Acute Bronchitis. 2000/1

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Introduction

Acute bronchitis is an acute respiratory infection characterised by cough productive of sputum which may be accompanied by wheezing. Viral causes include influenza, respiratory syncytial virus (RSV) and parainfluenza; bacterial causes include Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae and Bordetella pertussis.

The majority of patients with acute bronchitis who seek medical attention are treated exclusively in primary care. New episodes presenting in primary care are estimated from the Weekly Returns Service (WRS) of the Royal College of General Practitioners (see footnote).

Trends from year to year

Figure 1:Episodes of acute bronchitis in British general practice

Trends in rates of acute bronchitis episodes presenting in primary care by age group for years 1979-1998 are presented above. Rates of acute bronchitis increased in all age groups, reaching a peak in the early 1990s, declining thereafter. Acute bronchitis is commonest in children aged 0-4 years; followed by the elderly (aged 65 years and over) and is least common in those aged between 5 and 44 years. Between 1979 and 1993 the greatest increase occurred in the elderly.

Comparison with asthma

Figure 2:Episodes of asthma in British general practice

Trends in the incidence of asthma attacks are similar to those for acute bronchitis, increased until the early 1990s and declined thereafter in all the groups but particularly in children, but the rise in new episode incidence rates in the 1980s was greater for asthma than for acute bronchitis.

The frequency of new episodes of acute bronchitis is much higher than that for asthma attacks for most age groups, except for children aged 5-14 years. Therefore, in most age groups, a relatively small diagnostic shift away from acute bronchitis to asthma could considerably affect rates for the latter condition. However, the increased frequency of both conditions in the 1980s and early 1990s suggests that the increase in asthma was not due to a diagnostic shift away from acute bronchitis.

Seasonal variations

Figure 3:Mean weekly incidence of acute bronchitis in age groups 0-4 and 65+ years old

Acute bronchitis is commonest around the turn of the year. In young children aged 0-4 years, acute bronchitis episodes peaks just before the end of the year, but in persons aged 65 years and over the peak is 2 weeks later, in the first week of the year. This winter peak contrasts with the early autumn peak in incidence of acute asthma attacks (LAIA factsheet 93/4), but coincides with the months of highest mortality rates, particularly among the elderly.

Figure 4:Weekly average for incidence of respiratory diseases and number of deaths from all causes

A similar seasonal pattern of winter peaks in GP episodes among elderly patients is evident for acute upper and lower respiratory diseases included in the Weekly Returns Service. (Aggregated respiratory disease (ARD) represents the sum of new episodes of all respiratory conditions surveyed: acute bronchitis, common cold, influenza, influenza-like illness, acute tonsillitis, acute sinusitis, laryngitis/tracheitis, pneumonia/pneumonitis and pleurisy). It is striking how closely the seasonal variations in acute bronchitis and ARD among the elderly match those of deaths, regardless of cause. It is likely that acute respiratory infections are a common immediate cause of death for persons with non-respiratory disease.

Footnote

Since 1967, the Weekly Returns Service has collected information on episodes of disease presenting to general practitioners. Currently 72 practices with a registered population of 600,000 are surveyed. Doctors record their working diagnoses, specifying whether the patient is consulting about a new or an ongoing episode of disease. Results are collated on a weekly basis by the Royal College of General Practitioners Research Unit, Birmingham and published as an Annual Report. Weekly data are accessible from their web site.

Summary

• New episode rates of acute bronchitis and asthma rose in the 1980s but have fallen since the early 1990s.

• Acute bronchitis is commonest in pre-school children and elderly persons.

• Acute bronchitis peaks just before the New Year in pre-school children, but just after in the elderly.

• There is a marked temporal association between respiratory infections, including acute bronchitis and deaths from all causes.

We would like to thank Dr Andy Ross and Dr Douglas Fleming (RCGP Research Unit, Birmingham) for preparing this factsheet.