International comparisons of infant mortality– how can ... · Fig 1. Under 5 (0–4 years)...

International comparisons of infant mortality– how can administrative health data help us design effective prevention programmes? Ania Zylbersztejn and Pia Hardelid UCL Great Ormond Street Institute of Child Health

Why are we interested in international comparisons?

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Fig 1. Under 5 (0–4 years) mortality rates per 1000 live births by age at death in Western Europe in 2013 [1]

[1] Wang H, et al. Global, regional, and national levels of neonatal, infant, and under-5 mortality during 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 2014 Sep 13;384(9947):957-979.

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Early neonatal (0–6 days) Late neonatal (7–28 days) Post to neonatal (29–364 days) Childhood (1–4 years)

What can we learn from aggregate data?

Shortcomings of previous studies

• Aggregate data studies lack detail on low birth weight, prematurity, presence of congenital anomalies, or socio-economic status

• These studies can’t answer why children are dying at a higher rate in the UK

→ What should we be doing to prevent infant deaths in the UK?

Two approaches – comparing child mortality in England and Sweden

• What can we learn from aggregate data?

• Individual level analysis using national birth cohort studies

What can we learn from aggregate, routinely published data?

• Disaggregate the number of infant deaths and births by a key risk factor at birth (eg birth weight): – Should intervention efforts be focused before birth or

after birth, given the conditions a child is born with?

• Number of births and deaths by birthweight category and age at death (early neonatal, late neonatal, postneonatal infant mortality)

Excess Deaths: England & Wales vs Sweden

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< 1000g 1000-1499g 1500-2499g 2500-3499g ≥3500g

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Birthweight Category

0-6 days 7-27 days 28-365 days

• Unadjusted excess deaths: 1238 • Adjusted (for BW excess

deaths): 559

• Can take into account multiple risk factors

simultaneously

Individual level analysis using national birth cohort studies

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Characteristics of baby at birth:

Picture from: Achoubey, Wiki Commons, CC BY-SA 4.0

- Preterm birth

- Low birthweight

- Congenital malformations

- Multiplicity of pregnancy

- Sex

Sweden England &Wales

5.9% 7.1%

% of preterm births [2] (under 37 weeks)

Sweden England &Wales

4.3% 7.0%

% of babies with low-birthweight [2]

(under 2.5kg)

[2] Euro-Peristat project with SCPE and Eurocat. European Perinatal Health Report. The health and care of pregnant women and babies in Europe in 2010. May 2013.

Sweden England 4.9%

(3rd Trimester) 12%

(during) Sweden

England &Wales

1.6% 5.7%

% of teenage mothers in 2010 [2]

(under 20 years old)

% of mothers smoking during pregnancy [2]

Background: risk factors affecting early life mortality

https://upload.wikimedia.org/wikipedia/commons/4/46/Baby2.gif

Birth and maternal details

Hospitalisation Details

Death Registration Data

Swed

en

Medical Birth Register ~97-99% of all births

From 1987 to 2012

National Discharge Register

~ 99% of all public hospitalizations

From 1987 to 2013

Cause of Death Register From 1987 to 2013

Engl

and

Hospital Episode Statistics (HES) All National Health System (NHS) admitted patient care

From 1997 to 2014

~97% of all births

Office for National Statistics (ONS) Death

Registration Linked to HES since 1998

Datasets

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https://upload.wikimedia.org/wikipedia/commons/4/46/Baby2.gif

England N=6,099,617

(100% of all births in HES) 2003-2012

Sweden N=1,444,109

(100% of births) 1998-2012

England N=4,103,902

(67.3% of HES births)

Sweden N=1,443,558

(99.3% of births)

Births in hospitals with "poor" quality of data

Missing gestational age, maternal age, birth weight, gender or SES

Gestation <24 or birth weight <500

Death at 0-1 days after birth

n=1,558,842 (25.6%)

n=421,774 (6.9%)

n=14,260 (0.2%)

n=839 (0.01%)

n=6575 (0.5%) n=3765 (0.3%) n=210 (0.01%)

Comparable birth cohorts

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Country England Sweden

# of deaths (% of of deaths at 2-365 days)

4512 (46.3%)

1106 (47.4%)

Model 1

England (vs Sweden) 1.50 (1.40, 1.61)

Neonatal Mortality (2-27 days) – Cox PH model

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Neonatal Mortality (2-27 days) – Cox PH model Model 1 Model 2

England (vs Sweden) 1.50 (1.40, 1.61) 1.22 (1.14, 1.30)

Birth weight (baseline: 3.5+

kg)

0.5-1kg 32.17 (25.82, 40.08) 1-1.5kg 12.31 (10.07, 15.06)

1.5-2.5kg 6.33 (5.57, 7.19) 2.5-3.5kg 1.81 (1.66, 1.98)

Gestation (baseline: 39+

weeks)

24-27 14.54 (11.77, 17.97) 28-31 5.30 (4.41, 6.37) 32-34 3.29 (2.85, 3.79) 35-36 2.61 (2.31, 2.95) 37-38 1.61 (1.48, 1.75)

Girl vs Boy 0.79 (0.75, 0.83)

Model 1 Model 2 Model 3

England (vs Sweden) 1.50 (1.40, 1.61) 1.22 (1.14, 1.30) 1.02 (0.95, 1.10)


kg)

0.5-1kg 32.17 (25.82, 40.08) 17.05 (13.70, 21.21) 1-1.5kg 12.31 (10.07, 15.06) 8.01 (6.55, 9.80)

1.5-2.5kg 6.33 (5.57, 7.19) 5.50 (4.84, 6.24) 2.5-3.5kg 1.81 (1.66, 1.98) 1.80 (1.65, 1.97)


weeks)

24-27 14.54 (11.77, 17.97) 7.36 (5.96, 9.08) 28-31 5.30 (4.41, 6.37) 3.75 (3.12, 4.51) 32-34 3.29 (2.85, 3.79) 2.81 (2.43, 3.24) 35-36 2.61 (2.31, 2.95) 2.36 (2.09, 2.66) 37-38 1.61 (1.48, 1.75) 1.52 (1.40, 1.66)

Girl vs Boy 0.79 (0.75, 0.83) 0.84 (0.80, 0.89) Congenital Anomaly 7.42 (6.93, 7.94)

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Neonatal Mortality (2-27 days) – Cox PH model Model 1 Model 2 Model 3 Model 4

England (vs Sweden) 1.50 (1.40, 1.61) 1.22 (1.14, 1.30) 1.02 (0.95, 1.10) 0.99 (0.92, 1.06)


kg)

0.5-1kg 32.17 (25.82, 40.08) 17.05 (13.70, 21.21) 16.31 (13.10, 20.29) 1-1.5kg 12.31 (10.07, 15.06) 8.01 (6.55, 9.80) 7.67 (6.27, 9.38)

1.5-2.5kg 6.33 (5.57, 7.19) 5.50 (4.84, 6.24) 5.29 (4.66, 6.01) 2.5-3.5kg 1.81 (1.66, 1.98) 1.80 (1.65, 1.97) 1.77 (1.62, 1.93)


weeks)

24-27 14.54 (11.77, 17.97) 7.36 (5.96, 9.08) 7.47 (6.06, 9.22) 28-31 5.30 (4.41, 6.37) 3.75 (3.12, 4.51) 3.80 (3.17, 4.57) 32-34 3.29 (2.85, 3.79) 2.81 (2.43, 3.24) 2.84 (2.46, 3.28) 35-36 2.61 (2.31, 2.95) 2.36 (2.09, 2.66) 2.37 (2.10, 2.68) 37-38 1.61 (1.48, 1.75) 1.52 (1.40, 1.66) 1.53 (1.40, 1.66)

Girl vs Boy 0.79 (0.75, 0.83) 0.84 (0.80, 0.89) 0.84 (0.80, 0.89) Congenital Anomaly 7.42 (6.93, 7.94) 7.40 (6.91, 7.92)

Maternal Age (baseline: 30-35)

<20 1.25 (1.11, 1.39) 20-25 1.16 (1.07, 1.26) 25-30 1.10 (1.02, 1.18) 35-40 1.06 (0.97, 1.16) 40+ 1.31 (1.15, 1.49)

SES (baseline: least deprived 20%)

Most deprived 20% 1.10 (1.01, 1.20) More deprived 20-40% 0.98 (0.89, 1.08)

Middle 40-60% 0.88 (0.80, 0.97) Less deprived 20-40% 0.86 (0.78, 0.96)

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Country England Sweden

# of deaths (% of of deaths at 2-365 days)

5226 (53.7%)

1228 (52.6%)

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Post Neonatal Mortality (28-364 days) – Cox PH model Model 1

England (vs Sweden) 1.50 (1.41, 1.59)

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Model 1 Model 2

England (vs Sweden) 1.50 (1.41, 1.59) 1.24 (1.17, 1.32)


kg)

0.5-1kg 45.88 (36.28, 58.01) 1-1.5kg 15.73 (12.82, 19.29)

1.5-2.5kg 7.19 (6.47, 7.98) 2.5-3.5kg 2.01 (1.88, 2.16)


weeks)

24-27 4.35 (3.45, 5.48) 28-31 1.88 (1.55, 2.29) 32-34 1.77 (1.54, 2.02) 35-36 1.94 (1.75, 2.15) 37-38 1.54 (1.44, 1.65)

Girl vs Boy 0.75 (0.71, 0.79)

Post Neonatal Mortality (28-364 days) – Cox PH model

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Model 1 Model 2 Model 3

England (vs Sweden) 1.50 (1.41, 1.59) 1.24 (1.17, 1.32) 1.10 (1.04, 1.18)


kg)

0.5-1kg 45.88 (36.28, 58.01) 17.66 (14.03, 22.24) 1-1.5kg 15.73 (12.82, 19.29) 7.92 (6.47, 9.70)

1.5-2.5kg 7.19 (6.47, 7.98) 5.46 (4.92, 6.07) 2.5-3.5kg 2.01 (1.88, 2.16) 1.96 (1.83, 2.11)


weeks)

24-27 4.35 (3.45, 5.48) 1.73 (1.28, 2.17) 28-31 1.88 (1.55, 2.29) 1.14 (0.94, 1.38) 32-34 1.77 (1.54, 2.02) 1.38 (1.21, 1.58) 35-36 1.94 (1.75, 2.15) 1.64 (1.47, 1.81) 37-38 1.54 (1.44, 1.65) 1.40 (1.31, 1.50)

Girl vs Boy 0.75 (0.71, 0.79) 0.84 (0.80, 0.88) Congenital Anomaly 15.31 (14.47, 16.21)


Model 1 Model 2 Model 3 Model 4



kg)

0.5-1kg 45.88 (36.28, 58.01) 17.66 (14.03, 22.24) 16.02 (12.72, 20.18) 1-1.5kg 15.73 (12.82, 19.29) 7.92 (6.47, 9.70) 7.16 (5.85, 8.77)

1.5-2.5kg 7.19 (6.47, 7.98) 5.46 (4.92, 6.07) 4.96 (4.47, 5.51) 2.5-3.5kg 2.01 (1.88, 2.16) 1.96 (1.83, 2.11) 1.87 (1.74, 2.01)


weeks)

24-27 4.35 (3.45, 5.48) 1.73 (1.28, 2.17) 1.79 (1.43, 2.24) 28-31 1.88 (1.55, 2.29) 1.14 (0.94, 1.38) 1.18 (0.97, 1.43) 32-34 1.77 (1.54, 2.02) 1.38 (1.21, 1.58) 1.43 (1.26, 1.64) 35-36 1.94 (1.75, 2.15) 1.64 (1.47, 1.81) 1.67 (1.50, 1.85) 37-38 1.54 (1.44, 1.65) 1.40 (1.31, 1.50) 1.42 (1.33, 1.52)



<20 1.68 (1.53, 1.85) 20-25 1.31 (1.21, 1.41) 25-30 1.09 (1.02, 1.17) 35-40 0.96 (0.88, 1.04) 40+ 1.18 (1.03, 1.34)


Most deprived 20% 1.54 (1.41, 1.68) More deprived 20-40% 1.31 (1.19, 1.43) Middle 40-60% 1.10 (1.00, 1.22) Less deprived 20-40% 1.02 (0.92, 1.13)


Summary – individual level analysis of infant mortality in England and Sweden • Neonatal mortality (2-27 days):

– Once risk factors at birth adjusted for, no statistically significant differences in risk of death remained between England and Sweden

• Post neonatal mortality (28-364 days) – Significantly increased risk remained after adjustment

for risk factors present at birth; no statistically significant difference remained after further adjustment for socio-economic status

→The largest number of deaths could be prevented by preventing preterm birth/low birthweight, and congenital anomalies

Further work

• Analyses of early childhood mortality: – 1-4 years

• Cause specific mortality (‘healthcare amenable’) • Infections • SIDS/SUDI • Injuries

• International comparisons using national birth cohort studies can help us understand: – Differences in prevalence of risk factors for infant

mortality – where investments to prevent child deaths would have

the largest impact

• Need better individual level data for monitoring and research: – Routine linkage between birth registration, hospital

admission and mortality data

Summary – international comparisons

Acknowledgements

• Ania Zylbersztejn, Ruth Gilbert (UCL Great Ormond Street Institute of Child Health)

• Anders Hjern (CHESS, Karolinska Institute)

• Farr Institute (Funding)


Model 1 Model 2 Model 3 Model 4



kg)

0.5-1kg 32.17 (25.82, 40.08) 17.05 (13.70, 21.21) 16.31 (13.10, 20.29) 1-1.5kg 12.31 (10.07, 15.06) 8.01 (6.55, 9.80) 7.67 (6.27, 9.38)

1.5-2.5kg 6.33 (5.57, 7.19) 5.50 (4.84, 6.24) 5.29 (4.66, 6.01) 2.5-3.5kg 1.81 (1.66, 1.98) 1.80 (1.65, 1.97) 1.77 (1.62, 1.93)


weeks)

24-27 14.54 (11.77, 17.97) 7.36 (5.96, 9.08) 7.47 (6.06, 9.22) 28-31 5.30 (4.41, 6.37) 3.75 (3.12, 4.51) 3.80 (3.17, 4.57) 32-34 3.29 (2.85, 3.79) 2.81 (2.43, 3.24) 2.84 (2.46, 3.28) 35-36 2.61 (2.31, 2.95) 2.36 (2.09, 2.66) 2.37 (2.10, 2.68) 37-38 1.61 (1.48, 1.75) 1.52 (1.40, 1.66) 1.53 (1.40, 1.66)



<20 1.25 (1.11, 1.39) 20-25 1.16 (1.07, 1.26) 25-30 1.10 (1.02, 1.18) 35-40 1.06 (0.97, 1.16) 40+ 1.31 (1.15, 1.49)


Most deprived 20% 1.10 (1.01, 1.20) More deprived 20-40% 0.98 (0.89, 1.08)

Middle 40-60% 0.88 (0.80, 0.97) Less deprived 20-40% 0.86 (0.78, 0.96)

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Unadjusted neonatal mortality by SES England

Sweden

International comparisons of infant mortality– how can ... · Fig 1. Under 5 (0–4 years)...

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