Epidemiology of Asthma Applied Epidemiology module MSc in Health Sciences 2007-08

1. Epidemiology of AsthmaApplied Epidemiology moduleMSc in Health Sciences2007-08 Zoe Weir

2. Presentation Summary • What is asthma? • Epidemiology of asthma • Who? • Where? • When? UK Adult Children Europe Global

3. What is asthma? • Sources: • British Guidelines on the Management of Asthma. SIGN guideline, July 2007, • (2) Asthma fact sheet, Aug 2006. www.who.int.

4. What is asthma? • Diagnosis = clinical • Absence of agreed definition • International Consensus Report: • “a chronic inflammatory disorder of the airways.....in susceptible individuals, inflammatory symptoms are usually associated with widespread but variable airflow obstruction and an increase in airway response to a variety of stimuli. Obstruction is often reversible, either spontaneously or with treatment.”

5. What is asthma? • Shares symptoms with other disease processes • Wheeze • SOB • Chest tightness • Cough • Symptoms non-specific • Difficult diagnosis in younger children • Objective tests are available

6. What is asthma? • Aetiological factors

7. Epidemiology of Asthma Routine data sources Time Person Place

8. Epidemiology of Asthma Routine data sources Time Person ICD-10 classification Place

9. Definition problems... • Definitions – WHO • Symptomatic (wheeze, cough, SOB) • “diagnosis” • “those being treated by GP” • Definitions – WHEN • “ever” • “current”

10. Unhelpful sources of asthma routine data! • NEPHO – zilch! • APHO – zilch! • PHIU – zilch! • NHS North East – zilch! • Asthma disease register – unable to locate! • GPRD – have to pay! • Compendium of Health Statistics – have to pay! • DOH – one report which unable to access!

11. Helpful sources of asthma routine data • HES • www.statistics.gov.uk/ • Health Statistics Quarterly • The Health of Children and Young People • http://www.primis.nottingham.ac.uk/ • Health Survey for England • http://www.asthma.org.uk/ • http://www.laia.ac.uk/about.htm • http://www.ecrhs.org/ • WHO

12. Asthma vs the rest Source: The NHS Information Centre. National Quality and Outcomes Framework Statistics for England 2005/06

13. Asthma vs the rest • QOF limitations • GP underdiagnosis of asthma • Does not include patient s with asthma who have not received prescribed drugs in last 12 months • Patients can only appear on one disease register eg. COPD patients • Diagnosis varies with age and between doctors • “list inflation” • May reflect organisational factors • Comparison not standardised • Practice-based Source: The NHS Information Centre. National Quality and Outcomes Framework Statistics for England 2005/06

14. Asthma prevalence (person & time) Source: HSE, 2001

15. Asthma prevalence (person) Source: Health Statistics Quarterly, 2004.

16. Asthma Prevalence (person & time) 67.7 (67.0-68.4 73.7 (73.0-74.3) 67.3 (66.5-68.0) 76.9 (76.2-77.5) Source: Health Statistics Quarterly, 2004.

17. Asthma prevalence (person) Source: PRIMIS+ data

18. Asthma prevalence (person) Source: Health Statistics Quarterly, 2004.

19. Asthma Prevalence (place) Source: Health Statistics Quarterly, 2004

20. Asthma GP consultation rates (person & time) Source: Asthma UK. Where do we stand? Asthma in the UK today. 2004.

21. Asthma hospital admission rates (person & time) Source: Asthma UK. Where do we stand? Asthma in the UK today. 2004.

22. Finished Consultant Episodes for asthma (person) http://www.hesonline.nhs.uk/

23. Finished Consultant Episodes for asthma (person) http://www.hesonline.nhs.uk/

24. Finished Consultant Episodes for asthma (person) • Limitations to hospital activity data • Influenced by other factors • “episode-based” • Not available by practice or area http://www.hesonline.nhs.uk/

25. Asthma mortality (person & place) Source: Asthma UK. Where do we stand? Asthma in the UK today. 2004.

26. Asthma mortality (person & time) Source: Asthma UK. Where do we stand? Asthma in the UK today. 2004.

27. CHILDHOOD Source: http://www.statistics.gov.uk/

28. GP episodes, hospital admissions, and mortality (under 5’s) GPRD HES ONS

29. GP episodes, hospital admissions, and mortality (5-14 yrs)

30. EUROPE Sources: (1) Lung and Asthma Information Agency. Severe asthma across Europe. A review of available data. July 2005. (2) ENHIS. Prevalence of asthma and allergies in children. Fact sheet no 3.1, may 2007.

31. Prevalence - Children ISAAC

32. Limitations to ISAAC data • Data collected from specific centres only, therefore not country-representative. • Questionnaire-based (reporting by parents or self-reporting)

33. Prevalence -Adults ECRHS

34. Prevalence -Adults • Limitations to ECRHS data • Data out-of-date • Self-administered postal questionnaire • Re: severe symptoms

35. Hospital admission rates – adults and children

36. Mortality – adults and children UK 2.62 6.50 2.13 6.31

37. Mortality – adults and children • Limitations to data • ICD-9 still in some countries • overlap in coding of causes of death between asthma and other LRT diseases • “select” countries for comparison

38. GLOBAL Source: Global Strategy for Asthma Management and Prevention, Global Initiative for Asthma (GINA) 2007. Available from: http://www.ginasthma.org

39. World map of prevalence of asthma

40. World map of asthma case-fatality rates

41. Asthma Prevalence - Global

42. Summary (1) • Chronic and complex disease. • Absence of agreed definition. • Clinical diagnosis with non-specific symptoms different definitions data quality affected • Routine data sources limited!

43. Summary (2) • Asthma common condition. • Increase in asthma prevalence. • Prevalence peaks in the young and old. • More children admitted to hospital than adults. • Mortality rates higher in females. • Weak evidence of association with deprivation. • Asthma prevalence high in UK. • Asthma has a global effect.

44. Exhaustion + frustration!