Socioeconomic status and childhood solid tumor and lymphoma incidence in Canada

The authors examined the relation between neighborhood income, as a measure of socioeconomic status, and childhood cancer. Incident cases of childhood solid tumor and lymphoma in 1985-2001 were identified from provincial cancer registries in Canada. Residential postal codes at the time of diagnosis were used to assign cases to census neighborhoods. Person-years at risk were determined from quintiles of population by neighborhood income, sex, and 5-year age group, constructed using census population data. Poisson regression was used to calculate incidence rate ratios across neighborhood income quintiles. Compared with the incidence rate in the richest income quintile, moderately lower rate ratios of 0.73 (95% confidence interval: 0.63, 0.86) and 0.84 (95% confidence interval: 0.69, 1.04) were observed, respectively, for carcinomas and renal tumors in the poorest income quintile. No association was found for other types of cancer. Although a potential relation between socioeconomic status and childhood cancer cannot be excluded, the overall pattern seems compatible with random variation.     

Measles vaccination improves the equity of health outcomes: evidence from Bangladesh

OBJECTIVES: This paper asks whether measles vaccination can reduce socioeconomic differentials in under five mortality rates (U5MR) in a setting characterized by extreme poverty and high levels of childhood mortality. DESIGN: Longitudinal cohort study based on quasi experimental design. SETTING: Data come from the phased introduction of a measles vaccine intervention in Matlab, Bangladesh in 1982. Subjects: There were 16 270 Bangladeshi children aged 9-60 months. INTERVENTION: The intervention cohort received measles vaccine. MAIN OUTCOME MEASURES: Socioeconomic differentials in U5MR between the lowest and highest socioeconomic status (SES) quintiles in a cohort of 8135 vaccinated children and a cohort of unvaccinated age matched controls. Mantel-Haenszel rate ratios for the lowest to highest SES quintile were computed. SES was measured by factor analysis of maternal schooling, land holdings, dwelling size, and number of rooms. RESULTS: The U5MR ratio of lowest SES to highest was 2.27 (95% CI=1.62-3.19) in the unvaccinated population and 1.42 (95%CI=0.94-2.15) in the vaccinated population. The difference between unvaccinated and vaccinated U5MR ratios was statistically significant (p<0.10) and robust across alternative measures of SES. CONCLUSION: Children from the poorest quintile were more than twice as likely to die as those from the least quintile in the absence of measles vaccination. Universal distribution of measles vaccination largely nullified SES related mortality differentials within a high mortality population of children.     

Associations between socioeconomic status and cancer survival: choice of SES indicator may affect results

PURPOSE: Two previous studies, by Gorey et al. and Boyd et al., compared associations between socioeconomic status (SES) and cancer survival in Canada and the United States. Both studies used SES information from population censuses linked to cancer registries. This study investigates why two similar studies led to apparently conflicting results. METHODS: We conducted analyses following analytic details provided by the previously published studies to describe cancer survival in Toronto, Canada, and Detroit, MI. We examined the effects of choice of census indicators and census levels on the observed SES-related gradients in cancer survival. RESULTS: Significant associations between SES and cancer survival were observed in Toronto for several major disease sites when median household income was used as an SES indicator. Associations were weaker when a poverty indicator was used. In Detroit, similar SES gradients were observed by using both income and poverty as SES indicators. When SES quintiles were represented by income ranks, SES-associated survival gradients were much steeper in Detroit than Toronto. When SES was described by the median income in each quintile, gradients were similar in the two cities. CONCLUSIONS: The apparent contradiction in results of two previous studies is related to the choice of SES indicators. Poverty may not be an indicator of choice for such an intercountry comparison.     

A prospective study of childhood and adult socioeconomic status and incidence of type 2 diabetes in women

The influence of childhood socioeconomic status (SES) on incidence of type 2 diabetes mellitus has not previously been studied. The authors prospectively examined the association of childhood SES (father's occupation) with incidence of diabetes in 100,330 US women who were followed from 1980 to 2002. In 55,115 of those women, 10-year follow-up data (1992-2002) were also available on adult SES (spouse's education). In all, 6,916 new cases of type 2 diabetes were documented. Compared with women from white-collar occupational backgrounds, the multivariate-adjusted risks of diabetes were 1.08 (95% confidence interval (CI): 0.95, 1.23) among women whose fathers were laborers and 1.10 (95% CI: 1.03, 1.16) among women whose fathers were blue-collar or lower white-collar workers. Lower adult SES was associated with risk of diabetes independently of childhood SES. Compared with women whose spouses had graduate degrees, women whose spouses were high school graduates had a 1.16 times higher risk of incident diabetes (95% CI: 1.04, 1.29), while women whose spouses had college degrees were at 1.14 times the risk (95% CI: 1.01, 1.29). Compared with women with stable high SES from childhood to adulthood, women with declining SES had a 1.18 times higher risk of incident diabetes (95% CI: 1.06, 1.32). Higher body mass index among women with lower SES accounted for much of these rather modest associations between childhood and adult SES and risk of diabetes.     

Social class and the occurrence of traffic injuries and deaths in urban children

This paper examines motor vehicle traffic accident deaths and injuries to pedestrians and bicyclists (ICD-9 codes E813-E814) aged 0-14 years, by income quintile of area of residence. It is based on 92 deaths in urban Canada in 1981, 69 deaths in Montreal during the period 1979-1983, and 1,133 injuries which resulted in hospital care or police reports in Montreal in 1981. For injuries in Montreal, the pattern of socio-economic inequality in the annual incidence rates by quintile was very pronounced, completely regular and highly significant. The rate of injury to children living in the poorest neighbourhoods was four times that of children living in the least poor neighbourhoods. For both sexes, inequalities were much more pronounced for pedestrians compared to bicyclists. For deaths in Montreal and all of urban Canada, the inequality in the rates did not follow such a consistent pattern across the income quintiles, nor were the differences statistically significant in most cases, but the rates for each sex were consistently highest in the poorest income quintile. Socio-economic inequalities in the rates of death and injury were greater in girls than in boys. The results are discussed in the context of theories of etiology and strategies for prevention.     

An extended cost-effectiveness analysis of publicly financed HPV vaccination to prevent cervical cancer in China

IntroductionCervical cancer screening and existing health insurance schemes in China fall short of reaching women with prevention and treatment services, especially in rural areas where the disease burden is greatest. We conducted an extended cost-effectiveness analysis (ECEA) to evaluate public financing of HPV vaccination to prevent cervical cancer, adding new dimensions to conventional cost-effectiveness analysis through an explicit inclusion of equity and impact on financial risk protection.MethodsWe synthesized available epidemiological, clinical, and economic data from China using an individual-based Monte Carlo simulation model of cervical cancer to estimate the distribution of deaths averted by income quintile, comparing vaccination plus screening against current practice. We also estimated reductions in cervical cancer incidence, net costs to the government (HPV vaccination costs minus cervical cancer treatment costs averted), and patient cost savings, as well as the incremental government health care costs per death averted.ResultsHPV vaccination is cost-effective across all income groups when the cost is less than US $50 per vaccinated girl. Compared to screening alone, adding preadolescent HPV vaccination followed by cervical cancer screening in adulthood could reduce cancer by 44 percent across all income groups, while providing relatively higher financial protection to the poorest women. The absolute numbers of cervical cancer deaths averted and the financial risk protection from HPV vaccination are highest among women in the lowest quintile; women in the bottom income quintiles received higher benefits than those in the upper wealth quintiles. Patient cost savings represent a large proportion of poor women's average per capita income, reaching 60 percent among women in the bottom income quintile and declining to 15 percent among women in the wealthiest quintile.     

Racial and social class gradients in life expectancy in contemporary California

Life expectancy, or the estimated average age of death, is among the most basic measures of a population's health. However, monitoring differences in life expectancy among sociodemographically defined populations has been challenging, at least in the United States (US), because death certification does not include collection of markers of socioeconomic status (SES). In order to understand how SES and race/ethnicity independently and jointly affected overall health in a contemporary US population, we assigned a small-area-based measure of SES to all 689,036 deaths occurring in California during a three-year period (1999–2001) overlapping the most recent US census. Residence at death was geocoded to the smallest census area available (block group) and assigned to a quintile of a multifactorial SES index. We constructed life tables using mortality rates calculated by age, sex, race/ethnicity and neighborhood SES quintile, and produced corresponding life expectancy estimates. We found a 19.6 (±0.6) year gap in life expectancy between the sociodemographic groups with the longest life expectancy (highest SES quintile of Asian females; 84.9 years) and the shortest (lowest SES quintile of African–American males; 65.3 years). A positive SES gradient in life expectancy was observed among whites and African–Americans but not Hispanics or Asians. Age-specific mortality disparities varied among groups. Race/ethnicity and neighborhood SES had substantial and independent influences on life expectancy, underscoring the importance of monitoring health outcomes simultaneously by these factors. African–American males living in the poorest 20% of California neighborhoods had life expectancy comparable to that reported for males living in developing countries. Neighborhood SES represents a readily-available metric for ongoing surveillance of health disparities in the US.     

Suicide differentials in Australian males and females by various measures of socio-economic status, 1994-98

OBJECTIVES: To investigate Australian suicide differentials in males and females by three area-based measures of socio-economic status (SES). METHODS: Suicide data for 1994-98 were used to investigate area-based gradients of SES for the Index of Relative Socio-Economic Disadvantage (IRSED) (an overall measure of SES), the Index of Economic Resources (IER), and the Index of Education and Occupation (IEO), using Poisson regression models adjusting for age, country-of-birth and urban-rural residence. RESULTS: After adjusting for age, country-of-birth and urban-rural residence, significant increasing linear trends in suicide risk from high to low quintiles of SES were evident in males for the IRSED (an average multiplicative increase in suicide risk of 8% per quintile), IER (9% increase) and IEO (5% increase). For females, there was no evident SES gradient for the IRSED after adjusting for age, country-of-birth and urban-rural residence, but a significant positive linear trend from high to low quintiles of SES was found for the IER (6% increase per quintile). A significant decreasing linear trend (increasing suicide risk with increasing SES) was evident for the IEO (30% per quintle). CONCLUSION: Male suicide is positively associated with all three measures of SES examined. Female suicide is significantly associated with the IER (positive association) and IEO (negative), and because of this is not associated with the overall measure of SES. These findings partly explain why female suicide has been found to be poorly correlated with area-based measures of SES. IMPLICATIONS: Specific components of area-based socio-economic status provide a clearer picture of socio-economic suicide differentials in Australian females, with implications for population-based preventive strategies.     

Poverty,Marriage Timing,and Transitions to Adulthood in Nepal

This study examines the influence of household poverty during early childhood on schooling, workforce participation, and early marriage among adolescent girls in Nepal. Longitudinal data from the two‐wave panel of the Nepal Living Standards Survey (NLSS) were used to examine these relationships. For 5‐9‐year‐old girls contacted in NLSS I and again when aged 13–17 in NLSS II (N = 400), multinomial logit regression estimates indicate that household poverty during early childhood is associated with greater likelihood of marrying early or joining the workforce rather than remaining in school. Analyzing the data by household wealth quintiles reveals that these associations are largest for the second‐poorest quintile, not the poorest. This study highlights the role of household rather than individual characteristics in adolescent girls' decisionmaking.     

An evaluation of the Dietary Guidelines for Americans in relation to cancer occurrence

BACKGROUND: Although scientific knowledge regarding the influence of nutritional factors on health and disease serves as the basis for specific recommendations included in the Dietary Guidelines for Americans, limited empirical epidemiologic data are available to verify that adherence to the cluster of nutrition-related behaviors included in the Dietary Guidelines will reduce the incidence of disease. OBJECTIVE: We examined the association of compliance with the Dietary Guidelines and incident cancers. DESIGN: Data from a population-based cohort of postmenopausal women (n = 34 708) were examined. A dietary guidelines index was derived as a summary measure of compliance with the Dietary Guidelines, and the association of this index and cancer incidence was examined for all cancers combined and for site-specific cancers with > 100 events. RESULTS: For all cancers combined, the relative risks associated with the upper 4 quintiles of the dietary guidelines index in reference to the bottom quintile were 0.95 (95% CI: 0.87, 1.05) for quintile 2, 0.88 (95% CI: 0.80, 0.97) for quintile 3, 0.88 (95% CI: 0.80, 0.96) for quintile 4, and 0.85 (95% CI: 0.77, 0.93) for quintile 5 (P for trend < 0.01). Similar patterns in relative risks were found for cancers of the colon, bronchus and lung, breast, and uterus. In contrast, ovarian cancer incidence was positively associated with the dietary guidelines index. CONCLUSION: Our findings suggest that adherence to the cluster of nutrition-related behaviors included in the Dietary Guidelines for Americans may be associated with a lower risk of cancer.     

Survey error in measuring socio-economic risk factors of health status: a comparison of a survey and a census

BACKGROUND: Individuals of lower socio-economic status (SES) are less likely to participate in health surveys than individuals of a higher SES. It is, however, not known whether this difference in participation is associated with health status. This study sets out to assess whether a population health survey gives biased estimates of socio-economic inequalities in self-reported health. METHODS: We compared two independent cross-national data collections, a national health interview survey (n = 10,164) and a census (n = 8,491,528), both carried out in Belgium in 2001 and posing the same health question. We computed the prevalence ratios of poor subjective health among socio-economic groups. To estimate the bias, a relative odds ratio (ROR) was computed as the ratio of the survey prevalence ratio to the census prevalence ratio. RESULTS: Less-educated individuals had a lower risk of poor health status in the survey [Prevalence ratio = 1.66, 95% confidence interval (CI): 1.48-1.86] than in the census (Prevalence ratio = 2.23) leading to an underestimation of the risk associated with low education (ROR = 0.74, 95% CI 0.66-0.83). Compared with better-off groups, those who were not working or who were less educated were generally less likely to participate in the survey when they had a poor health status. CONCLUSIONS: Overall, the health survey underestimated the effects of low SES on poor health status, due to selection bias. We conclude that strategies to improve participation among disadvantaged socio-economic groups should be identified.     

The influence of neighborhood environment on the incidence of childhood asthma: a multilevel approach

Some ecological analyses suggest an influence of neighborhood environment on asthma outcomes. However, no previous study has applied a multilevel approach to assess an ecological effect of neighborhood environment on the incidence of childhood asthma accounting for individual risk factors. This study assessed the influence of neighborhood and individual-level factors on the incidence of childhood asthma among all children born in Rochester, Minnesota, between 1976 and 1979. We identified asthmatics among all children born in Rochester, between 1976 and 1983. We applied a multilevel survival model with the frailty term to assess the effects of neighborhood characteristics, such as mean family income per census tract (n = 16) from the 1980 census report and the status of whether a census tract faces intersections with major highways or railroads, on asthma incidence. The relative risks (RR) of neighborhood socioeconomic status (SES), the status of whether census tracts face intersections with highways or railroads and the variance of random effect of census tracts were calculated adjusting individual-level covariates for asthma, including gender, birth weight, mother's age at birth and parental educational level at birth. We found that the RR of developing asthma among children living in census tracts facing intersections with highways or railroads was 1.6 (95% CI: 1.1-2.2) compared to those who lived in census tracts not facing intersections, adjusting individual- and neighborhood-level covariates. The variance of the frailty term attributable to census tracts was small (0.0085) and was modified (from 0.004 to 0.0085, 112% change) by adding neighborhood covariates. The overall effects of individual-level factors on asthma incidence were independent of neighborhood environment. The influence of neighborhood environment on childhood asthma in a non-inner-city setting, like Rochester, Minnesota, was small to modest. Incorporating pertinent neighborhood-level covariates into multilevel models needs to be considered in assessing the random effect of clusters.     

Misclassification of income quintiles derived from area-based measures. A comparison of enumeration area and forward sortation area

BACKGROUND: Census-based methods are often used to estimate socioeconomic status. We assessed the agreement between Forward Sortation Area (FSA) and Enumeration Area (EA) derived income levels for all patients undergoing cardiac catheterization in Alberta, Canada, from 1995-1998. METHODS: Income quintiles were calculated from census data for FSA and EA level. FSA- and EA-derived income measures were compared for misclassification. Both methods were then applied to the data to determine 4-year survival by income grouping in 21,446 patients following catheterization. RESULTS: The variability in EA-derived incomes for any given FSA-derived income is large. Only 40% of income quintiles are in agreement between the methods. For EA-based analyses, there is a linear relationship between higher income and lower mortality across all quintiles, while for FSA-based analyses, only the lowest income quintile had significantly higher mortality. DISCUSSION: Assuming that FSA-based methods are more likely to misclassify income compared to EA-based measures, the results for the FSA-based analyses are more likely to be erroneous. EA-derived measures should therefore be used when individual data are not available.     

The nature of increased hospital use in poor neighbourhoods: findings from a Canadian inner city

The relationship between socioeconomic factors and hospital use is not well understood in the Canadian context. We used the 1991 Canada census and 1990-92 Ontario hospital discharge abstracts for residents of southeast Toronto to calculate crude and age-sex adjusted rates of hospital admission, bed days, and costs by quintile of low-income households. Population-based rates of admission to hospital, bed days and costs were all significantly related to census tract income (p < 0.01 for males and females). The number of admissions per person admitted was significantly associated with census tract income (p < 0.01 for males and females), but length of stay and resource intensity weight were not. Hospital costs were 50.0% higher for the poorest quintile of neighbourhoods than for the wealthiest and 35.8% higher than for the middle-income quintile. Poor urban neighbourhoods may require more resources than previously anticipated, related to higher hospital admission and readmission rates.     

Investigating socio-economic disparities in preterm birth: evidence for selective study participation and selection bias

Selective study participation can theoretically lead to selection bias. We explored this issue in the context of a multicentre cohort study of socio‐economic disparities in preterm birth. Women with singleton pregnancies were recruited from four large Montreal maternity hospitals and invited to return for an interview, vaginal examination and venepuncture at 24–26 weeks of gestation. We compared the observed preterm birth rate (ultrasound confirmed) among the 5146 cohort women to that expected based on all 108 724 Montreal Census Metropolitan Area (CMA) singleton births for 1998–2000. The observed preterm birth rate in the study cohort was 5.1%, compared with 6.3% in the CMA (P < 0.001) (unadjusted morbidity ratio [95% CI] = 0.80 [0.71, 0.90]). Within each stratum of maternal education and neighbourhood income (the latter based on postal code matched links to the 2001 Canadian census), cohort women had substantially lower rates of preterm birth than women from the CMA. No significant association between socio‐economic status (SES) and preterm birth was observed in the study cohort, except among ‘indicated’ (non‐spontaneous) cases. The association between neighbourhood income and preterm birth was biased to the null in the study cohort, with adjusted odds ratios in the poorest vs. richest quintiles of 1.01 [0.63, 1.64] in the cohort vs. 1.28 [1.18, 1.39] in the CMA, although no such bias was observed for the association with maternal education assessed at the individual level. We speculate that the lower‐than‐expected preterm birth rate and attenuated association between neighbourhood income and preterm birth may be related to selective participation by women more psychologically invested in their pregnancies. Investigators should consider the potential for biased associations in pregnancy/birth cohort studies, especially associations based on SES or race/ethnicity, and carry out sensitivity analyses to gauge their effects.     

Prognostic relevance of census-derived individual respondent incomes versus household incomes

BACKGROUND: Census-based measures of income derived from median income of a geographic area are often used in health research. Many national census surveys gather information on both the respondent's individual income and the income for the entire household, giving researchers a choice of census income measures. We compared the extent to which individual respondent income and household income (both obtained from census data) are associated with outcomes in a cohort of patients with cardiac disease. METHODS: We used data from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH), where postal codes were linked to the Postal Code Conversion File (PCCF) to determine each patient's census Dissemination Areas (DA). DA-derived median household income and median individual income were obtained from the 2001 Canadian Census and survival outcomes were then directly determined for income groupings defined by quintile. Two-year survival adjusted for age and sex was described with a proportional hazards analysis. RESULTS: There were 9,397 patients undergoing cardiac catheterization between January 1, 2001 and March 31, 2002, with complete DA-level median income measures. Household income quintiles yielded a wider spread of survival across quintiles (range of 2-year estimated survival, 91.8% to 95.9% for household income versus 92.8% to 95.6% for respondent income), as well as a more progressive decline in survival as income decreased. This progressive decline was not seen for the respondent income measure. CONCLUSIONS: The greater spread and progressive decline of survival for household income relative to respondent income leads us to conclude that household income is the better socio-economic determinant of health in our data and for the outcome measure we studied.     

Socio‐economic gradients in self‐reported diabetes for Indigenous and non‐Indigenous Australians aged 18–64

Objective : To examine and compare socio‐economic gradients in diabetes among Indigenous and non‐Indigenous Australians. Methods : I analysed weighted data on self‐reported diabetes and a range of socio‐economic status (SES) measures for 5,417 Indigenous and 15,432 non‐Indigenous adults aged 18–64 years from two nationally representative surveys conducted in parallel by the Australian Bureau of Statistics in 2004–05. Results : After adjusting for age, diabetes prevalence was significantly higher among those of lower SES in both Indigenous and non‐Indigenous populations. The age‐ and sex‐adjusted odds ratios (OR) for diabetes for the lowest versus the highest SES group were similar for the two populations on many variables. For example, the OR for the lowest quintile of equivalised household income (compared with quintiles 3–5 combined) was 2.3 (95% CI 1.6–3.4) for the Indigenous population and 2.0 (95% CI 1.5–2.8) for the non‐Indigenous population. However, Indigenous people of high SES had greater diabetes prevalence than low SES non‐Indigenous people on every SES measure examined. Conclusion : Socio‐economic status explains some but not all of the difference in diabetes prevalence between Indigenous and non‐Indigenous Australians. Other factors that may operate across the socio‐economic spectrum, such as racism, stress, loss and grief, may also be relevant and warrant further examination. Implications : Indigenous Australians do not constitute a homogeneous group with respect to socio‐economic status or diabetes prevalence, and this diversity must be recognised in developing measures to redress Indigenous health disadvantage.     

Socioeconomic status and lung cancer risk in Canada

BACKGROUND: Several epidemiological studies have found that lung cancer is inversely related to socioeconomic status (SES) and suggest it as a possible risk factor for lung cancer. This study examines SES and lung cancer risk in Canada. METHODS: Mailed questionnaires with telephone follow-up were used to obtain data on 3280 newly diagnosed, histologically confirmed lung cancer cases and 5073 population controls, between 1994 and 1997, in eight Canadian provinces. Measurement included information on SES, smoking habits, alcohol use, diet, residential and occupational histories and both residential and occupational exposure to environmental tobacco smoke (ETS). Odds ratios (OR) and 95% CI were derived from unconditional logistic regression analysis. RESULTS: Compared with high income adequacy, an increased risk was found among low income males and females, with adjusted OR of 1.7 (95% CI : 1.3-2.2) and 1.5 (95% CI : 1.1-2.0), respectively. Compared with < or = 8 years of education, the adjusted OR were 0.6 (95% CI : 0.5-0.7) and 0.6 (95% CI : 0.5-0.8) for > or = 14 years education among males and females, respectively. Lung cancer risk was significantly increased for males of some social classes. The population attributable risk for income adequacy, education and social class was 24%, 25% and 21% among males, respectively, and 14% and 19% for income adequacy and education among females, respectively, in this Canadian population. CONCLUSIONS: A statistically significant association between income adequacy, education social class and lung cancer risk was found.     

How socio-economic status contributes to participation in leisure-time physical activity

The aim of this cross-sectional study was to identify individual, social, and environmental contributors (mediators) to individual- and area-level differences in leisure-time physical activity across socio-economic groups. A two-stage stratified sampling design was used to recruit 20-65 year old adults (N=2194) living in 154 census collection districts of Adelaide, Australia (overall response rate: 12%). Participants completed two surveys six months apart (response rate on the second survey: 83%). Individual-level socio-economic status (SES) was assessed using self-report measures on educational attainment, household income, and household size. Area-level SES was assessed using census data on median household income and household size for each selected census district. Bootstrap generalized linear models were used to examine associations between SES, potential mediators, and leisure-time physical activity. The product-of-coefficient test was used to estimate mediating effects. All SES measures were independently associated with potential individual and social mediators of the SES-activity relationships. Individual- and area-level income was also associated with perceived neighborhood attributes. Self-efficacy and social support for physical activity explained virtually all of the differences in physical activity across educational attainment groups. Physical barriers to walking and access to public open space contributed in part to the explanation of differences in recreational walking across income groups. Yet, self-efficacy and social support were the key mediators of the observed relationships between individual- and area-level income and physical activity. This study suggests that in order to increase physical activity participation in the more disadvantaged segments of the population, comprehensive, multilevel interventions targeting activity-related attitudes and skills as well as social and physical environments are needed.