Epidemiology of Asthma Applied Epidemiology module MSc in

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

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

What is asthma? Sources: (1) British Guidelines on the Management of Asthma. SIGN guideline, July 2007, (2) Asthma fact sheet, Aug 2006. www. who. int.

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. ”

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

What is asthma? • Aetiological factors Host Factors Environmental factors Genes Allergens: mites, animals, pollen Sex Viral infections Obesity Tobacco smoke Occupational : chemicals, animal and plant proteins Air pollution

Epidemiology of Asthma Routine data sources Time Person Place

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

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

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!

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

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

QOF limitations Asthma vs the rest • 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

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

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

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.

Asthma prevalence (person) Source: PRIMIS+ data

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

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

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

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

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

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

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/

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

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

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

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

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

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.

Prevalence - Children ISAAC

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

ECRHS Prevalence -Adults

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

Hospital admission rates – adults and children

Mortality – adults and children UK 2. 62 2. 13 6. 50 6. 31

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

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

World map of prevalence of asthma

World map of asthma case-fatality rates

Asthma Prevalence - Global

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!

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.

Exhaustion + frustration!