Mortality in asthmatics over 15 yrs: a dynamic cohort study from 1983-1998. C.K. Connolly, S.M. Alcock, R.J. Prescott. #ERS Journals Ltd 2002. ABSTRACT: The Darlington and Northallerton long-term asthma study observes outcome in asthmatics in the light of potential explanatory variables recorded prospectively. This paper reports changes in mortality during the study, and assesses the relevant risk factors.All asthmatics attending secondary care were recruited at 5-yr intervals from 1983 and reviewed 5 yrs later. Demographic and functional variables, including a formal estimate of best function were recorded prospectively.The dynamic cohort comprised 1,148 asthmatics with 95% follow-up, enabling 612 observations in the period 1983/1988, 774 in 1988/93 and 823 in 1993/98, with 101, 111 and 100 deaths respectively. Principal risk factors for mortality were lower social class and best forced vital capacity. Mortality relative to 1983 halved by 1993/98 and was reduced against the Darlington population, despite an entry forced expiratory volume in one second of 84.7%. There was no change in predictive value of risk factors during the study period, or with date of entry.This study demonstrates a consistent reduction in mortality, which was not entirely a survivor effect, but may be associated with changes in management. By 1993/98 mortality approximated to that of the local reference population despite a lower than predicted forced expiratory volume in one second.

This study aimed to determine whether the changes in practice in the management of asthma since the early 1980s have improved standards (as assessed by higher actual/best function) and reduced the need for oral corticosteroids. All asthmatic outpatients were reviewed in 1980, 1983, 1988/89 and 1993/94. Therapeutic step, defined by suppressive medication alone, actual and best peak expiratory flow (PEF) were recorded. Cohorts from 1980, 1983 and 1988/89 were identified in whom best function was established on all subsequent occasions. Changes in practice demonstrated by cross-sectional review of all subjects were interpreted with the aid of longitudinal analysis of the cohorts. Attendance increased from 463 in 1980 to 772 in 1993/94. Between 1983 and 1993/94, the proportion maintained on inhaled corticosteroids increased from 49 to 84% with increased use of higher doses. Mean actual/best PEF rose from 80 to 87%, improving at each therapeutic step. The proportion needing rescue oral corticosteroids fell from 47 to 35% and maintenance oral corticosteroids from 20 to 9%. In the cohorts, there was a similar reduction in use of rescue corticosteroids, but not of maintenance oral corticosteroids. The study confirmed an increase in the use and dose of inhaled corticosteroids, and a better outcome at all treatment steps. The fall in the proportion of subjects dependent on oral corticosteroids was due to attrition, rather than weaning in later years.

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The Darlington/Northallerton prospective study of asthmatics referred to secondary care started in 1983, with review and new entry at 5-yr intervals. The principal outcome measures are: mortality (presented here), best function and therapeutic step. All adult asthmatics with > or = 15% peak flow (PEF) reversibility to > or = 200 l min-1 were included. Socio-demographic variables, PEF and spirometry were recorded prospectively. Best vital capacity (FVC) and PEF were assessed according to protocol. The mortality of the original cohort after 10 yr was expressed as standardized mortality ratio (SMR) against the local population, with history and pulmonary function at entry as explanatory variables. Ninety-five per cent follow-up was achieved in 628 subjects, with 173 deaths (29.1% of those traced). The excess death rate was nearly 50% (SMR 1.47, 95% CI 1.26-1.71), with 56% of deaths due to respiratory disease (expected 10%). After allowance for age and sex, there was a consistent inverse relationship between mortality and entry best FVC, increased risk of death 1.51 (95% CI 1.33-1.72) per 10% deficit of best FVC predicted. The risk of respiratory death was eight times greater, and of non-respiratory death three times greater, in the lowest compared with the highest quartile of best FVC. There were no interactions with smoking, but possible enhancement of the effect in the socially deprived. Best FVC was a particularly powerful predictor of mortality in subjects < 65 years at entry, in whom 64% of the excess deaths occurred. Most of the excess in respiratory deaths was not due to acute severe asthma but to the development of chronic obstructive pulmonary disease (COPD), as defined functionally, irrespective of smoking habit which made no further contribution to mortality.

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