Prevalence of Asthma Treated in General Practice. 99/1

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Introduction

The General Practice Research Database (GPRD) is a large national database of GP medical records collected from a panel of general practices spread throughout the UK. The database holds detailed anonymised individual patient records for over 3.5 million patients. It is widely used for research, particularly into drug safety issues, but can also be used to estimate disease prevalence and to describe treatment patterns in primary care.

This factsheet presents information on the prevalences of treated asthma in GPRD practices in England and Wales between 1994 and 1996. Cases of treated asthma were defined as patients with a current or past diagnosis of asthma and who were being treated with asthma drugs. Individual GPs may use different criteria for diagnosing asthma and have different thresholds for prescribing asthma therapy. Thus, as with other sources of GP data (for example, the Morbidity Surveys in General Practice, LAIA factsheet 96/3), the figures may not be representative of all British general practices. However, assuming individual diagnostic criteria are reasonably stable over time, these data are useful for following trends.

Prevalence by age and sex

Figure 1:Prevalence of treated asthma

The proportions of all registered patients in the General Practice Research Database who received asthma treatment in 1996 were highest in children, lowest in middle age and rose again in the elderly, with the prevalence in men almost doubling between ages 50 and 75. Some of this rise in the elderly may be due to chronic obstructive airways disease diagnosed as asthma, rather than true late onset asthma. In children and younger adolescents (ages 5-15), treated asthma was more common in boys than in girls, which is compatible with findings in recent population surveys of school children. From mid-adolescence until around age 75, treated asthma was more common in women.

Time trends in prevalence

Figure 2:Trends in prevalence of treated asthma, males

Figure 3:Trends in prevalence of treated asthma, females

Over the three year period 1994-1996 and allowing for changes in the age structure of the population, the overall prevalence of treated asthma increased from 6.5% to 6.7% in men and from 6.4% to 6.9% in women. However, rates were stable in children over this time period.

Time trends in treatment

Over the three year period 1994 to 1996, the proportion of patients with treated asthma who were prescribed both bronchodilators and inhaled corticosteroids or cromoglycate increased from 63% to 66%. The increase was most marked in children of pre-school age.

Figure 4:Percentage of patients with treated asthma prescribed both bronchodilators and inhaled corticosteroids/cromoglycate

In 1996, 65% of males and 67% of females with treated asthma were prescribed both bronchodilators and inhaled corticosteroids (or cromoglycate), 28% of males and 26% of females were prescribed bronchodilators alone and the remaining 7% were prescribed inhaled corticosteroids or cromoglycate alone.

Geographical regions

Figure 5:Age-standardised prevalence of treated asthma by sex and region

Analysis of the General Practice Research Database by former Regional Health Authority (RHA) areas for 1994 shows that there was relatively little geographical variation in prevalence of treated asthma. All regions are within 15% of the value for England & Wales. Age-standardised prevalence rates varied from 5.9% (SW Thames) to 7.1% (Mersey and East Anglian) for males and from 5.7% (NW Thames) to 7.4% (Mersey) for females.

Summary

• The General Practice Research Database, covering over 3.5 million patients nationally, offers important information about the prevalence and drug treatment of asthma in primary care.

• The proportion of patients treated for asthma was similar in all regions of England and Wales.

• The prevalence of treated asthma was highest in children, affecting 12% of boys and 10% of girls aged 5-15. Throughout most of adult life, the prevalence was higher in women than in men.

• Between 1994-1996, the prevalence of treated asthma increased slightly in adults, particularly in women. The prevalence was stable in children.

• In 1996, about two-thirds of asthma patients were treated with both symptomatic ("reliever") and prophylactic ("preventer") medication and this proportion is tending to increase.

Footnote

Most data presented in this factsheet are taken from Office for National Statistics, Key Health Statistics from General Practice 1996, Series MB6 No.1. London: The Stationery Office, 1998.