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