Measuring Asthma Prevalence and Severity in

Children

Lara Akinbami, MDInfant and Child Health Studies Branch

National Center for Health Statistics

Overview

National trends in childhood asthma prevalence, hospitalization and mortality, 1980 to 2000

Racial disparities in asthma prevalence, hospitalization and mortality

NCHS systems with asthma data

Prevalence National Health Interview Survey (NHIS):

household survey

Hospitalizations National Hospital Discharge Survey (NHDS):

record abstraction

Mortality National Vital Statistics System (NVSS):

death certificate data

Asthma prevalence

Asthma prevalence, 1980-96, lifetime diagnosis & asthma attack prevalence, 1997-2000, NHIS

0

20

40

60

80

100

120

140

1980 1985 1990 1995 2000

Pre

vale

nce

per

1,00

0 ch

ildre

n

Asthma prevalence (4.3% per yr )

Asthma lifetime diagnosis

Asthma attack prevalence

National Health Interview Survey1997 redesign

Purpose of the redesign Improve data quality Simplify the survey Reduce the questionnaire length

The redesign involved Survey restructuring Changes in NHIS core questions

1980-1996 NHIS core

Redesigned (1997-2000) NHIS

core

Screener question:

(None) Has a doctor or other healthprofessional ever told you that your child had asthma?

Past 12 months question:

During the past 12 m, did anyone in the family have asthma?

IF YES: During the past 12 m, has your child had an episode of asthma or an asthma attack?

Asthma prevalence, 1980-96, lifetime diagnosis & asthma attack prevalence, 1997-2000, NHIS

0

20

40

60

80

100

120

140

1980 1985 1990 1995 2000

Pre

vale

nce

per

1,00

0 ch

ildre

n

Asthma prevalence (4.3% per yr )

Asthma lifetime diagnosis

Asthma attack prevalence

Measuring the 1997 redesign impact: NHIS Child Health Supplement

NHIS includes periodic supplements on selected health topics: 1981 and 1988 Child Health Supplement

In-depth survey of child health

Asthma questions included

1980-1996 NHIS core

Redesigned (1997-2000) NHIS

core

NHIS Child Health

Supplement (1981, 1988)

Screener question:

(None) Has a doctor or other health professional ever told you that your child had asthma?

Did your child ever have asthma?

Past 12 months question:

During the past 12 m, did anyone in the family have asthma?

IF YES: During the past 12 m, has your child had an episode of asthma or an asthma attack?

IF YES: Did your child have asthma in the past 12 m?

1981 and 1988 Core and Child Health Supplement (CHS) asthma prevalence

estimates

1981 1988

Core question

3.8% 5.1%

CHS questions

3.2% 4.3%

% difference 18.2 18.6

Asthma prevalence (1980-96), and modified asthma attack prevalence (1997-2000), NHIS

0

20

40

60

80

100

120

140

1980 1985 1990 1995 2000

Pre

va

len

ce

pe

r 1

,00

0 c

hild

ren

Asthma prevalence

Asthma attack prevalence

High and low modified estimates

Summary: NHIS redesign impact on prevalence estimates

Most of the apparent decrease in 1997 resulted from the redesign

If the survey was not changed, 1997-2000 estimates would have been ~ 20% higher

This is likely an underestimate of the impact of the redesign

2001 NHIS: additional asthma question

“Does your child STILL have asthma?”

Will provide an estimate of current asthma prevalence

Estimate still won’t be directly comparable to pre-1997 estimates

Asthma hospitalizations

Childhood asthma hospitalizations

Asthma hospitalization can be used as an indicator of severity

However, asthma is a condition sensitive to access to high quality ambulatory health care

Hospitalization data measures events rather than persons

Asthma hospitalizations for children 0-17 years, 1980-2000 NHDS

0

5

10

15

20

25

30

35

40

1980 1985 1990 1995 2000

Per 1

0,00

0 ch

ildre

n

1.4% per year increase

Asthma mortality

Childhood asthma mortality

Rare event

But, avoidable

Also affected by factors in addition to prevalence and severity Health care utilization Patient education and “compliance”

Asthma deaths, children 0-17 years, 1980-2000, NVSS

0

1

2

3

4

5

1980 1985 1990 1995 2000

Per 1

,000

,000

chi

ldre

n

3.4% per year increase

ICD-9 ICD-10

Asthma deaths, children 0-17 years, 1980-2000, NVSS

0

1

2

3

4

5

1980 1985 1990 1995 2000

Per 1

,000

,000

chi

ldre

n

3.4% per year increase

ICD-9 ICD-10

Summary of trends in childhood asthma

Increasing burden of childhood asthma from 1980 to the mid 1990s

Recent plateau in asthma attack prevalence, hospitalizations and deaths

Complications: NHIS redesign, ICD code change

Racial disparities in asthma

Racial disparities in asthma

Widespread perception: minorities have much higher asthma prevalence

Minorities also at higher risk for poor outcomes

Impact of socioeconomic status on disparities

Racial disparities: asthma prevalence, hospitalization, and mortality

Attack prevalence (1998)

Per 100

Hospitalization (1998-99)

Per 10,000

Mortality (1997-98)

Per 1,000,000

Non-Hispanic White

5.2 15.5 2.2

Non-Hispanic Black

6.8 56.9 10.1

Rate Ratio (black/white)

1.3 3.7 4.6

Racial and income disparities in asthma: NHIS

Race and income data available

NHIS contains prevalence and morbidity data

Survey years 1993-1996 grouped for adequate sample size

Children 3 years excluded due to diagnostic uncertainty

Average annual asthma prevalence, 1993-1996, children 3-17 years

8.48

7.1 7.3

0

2

4

6

8

10

Ast

hm

a p

reva

len

ce (

%)

Black poor

Black nonpoor

White poor

White nonpoor

Activity limitation due to asthma, 1993-1996, children 3-17 years with asthma

49.1

1923.2 21

0

10

20

30

40

50

60

% w

ith

act

ivit

y li

mit

atio

ns

Black poor

Black nonpoor

White poor

White nonpoor

Racial disparities in health care use

NHIS has information about Health care use: asthma doctor visits Severity: asthma bed days

Use disability ratio Adjust health care use for severity of

illness The higher the ratio, the more health care

utilized per unit of severity

Doctor contacts & bed days due to asthma in the past 2 weeks, children 3-17 years

Doctor contacts (mean)

Bed days

(mean)

Ratio:

Doctor contacts per bed days

Black poor 0.08 0.61 0.13

Black nonpoor 0.06 0.24 0.26

White poor 0.11 0.48 0.22

White nonpoor 0.09 0.21 0.42

Summary of racial disparities in asthma

Disparities in asthma morbidity and mortality > prevalence disparities

Black poor children underuse ambulatory care given their greater morbidity

It is not likely that disparities in prevalence drive the very large disparities in asthma hospitalizations and mortality

Overall summary of childhood asthma

Dramatic increase in the asthma burden among children until mid-1990s

Recent plateau in asthma attack prevalence, hospitalizations, and mortality

Minority and poor children face: Only slightly higher risk of having asthma Much higher risk of morbidity Inappropriately low use of ambulatory care Much higher risk of mortality

Acknowledgements

National Center for Health Statistics, CDC:Ken Schoendorf, MD, MPHJennifer Parker, PhDJulia Rhodes, PhD

Vanderbilt University:Bonnie LaFleur, PhD

National Center for Environmental Health, CDCJeanne Moorman, PhD