The influence of community well-being on mortality among Registered First Nations people

Health Reports

by Lisa N. Oliver, Chris Penney and Paul A. Peters

Release date: July 20, 2016

Aboriginal groups in Canada experience higher rates of mortality and morbidity than do non-Aboriginal people. A number of studies have compared the health status of Aboriginal and non-Aboriginal populations, but few have explored the broader determinants of health and mortality among Aboriginal populations.

Lower socioeconomic status, measured by variables such as income, education and employment, is associated with higher levels of mortality. High mortality rates among the First Nations population can be partially explained by individual socioeconomic characteristics, but differences persist when these factors are taken into account.

A growing body of research has examined the impact of community characteristics on health. Residing in a low-income neighbourhood or community has been associated with poorer health outcomes and increased mortality. However, studies specifically examining the impact of community characteristics on health outcomes among Aboriginal populations in Canada are rare. One analysis based on the Aboriginal Children’s Survey found that off-reserve First Nations people in neighbourhoods with a higher percentage of renters tended to have poorer mental health even when the influence of individual and family socioeconomic factors was controlled. Several studies have linked overcrowding, isolation, income, and community control in First Nations communities with outcomes such as tuberculosis, hepatitis A, and hospitalizations. However, these studies did not examine the impact of individual and community characteristics simultaneously.

The Community Well-Being index (CWB) contains education, labour force, income, and housing components. This study uses the 1991-to-2006 Census Mortality and Cancer Cohort to assess the influence of community factors as measured by the CWB and individual characteristics on the mortality of individuals who identified as Registered First Nations people or Indian band members.

Data and methods

Data

The data are from the 1991-to-2006 Census Mortality and Cancer Cohort, a 15% sample (n = 2,735,150) of the non-institutional population aged 25 or older.Note 7 The cohort was tracked for mortality from June 4, 1991 through December 31, 2006.

Respondents to the 1991 Census long-form questionnaire were eligible to be linked to the Canadian Mortality Database using a probabilistic linkage, as names were not captured on the census database. Eligible census respondents were linked to a 1990 and 1991 nominal tax-filer data list that contained common variables (date of birth, postal code, spousal date of birth) and encrypted names. The census and encrypted names were linked to the Canadian Mortality Database. Because encrypted names were required from the tax-filer data, only tax-filers could be followed for mortality. The probabilistic linkage meant that all groups were not equally likely to be linked. Specifically, people reporting Aboriginal ancestry were less likely to be linked than were those with non-Aboriginal ancestry.

Eligibility

Everyone aged 25 or older enumerated by the 1991 Census long-form was eligible to be part of the cohort. In most of Canada, the long-form questionnaire was administered to one in five households, but it was administered on a 100% basis to residents of several remote and northern communities, Indian reserves and settlements, and non-institutional collective dwellings. However, 78 Indian reserves and settlements, with a population of approximately 38,000, were not enumerated or incompletely enumerated, and thus, could not be included in the cohort.

Data quality reports found that 3.4% of Canadian residents were missed by the 1991 Census. Compared with the enumerated population, these people were more likely to be young, mobile, low-income, homeless, or of Aboriginal ancestry.

The present analysis was based on 57,300 cohort members who, on the 1991 Census, reported that they were members of an Indian band or a Registered Indian as defined by the Indian Act. Throughout the remainder of this study, they are referred to as Registered First Nations people. Cohort members who reported their ethnic origin (ancestry) as North American Indian, but did not report membership in an Indian band or being a Registered Indian, were not included.

Individual characteristics

Socioeconomic characteristics of individuals were derived from the 1991 Census: marital status, labour force status, income adequacy, educational attainment, and housing quality. Three marital status categories were specified: legally married/common-law, divorced/separated/widowed, and single. Three categories of labour force status were used: employed, unemployed, and not in the labour force. The measure of income adequacy was based on quintiles of economic family income; to account for regional differences in income, quintiles were constructed within each Census Metropolitan Area (CMA)/Census Agglomeration (CA) and in all other areas.

Highest level of educational attainment was grouped into four categories: less than secondary school graduation, secondary school graduation, some postsecondary, and university degree.

Housing quality was assessed by a dichotomous variable indicating if respondents lived in a dwelling that needed major repairs.

To track residential mobility, individual census records were linked to postal code data obtained from tax files submitted between 1990 and 2007. For 76.7% of cohort members, complete postal code information was available from the tax-filer data. Among most (99.8%) of those with incomplete information, postal code could be imputed from previous tax-filer years; information for the remaining 0.2% was imputed from census data. A change in postal code over the 16-year follow-up signalled a residential move. Three categories were created: non-movers; short movers (within a Census Subdivision or Census Division); and long movers (across Census Divisions or provinces). This does not cover all moves. Because some Indian Reserves/Settlements and small municipalities have a single postal code, moves within these areas would be missed. As well, multiple moves within a single year, or if the tax-filer used a previous address (not the actual address), could not be detected.

Community measures

The Community Well-Being index (CWB measures the social and economic well-being of communities based on data from the Census of Canada.Note 18 The CWB is calculated at the Census Subdivision (CSD) level. The CWB consists of seven indicators in four equally weighted components: education, income, labour force activity, and housing. These indicators are also important determinants of health. The seven CWB indicators are combined into an index between 0 and 100.

For the population aged 20 or older, the CWB education component identifies the percentage whose highest level of attainment is at least secondary graduation, and for the population aged 25 or older, the percentage with at least a university degree. The labour force component consists of labour force participation and percentage of the labour force who are employed or unemployed. The income component is income per capita, calculated as total community income divided by total population. The housing component is comprised of an indicator of crowding (percentage of population in dwellings with more than one person per room) and an indicator of dwelling quality (percentage in dwellings that need major repairs). Information about the CWB and its application to the First Nations population is available elsewhere. The CWB is analysed as a dichotomous variable using the average for First Nations communities in 1991 as a cut-point.

Metropolitan Influence Zone (MIZ) was used to assess the remoteness of a municipality. MIZ assigns a category to municipalities outside a CMA/CA based on the percentage of the employed labour force who commute to work in the CMA/CA. The four categories are: strong, moderate, weak or no MIZ. People living in a moderate or strong MIZ were combined into a single category because preliminary models indicated that mortality did not differ significantly between them.

Age-standardized mortality rates

Age-standardized mortality rates (ASMRs) were calculated per 100,000 person-years at risk by sex for individual and community variables, using the direct method. The population for age-standardization was the age distribution, in five-year age groups, of cohort members who self-identified as Registered Indians under the Indian Act, were members of an Indian band/First Nation, or had Aboriginal ancestry. Variances derived with the Spiegelman method were used to calculate confidence intervals.

Cox proportional hazards models

For in-scope cohort members, person-days of follow-up were calculated from baseline (June 4, 1991) to the date of death, emigration, or end of the study (December 31, 2006). Cox proportional hazards survival models were used to examine the influence of community factors and individual characteristics on mortality among Registered First Nations cohort members.

Three sets of models were run. The first set included only the CWB components; the second, only individual characteristics. The purpose of these models was to examine the effects of community and individual characteristics separately.

The third set of models consisted of both the CWB components and individual characteristics in order to determine the extent to which the effects of CWB indicators are attenuated with the addition of individual characteristics.

All models were stratified by sex and five-year age group. Ties were handled using the Efron method.

Read more: http://www.statcan.gc.ca/pub/82-003-x/2016007/article/14646-eng.htm

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