Measuring Asthma Prevalence and Severity in Children

1. Measuring Asthma Prevalence and Severity in Children Lara Akinbami, MD Infant and Child Health Studies Branch National Center for Health Statistics

2. Overview • National trends in childhood asthma prevalence, hospitalization and mortality, 1980 to 2000 • Racial disparities in asthma prevalence, hospitalization and mortality

3. 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

4. Asthma prevalence

5. Asthma prevalence, 1980-96, lifetime diagnosis & asthma attack prevalence, 1997-2000, NHIS Asthma lifetime diagnosis Asthma prevalence (4.3% per yr ) Asthma attack prevalence

6. 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

8. Asthma prevalence, 1980-96, lifetime diagnosis & asthma attack prevalence, 1997-2000, NHIS Asthma lifetime diagnosis Asthma prevalence (4.3% per yr ) Asthma attack prevalence

9. 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

11. 1981 and 1988 Core and Child Health Supplement (CHS) asthma prevalence estimates

12. Asthma prevalence (1980-96), and modified asthma attack prevalence (1997-2000), NHIS High and low modified estimates Asthma prevalence Asthma attack prevalence

13. 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

14. 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

15. Asthma hospitalizations

16. 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

17. Asthma hospitalizations for children 0-17 years, 1980-2000 NHDS 1.4% per year increase

18. Asthma mortality

19. Childhood asthma mortality • Rare event • But, avoidable • Also affected by factors in addition to prevalence and severity • Health care utilization • Patient education and “compliance”

20. Asthma deaths, children 0-17 years, 1980-2000, NVSS ICD-9 ICD-10 3.4% per year increase

21. Asthma deaths, children 0-17 years, 1980-2000, NVSS ICD-9 ICD-10 3.4% per year increase

22. 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

23. Racial disparities in asthma

24. 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

25. Racial disparities: asthma prevalence, hospitalization, and mortality

26. 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

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

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

29. 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

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

31. 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

32. 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

33. Acknowledgements National Center for Health Statistics, CDC: Ken Schoendorf, MD, MPH Jennifer Parker, PhD Julia Rhodes, PhD Vanderbilt University: Bonnie LaFleur, PhD National Center for Environmental Health, CDC Jeanne Moorman, PhD