Papers

Age specific trends in asthma mortality in England and Wales, 1983-95: results of an observational study

^a Southampton University Department of Medical Statistics and Computing, Southampton General Hospital, Southampton S016 6YD, ^b Southampton University Department of Medicine, Southampton General Hospital

Correspondence to: Dr Campbell m.j.campbell@soton.ac.uk

	Abstract

Top Abstract Introduction Method Results Discussion Appendix References

Objective: To determine trends in asthma mortality by age group in England and Wales during 1983-95.
Design: Observational study.
Setting: England and Wales.
Subjects: All deaths classified as having an underlying cause of asthma registered from 1 January 1983 to 31 December 1995.
Main outcome measure: Time trends for age specific asthma deaths.
Results: Deaths in the age group 5-14 years showed an irregular downward trend during 1983-95; deaths in the age groups 15-44, 45-64, and 65-74 years peaked before 1989 and then showed a downward trend; and deaths in the age group 75-84 years peaked between 1988 and 1993 and subsequently dropped. Trends were: age group 5-14 years, 6% (95% confidence interval 3% to 9%); 15-44 years, 6% (5% to 7%); 45-64 years, 5% (4% to 6%); 65-74 years, 2% (1% to 3%). Deaths in the 75-84 and 85 and over categories plateaued.
Conclusions: There are downward trends in asthma mortality in Britain, which may be due to increased use of prophylactic treatment.

	Introduction

Top Abstract Introduction Method Results Discussion Appendix References

It is now over 10 years since trends and seasonality in asthma mortality were investigated in England and Wales,^{1 2 3} and the long term trends over the period 1974-84 were found to be increasing. We aimed at updating these findings in the light of changing views on the appropriateness of treatment for asthma, increasing concerns in relation to environmental effects on asthma, and also concerns on admission rates for asthma.⁴

	Method

Top Abstract Introduction Method Results Discussion Appendix References

The data were obtained from the Office of Population Censuses and Surveys (now the Office for National Statistics). They consisted of all deaths classified as having an underlying cause of asthma (International Classification of Diseases, ninth revision (ICD-9), codes 493.0 to 493.9 inclusive) registered in England and Wales from 1 January 1983 to 31 December 1995. Some coding procedures were changed in 1983, so the data were analysed including and excluding that year to see if the change affected conclusions. Data included the date of death, cause of death, sex of subject, and age at death. Annual age specific population sizes and death rates for all respiratory deaths (ICD-9 codes 460-519) were obtained from Office of Population Censuses and Surveys publications.

For analysis the data were split into seven age groups, coinciding with the Office of Population Censuses and Surveys age classifications 0-4, 5-14, 15-44, 45-64, 65-74, 75-84, and 85 years and over. The number of people alive during each year in these age groups was obtained from census projections. Deaths were aggregated into years. The appendix describes the method of analysis.

	Results

Top Abstract Introduction Method Results Discussion Appendix References

In total, 23 311 asthma deaths were registered between 1 January 1983 and 31 December 1995. The proportions of these deaths in each age group 0-4, 5-14, 15-44, 45-64, 65-74, 75-84, and 85 and over were 0.5%, 1%, 12%, 27%, 26%, 24%, and 10% respectively.

Figure 1) shows the yearly asthma death rates plotted on a log scale for each age group. Table 1) gives the results of the Poisson analysis. Little could be made of the data for the under 5s because the numbers were too small. For all age groups except 5-14 there was a significant quadratic term. For each age group between 15 and 74 both linear and quadratic terms were negative, implying an accelerating decline which started before 1989. For subjects aged 75-84 the linear term was positive, suggesting that mortality initially rose and then either peaked or plateaued after 1989. Visual inspection of the data suggests that for those aged 75-84 there was a drop in 1994 and 1995, but for those aged 85 and over no decline was evident.

View larger version (25K): [in this window] [in a new window]   Fig 1 Death rates from asthma per million population by age group from 1983 to 1995

Excluding 1983 made little difference to the results. As the model was on a log scale, disregarding the quadratic term we can interpret the linear coefficients as a proportionate drop. Hence for deaths between 5 and 14 years of age the drop was about 6% a year (95% confidence interval 3% to 9% ), for deaths at ages 15-44 years it was also 6% (5% to 7%), for deaths at ages 45-64 years it was 5% (4% to 6%), and for deaths at ages 65-74 years it was 2% (1% to 3%). For deaths in subjects aged 75 and over the rate was flat.

Total respiratory deaths also decreased after about 1991 in subjects aged 5-14 and 15-44. In 1991 as a proportion of all respiratory deaths asthma deaths accounted for 44% among subjects aged 5-14 years, 31% among those aged 15-44, 11% among those aged 45-64, and 2% among those over 65.

	Discussion

Top Abstract Introduction Method Results Discussion Appendix References

In contrast with studies up to the mid-1980s^{1 2 3} which showed increasing mortality, we have shown that since the late 1980s asthma mortality in England and Wales seems to have dropped except among people aged over 85. Other countries have had different experiences. In Scotland mortality was stable between 1975 and 1989 for 5-44 year olds.⁵ In France a peak in mortality for both the under 35s and over 35s was observed from 1985 to 1987; this was attributed to influenza epidemics, and though death rates were lower subsequently there was no evidence of a trend.⁶ In contrast, deaths in New Zealand at ages 5-54 years showed a downward trend from 1986 to 1992.⁷

Trends in asthma mortality among children are reflected in the trends in asthma admissions to hospital. Routine data for asthma admissions are not available for England after 1985, but for Wales admissions showed a steady rise from 1983 to 1988 and then a drop in 1989 and 1990.⁴ Age standardised death rates seem to reflect this trend.

There has been considerable concern in the medical community and in the public domain over reports of increasing asthma prevalence.⁸ It is encouraging to note that even with a background of increasing prevalence there were downward trends in mortality in the under 75s in the five to seven years before 1995. It is possible that these trends were a result of increased awareness among physicians and patients of the inflammatory basis of asthma and the need for prophylactic treatment, particularly in view of the increased prescribing of corticosteroids as a proportion of all prescriptions for asthma.⁹ Diagnostic transfer is a possibility, but it is reassuring that respiratory deaths are also dropping in younger people. The accuracy of death certification in asthma was not good in 1979 but has been shown to be more accurate for younger people.¹⁰ In old people asthma deaths form only a small proportion of all respiratory deaths and it would be impossible to quantify the extent of diagnostic transfer.

The trends in asthma mortality may be related to the increased use of prophylactic treatment, the use of which should continue to be encouraged.

	Appendix

Top Abstract Introduction Method Results Discussion Appendix References

Analysis was by Poisson regression in STATA.¹¹ The midyear population was included as an "offset," which ensured the analysis was based on a rate and allowed for changes in the age structure of the population. Checks for overdispersion and serial correlation of the residuals were carried out but it was not found necessary to make allowances for them. Trend terms were centred on the midyear 1989. When the linear and quadratic terms were negative this implied that the fitted model peaked before 1989. When the linear term was positive and the quadratic term was negative this implied that the model had peaked or plateaued or was expected to peak or plateau after 1989. When both coefficients were positive an increasing and accelerating rate was implied.

	Acknowledgements

We thank the Office for National Statistics (formerly the Office of Population Censuses and Surveys) for the data and Mr S A Julious for additional references.

Funding: None.

Conflict of interest: None.

	References

Top Abstract Introduction Method Results Discussion Appendix References

1. Khot A, Burn R. Seasonal variation and time trends of deaths from asthma in England and Wales 1960-82. BMJ 1984;289:233-4.
2. Burney PGJ. Asthma mortality in England and Wales: evidence for a further increase, 1974-84. Lancet 1986;ii:323-6.
3. Khot A, Burn R. Deaths from asthma. BMJ 1984;289:557.
4. Hyndman SJ, Williams DRR, Merrill SL, Lipscombe JM, Palmer CR. Rates of admission to hospital for asthma. BMJ 1994;308:1596-600. [Abstract/Free Full Text]
5. Mackay TW, Wathen CG, Sudlow MF, Elton RA, Caulton E. Factors affecting asthma mortality in Scotland. Scott Med J 1992;37:5-7.
6. Cadet B, Robine JM, Leibovici D. Dynamic of asthma mortality in France: seasonal variation and peaking of mortality in 1985-87. Rev Epidemiol Sante Publique 1994;42:103-18. [Medline]
7. Garrett J, Kolle J, Richards G, Whitelock T, Rae H. Major reduction in asthma morbidity and continued reduction in mortality in New Zealand. What lessons have been learned? Thorax 1995;50:303-11.
8. Phelan PD. Asthma in childhood: epidemiology. BMJ 1994;308:1584-5. [Free Full Text]
9. Baldwin DR, Ormerod LP, Mackay AD, Stableforth DE. Change in hospital management of acute severe asthma by general and thoracic physicians in Birmingham and Manchester during 1978 and 1985. Thorax 1990;45:130-5. [Abstract/Free Full Text]
10. BTA Research Committee. Accuracy of death certificates in bronchial asthma. Thorax 1984;39:505-9.
11. StatCorp. Stata statistical software: release 5.0. College Station, Texas: Stata Corporation, 1997.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Relevant Articles

Asthma

Hilary Pinnock and Rupal Shah
BMJ 2007 334: 847-850. [Extract] [Full Text] [PDF]

Trends in asthma mortality

M J Campbell, S T Holgate, S L Johnston, Carol A Johnson, David M Mannino, Annette Ashizawa, W T Berrill, Philip McLoone, David S Morrison, Balvinder Kaur, and Barbara Butland
BMJ 1997 315: 1012. [Extract] [Full Text]

This article has been cited by other articles:

• Greening, A. P., Stempel, D., Bateman, E. D., Virchow, J. C. (2008). Managing asthma patients: which outcomes matter?. ERR 17: 53-61 [Abstract] [Full text]  
• Stow, P. J, Pilcher, D., Wilson, J., George, C., Bailey, M., Higlett, T., Bellomo, R., Hart, G. K, and the Australian & New Zealand Intensive Care So, (2007). Improved outcomes from acute severe asthma in Australian intensive care units (1996 2003). Thorax 62: 842-847 [Abstract] [Full text]  
• Pinnock, H., Shah, R. (2007). Asthma. BMJ 334: 847-850 [Full text]  
• Ross Anderson, H, Gupta, R., Strachan, D. P, Limb, E. S (2007). 50 years of asthma: UK trends from 1955 to 2004. Thorax 62: 85-90 [Abstract] [Full text]  
• van der Merwe, L, de Klerk, A, Kidd, M, Bardin, P G, van Schalkwyk, E M (2006). Case-control study of severe life threatening asthma (SLTA) in a developing community. Thorax 61: 756-760 [Abstract] [Full text]  
• Panickar, J R, Dodd, S R, Smyth, R L, Couriel, J M (2005). Trends in deaths from respiratory illness in children in England and Wales from 1968 to 2000. Thorax 60: 1035-1038 [Abstract] [Full text]  
• Johnston, S. L. (2005). Overview of Virus-induced Airway Disease. Proc Am Thorac Soc 2: 150-156 [Abstract] [Full text]  
• Hubbard, R., West, J. (2004). Commentary: Does the presence of asthma increase the incidence of coronary heart disease?. Int J Epidemiol 33: 749-750 [Full text]  
• Myatt, T. A., Johnston, S. L., Zuo, Z., Wand, M., Kebadze, T., Rudnick, S., Milton, D. K. (2004). Detection of Airborne Rhinovirus and Its Relation to Outdoor Air Supply in Office Environments. Am. J. Respir. Crit. Care Med. 169: 1187-1190 [Abstract] [Full text]  
• Picard, E., Barmeir, M., Schwartz, S., Villa, Y., Goldberg, S., Virgilis, D., Kerem, E. (2002). Rate and Place of Death From Asthma Among Different Ethnic Groups in Israel: National Trends 1980 to 1997. Chest 122: 1222-1227 [Abstract] [Full text]  
• Lanes, S F, Garcia Rodriguez, L A, Huerta, C (2002). Respiratory medications and risk of asthma death. Thorax 57: 683-686 [Abstract] [Full text]  
• Connolly, C.K., Alcock, S.M., Prescott, R.J. (2002). Mortality in asthmatics over 15 yrs: a dynamic cohort study from 1983-1998. Eur Respir J 19: 593-598 [Abstract] [Full text]  
• Allen, S C, Ragab, S (2002). Ability to learn inhaler technique in relation to cognitive scores and tests of praxis in old age. Postgrad. Med. J. 78: 37-39 [Abstract] [Full text]  
• Kips, J C, Pauwels, R A (2001). Low dose inhaled corticosteroids and the prevention of death from asthma. Thorax 56: ii74-78 [Full text]  
• Inwald, D., Roland, M., Kuitert, L., McKenzie, S. A, Petros, A. (2001). Oxygen treatment for acute severe asthma. BMJ 323: 98-100 [Full text]  
• Zar, H.J., Stickells, D., Toerien, A., Wilson, D., Klein, M., Bateman, E.D. (2001). Changes in fatal and near-fatal asthma in an urban area of South Africa from 1980-1997. Eur Respir J 18: 33-37 [Abstract] [Full text]  
• Fleming, D M, Sunderland, R, Cross, K W, Ross, A M (2000). Declining incidence of episodes of asthma: a study of trends in new episodes presenting to general practitioners in the period 1989-98. Thorax 55: 657-661 [Abstract] [Full text]  
• Fleming, D M, Cross, K W, Sunderland, R, Ross, A M (2000). Comparison of the seasonal patterns of asthma identified in general practitioner episodes, hospital admissions, and deaths. Thorax 55: 662-665 [Abstract] [Full text]  
• Kramarz, P., DeStefano, F., Gargiullo, P. M., Davis, R. L., Chen, R. T., Mullooly, J. P., Black, S. B., Shinefield, H. R., Bohlke, K., Ward, J. I., Marcy, M. S., for the Vaccine Safety Datalink Team, (2000). Does Influenza Vaccination Exacerbate Asthma?: Analysis of a Large Cohort of Children With Asthma. Arch Fam Med 9: 617-623 [Abstract] [Full text]  
• Hoskins, G, McCowan, C, Neville, R G, Thomas, G E, Smith, B, Silverman, S (2000). Risk factors and costs associated with an asthma attack. Thorax 55: 19-24 [Abstract] [Full text]  
• (1999). Implementation of the guidelines. CMAJ 161: s60-62 [Full text]  
• VEEN, J. C. C. M.i.`t, SMITS, H. H., HIEMSTRA, P. S., ZWINDERMAN, A. E., STERK, P. J., BEL, E. H. (1999). Lung Function and Sputum Characteristics of Patients with Severe Asthma During an Induced Exacerbation by Double-Blind Steroid Withdrawal. Am. J. Respir. Crit. Care Med. 160: 93-99 [Abstract] [Full text]  
• Campbell, M J, Holgate, S T, Johnston, S L, Johnson, C. A, Mannino, D. M, Ashizawa, A., Berrill, W T, McLoone, P., Morrison, D. S, Kaur, B., Butland, B. (1997). Trends in asthma. BMJ 315: 1012-1012 [Full text]