A population-based cohort of adults with asthma: mortality and participation in a long-term follow-up

Abstract

Background and objective: Asthma is a major public health concern. The aim of this study was to characterize a large population-based cohort of adults with asthma, and to study factors associated with all-cause mortality and non-participation in a long-term follow-up. Design: Random and stratified samples from five population-based cohorts were clinically examined during 1986–2001, and all subjects with asthma were included in the study (n = 2055, age 19–72 years, 55% women). Independent associations between different risk factors and (i) mortality and (ii) non-participation in a clinical follow-up in 2012–2014 were estimated. Results: In 1986–2001, 95% reported any wheeze and/or attacks of shortness of breath in the past 12 months, and/or asthma medication use. Over the up to 28 years of follow-up time, the cumulative mortality was 22.7%. Male gender, current smoking, and lower forced expiratory volume in 1 sec of predicted (FEV1% of predicted) were independent risk factors for mortality, while obesity was associated with non-participation in the follow-up. Older ages, ischemic heart disease, and low socioeconomic status were associated with both mortality and non-participation. Conclusions: The risk factors associated with mortality in this adult population-based asthma cohort were similar to those commonly identified in general population samples, i.e. male gender, current smoking, and lower FEV1% of predicted, while obesity was associated with non-participation in a long-term follow-up. Ischemic heart disease, low socioeconomic status, and older ages were associated with both mortality and non-participation.

Severe asthma—A population study perspective

“…Among the strengths of this population study are the high participation rates and limited selection bias, and that our asthma cohort seems to well reflect the distribution of asthma in the Swedish population of same age . A weakness when estimating prevalence might be the long recruitment period, but because both remission and incidence is low among adults we believe this bias is limited.…”

“…The asthma cohort included all patients with physician‐diagnosed asthma, or report of ever having had asthma and, furthermore, those without asthma diagnosis prior to the surveys but who had a medical history of asthma together with physiologically verified bronchial variability or asthma medication, comprising all together 2055 adults. The origins of the cohort, the criteria for inclusion and mortality during follow‐up have been described in detail elsewhere and are summarized in Figure .…”

“…In 2012‐2014, all subjects in the asthma cohort who were alive and still living in Norrbotten were invited to a clinical follow‐up including a detailed structured interview including assessment of asthma treatment during the last 12 months, pre‐ and post‐bronchodilator spirometry, skin prick testing, blood sampling, and measurements of height and weight . Of the 1425 invited, 1006 (71%) participated.…”

“…The study sample consisted of adults with asthma identified at clinical examinations performed between 1986 and 2001 of four cohorts derived from the general population of the northernmost county of Sweden, Norrbotten, and of adults with incident asthma identified in a case‐referent study in the county . Studies of non‐responders have shown none or only limited bias due to non‐response, and the participation rates in the clinical examinations of the cohorts were 67%‐91% . The asthma cohort included all patients with physician‐diagnosed asthma, or report of ever having had asthma and, furthermore, those without asthma diagnosis prior to the surveys but who had a medical history of asthma together with physiologically verified bronchial variability or asthma medication, comprising all together 2055 adults.…”

Possible risk factors for poor asthma control assessed in a cross-sectional population-based study from Telemark, Norway

“…Our results showed that post-bronchodilator FEV 1 was reduced in patients with poor asthma control (Table 4). A previous Swedish study reported that FEV 1 was associated with mortality [25], and a similar study from the US indicated that low FEV 1 was associated with increased mortality among patients with asthma [26]. However, in the Swedish study, postbronchodilator tests were available only for parts of the cohort, while it is not clear whether the latter study used pre-or post-bronchodilator spirometry.…”