is health made or bought? new evidence on the roles of work and income as determinants of health
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Is Health Made or Bought? New Evidence on the Roles of Work and Income as Determinants of Health. the debates: psycho-social or neo-material; role of income inequality? new data: 1991 Census mortality linkage method: examine gradients in detail. Michael Wolfson, Statistics Canada - PowerPoint PPT PresentationTRANSCRIPT
CPHA June 2008
Is Health Made or Bought? New Evidence on the Roles of Work and Income as Determinants of Health
Michael Wolfson, Statistics Canada
with Philippe Fines, Geoff Rowe, and Russell Wilkins and financial support from the Canadian Population
Health Initiative of CIHI
the debates: psycho-social or neo-material; role of income inequality?
new data: 1991 Census mortality linkage method: examine gradients in detail
CPHA June 2008
Alternate Hypotheses background: there is a significant and pervasive
gradient in health with socio-economic status over-simplified statement of alternate
hypotheses: health is “made” – the main factor determining
the gradient is individuals’ rank in society, particularly the psycho-social aspects of their position in paid work
health is “bought” – the main factor is purchasing power / command over resources
CPHA June 2008
Brief Review of Literature (I)(Wilkinson, BMJ, 1997)
“Is the health disadvantage of the least well off part of the population mainly a reflection of the direct physiological effects of lower absolute material standards (of bad housing, poor diets, inadequate heating, and air pollution), or is it more a matter of the direct and indirect effects of differences in psychosocial circumstances associated with social position – of where you stand in relation to others? …
“Evidence … suggests that the psychosocial effects of social position account for the larger part of health inequalities.”
CPHA June 2008
Brief Review of Literature (II)(Siegrist and Marmot, SSM, 2004)
“It is unlikely that there will be a single explanation of social inequalities in health. … one explanatory framework (is) exposure to adverse psychosocial environments during midlife, particularly at work.
“We argue that exposure to an adverse psychosocial environment, in terms of job tasks, defined by high demands and low control and/or by effort–reward imbalance, elicits sustained stress reactions with negative long-term consequences for health.”
CPHA June 2008
Brief Review of Literature (III)(Lynch, Kaplan et al., BMJ, 2000)
“The neo-material interpretation says that health inequalities result from the differential accumulation of exposures and experiences that have their sources in the material world. …
“Under a neo-material interpretation, the effect of income inequality on health reflects a combination of negative exposures and lack of resources held by individuals, along with systematic underinvestment across a wide range of human, physical, health, and social infrastructure.”
CPHA June 2008
Marmot et al. Theory
Brunner and Marmot, OUP, 2006
CPHA June 2008
Note on Income Inequality (I) there would be no observable gradient if everyone
had the same SES hence income inequality (i.e. variation in incomes,
and SES more generally) is necessary to observe gradients (i.e. health inequalities) in the first place
the gradient itself is a relationship at the individual level – between income and health
there are also many analyses at the “meso” level of the relationship between inequality and health
CPHA June 2008
(5 countries and their cities)
0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28
Median Share of Income
200
300
400
500
600
Work
ing A
ge (
25-6
4)
Mort
alit
y
US AUSSWEUKCAN
New York
Stockholm
Sydney
Income Inequality and Working-Age Mortality528 Metropolitan Areas in Five Countries, 1990/91
Toronto
London
Ross et al., 2002
0 5 10 15 20Unemployment Rate
600
700
800
900
Mort
alit
y R
ate
pe
r 1
00
,00
0 P
op
ula
tion
The Relationship Between Unemployment and Mortality
Metropolitan Areas in Canada (1991) and the United States (1990)
Victoria
Toronto
Vancouver
Montreal
St. John's
Shawinigan
NewYorkNY
LosAngelesCA
RochesterMN
U.S. met. areas - weighted linear fit (slope not significant)Can. met. areas - weighted linear fit
Kelowna
BiloxiMS
n.b. both ecological measures
CPHA June 2008
Note on Income Inequality (II) inequality is a property of population groups (e.g. cities,
countries), not individuals, and is sometimes correlated with mortality rates, also a meso level property
the SES gradient in health is an individual-level relationship one approach: is there, over and above an individual level SES
gradient, an independent role for meso level characteristics but Wilkinson, “Rather than income inequality being about
something different, it is telling us more about the effect of class on health…” (personal communication)
“All societies … have hierarchies. Yet the magnitude of the social gradient in health varies among societies and within a society over time.” (Marmot, JAMA 2006)
CPHA June 2008
U.S. Income Distribution and Income Gradient, 1991
0 50,000 100,000 150,000 200,000
Population Density
Relative Risk (RR) +/- 95% Confidence Interval for beta
RR = 1
Mean Income
(Wolfson et al., BMJ, 1999)
CPHA June 2008
Income Inequality and the Shape of the Mortality Gradient – Are They Linked?
relative risk (gradients) or population (%)
income
“Swedish” Income
Distribution
“Swedish” Mortality Gradient
“UK” Income
Distribution
“UK” Mortality Gradient
CPHA June 2008
Note on Dual Labour Markets long history in labour economics re dual
or segmented labour market theories essential (simplified) idea – labour market
is segmented with two groups of workers permanents – have stable career-oriented
jobs, generally in large organizations with good internal promotion possibilities
temporaries – hold a sequence of short-term unstable jobs, frequently unemployed
CPHA June 2008
From Theory to Empirical Test: Hypothesis Restated
if job circumstances (especially demand-control and effort-reward imbalances, and civil service “grade” per Whitehall) are the main drivers of the gradient,
then a dollar of own wage income should be a stronger marker of the relevant aspects of social position than a dollar of income from any other source
CPHA June 2008
Alternative Measures of Income – own wages vs all other household income
Income Source
Self Rest of Househol
d
Working
Investments
Transfers
(less Taxes)
CPHA June 2008
Overview of 1991 Census – Mortality Linkage
Data sources 1991 census (+post-censal disability survey,
HALS) 1991-2001 death records (CMDB)
15% sample of population aged 25+ ≈ 3 out of 4 long-form census households ≈ 2.7 million records for individuals
Follow-up for deaths 1991-2001 ≈ 28 million person-years at risk ≈ 260,000 deaths
CPHA June 2008
Comparison of Life Table and 1991 Census Cohort Survival Rates
0
10
20
30
40
50
60
70
80
90
100
25 40 55 70 85
Males - Cohort
Males - Life Table
Females - Cohort
Females - Life Table
age groups followed
deaths followed
CPHA June 2008
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
0 25 50 75
Total Household Income
95% CI low
95% CI high
Own Wages
95% CI low
95% CI high
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
0 25 50 75
Total Household Income
95% CI low
95% CI high
Own Wages
95% CI low
95% CI high
10 Year Relative Mortality Hazards by Sex and Type of Income ($000s)
19.5%
49.3% 91.3%
36.3%males females
income $000s income $000sreference income group, relative
risk = 1
CPHA June 2008
population joint distns
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
20
53
93
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
15
33
63
93
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
males
females
females
males
own wages
all other household
income
own wages
CPHA June 2008
Contour Plots of Joint Distributions of Own Wages and All Other Household Income ($000s), Males and Females
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
femalesmales
all other household income
own wages
CPHA June 2008
Contour Plots of Joint Distributions of Own Wages and All Other Household Income ($000s), Males and Females
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
-10 0 5 10 15 20 25 33 43 53 63 73 83 93 125
0
5
10
15
20
25
33
43
53
63
73
83
93
125
femalesmales
all other household income
own wages
CPHA June 2008
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
0 25 50 75 100 125
Own Wages
All Other Income
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
0 25 50 75 100 125
Own Wages
All Other Income
Jointly Estimated Gradients
males females
income $000s income $000sreference income group, relative
risk = 1
CPHA June 2008
Contour Plot of Relative Mortality Hazard if “Health is (Entirely) Made”
own wage
income
other household income
CPHA June 2008
Contour Plot of Relative Mortality Hazard if “Health is Bought”
own wage
income
other household income
CPHA June 2008
Estimated and Lightly Smoothed Contour Plots of Relative Mortality Hazards: own wages on vertical axis, other household income on horizontal ($000s)
1 11 21 31 41 51 61 71
1
11
21
31
41
51
61
71
1 11 21 31 41 51 61 71
1
11
21
31
41
males females
CPHA June 2008
Summary Interpretation of Results (I)
IF dollar amounts of wages are a good proxy for workplace psycho-social factors,
then these factors have at most a small incremental effect on mortality risks among the working-age population
over and above the effects of factors which are proxied by money income in general
CPHA June 2008
Summary Interpretation of Results (II)
there are significant male-female differences workplace factors, to the extent proxied by own
wages, are more important for men compared to factors proxied by other household income
own wages are less important for women – though note that the main component in other household income for women is husbands’ wages
CPHA June 2008
Summary Interpretation of Results (III)
note that (in fact) this is not a general test of psycho-social vs neo-material theories the apparent protective effects of an extra dollar
of other household income could still be a reflection of, or a marker for, an unobserved psycho-social factor
but if there are such psycho-social factors, they must be operating via pathways more general and pervasive than those unique to the work place
CPHA June 2008
Concluding Thoughts: General
general implication: health is more likely bought than made i.e. impacts of workplace psycho-social factors
are at most small relative to “what money in general buys or reflects”
at least in Canada, perhaps as compared to the UK
this analysis is just a beginning re exploiting full potential of this 1991 census–mortality linkage with 28 million person-years of follow-up
CPHA June 2008
Concluding Thoughts: Caveats and (Exciting!) Next Steps
need to distinguish different household types - e.g. couples, lone parents, 3+ adult households
add other covariates such as educational attainment, occupation / industry, ethnicity, …
begin exploring conjectures re dual labour markets should have adequate statistical power for multi-
level analysis – especially [ income inequality ↔ mortality ] versus [ unemployment ↔ mortality ] results, and (reframed) Wilkinson hypothesis