Clinical and epidemiological approaches to the life course

1
Clinical and epidemiological approaches to the
life course

• Shah Ebrahim
• Department of Epidemiology Population Health
• London School of Hygiene Tropical Medicine

2
Overview

• Clinical perspectives and applications
• Service organisation
• Health promotion
• Epidemiological perspectives
• Theoretical models
• Fetal growth
• Economic hardship
• Childhood diet
• Clinical and preventive applications

3
What is a life course approach for clinicians

• Taking a social history
• Measuring growth trajectories in childhood
• Importance of continuity of care
• Milestones birth, school, job, marriage,
  children, retirement, death
• Understanding that the patients current
  experience is rooted in earlier experiences of
  health care

4
Clinical perspectives

• Services are organised to reflect lifecourse
  (obstetrics, child health, adult medicine,
  geriatrics)
• BUT, this fragments understanding of health
  problems in families and communities
• Primary care can (used to?) take a cradle to
  grave perspective

5
WHOs policy on ageing has adopted a life course
approach
http//www.who.int/hpr/ageing/
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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 psychosocial pathways that
operate across the life course and influence the
development of chronic diseases.
What is a life course approach?
7
...recent progress has shown a) that the health
of the adult is dependent upon the health of the
child.....and....b) that the health of the
child is dependent upon the health of the infant
and its mother. George Newman 1914 CMO
Board of Education
8
Theoretical life course models

• Critical and sensitive period models
• with or with out later 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 2002
9
Critical and sensitive periods

• Critical period a time period only during which
  an exposure has an effect.
• Thalidomide and limb abnormalities
• Oestrogen use in early pregnancy and vaginal
  cancer
• 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

10
Theoretical life course models

• Critical and sensitive period models
• with or with out later 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 2002
11
Accumulation model independent risks
O U T C O M E M E A S U R E
A
Ainactivity, Bhigh blood pressure, Chigh
blood cholesterol
B
C
Kuh et al (In Press)
12
Accumulation model risk clustering
O U T C O M E M E A S U R E
D
A
C
B
D Metabolic syndrome
Kuh et al
13
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
14
Chains of risk model additive
ADrinking, Bhigh blood pressure, C depression
O U T C O M E M E A S U R E
A
C
B
Kuh et al
15
Chains of risk model trigger
Ahouse dust mite, B asthma attacks, C school
absence
O U T C O M E M E A S U R E
A
C
B
Kuh et al
16
Lifecourse influences on respiratory disease
(Ben-Shlomo Kuh 1999)
Poor educational attainment
Poor adult SES
Poor childhood SES
Air pollution Poor adult diet Smoking
Air pollution Passive smoking Poor nutrition
Occupational hazards
Infant Respiratory Infections
Childhood chest illness
Rapid decline in lung function/ adult lung
disease
Poor growth in utero
Poor lung development
Asthmatic tendency or Genetic predisposition
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Interactions between intra-uterine and later life
exposures
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CHD Incidence by Birthweight and BMI The
Caerphilly Study (Frankel et al 1996)
Percent
p0.0005
p0.5
p0.5
BMI TERTILE
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Accumulation of risk across the life course
20
Odds ratios for disability in 1994 by economic
hardship between 1965 and 1983
IADL
ADL
Lynch JW et al, New Eng J Med, 19973371889-95
21
Poor health at age 33 cumulative SES (birth -
33yrs)
worst
best
Source Power et al, 1999
22
The Boyd-Orr Study long term follow up from
childhood, 1937
23
Energy intake in childhood and cancer risk Boyd
Orr study
Frankel et al, BMJ 1998
24
Household income, 1937/9 and walking speed in
2003, mean age 70
Time to walk 6m.
3.2 reduction in walking time per category
increase in income, p0.04
high
low
Weekly household income, 1937/9
25
Clinical and public health applications
26
Schematic representation of the life course of
ventilatory function
50
40
30
Level of lung function
20
Level below which
symptoms may occur
10
0
0
10
20
30
40
50
60
70
80
90
100
Years of life
taken from Strachan (1997)
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Life course development in physical capacity and
effects of a threshold for independent living.
Physical capacity
Threshold for independent living
Age
28
Life course development in physical capacity and
effects of a threshold for independent living.
Physical capacity
Reducing the threshold for older people
Threshold for independent living
Age
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Life course development in physical capacity and
effects of a threshold for independent living.
1 Early life interventions to ensure max. peak
capacity 2 Adult interventions to slow rate of
decline in capacity 3 Late life interventions
to maintain capacity above thresholds 4
remedial therapy to restore quality of life
Physical capacity
2
1
3
4
Threshold for independent living
Age
30
Life course epidemiology

• Extends the fetal origins of adult disease
  hypothesis
• Greater explanatory power than simpler causal
  models
• Provides a means of developing novel prevention
  strategies

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Conclusions

• Clinical perspectives on life course could
  dramatically influence health promotion
  activities
• Epidemiological perspectives are leading to new
  understanding of aetiology which is fundamental
  to development of successful preventive
  programmes
• A life course approach emphasises that
  opportunities for prevention are not confined to
  any one period
• Evaluations of the effects and costs of
  interventions at different points in the life
  course are needed