast cancer risk factors are closely intertwined with the patient's cultural background, which may contribute to breast cancer aggregations within families. The difficult questions are: (1) does a truly hereditary breast cancer subset exist; (2) which familial aggregations are hereditary; and (3) is the hereditary form distinctive from its sporadic counterpart? These queries will be resolved once biomarkers are identified that show high sensitivity and specificity with genotype. The authors provide a review of this subject and will focus on their recent discovery of increased in vitro hyperdiploidy in cultured skin fibroblasts from patients with or at risk for hereditary breast cancer. The authors discuss findings from their study of family histories in 225 consecutively ascertained patients with verified breast cancer from the Creighton University School of Medicine Oncology Clinic. Findings consistent with an hereditary breast cancer syndrome were identified in 5% of the patients. Given the 112,000 new cases of breast cancer in the United States in 1982, the authors estimate that with a confidence coefficient of 0.95 between 2410 and 8790 of these individuals will manifest hereditary breast cancer. Specific surveillance/management programs should be geared to high-risk members of these families in which cancer yield will be predictable.