Caroline Shaw

Patterns of Disparity: Ethnic and Socio-economic Trends in Breast Cancer Mortality in New Zealand

ObjectiveTo test whether trends in breast cancer mortality varied by ethnicity and socio-economic position during the 1980s and ‘90s in New Zealand.MethodsFour cohorts of the entire New Zealand population for 1981–84; 86–89; 91–94 and 96–99 allowed direct determination of socio-economic trends in breast cancer mortality. For ethnicity, unlinked routine census and mortality data were used with adjustment factors for undercounting of Māori and Pacific deaths.ResultsMāori and non-Māori non-Pacific mortality rates changed little until mid-1990s with Māori experiencing 25% higher mortality. In 1996–99, Māori rates increased notably to become 68% higher than non-Māori non-Pacific (SRR 1.68; 95% CI: 1.49–1.90). Pacific women experienced an approximate three-fold increase in breast cancer mortality over time.There appeared to be reducing mortality among higher income and education groups but trends within socio-economic groups were not statistically significant. Nevertheless, by 1996–99, there was a significant 22% excess mortality (SRR 1.22; 95% CI: 1.01–1.49) for low compared with high-income groups.ConclusionsWidening ethnic, and probably, socio-economic disparities in breast cancer mortality are likely due to both underlying incidence and differential survival trends. Disparities are likely to increase once the full differential mortality benefits of screening impact on the population.

Do social and economic reforms change socioeconomic inequalities in child mortality? A case study: New Zealand 1981–1999

Background: Socioeconomic inequalities in child mortality are known to exist; however the trends in these inequalities have not been well examined. This study examines the trends in child mortality inequality between 1981 and 1999 against the background of the rapid and dramatic social and economic restructuring in New Zealand during this time period. Methods: Record linkage studies of census and mortality records of all New Zealand children aged 0–14 years on census night 1981, 1986, 1991, 1996, each followed up for three years for mortality between ages 1–14 years. Socioeconomic position was measured using maternal education, household income, and highest occupational class in the household. Standardised mortality rates, rate ratios, and rates differences as well as regression based measures of inequality were calculated. Results: Mortality in all socioeconomic groups fell between 1981 and 1999. Socioeconomic inequality in child mortality existed by all measures of socioeconomic position, however only trends by income suggested a change over time: the relative index of inequality increased from 1.5 in 1981–84 to 1.8 in 1996–99 (p trend 0.06), but absolute inequality remained stable (slope index of inequality 15/100 000 in 1981–84 and 14/100 000 in 1996–99. Conclusions: Dramatic changes in income in New Zealand possibly translated into increasing relative inequality in child mortality by income, but not by education or occupational class. The a priori hypothesis that socioeconomic inequalities in child mortality would have increased in New Zealand during a period of rapid structural reform and widening income inequalities was only partly supported.

Social inequalities or inequities in cancer incidence? Repeated census-cancer cohort studies, New Zealand 1981–1986 to 2001–2004

BackgroundWe examine incidence trends for 18 adult cancers, by ethnicity and socioeconomic position in New Zealand.MethodsThe 1981 to 2001 censuses were linked to subsequent cancer registrations, giving 47.5 million person-years of follow-up.ResultsEthnicity: Pooled over time, differences were marked: Pacific and Māori rates of cervical, endometrial, stomach and pancreatic cancers were 1.5–2.5 times European/Other rates; Māori, Pacific and Asian rates of liver cancer were 5 times European/Other; European/Other rates of colorectal, bladder and brain cancers were 1.5–2 times the rates of other groups and melanoma rates 5–10 times higher; Pacific and Asian kidney cancer rates were half those of Māori and European/Other.Over time, Māori and Pacific rates of cervical cancer fell faster and Māori rates of colorectal and breast cancer increased faster, than European/Other rates. Male lung cancer rates decreased for European/Other, were stable for Māori and increased for Pacific. Female lung cancer rates increased for all ethnic groups.Income: Other than lung (rate ratio 1.35 men, 1.56 women), cervical (1.35) and stomach cancer (1.23), differences in incidence by income were modest or absent.ConclusionsTobacco explains many of the social group trends and differences and constitutes an inequity. Cervical cancer trends are plausibly explained by screening and sexual practices. Faster increases of colorectal and breast cancer among Māori are presumably due to changes in dietary and reproductive behaviour, but the higher Māori breast cancer rate is unexplained.Ethnic differences in bladder, brain, endometrial and kidney cancer cannot be fully explained.

Ethnic and socioeconomic trends in breast cancer incidence in New Zealand

BackgroundBreast cancer incidence varies between social groups, but differences have not been thoroughly examined in New Zealand. The objectives of this study are to determine whether trends in breast cancer incidence varied by ethnicity and socioeconomic position between 1981 and 2004 in New Zealand, and to assess possible risk factor explanations.MethodsFive cohorts of the entire New Zealand population for 1981-86, 1986-1991, 1991-1996, 1996-2001, and 2001-2004 were created, and probabilistically linked to cancer registry records, allowing direct determination of ethnic and socioeconomic trends in breast cancer incidence.ResultsBreast cancer rates increased across all ethnic and socioeconomic groups between 1981 and 2004. Māori women consistently had the highest age standardised rates, and the difference between Māori and European/Other women increased from 7% in 1981-6 to 24% in 2001-4. Pacific and Asian women had consistently lower rates of breast cancer than European/Other women over the time period studied (12% and 28% lower respectively when pooled over time), although young Pacific women had slightly higher incidence rates than young European/other women. A gradient between high and low income women was evident, with high income women having breast cancer rates approximately 10% higher and this difference did not change significantly over time.ConclusionsDifferences in breast cancer incidence between European and Pacific women and between socioeconomic groups are explicable in terms of known risk factors. However no straightforward explanation for the relatively high incidence amongst Māori is apparent. Further research to explore high Māori breast cancer rates may contribute to reducing the burden of breast cancer amongst Māori women, as well as improving our understanding of the aetiology of breast cancer.

Trends in colorectal cancer mortality by ethnicity and socio-economic position in New Zealand, 1981-99: one country, many stories

Background:Ethnicity and socio‐economic position are important determinants of colorectal cancer (CRC) mortality. In this paper, we determine trends in colorectal cancer mortality by ethnicity and socioeconomic position in New Zealand.

Ethnic and socioeconomic trends in testicular cancer incidence in New Zealand

Ethnic differences in testicular cancer incidence within countries are often sizeable, with white populations consistently having the highest ethnic‐specific rates. Many studies have found that high socioeconomic status is a risk factor for testicular cancer. The objectives of this article are to test whether trends in testicular cancer incidence have varied by ethnicity and socioeconomic position in New Zealand between 1981 and 2004. Five cohorts of the entire New Zealand population for 1981–1986, 1986–1991, 1991–1996, 1996–2001 and 2001–2004 were created, and probabilistically linked to cancer registry records, allowing direct determination of ethnic and household income trends in testicular cancer incidence. There were more than 2,000 cases of testicular cancer over the study period. We found increasing rates of testicular cancer for all ethnic and income groups since 1990s. Maori had higher rates, and Pacific and Asian lower rates than European/other men with rate ratios pooled over time of 1.51 (95% CI 1.31–1.74), 0.40 (95% CI 0.26–0.61) and 0.54 (95% CI 0.31–0.94), respectively. Overall, men with low incomes had higher risk of testicular cancer than those with high incomes (pooled rate ratio for lowest to highest income groups = 1.23; 95% CI 1.05–1.44). There was no strong evidence that disparities in testicular cancer incidence have varied by ethnicity or household income over time. Given the lack of understanding of the etiology of testicular cancer, the unusual patterns identified in the New Zealand context may provide some etiological clues for future novel research.

How Does Self-Reported History of Stroke Compare to Hospitalization Data in a Population-Based Survey in New Zealand?

Background and Purpose— There is mixed evidence concerning the validity of self-reported history of stroke in population-based studies. We aimed to examine the validity of self-reported stroke using hospitalization with a primary diagnosis of stroke as the reference group. Methods— Self-reported history of stroke was taken from the Survey of Families, Income, and Employment (N=18 950; 2004–2005) and defined as a respondent answering yes to the question, “Have you ever been told by a doctor that you have had a stroke?”. Survey of Families, Income, and Employment respondents consented to link their data to the New Zealand Health Information Service records of publically funded hospitalizations between 1990 and 2006. We calculated positive predictive value, sensitivity, and specificity of self-reported stroke against hospitalization for stroke. Results— Approximately 2% of the adult Survey of Families, Income, and Employment population reported they had been told by a doctor that they had a stroke. Only 1% had evidence of hospitalization for stroke since 1990. The sensitivity of self-reported stroke was 73% and specificity was 98%. However, the positive predictive value, people who reported having a stroke with confirmation of hospitalization for stroke, was low at 29%. Conclusions— The use of self-reported stroke will most likely overestimate the prevalence of stroke. A combination of methods is required to determine prevalence in population-based studies.

Risk factors for cryptorchidism

Undescended testis — known as cryptorchidism — is one of the most common congenital abnormalities observed in boys, and is one of the few known risk factors for testicular cancer. The key factors that contribute to the occurrence of cryptorchidism remain elusive. Testicular descent is thought to occur during two hormonally-controlled phases in fetal development — between 8–15 weeks (the first phase of decent) and 25–35 weeks gestation (the second phase of descent); the failure of a testis to descend permanently is probably caused by disruptions to one or both of these phases, but the causes and mechanisms of such disruptions are still unclear. A broad range of putative risk factors have been evaluated in relation to the development of cryptorchidism but their plausibility is still in question. Consistent evidence of an association with cryptorchidism exists for only a few factors, and in those cases in which evidence seems unequivocal the factor is likely to be a surrogate for the true causal exposure. The relative importance of each risk factor could vary considerably between mother–son pairs depending on an array of genetic, maternal, placental and fetal factors — all of which could vary between regions. Thus, the role of causative factors in aetiology of cryptorchidism requires further research.

Understanding the determinants of consent for linkage of administrative health data with a longitudinal survey

Abstract The Survey of Families, Income and Employment (SoFIE) is a panel income study with a health component, including data linkage to national health databases. This paper investigates factors that predict consent to data linkage. SoFIE participants were asked permission to link their SoFIE records to administrative health data in Wave 3 of data collection. Logistic regression was used to investigate the association of sociodemographic variables with consent to record linkage. Of Wave 3 participants 79.4% consented to health record linkage. Taking into account prior attrition, consent and matching the overall participation rate was 60.9%. Participants reporting Māori, Pacific and Asian ethnicity had lower odds of consenting. There was a strong relationship between the presence of co-morbid disease and consent to linkage. This study has shown that consent to link health information to survey records was high and the survey provides a rich and unique dataset for longitudinal analyses.

Commentary: Inequalities in cancer screening programmes

Screening for cancer is intuitively attractive. Well-run cancer screening programmes can save lives, reduce morbidity, provide reassurance to individuals about their health and encourage a focus on prevention and early detection. Despite the intuitive appeal, the harmful effects of screening (both potential and actual) are well documented. Harm to an individual includes over-diagnosis and treatment of questionable abnormalities, anxiety for those with false positive results and false reassurance for those with false negative results. One of the important, but often not well articulated, harmful effects at a population level is the potential for cancer screening to increase health inequalities between population groups. Screening can be divided into two types. First, there are ‘organized screening’ programmes, which work within pre-agreed structures, policies and standards, and typically focus on mortality reduction for screened individuals. Secondly, there is ‘opportunistic screening’ where screening occurs either as a result of a request from an individual or from contact with a health professional who offers the screening test. In this issue, Palencia et al. combine individual-level data from the WHO World Health Survey covering 22 European countries, with information about the organizational structures of breast and cervical cancer screening programmes within countries, to examine in multi-level analyses whether socioeconomic disparities in breast and cervical screening participation are affected by the type of screening offered. They found that for breast cancer screening, there was higher participation in screening in countries with organized programmes, but no such pattern was seen for cervical cancer screening. For both breast and cervical cancers, socio-economic inequalities in participation measured both on relative and absolute scales were more likely to be found in countries without organized screening programmes. One of the arguments for organized screening is that participation rates are likely to be optimized. Therefore, the finding that cervical cancer screening participation was not affected by the type of screening was surprising. It is worth noting that, while in the study by Palencia et al. participation in cervical screening was measured using a cut-off point of screening in the previous 3 years, all five countries with national (organized) cervical screening programmes recommend intervals of 5 years for at least some women (in the UK, Denmark and Sweden recommendations vary by age). In contrast, almost all of the countries included in this study with opportunistic screening recommend screening intervals of 1–3 years. As a consequence, it is possible that screening participation was underestimated in countries with organized screening. This is not true for breast cancer screening as almost all countries, regardless of how screening is organized, recommend screening at either a 2or 3-year interval. Four other important points should be made. First, while the paper by Palencia et al. focuses on socioeconomic inequalities determined by education level, such inequalities can occur on many axes e.g. ethnicity, gender, geography, age, sexuality and disability. Although most social determinants of health are not controlled by the health sector, there is increasing evidence that health-care systems, including screening programmes, can actively alter inequalities in health outcomes. The ‘inverse equity hypothesis’ describes how inequalities in health care occur as new health interventions are introduced. This theory suggests that as a new intervention is introduced into a population, those that are most deprived, and usually most in need of the intervention, are most likely to take it up later and at a lower rate than more privileged groups. An example of this hypothesis in action occurred with the introduction of the breast cancer screening programme in Published by Oxford University Press on behalf of the International Epidemiological Association