Long-term health conditions among household families in Aotearoa New Zealand: cross-sectional analysis of integrated Census and administrative data.

AIM: Little is known about the extent to which families in Aotearoa New Zealand are affected by long-term health conditions (HCs). This study aimed to explore the rates of nine selected HCs among New Zealand family members within the same household. METHOD: Linked population and administrative health data were obtained for families living in the same household according to the 2013 New Zealand Census (N=1,043,172). Health data (2008-2013) were used to ascertain whether people in these families (N=3,137,517) received treatment or services for nine selected HCs: cancer, chronic obstructive pulmonary disease, heart disease, diabetes, dementia, gout, stroke, traumatic brain injury (TBI), or mental health/behaviour conditions (MHBCs). RESULTS: Over 60% of families included at least one person with a HC, and this rate was higher among multi-generation families (73.9%). The most common HCs were MHBCs (39.4% of families), diabetes (16.0%) and TBI (13.9%). At the highest level of socio-economic deprivation, 57.6% of children aged under 18 years lived with a family member who had a HC. CONCLUSION: Three in five New Zealand household families included someone with at least one of nine selected HCs, with differences in the proportion affected according to family composition, socio-economic status and an individual's ethnicity. This suggests that there are a substantial number of people at risk of the poor outcomes associated with the experience of HCs within their family.

Does diabetes affect breast cancer survival?

OBJECTIVES: The objective of this study is to investigate the influence of diabetes on breast cancer-specific survival among women with breast cancer in Aotearoa/New Zealand. METHODS: This study included women diagnosed with invasive breast cancer between 2005 and 2020, with their information documented in the Te Rehita Mate Utaetae-Breast Cancer Foundation National Register. Breast cancer survival curves for women with diabetes and those without diabetes were generated using the Kaplan-Meier method. The hazard ratio (HR) of breast cancer-specific mortality for women with diabetes compared to women without diabetes was estimated using the Cox proportional hazards model. RESULTS: For women with diabetes, the 5-year and 10-year of cancer-specific survival were 87% (95% CI: 85%-88%) and 79% (95% CI: 76%-81%) compared to 89% (95% CI: 89%-90%) and 84% (95% CI: 83%-85%) for women without diabetes. The HR of cancer-specific mortality for patients with diabetes compared to those without diabetes was 0.99 (95% CI: 0.89-1.11) after adjustment for patient demographics, tumor characteristics, and treatments. Age at cancer diagnosis and cancer stage had the biggest impact on the survival difference between the two groups. When stratified by cancer stage, the cancer-specific mortality between the two groups was similar. CONCLUSIONS: While differences in survival have been identified for women with diabetes when compared to women without diabetes, these are attributable to age and the finding that women with diabetes tend to present with more advanced disease at diagnosis. We did not find any difference in survival between the two groups due to differences in treatment.

The growing cancer burden: Age-period-cohort projections in Aotearoa New Zealand 2020-2044.

BACKGROUND: Cancer is a major cause of premature death and inequity, and global case numbers are rapidly expanding. This study projects future cancer numbers and incidence rates in Aotearoa New Zealand. METHODS: Age-period-cohort modelling was applied to 25-years of national data to project cancer cases and incidence trends from 2020 to 2044. Nationally mandated cancer registry data and official historical and projected population estimates were used, with sub-groups by age, sex, and ethnicity. RESULTS: Cancer diagnoses were projected to increase from 25,700 per year in 2015-2019 to 45,100 a year by 2040-44, a 76% increase (2.3% per annum). Across the same period, age-standardised cancer incidence increased by 9% (0.3% per annum) from 348 to 378 cancers per 100,000 person years, with greater increases for males (11%) than females (6%). Projected incidence trends varied substantially by cancer type, with several projected to change faster or in the opposite direction compared to projections from other countries. CONCLUSIONS: Increasing cancer numbers reinforces the critical need for both cancer prevention and treatment service planning activities. Investment in developing new ways of working and increasing the workforce are required for the health system to be able to afford and manage the future burden of cancer.

Equity of Cancer and Diabetes Co-Occurrence: A National Study With 44 Million Person-Years of Follow-Up.

PURPOSE: The co-occurrence of diabetes and cancer is becoming increasingly common, and this is likely to compound existing inequities in outcomes from both conditions within populations. METHODS: In this study, we investigate the co-occurrence of cancer and diabetes by ethnic groups in New Zealand. National-level diabetes and cancer data on nearly five million individuals over 44 million person-years were used to describe the rate of cancer in a national prevalent cohort of peoples with diabetes versus those without diabetes, by ethnic group (Maori, Pacific, South Asian, Other Asian, and European peoples). RESULTS: The rate of cancer was greater for those with diabetes regardless of ethnic group (age-adjusted rate ratios, Maori, 1.37; 95% CI, 1.33 to 1.42; Pacific, 1.35; 95% CI, 1.28 to 1.43; South Asian, 1.23; 95% CI, 1.12 to 1.36; Other Asian, 1.31; 95% CI, 1.21 to 1.43; European, 1.29; 95% CI, 1.27 to 1.31). Maori had the highest rate of diabetes and cancer co-occurrence. Rates of GI, endocrine, and obesity-related cancers comprised a bulk of the excess cancers occurring among Maori and Pacific peoples with diabetes. CONCLUSION: Our observations reinforce the need for the primordial prevention of risk factors that are shared between diabetes and cancer. Also, the commonality of diabetes and cancer co-occurrence, particularly for Maori, reinforces the need for a multidisciplinary, joined-up approach to the detection and care of both conditions. Given the disproportionate burden of diabetes and those cancers that share risk factors with diabetes, action in these areas is likely to reduce ethnic inequities in outcomes from both conditions.

Impact of diabetes on surgery and radiotherapy for breast cancer.

PURPOSES: This study aims to examine whether diabetes has an impact on the use of surgery and adjuvant radiotherapy in treating women with localised breast cancer. METHODS: Women diagnosed with stage I-III breast cancer between 2005 and 2020 were identified from Te Rehita Mate Utaetae-Breast Cancer Foundation New Zealand National Register, with diabetes status determined using New Zealand's Virtual Diabetes Register. The cancer treatments examined included breast conserving surgery (BCS), mastectomy, breast reconstruction after mastectomy, and adjuvant radiotherapy after BCS. Logistic regression modelling was used to estimate the adjusted odds ratio (OR) and 95% confidence interval (95% CI) of having cancer treatment and treatment delay (> 31 days) for patients with diabetes at the time of cancer diagnosis compared to patients without diabetes. RESULTS: We identified 25,557 women diagnosed with stage I-III breast cancer in 2005-2020, including 2906 (11.4%) with diabetes. After adjustment for other factors, there was no significant difference overall in risk of women with diabetes having no surgery (OR 1.12, 95% CI 0.94-1.33), although for patients with stage I disease not having surgery was more likely (OR 1.45, 95% CI 1.05-2.00) in the diabetes group. Patients with diabetes were more likely to have their surgery delayed (adjusted OR of 1.16, 95% CI 1.05-1.27) and less likely to have reconstruction after mastectomy compared to the non-diabetes group-adjusted OR 0.54 (95% CI 0.35-0.84) for stage I cancer, 0.50 (95% CI 0.34-0.75) for stage II and 0.48 (95% CI 0.24-1.00) for stage III cancer. CONCLUSIONS: Diabetes is associated with a lower likelihood of receiving surgery and a greater delay to surgery. Women with diabetes are also less likely to have breast reconstruction after mastectomy. These differences need to be taken in to account when considering factors that may impact on the outcomes of women with diabetes especially for Maori, Pacific and Asian women.

Association of diabetes and breast cancer characteristics at diagnosis.

PURPOSE: This study aims to examine the association of diabetes and breast cancer characteristics at diagnosis in Aotearoa/New Zealand. METHODS: Patients diagnosed with invasive breast cancer between 2005 and 2020 were identified from the National Breast Cancer Register. Logistic regression modeling was used to estimate the adjusted odds ratio (OR) of having stage III-IV cancer and the OR of having stage IV cancer for women with diabetes compared to those without diabetes. The adjusted OR of having screen-detected breast cancers for patients aged 45-69 years with diabetes compared to patients without diabetes was estimated. RESULTS: 26,968 women were diagnosed with breast cancer, with 3,137 (11.6%) patients having diabetes at the time of cancer diagnosis. The probability of co-occurrence of diabetes and breast cancer increased with time. Maori, Pacific and Asian women were more likely to have diabetes than European/Others. The probability of having diabetes also increased with age. For patients with diabetes, the probability of being diagnosed with stage III-IV cancer and stage IV cancer was higher than for patients without diabetes (OR 1.14, 95% CI 1.03-1.27; and 1.17, 95% CI 1.00-1.38). Women aged 45-69 years with diabetes were more likely to have screen-detected cancer than those without diabetes (OR 1.13, 95% CI 1.02-1.26). CONCLUSIONS: The co-occurrence of diabetes and breast cancer is becoming more common. Overall there is a small but significant adverse impact of having advanced disease for women with diabetes that is found at the time of breast cancer diagnosis, and this may contribute to other inequities that occur in the treatment pathway that may impact on patient outcomes.

Cancer and diabetes co-occurrence: A national study with 44 million person-years of follow-up.

The number of new cases of cancer is increasing each year, and rates of diabetes mellitus are also increasing dramatically over time. It is not an unusual occurrence for an individual to have both cancer and diabetes at the same time, given they are both individually common, and that one condition can increase the risk of the other. In this manuscript, we use national-level diabetes (Virtual Diabetes Register) and cancer (New Zealand Cancer Registry) data on nearly five million individuals over 44 million person-years of follow-up to examine the occurrence of cancer amongst a national prevalent cohort of patients with diabetes. We completed this analysis separately by cancer for the 24 most commonly diagnosed cancers in Aotearoa New Zealand, and then compared the occurrence of cancer among those with diabetes to those without diabetes. We found that the rate of cancer was highest amongst those with diabetes for 21 of the 24 most common cancers diagnosed over our study period, with excess risk among those with diabetes ranging between 11% (non-Hodgkin's lymphoma) and 236% (liver cancer). The cancers with the greatest difference in incidence between those with diabetes and those without diabetes tended to be within the endocrine or gastrointestinal system, and/or had a strong relationship with obesity. However, in an absolute sense, due to the volume of breast, colorectal and lung cancers, prevention of the more modest excess cancer risk among those with diabetes (16%, 22% and 48%, respectively) would lead to a substantial overall reduction in the total burden of cancer in the population. Our findings reinforce the fact that diabetes prevention activities are also cancer prevention activities, and must therefore be prioritised and resourced in tandem.

Changing social inequalities in smoking, obesity and cause-specific mortality: Cross-national comparisons using compass typology.

BACKGROUND: In many countries smoking rates have declined and obesity rates have increased, and social inequalities in each have varied over time. At the same time, mortality has declined in most high-income countries, but gaps by educational qualification persist-at least partially due to differential smoking and obesity distributions. This study uses a compass typology to simultaneously examine the magnitude and trends in educational inequalities across multiple countries in: a) smoking and obesity; b) smoking-related mortality and c) cause-specific mortality. METHODS: Smoking prevalence, obesity prevalence and cause-specific mortality rates (35-79 year olds by sex) in nine European countries and New Zealand were sourced from between 1980 and 2010. We calculated relative and absolute inequalities in prevalence and mortality (relative and slope indices of inequality, respectively RII, SII) by highest educational qualification. Countries were then plotted on a compass typology which simultaneously examines trends in the population average rates or odds on the x-axis, RII on the Y-axis, and contour lines depicting SII. FINDINGS: Smoking and obesity. Smoking prevalence in men decreased over time but relative inequalities increased. For women there were fewer declines in smoking prevalence and relative inequalities tended to increase. Obesity prevalence in men and women increased over time with a mixed picture of increasing absolute and sometimes relative inequalities. Absolute inequalities in obesity increased for men and women in Czech Republic, France, New Zealand, Norway, for women in Austria and Lithuania, and for men in Finland. Cause-specific mortality. Average rates of smoking-related mortality were generally stable or increasing for women, accompanied by increasing relative inequalities. For men, average rates were stable or decreasing, but relative inequalities increased over time. Cardiovascular disease, cancer, and external injury rates generally decreased over time, and relative inequalities increased. In Eastern European countries mortality started declining later compared to other countries, however it remained at higher levels; and absolute inequalities in mortality increased whereas they were more stable elsewhere. CONCLUSIONS: Tobacco control remains vital for addressing social inequalities in health by education, and focus on the least educated is required to address increasing relative inequalities. Increasing obesity in all countries and increasing absolute obesity inequalities in several countries is concerning for future potential health impacts. Obesity prevention may be increasingly important for addressing health inequalities in some settings. The compass typology was useful to compare trends in inequalities because it simultaneously tracks changes in rates/odds, and absolute and relative inequality measures.

An estimate of limited duration cancer prevalence in New Zealand using 'big' data.

AIMS: Increases in cancer survival may increase cancer prevalence and demand for healthcare. We aimed to estimate cancer prevalence in the New Zealand population. METHODS: We used national linked health, social and census datasets from the Stats NZ Integrated Data Infrastructure to identify the number of New Zealand residents who had at least one cancer diagnosis in New Zealand. We included all primary cancers recorded on the New Zealand Cancer Registry from January 1995 to June 2013, and used the 2013 census for demographic and socioeconomic data. RESULTS: On 30 June 2013, 140,600 of 4,438,900 (3.2%) New Zealand residents had been diagnosed with cancer in the last 18.5 years. In ≥15 year olds, the age-standardised prevalence of cancer diagnosed 0 to ≤1 year, and >1 to ≤5 years, prior to 30 June 2013 was 0.4% and 1.1% in men and 0.3% and 0.9% in women, respectively. Over the 18.5-year period prevalence was greatest in the oldest ages, European/Other, highest qualified, highest income, least deprived, ex-smokers, and Canterbury, Bay of Plenty and Nelson/Marlborough District Health Boards (age-standardised). CONCLUSIONS: Groups with the highest survival and the greatest access to healthcare had the highest cancer prevalences.

Cancer control in the Pacific: big challenges facing small island states.

This Series paper describes the current state of cancer control in Pacific island countries and territories (PICTs). PICTs are diverse but face common challenges of having small, geographically dispersed, isolated populations, with restricted resources, fragile ecological and economic systems, and overburdened health services. PICTs face a triple burden of infection-related cancers, rapid transition to lifestyle-related diseases, and ageing populations; additionally, PICTs are increasingly having to respond to natural disasters associated with climate change. In the Pacific region, cancer surveillance systems are generally weaker than those in high-income countries, and patients often present at advanced cancer stage. Many PICTs are unable to provide comprehensive cancer services, with some patients receiving cancer care in other countries where resources allow. Many PICTs do not have, or have poorly developed, cancer screening, pathology, oncology, surgical, and palliative care services, although some examples of innovative cancer planning, prevention, and treatment approaches have been developed in the region. To improve cancer outcomes, we recommend prioritising regional collaborative approaches, enhancing cervical cancer prevention, improving cancer surveillance and palliative care services, and developing targeted treatment capacity in the region.

Socioeconomic and Tobacco Mediation of Ethnic Inequalities in Mortality over Time: Repeated Census-mortality Cohort Studies, 1981 to 2011.

BACKGROUND: Racial/ethnic inequalities in mortality may be reducible by addressing socioeconomic factors and smoking. To our knowledge, this is the first study to estimate trends over multiple decades in (1) mediation of racial/ethnic inequalities in mortality (between Maori and Europeans in New Zealand) by socioeconomic factors, (2) additional mediation through smoking, and (3) inequalities had there never been smoking. METHODS: We estimated natural (1 and 2 above) and controlled mediation effects (3 above) in census-mortality cohorts for 1981-1984 (1.1 million people), 1996-1999 (1.5 million), and 2006-2011 (1.5 million) for 25- to 74-year-olds in New Zealand, using a weighting of regression predicted outcomes. RESULTS: Socioeconomic factors explained 46% of male inequalities in all three cohorts and made an increasing contribution over time among females from 30.4% (95% confidence interval = 18.1%, 42.7%) in 1981-1984 to 41.9% (36.0%, 48.0%). Including smoking with socioeconomic factors only modestly altered the percentage mediated for males, but more substantially increased it for females, for example, 7.7% (5.5%, 10.0%) in 2006-2011. A counterfactual scenario of having eradicated tobacco in the past (but unchanged socioeconomic distribution) lowered mortality for all sex-by-ethnic groups and resulted in a 12.2% (2.9%, 20.8%) and 21.2% (11.6%, 31.0%) reduction in the absolute mortality gap between Maori and Europeans in 2006-2011, for males and females, respectively. CONCLUSIONS: Our study predicts that, in this high-income country, reducing socioeconomic disparities between ethnic groups would greatly reduce ethnic inequalities in mortality over the long run. Eradicating tobacco would notably reduce ethnic inequalities in absolute but not relative mortality.

Changing smoking-mortality association over time and across social groups: National census-mortality cohort studies from 1981 to 2011.

The difference in mortality between current and never-smokers varies over time, affecting future projections of health gains from tobacco control. We examine this heterogeneity by sex, ethnicity and cause of death on absolute and relative scales using New Zealand census data. These data included smoking status, and were linked to subsequent mortality records in 1981-84, 1996-99 and 2006-11 for 25-74 year olds (16.1 million person-years of follow-up). Age-standardised mortality rates and rate differences (SRDs) were calculated comparing current to never-smokers, and Poisson regression was used to adjust for multiple socioeconomic factors and household smoking. We found that mortality declined over time in never-smokers; however, mortality trends in current-smokers varied by sex, ethnicity and cause of death. SRDs were stable over time in European/Other men, moderately widened in European/Other women and markedly increased in Maori men and women (Indigenous population). Poisson smoking-mortality rate ratios (RRs) increased from 1981-84 to 1996-99 with a moderate increase from 1996-99 to 2006-11 (RRs 1.48, 1.77, 1.79 in men and 1.51, 1.80, 1.90 in women). Socioeconomic confounding increased over time. In summary, this marked heterogeneity in smoking-mortality RRs over time has implications for estimating the future health and inequality impacts of tobacco control interventions.

Changing ethnic inequalities in mortality in New Zealand over 30 years: linked cohort studies with 68.9 million person-years of follow-up.

BACKGROUND: Internationally, ethnic inequalities in mortality within countries are increasingly recognized as a public health concern. But few countries have data to monitor such inequalities. We aimed to provide a detailed description of ethnic inequalities (Maori [indigenous], Pacific, and European/Other) in mortality for a country with high quality ethnicity data, using both standard and novel visualization methods. METHODS: Cohort studies of the entire New Zealand population were conducted, using probabilistically-linked Census and mortality data from 1981 to 2011 (68.9 million person years). Absolute (standardized rate difference) and relative (standardized rate ratio) inequalities were calculated, in 1-74-year-olds, for Maori and Pacific peoples in comparison to European/Other. RESULTS: All-cause mortality rates were highest for Maori, followed by Pacific peoples then European/Other, and declined in all three ethnic groups over time. Pacific peoples experienced the slowest annual percentage fall in mortality rates, then Maori, with European/Other having the highest percentage falls - resulting in widening relative inequalities. Absolute inequalities, however, for both Maori and Pacific males compared to European/Other have been falling since 1996. But for females, only Maori absolute inequalities (compared with European/Other) have been falling. Regarding cause of death, cancer is becoming a more important contributor than cardiovascular disease (CVD) to absolute inequalities, especially for Maori females. CONCLUSIONS: We found declines in all-cause mortality rates, over time, for each ethnic group of interest. Ethnic mortality inequalities are generally stable or even falling in absolute terms, but have increased on a relative scale. The drivers of these inequalities in mortality are transitioning over time, away from CVD to cancer and diabetes; such transitions are likely in other countries, and warrant further research. To address these inequalities, policymakers need to enhance prevention activities and health care delivery, but also support wider improvements in educational achievement and socioeconomic position for highest need populations.

A Typology for Charting Socioeconomic Mortality Gradients: "Go Southwest".

BACKGROUND: Holistic depiction of time-trends in average mortality rates, and absolute and relative inequalities, is challenging. METHODS: We outline a typology for situations with falling average mortality rates (m↓; e.g., cardiovascular disease), rates stable over time (m-; e.g., some cancers), and increasing average mortality rates (m↑; e.g., suicide in some contexts). If we consider inequality trends on both the absolute (a) and relative (r) scales, there are 13 possible combination of m, a, and r trends over time. They can be mapped to graphs with relative inequality (log relative index of inequality [RII]; r) on the y axis, log average mortality rate on the x axis (m), and absolute inequality (slope index of inequality; SII; a) as contour lines. We illustrate this by plotting adult mortality trends: (1) by household income from 1981 to 2011 for New Zealand, and (2) by education for European countries. RESULTS: Types range from the "best" m↓a↓r↓ (average, absolute, and relative inequalities all decreasing; southwest movement in graphs) to the "worst" m↑a↑r↑ (northeast). Mortality typologies in New Zealand (all-cause, cardiovascular disease, nonlung cancer, and unintentional injury) were all m↓r↑ (northwest), but variable with respect to absolute inequality. Most European typologies were m↓r↑ types (northwest; e.g., Finland), but with notable exceptions of m-a↑r↑ (north; e.g., Hungary) and "best" or southwest m↓a↓r↓ for Spain (Barcelona) females. CONCLUSIONS: Our typology and corresponding graphs provide a convenient way to summarize and understand past trends in inequalities in mortality, and hold potential for projecting future trends and target setting.

A screening program to test and treat for Helicobacter pylori infection: Cost-utility analysis by age, sex and ethnicity.

BACKGROUND: The World Health Organization recommends all countries consider screening for H. pylori to prevent gastric cancer. We therefore aimed to estimate the cost-effectiveness of a H. pylori serology-based screening program in New Zealand, a country that includes population groups with relatively high gastric cancer rates. METHODS: A Markov model was developed using life-tables and morbidity data from a national burden of disease study. The modelled screening program reduced the incidence of non-cardia gastric cancer attributable to H. pylori, if infection was identified by serology screening, and for the population expected to be reached by the screening program. A health system perspective was taken and detailed individual-level costing data was used. RESULTS: For adults aged 25-69 years old, nation-wide screening for H. pylori was found to have an incremental cost of US$196 million (95% uncertainty interval [95% UI]: $182-$211 million) with health gains of 14,200 QALYs (95% UI: 5,100-26,300). Cost per QALY gained was US$16,500 ($7,600-$38,400) in the total population and 17% (6%-29%) of future gastric cancer cases could be averted with lifetime follow-up. A targeted screening program for Maori only (indigenous population), was more cost-effective at US$8,000 ($3,800-$18,500) per QALY. CONCLUSIONS: This modeling study found that H. pylori screening was likely to be cost-effective in this high-income country, particularly for the indigenous population. While further research is needed to help clarify the precise benefits, costs and adverse effects of such screening programs, there seems a reasonable case for policy-makers to give pilot programs consideration, particularly for any population groups with relatively elevated rates of gastric cancer.

Changing socioeconomic inequalities in cancer incidence and mortality: Cohort study with 54 million person-years follow-up 1981-2011.

Cancer is increasingly responsible for the mortality gap between high and low socioeconomic position groups in high-income countries. This study investigates which cancers are contributing more to socioeconomic gaps in mortality and how this changes over time.New Zealand census data from 1981, 1986, 1991, 1996, 2001 and 2006, were linked to three to five years of subsequent mortality and cancer registrations, resulting in 54 and 42 million years of follow-up cancer incidence and mortality, respectively. Age- and ethnicity-standardised cancer mortality rates and the slope index of inequality (SII) by income were calculated.The contribution of cancer to absolute inequalities (SII) in mortality increased from 16 to 27% for men and from 12 to 31% for women from 1981-84 to 2006-11, peaking in 1991-94 for men and in 1996-99 for women and then levelling off, parallel to peaks in lung cancer inequalities. Lung cancer was the largest driver of cancer inequality trends (49% of the cancer mortality gap in 1981-84 to 33% in 2006-11 for men and 32 to 33% for women) followed by colorectal cancer in men (2 to 11%) and breast cancer in women (declining from 44 to 13%). Women in the lowest income quintile experienced no decline in cancer mortality.The contribution of cancer to income inequalities in all-cause mortality has expanded in this high-income country. Action to address socioeconomic inequalities should prioritise equitable tobacco control, obesity control and improved access to cancer screening, early diagnosis and high quality treatment for those with the lowest incomes.

The contribution of Helicobacter pylori to excess gastric cancer in Indigenous and Pacific men: a birth cohort estimate.

BACKGROUND: The reasons for higher gastric cancer incidence rates in indigenous populations are debated. METHODS: We quantify the role of Helicobacter pylori in excess gastric cancer incidence in Maori and Pacific men in New Zealand. Age-standardized gastric cancer rate ratios for 1981-2004 were calculated in Maori and Pacific men compared with European/other men born in 1926-1940 and in 1941-1955. Rate ratios were then compared with those restricted to H. pylori prevalent populations. RESULTS: H. pylori contributed substantially to excess gastric cancer incidence in Maori men (50%, 61%) and Pacific men (71%, 82%) in both cohorts. CONCLUSIONS: Policy should focus on reducing the acquisition and prevalence of H. pylori infection in these populations.

Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up.

BACKGROUND: Cancer makes up a large and increasing proportion of excess mortality for indigenous, marginalised and socioeconomically deprived populations, and much of this inequality is preventable. This study aimed to determine which cancers give rise to changing ethnic inequalities over time. METHODS: New Zealand census data from 1981, 1986, 1991, 1996, 2001, and 2006, were all probabilistically linked to three to five subsequent years of mortality (68 million person-years) and cancer registrations (87 million person years) and weighted for linkage bias. Age-standardised rate differences (SRDs) for Maori (indigenous) and Pacific peoples, each compared to European/Other, were decomposed by cancer type. RESULTS: The absolute size and percentage of the cancer contribution to excess mortality increased from 1981-86 to 2006-11 in Maori males (SRD 72.5 to 102.0 per 100,000) and females (SRD 72.2 to 109.4), and Pacific females (SRD -9.8 to 42.2) each compared to European/Other. Specifically, excess mortality (SRDs) increased for breast cancer in Maori females (linear trend p < 0.01) and prostate (p < 0.01) and colorectal cancers (p < 0.01) in Maori males. The incidence gap (SRDs) increased for breast (Maori and Pacific females p < 0.01), endometrial (Pacific females p < 0.01) and liver cancers (Maori males p = 0.04), and for cervical cancer it decreased (Maori females p = 0.03). The colorectal cancer incidence gap which formerly favoured Maori, decreased for Maori males and females (p < 0.01). The greatest contributors to absolute inequalities (SRDs) in mortality in 2006-11 were lung cancer (Maori males 50 %, Maori females 44 %, Pacific males 81 %), breast cancer (Maori females 18 %, Pacific females 23 %) and stomach cancers (Maori males 9 %, Pacific males 16 %, Pacific females 20 %). The top contributors to the ethnic gap in cancer incidence were lung, breast, stomach, endometrial and liver cancer. CONCLUSIONS: A transition is occurring in what diseases contribute to inequalities. The increasing excess incidence and mortality rates in several obesity- and health care access-related cancers provide a sentinel warning of the emerging drivers of ethnic inequalities. Action to further address inequalities in cancer burden needs to be multi-pronged with attention to enhanced control of tobacco, obesity, and carcinogenic infectious agents, and focus on addressing access to effective screening and quality health care.