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

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ABSTRACT

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 Māori (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 Māori 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.

Results: Specifically, excess mortality (SRDs) increased for breast cancer in Māori females (linear trend p < 0.01) and prostate (p < 0.01) and colorectal cancers (p < 0.01) in Māori males. The incidence gap (SRDs) increased for breast (Māori and Pacific females p < 0.01), endometrial (Pacific females p < 0.01) and liver cancers (Māori males p = 0.04), and for cervical cancer it decreased (Māori females p = 0.03). The colorectal cancer incidence gap which formerly favoured Māori, decreased for Māori males and females (p < 0.01).

Results: The greatest contributors to absolute inequalities (SRDs) in mortality in 2006–11 were lung cancer (Māori males 50 %, Māori females 44 %, Pacific males 81 %), breast cancer (Māori females 18 %, Pacific females 23 %) and stomach cancers (Māori 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.

Electronic supplementary material: The online version of this article (doi:10.1186/s12885-016-2781-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

Decomposition of absolute ethnic inequalities in cancer mortality by major contributing cancer types, comparing Māori and Pacific peoples with European/Other in males and females aged 1–74 years in New Zealand. *Note some cancer types are excluded due to small numbers
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Fig3: Decomposition of absolute ethnic inequalities in cancer mortality by major contributing cancer types, comparing Māori and Pacific peoples with European/Other in males and females aged 1–74 years in New Zealand. *Note some cancer types are excluded due to small numbers

Mentions: Table 1 shows ethnic inequalities in cancer mortality increased from 1981 to 2011 particularly in females. For example, in the 2006–11 cohort, the overall mortality rate from cancer was 202.0 per 100 000 Māori females and 92.6 in European/Other, an overall SRD of 109.4 excess deaths per 100 000 (Table 1; and the net height of the 2006–11 bar in Fig. 3, SRD = 114 – 5). From 1981–84 to 2006–11 the cancer mortality in European/Other females decreased significantly from 110.6 to 92.6 per 100 000 population (p = 0.01) but the cancer mortality rate for Māori females appeared to have increased (182.8 to 202.0, p = 0.09). Subsequently, absolute inequalities (SRD) for Māori females increased from 72.2 to 109.4 deaths per 100 000 (p = 0.01) (Table 1; and the net height of the bars in Fig. 3). There was a similar increase in inequalities for Pacific females (SRDs −9.8 to 42.2, p = 0.03) and some suggestive increase for Māori males (72.5 to 102.0, p = 0.17).Table 1


Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up
Decomposition of absolute ethnic inequalities in cancer mortality by major contributing cancer types, comparing Māori and Pacific peoples with European/Other in males and females aged 1–74 years in New Zealand. *Note some cancer types are excluded due to small numbers
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5037611&req=5

Fig3: Decomposition of absolute ethnic inequalities in cancer mortality by major contributing cancer types, comparing Māori and Pacific peoples with European/Other in males and females aged 1–74 years in New Zealand. *Note some cancer types are excluded due to small numbers
Mentions: Table 1 shows ethnic inequalities in cancer mortality increased from 1981 to 2011 particularly in females. For example, in the 2006–11 cohort, the overall mortality rate from cancer was 202.0 per 100 000 Māori females and 92.6 in European/Other, an overall SRD of 109.4 excess deaths per 100 000 (Table 1; and the net height of the 2006–11 bar in Fig. 3, SRD = 114 – 5). From 1981–84 to 2006–11 the cancer mortality in European/Other females decreased significantly from 110.6 to 92.6 per 100 000 population (p = 0.01) but the cancer mortality rate for Māori females appeared to have increased (182.8 to 202.0, p = 0.09). Subsequently, absolute inequalities (SRD) for Māori females increased from 72.2 to 109.4 deaths per 100 000 (p = 0.01) (Table 1; and the net height of the bars in Fig. 3). There was a similar increase in inequalities for Pacific females (SRDs −9.8 to 42.2, p = 0.03) and some suggestive increase for Māori males (72.5 to 102.0, p = 0.17).Table 1

View Article: PubMed Central - PubMed

ABSTRACT

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 Māori (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 Māori 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.

Results: Specifically, excess mortality (SRDs) increased for breast cancer in Māori females (linear trend p < 0.01) and prostate (p < 0.01) and colorectal cancers (p < 0.01) in Māori males. The incidence gap (SRDs) increased for breast (Māori and Pacific females p < 0.01), endometrial (Pacific females p < 0.01) and liver cancers (Māori males p = 0.04), and for cervical cancer it decreased (Māori females p = 0.03). The colorectal cancer incidence gap which formerly favoured Māori, decreased for Māori males and females (p < 0.01).

Results: The greatest contributors to absolute inequalities (SRDs) in mortality in 2006–11 were lung cancer (Māori males 50 %, Māori females 44 %, Pacific males 81 %), breast cancer (Māori females 18 %, Pacific females 23 %) and stomach cancers (Māori 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.

Electronic supplementary material: The online version of this article (doi:10.1186/s12885-016-2781-4) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus