Transcript Poverty & Inequalities in Health

The association between early life
socioeconomic position and adult
health, from mortality to preclinical
disease. What do we know?
Bruna Galobardes
Department of Social Medicine
University of Bristol, UK
National Poverty Center, March 2009
What is a life course approach?
A life course approach in epidemiology
investigates the long term effects on health
and chronic disease risk of physical and
social hazards during gestation, childhood,
adolescence, young adulthood and later adult
life (and across generations).
It studies the biological, behavioural and
social pathways that operate across the life
course and influence the development of
chronic diseases.
“It is insufficient to glibly state that all
health and social outcomes are due to
life course influences. This is
analogous to stating that all health is a
function of genetic and environmental
exposures. Whilst factually correct it
does not further our understanding of
aetiology or help policy formulation.”
Ben-Shlomo & Kuh (Lifecourse approach to
chronic disease epidemiology, 2nd edition)
Life course epidemiology – stating the obvious?
“The
ringing in your ears – I think I can help!”
Early life socioeconomic position
(SEP) and cause-specific mortality:
is the association established?
The importance of looking at specific
causes of death:
helps establishing causal associations
and describing the pathways that link
early socioeconomic circumstances with
later disease.
Evidence from :
Systematic review of individual-level
studies
Ecological studies
Migration and place of birth studies
Long-term disease trends
Evidence from individual-level studies:
Bruna Galobardes, George Davey Smith and John W.
Lynch
Epidemiologic Reviews 2004;26:7-21
J Epidemiol Community Health 2008;62:387-90
Ann Epidemiol 2006;16:91-104
The systematic reviews on mortality are based on at least
125,961 deaths (66 558 deaths in a Swedish study and 20
887 deaths in a study from Norway) from 40 studies (some
reported in more than one publication): 38 prospective, 2
case-control, 1 cross-sectional.
Inclusion criteria: individual-level studies, adult mortality (studies
reporting grouped fatal and non-fatal events were excluded or
inclusion of hypertension in the outcome definition)
Countries: United Kingdom, Sweden, Finland, Norway, Denmark,
Netherlands, United States, Russia, France, Belgium and South
Korea.
Birth cohorts: The majority included people born during or before
the 1940s and 1950s, and the youngest birth cohorts dated from the
late-1950s to the 1960s.
In the initial review 19 of the 29 studies measured the participants’
SEP during childhood or young adulthood. The remainder obtained
data by participant recall during adulthood.
The father’s occupation was the most common indicator.
Main conclusions:
Most studies support an association between
childhood socioeconomic position and overall
mortality.
Not all causes of death are equally related to
childhood socioeconomic conditions.
Main conclusions:
• Childhood SEP is particularly important for mortality from stomach
cancer.
• Childhood SEP was particularly important for haemorrhagic stroke but
there was not consistency across studies.
• Childhood circumstances contribute, together with socioeconomic
conditions in adult life, in determining mortality from coronary heart
disease, liver and lung cancer, respiratory-related deaths and diabetes.
The relative contribution of child-versus-adult circumstances varied in
different contexts.
• Childhood circumstances may contribute to external (including
unintentional injuries and homicide) and alcohol-related causes of death,
especially in northern European countries.
• There is no evidence for an association with overall non-smokingrelated cancers.
Stomach cancer mortality
Davey Smith, Hart, Blane et al. BMJ 1998;316;1631-1635
Infant mortality in 1921-3 and stomach cancer rates
in 1991-3 for men aged 65-74
Leon & Davey Smith BMJ 2000;320:1705-6
Migration studies: Risk of stomach cancer in first and second
generation migrants in Sweden
First generation
Stomach
Birth region
Men
Nordic countries
Eastern Europe
Western Europe
Asia
North America
South America
Africa
All foreign born
O
359
234
135
30
27
7
8
800
SIR
1.19
1.60
1.07
1.62
0.72
1.39
1.10
1.24
Women
95% CI
1.07-1.32
1.40-1.82
0.89-1.26
1.09-2.31
0.47-1.04
0.55-2.88
0.47-2.19
1.16-1.33
O
327
89
71
17
21
3
0
528
SIR
1.27
1.45
1.10
2.58
1.04
1.17
0.00
1.27
Second generation
By father's birth
country
Population
Sweden
Nordic countries
Eastern Europe
Western Europe
North America
Asia
All descendants
Mean follow-up
26
21
19
21
22
9
18
O
113,281
1,646
688
656
214
158
3,460
SIR
1.00
0.94
0.98
0.98
0.99
0.90
0.96
Hemminki & Li Int J Cancer 2002;99:229-37
95% CI
0.99-1.01
0.82-0.96
0.89-1.11
0.74-1.05
0.11-4.22
0.75-1.14
0.94-0.99
95% CI
1.14-1.42
1.16-1.78
0.86-1.38
1.50-4.14
0.64-1.60
0.22-3.47
0.00-2.54
1.17-1.39
Stroke mortality
Lawlor et al. Lancet 2002;360:1818-23
Evidence from disease trends …
Lawlor et al. Lancet 2002;360:1818-23
Evidence from disease trends …
Lawlor et al. Lancet 2002;360:1818-23
Evidence from individual level studies …
Childhood social class and stroke subtype:
Manual vs.
non-manual
Haemorrhagic
Manual vs.+
non-manual
2.84 (1.12-7.20) 3.22 (1.15-9.03)
Ischaemic
1.25 (0.77-2.03) 0.92 (0.53-1.61)
+risk factor adjusted
Hart and Davey Smith; J Epidemiol Community Health 2003
Evidence from individual level studies …
Hart et al. JECH 2003;57:385-91
“studies from Sweden and Norway, and the
mothers of the 1958 cohort found both types of
stroke, ischemic and hemorrhagic, had a similar
social patterning thus not supporting earlier
reports where worse childhood SEP was a
stronger predictor for hemorrhagic stroke “
Galobardes, Davey Smith, Lynch. J Epidemiol Community
Health 2008;62:387-90
Cardiovascular disease mortality and
morbidity
Those who experienced worse socioeconomic conditions in their
childhood, independently of their circumstances during adult life,
generally were at greater risk for developing and dying of CVD:
Davey Smith, Hart, Blane et al. BMJ 1998;316;1631-1635
Sinhg-Manoux, Ferrie, Chandola et al. Int J Epidemiol 2004;33:1072-1079
The relative contribution of child-versus-adult socioeconomic conditions
varied in different contexts:
Smoking: Different life course exposure to tobacco smoking may explain
the relative different contributions of child versus adult SEP on CHD in
different countries.
In US: Childhood SEP more important. Alameda County study in the
United States, those from poorer backgrounds during childhood were less
likely to quit and therefore had smoked more throughout their lives,
despite the socioeconomic reversals in smoking pattern in the adult
population.
Netherlands: Conversely, a cross-sectional study of a younger population
showed that smoking was influenced more by adult SEP.
• Pre-clinical CVD – atherosclerosis:
At the time of publication of the systematic review there were 2 studies
measuring carotid intima media thickness (a measure of the width of the
artery wall) or carotid stenosis. Both studies reported higher levels of
atherosclerosis among women but not among men.
More recent studies (“not systematic”) :
Multi-Ethnic Study of Atherosclerosis (MESA): Childhood SEP was
independently associated with subclinical IMT in both men and women.
Young Finns study, parental occupation in childhood or young adulthood of
the participant was not associated with IMT or flow mediated vasodilation.
Atherosclerosis Risk in Communities Study (ARIC, US): “Lower cumulative
life course SEP was associated with higher burden of subclinical
atherosclerosis”
Issues to consider:
Confounding by adult SEP
Does the association persist among younger cohorts?
Effects across generations
Confounding by adult SEP
Glasgow Alumni Cohort study: >90% class I and II in adulthood
Galobardes et al. JECH 2006;60:527-9
Does the association persist among younger cohorts?
Younger cohort
Older cohort
All cause
1.27(1.24, 1.30) 1 1.44 (1.27, 1.63) 3
1.41 (1.34, 1.48) 2
CVD
1.54 (1.45, 1.64) 1 1.52 (1.24, 1.87) 3
2.17 (1.89, 2.49) 2
Stomach
cancer
1.32 (1.10, 1.59) 1
2.06 (0.93, 4.57) 3
2
2.34 (1.54, 3.54)
Swedish cohort (Lawlor et al, 2007); 2 Norwegian cohort (Naess et al, in
press; 3 Collaborative study (Davey Smith et al. 1998)
1
Younger birth cohorts have not experienced the level of
socioeconomic strain previous birth cohorts had, however,
the association between childhood SEP and mortality can
still be found
Effects across generations:
Osler et al. JECH 2005;59:38-41
Effects across generations:
Osler et al. JECH 2005;59:38-41
Models / pathways can explain life course
inequalities in health:
Cumulative vs. interaction
Importance of education
Genetic/in-utero vs. environment
Theoretical life course
models
• Critical period model

with or with out later effect modifier

with later life effect modifier
• Accumulation of risk

with independent and uncorrelated insults

with correlated insults

“risk clustering”

“chains of risk” with additive or trigger
pathways
Ben-Shlomo & Kuh IJE 2002
Critical and sensitive periods
• Critical period – a time period only during
which an exposure has an effect.
– Thalidomide and limb abnormalities
– Imprinting of parental characteristics (Lorenz)
• Sensitive period - a time period during
which an exposure has a greater effect than
outside this period
– Learning a second language in childhood
– Clinical disease associated with infectious
disease exposure
Theoretical life course models
• Critical period model

with or with out later effect modifier

with later life effect modifier
• Accumulation of risk

with independent and uncorrelated insults

with correlated insults

“risk clustering”

“chains of risk” with additive or trigger
pathways
Ben-Shlomo & Kuh IJE 2002
Accumulation model – independent risks
TIME
O
U
T
C
O
M
E
A
B
C
Kuh et al (JECH 2003:57:778-783)
M
E
A
S
U
R
E
Accumulation model – risk clustering
TIME
D
A
B
C
O
U
T
C
O
M
E
M
E
A
S
U
R
E
Kuh et al (JECH 2003:57:778-783)
Chains of risk model – trigger
TIME
A
B
C
O
U
T
C
O
M
E
M
E
A
S
U
R
E
Kuh et al (JECH 2003:57:778-783)
Chains of risk model – additive
TIME
A
B
C
O
U
T
C
O
M
E
M
E
A
S
U
R
E
Kuh et al (JECH 2003:57:778-783)
Relative death rates (95% CI) by cumulative social class,
adjusted for age and risk factors, for men in West of Scotland
Collaborative Study (Davey Smith et al 1997)
Cumulative Social Class
All 3 nonmanual
2 nonmanual
2 manual
All 3
manual
P value for
trend
Age
adjusted
1
1.29
(1.08, 1.56)
1.45
(1.21, 1.73)
1.71
(1.46, 2.01)
< 0.0001
Age & risk
factor
1
1.30
(1.08, 1.57)
1.33
(1.11, 1.60)
1.57
(1.33, 1.85)
< 0.0001
Age
adjusted
1
1.51
(1.16, 1.98)
1.90
(1.47, 2.45)
1.94
(1.53, 2.45)
< 0.0001
Age & risk
factor
1
1.57
(1.20, 2.05)
1.78
(1.37, 2.31)
1.92
(1.51, 2.45)
< 0.0001
All cause
CVD
Importance of education
Lawlor et al AJE 2006;164:907-15
Genetic/in-utero vs. environment
*
* 1.69, ** 1.76
Osler et al. IJE 2006;35:1272-77
**
Genetic/in-utero vs. environment
Explanations for these findings …
Genetic/in-utero vs. environment
Underlying genetic mechanism
• Genetic factor
poor health
•Inherited personality traits
low SEP
SEP
health-related behaviours
• IQ
Prenatal programming effect the mother’s lifestyle and health
during pregnancy child’s foetal development
Assortative mating: father/partner will have similar SEP and health
Genetic/in-utero vs. environment
Chance finding
Selection bias
Osler et al. IJE 2006;35:1272-77
Barker & Osmond BMJ 2000;293:1271-75.
Mortality rates per 10,000 person years 1990-94 by
indices of housing conditions in 1960 and household
income in 1990, Oslo
Men
Women
1960
1990
1960
1990
1 (poor)
48
59
27
32
2
49
55
20
25
3
38
37
18
20
4
30
26
15
16
5
29
27
13
15
6
26
23
19
13
7 (well off)
20
18
17
9
Index values
From: Claussen et al. J Epidemiol Community Health 2003;57:40-45.
All cause mortality by cumulative
social class and car driving
Yes
No
Hazard ratios
2.5
2
1.5
1
0.5
0
3 NM
2 NM 1M
1 NM 2 M
Cumulative social class
Davey Smith et al, BMJ 1997
3M
Cardiovascular mortality according to
cumulative risk indicator (father’s social class,
adulthood social class, smoking, alcohol use)
N
4 favourable (0
unfavourable)
3 favourable (1
unfavourable)
CVD deaths
Relative risk
517
47
1
1299
227
1.99 (1.45 - 2.73)
2 favourable (2
unfavourable)
1606
354
2.60 (1.92 - 3.52)
1 favourable (3
unfavourable)
1448
339
2.98 (2.20 - 4.05)
0 favourable (4
unfavourable)
758
220
4.55 (3.32 - 6.24)
Davey Smith and Hart AJPH 2002
Poor health at age 33 & cumulative SES (birth - 33yrs)
25
% fair/ poor health
20
15
10
men
women
5
0
4
Best
5
6
7
8
9
10
11
lifetime
SESscore
score
Lifetime
SEP
12
13
14
15
16
Worst
Source: Power et al, 1999
Age adjusted relative rates of CVD mortality by
father’s social class and adulthood social class
Screening social class
Father’s social class
Non manual
Manual
Non manual
Manual
1
1.45 (1.04-2.01)
1.56 (1.29-1.88)
1.86 (1.56-2.22)
Davey Smith and Hart, AJPH 2002
Relative index of inequality according to 1960 and
1990 socio-economic position: all-cause mortality
1960 RII
1990 RII
1960 RII adjusted
for 1990 SEP
1990 RII adjusted
for 1960 SEP
Men
2.63 (2.06 to 3.35) 3.14 (2.44 to 4.04) 2.48 (1.94 to 3.16)
3.00 (2.33 to 3.86)
Women
1.55 (1.12 to 3.13) 2.50 (1.77 to 3.53) 1.47 (1.06 to 2.04)
2.45 (1.73 to 3.47)
From: Claussen et al. J Epidemiol Community Health 2003;57:40-45.
Evidence from ecological studies …
Leon & Davey Smith BMJ 2000;320:1705-6
Chains of risk
“The impact of some factor in childhood
may lie less in the immediate behavioural
change it brings about than in the fact it sets
into motion a chain reaction in which one
‘bad’ thing leads to another, or, conversely,
that a good experience makes it more likely
that another one will be encountered.”
Rutter 1988
Rosvall et al. BMC Public Health 2006;6:203-