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