Respiratory diseases are one of the most common forms of ill-health. They are also a leading cause of hospitalisation and death.

Asthma has become more common over the last 30 years, but we still do not know why this is. Scientists believe there may be many contributory factors which are a result of our changing lifestyles. For example, we are more likely to have centrally heated homes with fitted carpets and little ventilation, ideal conditions for the house-dust mite, a very common asthma trigger that lives in soft furnishings. Our diets now include fewer fresh foods some: evidence suggests that eating plenty of fruit and vegetables can help to reduce asthma symptoms. Other theories include less exposure of young children to infections than previously. This would explain why younger siblings and children who attend day nurseries have a lower risk of developing asthma. Asthma develops more commonly in children whose parents smoke (RCP 1992). Although both tobacco smoke pollution and other air pollution can cause or exacerbate symptoms in people who already have asthma, there is no evidence that air pollution other than tobacco smoke actually causes asthma.

A European Commission survey has reported that 13% of people over 15in the UK have had asthma at some point in their lives. National Asthma Campaign experts say this matches its own statistic, which puts the number of Britons diagnosed with the condition at eight million.

The UK figure was the highest in the survey of 16 European Union memberstates, with runners-up Finland (11%) and Ireland (10.5%) not far behind. Lowest in the table were Germany, with less than 4% of the population saying they had asthma, and Spain, with a total of 4.4%.

The impact of asthma is felt throughout the UK and within every community. An average primary care organisation dealing with 330,000 people can expect to be treating 45,000 people for asthma, with 439 emergency hospital admissions emergency and eight deaths due to asthma each year.

Despite the significance of chronic respiratory conditions such as asthma, thereare no routine NHS information systems that enable us to look at the differing prevalence across London. Though there are some local analysis (eg based on local health surveys or around individual general practices or hospitals), our main sources of information across London have to be based on the most severe manifestation of illness when people are admitted to hospital or die.

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Respiratory conditions (acute and chronic) were the single main cause of emergency admissions during a four year study period (1997-2001) in London (Damiani & Dixon). However the total number of emergency admissions in the region fell in each consecutive year, from 465,470 in 1997/98 to 445,747 in 2000/01 - a decrease of four per cent.

This study showed that the biggest seasonal variation in emergency admissions was due to diseases of the respiratory system, with a peak each year in early January. There were six clinical conditions that caused this peak in admissions:

Young children occupied a high number of bed days, but the average length of stay was low - not more than two or three days. For those aged about 60 or over, there were a high number of admissions, nd also a very high number of bed days used by these patients, because the average length of stay steadily rose with age (reaching the peak of 17 days at the age of 95).

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Respiratory diseases are a major cause of death, especially in the elderly. In 2001, approximately 8.3% of all deaths in London were from respiratory disease, mainly pneumonia, bronchitis and emphysema. London has significantly high Standardised Mortality Ratios (SMR) for respiratory disease and in particular pneumonia. In younger age bands, deaths from pneumonia are usually rare, though in recent years the figures have increased due to HIV related illness, especially in younger men in Inner London.

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Source of data for respiratory diseases. A wide range of epidemiological data relating to respiratory disease is available in published volumes in scientific journals and datasets. This data can be used to examine trends, geographical variations and the need for services. The Department of Health publishes public health and immunisation statistics. The Office for national Statistics publishes data on mortality, cancer registrations and congenital respiratory tract malformations. The Public health Laboratory Service Communicable Disease Surveillance Centre publishes data on infectious disease notifications and laboratory reports. Information on primary care contacts is available from decennial morbidity surveys, computerised general practice records and weekly returns from "spotter practices".

Several large surveys give information on symptom and disease prevalence. Results are generally found in scientific journals. Some datasets are available for analysis.

Date	Title	Format	View
13 Jun 2005	Asthma UK Website
13 Jun 2005	Asthma UK website: UK tops asthma table
13 Jun 2005	British Lung Foundation Website: Lung Disease in London
13 Jun 2005	British Thoracic Society Website

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Date	Title	Format	View
17 May 2005	Mortality from Pneumonia, 1999 and 2001 Pooled, Local Authority and PCT level
8 Jan 2004	Mortality from Asthma: Years of Life Lost (YLL), 1999 and 2001 Pooled, Local Authority and PCT level
8 Jan 2004	Mortality from Bronchitis and Emphysema: Years of Life Lost, 1999 and 2001 Pooled, Local Authority and PCT level
8 Jan 2004	Mortality from Pneumonia: Years of Life Lost, 1999 and 2001 Pooled, Local Authority and PCT Level
8 Jan 2004	Proportion of People with Wheeze or Diagnosed Asthma, 1994-1996, London Health Authorities

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• Damiani M, Dixon J. Managing the pressure. London: King's Fund, 2002
• Royal College of Physicians of London. Smoking and the Young. London: RCP, 1992

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