Herhaling titel van presentatie Estimating mortality by socio-economic status using unlinked data Estimating social inequalities in HLE: Challenges and opportunities 10 February, 2012 Sylvie Gadeyne, Patrick Deboosere Interface Demography, Vrije Universiteit Brussel

Vrije Universiteit Brussel Interface Demography 2 Herhaling titel van presentatie Objective O BJECTIVE o Investigate the differences between mortality and social inequalities in mortality estimated with linked data and mortality and social inequalities in mortality estimated with unlinked data o Focus on mortality C ONTEXT : DATA AVAILABILITY ? o Before the 1990s, relatively few studies on social inequalities in mortality in Belgium o At the individual level, there were few data to investigate these social inequalities o Some studies: infant and child mortality, research at the aggregate level

Vrije Universiteit Brussel Interface Demography 3 Herhaling titel van presentatie New data sources o Research on mortality inequalities has been boosted in Belgium by the availability of new data sources since the nineties o Surveys o For example: the Belgian Health Interview Survey o Mortality follow-up of the census o Mid 1990s: construction of the ‘National Mortality Databank’ (Interface Demography in cooperation with Statistics Belgium) o The National Mortality Databank: several phases o Linkage census and mortality data o Linkage census and mortality data

Vrije Universiteit Brussel Interface Demography 4 Herhaling titel van presentatie National Mortality Databank o The National Mortality Databank: first phase o Linkage for all-cause mortality: March March 1996 S ocio-economic data<Census 1991 Mortality data <National Register follow-up of five years (60 months) o Linkage for cause specific mortality: March December 1995 S ocio-economic data<Census 1991 Mortality data <Death Certificates follow-up of almost five years (58 months)

Vrije Universiteit Brussel Interface Demography 5 Herhaling titel van presentatie National Mortality Databank o The National Mortality Databank: second phase o Linkage for all-cause mortality: October December 2004 S ocio-economic data<Census 2001 Mortality data <National Register follow-up of more than 3 years (39 months) o Linkage for cause specific mortality: January December 2005 S ocio-economic data<Census 2001 Mortality data <Death Register follow-up of two years (24 months) Brussels CR: follow-up (39 months)

Vrije Universiteit Brussel Interface Demography 6 Herhaling titel van presentatie A ‘new’ reserach line o The new data availability has allowed ID for developing a research line concerning inequalities in mortality, morbidity and health o Some examples o Educational differences in life expectancy ( ) o Applying prevalence of good health: healthy life expectancy by education, region… in cooperation with the WIV

Vrije Universiteit Brussel Interface Demography 7 Herhaling titel van presentatie A ‘new’ reserach line o Research in all cause mortality o Socio-economic inequalities in mortality risks among men and women o Using several indicators of socioeconomic status: education, long term income (housing quality), activity status, professional class and type of income o Focusing on detailed indicators: sector of employment (ISCO) o Focus on less obvious age groups: young-aged and old-aged o Doctoral research of P. Deboosere (2007) o European projects: comparative research of mortality inequalities

Vrije Universiteit Brussel Interface Demography 8 A ‘new’ reserach line o Inequalities in all cause mortality o Investigating the evolution of educational inequalities between (TAHIB) and , in cooperation with WIV P. Deboosere, S. Gadeyne, H. Van Oyen (2009)

Vrije Universiteit Brussel Interface Demography 9 Herhaling titel van presentatie A ‘new’ reserach line o Inequalities in cause specific mortality o Distinguishing the most important cause groups of death o Doctoral research of S. Gadeyne 2005 o Focusing on specific causes of death o Doctoral research of H. Vandenheede (2011): diabetes (mortality using the linked data, morbidity using the Health Surveys) o Focus on breast cancer (as one of the exception on the general pattern of a negative gradient) o International comparative studies: Belgium & Europe (stroke, lung cancer, suicide, diabetes, …) o The most important advantage of linked data? o Linkage based on the register number or unique identification key, deterministic linkage o Linked information applies to the same person o Numerator-denominator bias is excluded

Vrije Universiteit Brussel Interface Demography 10 Herhaling titel van presentatie Question Mark??? o How will we study mortality and morbidity inequalities in the future? o Health studies: Health Surveys and other surveys o Mortality? o Classic census does not exist anymore o Linkage between other data sources and register data? The Crossroads Bank for Social Security o Unlinked method? o Numerator and denominator of the mortality rates by SES come from different sources o Consequences? Objective: To study the differences resulting from the use of the linked versus the unlinked data in calculating socio-economic inequalities in mortality and life expectancy

Vrije Universiteit Brussel Interface Demography 11 ‘Linked’ & ‘unlinked’ life expectancy H EALTHY LIFE EXPECTANCY BY SOCIO - ECONOMIC STATUS o Healthy life expectancy o Several possibilities o Most often: Sullivan Method o Prevalence of good health o Life tables: based on death rates o Linked and unlinked data to calculate death rates and establish life tables o Socio-economic status o Indicator: education o Data on education available for all individuals aged and older o Relatively stable indicator of socioeconomic status o Most important: data available in the census and in the certificates

Vrije Universiteit Brussel Interface Demography 12 Herhaling titel van presentatie ‘Linked’ & ‘unlinked’ life expectancy C OMPARING THE LINKED AND THE UNLINKED METHOD o Life expectancy by educational status o Point of departure of life tables o Age-specific mortality rates by educational status o Numerator: number of deaths by educational status and age o Denominator: number of person years lived by educational status and age o Brussels Capital ID o Linked data: mortality follow-up of the census 2001 ( ) o Unlinked data: census 2001 and death certificates ( )

Vrije Universiteit Brussel Interface Demography 13 Herhaling titel van presentatie Comparing methods C OMPARING THE LINKED AND UNLINKED METHOD o Linked data o Numerator (number of deaths by educational class) and denominator (number of person years lived by educational class) both come from the same dataset = mortality follow-up of the census 2001 o Linkage o census 2001 data linked to register data on mortality for o unique identification key o information applies to the same person o numerator and denominator in the same dataset

Vrije Universiteit Brussel Interface Demography 14 Herhaling titel van presentatie Comparing methods C OMPARING THE LINKED AND UNLINKED METHOD o Unlinked method o Denominator (person years lived by socioeconomic status) < census 2001 o Numerator (number of deaths by educational status) < death certificates  numerator and denominator are provided by different data sources  numerator-denominator bias o Calculation o Mortality rates are calculated using the linked and unlinked data o Rates are transformed into probabilities to establish life tables o Indicators resulting from both datasets are compared

Vrije Universiteit Brussel Interface Demography 15 Herhaling titel van presentatie Results L IFE EXPECTANCY IN THE LINKED AND THE UNLINKED METHOD Table 1: Life expectancy at age 20 by educational level and sex, the linked and the unlinked method compared

Vrije Universiteit Brussel Interface Demography 16 Herhaling titel van presentatie Results U SE OF UNLINKED DATA o Considerable bias o Mortality rates by educational level are significantly underestimated in the unlinked method (table 1) o Both among men and women o And for all educational levels o Exception: the group for which information on educational level is missing: overestimation of mortality o Resulting in a considerable bias: o life expectancy by educational level is higher using the unlinked data, except for the missing group

Vrije Universiteit Brussel Interface Demography 17 Herhaling titel van presentatie Results D IFFERENCES BETWEEN AGE - SPECIFIC MORTALITY RATES IN THE LINKED AND THE UNLINKED METHOD Figure 1: Absolute difference between the age-specific mortality rates estimated with unlinked data and those estimated with linked data

Vrije Universiteit Brussel Interface Demography 18 Herhaling titel van presentatie Results D IFFERENCES BETWEEN AGE - SPECIFIC MORTALITY RATES IN THE LINKED AND THE UNLINKED METHOD Figure 2: Relative difference between the age-specific mortality rates estimated with unlinked data and those estimated with linked data

Vrije Universiteit Brussel Interface Demography 19 Herhaling titel van presentatie Results D IFFERENCES BETWEEN SOCIAL INEQUALITIES IN THE LINKED AND THE UNLINKED METHOD Figure 3a: Rate ratio (primary education/tertiary education) by age and sex, the linked (L) and unlinked method (U-L) compared, men

Vrije Universiteit Brussel Interface Demography 20 Herhaling titel van presentatie Results D IFFERENCES BETWEEN SOCIAL INEQUALITIES IN THE LINKED AND THE UNLINKED METHOD Figure 3b: Rate ratio (primary education/tertiary education) by age and sex, the linked (L) and unlinked method (U-L) compared, women

Vrije Universiteit Brussel Interface Demography 21 Herhaling titel van presentatie Results U SE OF UNLINKED DATA o Bias o Not only are the levels of mortality biased o Social inequalities in mortality are biased too (figure 3a and figure 3b) o For example: mortality ratio primary/tertiary o Men: o At young age: overestimation of inequalities (factor 2,5) o From and 70 years on: underestimation o From years on: comparable inequalities o Women: o Young age: overestimation of inequalities o Between ad 70-74: comparable inequalities o Old age: overestimation of inequalities

Vrije Universiteit Brussel Interface Demography 22 Herhaling titel van presentatie Results U SE OF UNLINKED DATA o Explaining the bias o Quality of the educational information in the death certificates o Very high percentage of missing information for education o More than 70% of the deaths in the certificates have a missing value for education o This group with a missing value for education has a very high mortality in the unlinked method (table 1)

Vrije Universiteit Brussel Interface Demography 23 Herhaling titel van presentatie Results U SE OF UNLINKED DATA o Figure 4: Percentage of missing values for educational levels by sex and age: certificates and census data compared

Vrije Universiteit Brussel Interface Demography 24 Herhaling titel van presentatie Recommendations I MPLICATIONS OF THE RESULTS o If mortality and social inequalities need to be investigated through unlinked data, educational level should be registered correctly and exhaustively in the certificates o Alternatively, respondents for whom educational data are missing o could be distributed in such a way that the educational distribution of the total population in the census 2001 is respected o educational information could be derived from other socioeconomic characteristics, such as professional class

Vrije Universiteit Brussel Interface Demography 25 Herhaling titel van presentatie Recommendations I MPLICATIONS OF THE RESULTS o even if educational level is registered correctly in the certificates, errors can occur when using non-linked datasets to compute mortality rates by educational level o differing registration of education in both data sets, technical problems, registration errors in mortality o Best option: linked data o the firmest basis to calculate mortality rates by educational level o the 2001 census was the last ‘classical’ census in Belgium o it will be replaced by an administrative census o in this administrative census the registration of education is not assured for the total population in Belgium o this definitely has repercussions for the follow-up of social inequalities in mortality

Vrije Universiteit Brussel Interface Demography 26 Herhaling titel van presentatie Recommendations O THER POSSIBILITIES ? o Crossroads Bank Social Security? o Explorative analyses of these data o Sample of the total population o Mortality by class of income: quite good results o Integration of information on educational level? o To be continued!

Vrije Universiteit Brussel Interface Demography Thank you for your attention