Epidemiology of Asthma Applied Epidemiology module MSc in Health Sciences Zoe Weir

Presentation Summary What is asthma? Epidemiology of asthma – Who? – Where? – When? Adult Children EuropeGlobal UK

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

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 FactorsEnvironmental factors GenesAllergens: mites, animals, pollen SexViral infections ObesityTobacco smoke Occupational : chemicals, animal and plant proteins Air pollution

Epidemiology of Asthma Person Time Place Routine data sources

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

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 – Health Statistics Quarterly Health Statistics Quarterly – The Health of Children and Young People The Health of Children and Young People Health Survey for England WHO

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

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

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

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

Asthma Prevalence (person & time) 67.7 ( ( ) 67.3 ( ) 76.9 ( ) 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

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

Finished Consultant Episodes for asthma (person)

Finished Consultant Episodes for asthma (person)

Finished Consultant Episodes for asthma (person) Limitations to hospital activity data Influenced by other factors “episode-based” Not available by practice or area

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

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

CHILDHOOD Source:

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 (2) ENHIS. Prevalence of asthma and allergies in children. Fact sheet no 3.1, may 2007.

Prevalence - Children ISAAC

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

Prevalence -Adults ECRHS

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

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) Available from:

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!