ASTHMA - TRENDS IN HOSPITAL ADMISSIONS

Data from the Lung and Asthma Information Agency (LAIA) show two decades of increasing asthma admissions, especially among pre-school children

LAIA's factsheet, "Trends In Hospital Admissions For Asthma", illustrates the considerable rise in admissions in England and Wales with a discharge diagnosis of asthma through the 1970s and 1980s. The total increased from just under 20,000 per year in the early 1960s, to 80,000 per year by the late 1980s.

Recently, numbers appear to have stabilised at around 100,000 per year. The increase is most noticeable in children, who currently account for almost half of all asthma admissions.

Possible reasons for this increase include changes in:

• prevalence
• disease severity or chronicity
• medical care, lowering the threshold for admission or increasing the numbers of re-admissions
• changes in data collection systems
• the diagnosis and coding of disease

Children

The largest increases in admission rates occurred in children, most notably in the youngest age group. Among pre-school children in England and Wales, admissions went up from four per 10,000 in 1962 to almost 80 per 10,000 by 1985. Rates now appear to have stabilised at around 100 per 10,000 per year.

A similar pattern is seen in children aged between 5 and 9 years, where rates have increased six-fold. In Scotland, the rates began to rise later, and there is a suggestion that they are still increasing.

Studies have established that these increases cannot be completely explained by an increase in re-admissions, diagnostic transfer from related categories such as acute bronchitis or pneumonia, or changes in the threshold of admission.

The proportion of all paediatric admissions attributable to asthma is increasing, and it is thought that the pattern of medical care in childhood asthma has been changing.

A variety of factors have been suggested, including more self-referral to A&E departments during acute attacks, and an increase in referral of acute asthma by GPs. These would tend to increase the likelihood of children with acute asthma being admitted to hospital, regardless of any change in the occurrence of acute attacks.

Adults

Admission rates in adults increased slightly through the 1960s, declined during the 1970s, then began to rise again from 1980. Current trends are not entirely consistent.

Up to the age of 44, rates are still increasing, whereas among the 45 to 64 age group they may have started to decrease. Rates among people aged 65 and above are still increasing, perhaps due to diagnostic transfer from other categories of obstructive disease.

Age and sex

Currently, 32 per cent of admissions are children aged up to 4 years, and a further 19 per cent are 5 to 14-year-olds. Boys are twice as commonly admitted as girls. After age 15, this pattern reverses, and women have a higher admission rate that men.

Data sources

Until 1982, data on admissions in England and Wales were available in the form of a random 10 per cent sample of all discharges and deaths. Then in 1982, Wales started to collect its data separately, with 100 per cent coverage.

Since the changes in NHS information systems were implemented in 1987, English data have been based on a 25 per cent sample. Wales also joined that system in 1991. Diagnostic coverage was incomplete in the earlier years, so the data have been adjusted using published factors. Scottish data are more complete. The numbers have been based on 100 per cent coverage since 1968, and there have been no breaks or changes in the data collection system.