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Socioeconomic Status and Health

Socioeconomic Status and Health. An overview of the evidence for a connection between wealth and health Ottawa, August, 2006. Sections. Which indicators of “health” & wealth to use? Individual evidence for link between SES and health Comparisons between societies

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Socioeconomic Status and Health

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  1. Socioeconomic Status and Health An overview of the evidencefor a connectionbetween wealth and health Ottawa, August, 2006

  2. Sections • Which indicators of “health” & wealth to use? • Individual evidence for link between SES and health • Comparisons between societies • Comparisons within societies (Britain, USA, Canada) • Societal level income inequality and health

  3. Health Indicators • All-cause mortality • Gives an overview; non-specific; doesn’t weight by age • Infant mortality • Sensitive to socio-economic development & to medical care • PYLL • Selects causes; weights by age at death • Morbidity indicators • Usually partial coverage; how available? • QoL • Captures non-fatal outcomes; subjective (bias?)

  4. Socioeconomic Indicators • No ideal indicator. Some options: • Wealth • Income readily measurable (in most societies), but only covers part of the picture; doesn’t apply well to elderly, to housewives, etc. Individual or family income? How to correct for family size? • Occupation • Reasonably comparable across countries; may have direct relevance to health (exposures, hazards); difficult to classify & score; doesn’t apply well to retired, housewives, children, etc. • Education • May be driving force behind occupation and income; permanent & unaffected by market fluctuations; applies to those not in labour force; established early in life so may not reflect subsequent changes • Composite indicators • Blend of above; choice of weights for components is difficult.

  5. 1. Socioeconomic Status and Health (1a) Comparisons Between Societies

  6. The Preston Curve (Preston SH. Population Studies 1975;29:231-248)Note the non-linearity of the relationship. This becomes crucial in subsequent argumentsas we compare individual and aggregate statistics Data source: World Bank Report, 1983

  7. Sixteen years later: have things changed? As before, the health of the rich is not much affected by changes in income, so transfers from rich to poor would improve overall health. Hence, poverty is important in poor countries and the equity of income distribution is important in richer countries. Source: 1998 World Bank Report

  8. Will throwing money at it help? Expenditures & Health Outcomes The link between nationalhealth care spendingand level of health is curvilinear. Among poor countries,expenditures quicklyreduce infant mortalityand this greatly extends average life expectancy.But once infant mortality islow, increasing expenditureshave less effect. Compare Cuba with the US.How does Cuba do it? Is life expectancy the best health indicator? What would you suggest? So, will paying doctors more make them work harder, or will they say “Thanks!” and go play golf?

  9. (1b) Inequalities Within Societies Data from Britain, where most of the analyses began. Consider mortality in ages 15 – 64, i.e. adult, but premature mortality

  10. Have things improved? Certainly! Standardized mortality rates, England and Wales, 1841 to 1971 Males Females Source: Townsend P, Davidson N. Inequalities in health: the Black Report. Penguin books, 1992

  11. However: there are major inequities. An early example: the Black Report Age-Standardized Mortality Rates per 1,000 at Ages 15 to 64 by Occupational Class, United Kingdom, 1971 Source: Townsend P, Davidson N. Inequalities in health: the Black Report. Penguin books, 1992

  12. Life expectancy in England and Wales, by social class, 1972-76 and 1992-96 Source: Marmot M. Perspec Biol Med 2003; 46 (Suppl 3): Table 1

  13. The Side-effects of Success:Mortality from cardiovascular disease, England and Wales • In 1971, cardiovascular disease showed relatively little SES gradient. • By 1991, a strong gradient had appeared, due to the differential success in prevention across the occupational categories. There was almost no reduction in mortality among unskilled people, but people in the professional category had reduced their mortality risk to one-third. • So, much of the SES gradient we see today results from differential access to, and uptake of, preventive care across social groups.

  14. The effect holds for both sexes:SMR by Occupational Class for Ages 15 to 64, England & Wales, 1970-72

  15. And for many individual causes of death:Respiratory Deaths for Ages 15-64 by Occupational Class,England & Wales, 1970-72

  16. And also among children All-cause SMRs (ages 0 – 14) by occupational class, England & Wales, 1970-72

  17. Most of the Effect Lies at Low Income Levels: Earnings and SMRs (UK, 1970) SMR 1970 Earnings: Pounds per Week Source: Wilkinson: Class and Health,1986: pg. 110

  18. Is it only premature mortality that shows a social gradient?SMRs by occupational class and age at death. England & Wales, 1981-83 Occupationalclass The class gradientcontinues up to include deathsat old age Age at death Source: Whitehead M. The Health Divide, table 11. Penguin books, 1992.

  19. And disparities appear to be increasing…Trends in SMRs over Timein UK Men Aged 15 - 64 Unskilled Partly Skilled Skilled Manual Intermediate Professional Source: Wilkinson RG: Class and Health. London, Tavistock, 1986: Table 1.1

  20. The effect occurs from birth:Perinatal Death Rates (up to day 7) by Occupational Class: England & Wales, 1970-79 Class V Class I Source: Wilkinson RG: Class and Health. London, Tavistock, 1986: Table 6.8

  21. Postneonatal Death Rates (28 days-1yr.) by Social Class: England & Wales, 1970-79 S.C. V S.C. I Source: Wilkinson RG: Class and Health. London, Tavistock, 1986: Table 6.7

  22. Whitehall 2 Cohort Study: Mortality Trends over Time in Men Initially Aged 40-64 Cumulative Probability of death (per cent) “Other” Clerical Professional & Executive Administrative Year of follow-up Source: Marmot et al. Lancet 1991;337:1387-1393

  23. Potential Years of Life Lost (All Causes) England & Wales, 1971 – 1991Message: there are two-fold differences in mortality rates across occupational groups. The deficit occurs mainly from the lowest class. While overall mortality rates have fallen over the 20 years, the inequality has remained. Occupational Class V IV III II I

  24. Potential Years of Life Lost (Accidents & Violence). England & Wales, 1971 - 1991 Social Class V IV III II I

  25. The Black Report was published in 1980 and, despite government attempts to hide it, produced significant reactions • For example, the British Health Education Council published The Health Divide in 1988. It focused on ‘inequities’ (inequalities perceived as being unfair) • Other countries in Europe began to investigate whether they, too, experienced health disparities. Many countries reported to the WHO that health disparities increased during the 1980s. • This shifted health disparities up the political agenda • Marmot (2003): “The point I wish to draw out of these figures is that if the life expectancy gap can increase, it can, in principle, decrease. If we think this is a problem worth tackling, the challenge is to understand the reasons for the social gradient in order to do something about it.”

  26. (ii) Data from Canada, where Statistics Canada began to take notice in the 1990s

  27. Crude and age- standardized mortality rates, Canada, 1920-2000 Deaths per 1000 population

  28. Age-standardized mortality rates from cardiovascular disease, Canada, 1951-1995 Deaths per 100,000 population

  29. Deaths avoided due to declining death rates in Canada: Numbers of deaths that would have occurred in 1989 if 1971 rates had applied. Age Males Females Total < 1 2,336 1,680 4,016 1 - 14 896 599 1,495 15 - 34 1,373 822 2,195 35 - 54 5,547 2,597 8,144 55 - 74 12,265 7,238 19,503 75 + 5,707 12,037 17,744 Totals 28,124 24,973 53,097

  30. Life expectancy at birth by age and sex, Canada, 1921-2000 Life expectancy (years)

  31. So, what about Social Class?Life Expectancy at Birth, Canada, 1971 and 1986 Years Females, 1986 Females, 1971 Males, 1986 Males, 1971 (High) Income Quintiles (Low)

  32. 2 3 4 5 1 2 3 4 5 Income adequacy quintiles Remaining life expectancy at age 25 in Canada by sex and income quintile,non-institutionalized population, 1991 to 2001 Women Men

  33. Life expectancy at birth, by income quintile, urban Canada, 1971 & 1986 • Income classified by proportion of census tract falling below Stats Canada low income threshold • Quintiles within each CMA • Apparently, gradient leveled somewhat by 1986 • Wilkins et al. Health Reports 1988;1:137 High Low

  34. Cumulative fetal and infant mortality by weeks since beginning of pregnancy, by maternal education, Québec, 1990-91 Per 1000 total births Weeks since beginning of pregnancy

  35. Infant Mortality by quintiles of wealth, Canada 1971 - 1996 per 1,000 Source; Russ Wilkins, “Socioeconomic inequality in health outcomes.”Statistics Canada, 2003

  36. Potentially Modifiable Mortality • Potential years of life lost, Canada 1986, prior to age 75 • Includes infant deaths • For each cause they subtracted rates in quintile 1 from other quintiles. The result is expressed as a percentage: how much improvement would occur if everyone had the rate in the highest income quintile?

  37. Diminishing Disparities in Infant Mortality, Canada 1971 - 1996 Poor-RichTotal-Rich Excess Year RD RR RD RR Deaths • 1971 9.8 1.97 4.8 1.47 2028 • 1986 4.8 1.82 1.7 1.29 666 • 1991 2.9 1.64 1.3 1.29 577 • 1996 2.6 1.67 1.3 1.33 513 RD = difference in infant mortality rates between rich and poor; RR = ratio of mortality rates, poor : rich; Excess deaths = number of deaths that would have been avoided had death rates for rich applied to all deaths Source: Russ Wilkins, “Socioeconomic inequality in health outcomes”, 2003

  38. Low Income and Low Birth Weight Ottawa Area, 1991 % Rates of Low Birth Weight, 1990-92 Vanier Ottawa Gloucester Nepean Kanata Percentage of Families Below Low Income Cutoff (Ross & Wolfson, Statistics Canada)

  39. The Barker hypothesis. Why is birth weight important?Death rates from IHD by birth weight (n = 15,726) Death Rate Birthweight (kg) Source:Barker DJP et al. Weight in infancy and death from ischaemic heart disease. Lancet 1989;I:577-580

  40. Examples of associations between SES indicators: Income and School Achievement Eastern Ontario, 1996-97 % of children scoring below Ontario standards Vanier Cornwall Kingston Gloucester Ottawa Kanata Percentage of Families Below Low Income Cutoff (Educational Quality Assurance Office of Ontario)`

  41. Prevalence of obesity among women, by SES and by SES of parents Prevalence% (N in each group ranges from 291 to 362) Socioeconomic status Note that both obesity, and improvement in obesity, are related to SES. Lower SES women are more often obese than their parents; higher SES slightly less obese Source: Goldblatt PB et al. Social factors in obesity. JAMA 1965;192:1039-1044.

  42. Prevalence of high blood pressure, high cholesterol and obesity, Canada, 1986-92, by educational level Percentage Years of Education Source: Federal Task force on Population Health, 1996

  43. Prevalence of Activity Limitation (ages 15+), Canada, 1991 Percentage (High) Income Quintiles (Low) Statistics Canada. Report of 1991GSS.

  44. (iii) U.S.A.

  45. The effect of income is much greater among poor people. Data from U.S. National Longitudinal Mortality Survey (1980-1990)(graph based on a logit model of the data) 10-year age-adjusted probability of dying Family Income in 1980 $ Source: Deaton A. Health, inequality and economic development www2.cid.harvard.edu/cidmh/wg1_paper3.pdf

  46. And race has a greater effect among the poor:Life Expectancy at age 45 by Family Income, Race and Sex. United States, averaged over 1979-89 White Females Black Females White Males Black Males Life Expectancy at age 45 <$10,000 $10,000- $15,000- 25,000+ $14,999 $24,999 Family Income Source: GA Kaplan et al. In: Promoting Health: Intervention Strategies from Social and Behavioral Research. Institute of Medicine, 2000, page 40

  47. Low Birth weight, by Education and Race / Ethnicity, United States, 1996 Years of Education Low Birthweight per 1,000 Live Births White Black Hispanic Native Asian Source: GA Kaplan et al. In: Promoting Health: Intervention Strategies from Social and Behavioral Research. Institute of Medicine, 2000, page 44

  48. Mortality by family income, MRFIT <7.5 10 15 20 25 30 Annual family income in thousands of US dollars

  49. 2. Income Inequality and Health Hypothesis since late 1970s – Rodgers, Flegg and others. Mortality rises with range of incomes (Gini coefficient) seen in societies. The Wilkinson Hypothesis (1990s): for defined geographical areas, mortality rises with the level of disparity in incomes. Corollary: occupation and education gradients in health do not occur in societies with low income disparities. As countries become wealthier and move through the epidemiologic transition, the leading cause of differences in mortality changes from material deprivation to social disadvantage. Material deprivation provokes poverty and infectious disease; social disadvantage provokes stress and chronic disease.

  50. One measure of Income Inequality: Gini Coefficient L(s) lies below line of equality when income inequality favours the rich Gini coefficient is twice the area between the curve and the line of equality It is about 0.32 for Canada (2006) % of income 100 L(s) 0 100 % of population

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