Outcome of children of parents with atopic asthma and transient childhood wheezy bronchitis

The Aberdeen Children of the 1950s cohort study: background, methods and follow-up information on a new resource for the study of life course and intergenerational influences on health

In this paper we introduce and describe in detail an addition to the UK's population-based resources for the investigation of biological and social influences on health across the life course and between generations: the Aberdeen Children of the 1950s study. We also provide an account of postwar Aberdeen when study members were growing up, report on findings of analyses of data from the original survey on which this study is based and its follow-up, assess the strengths and limitations of the study, and outline current and future research directions. This cohort comprises individuals born in Aberdeen, Scotland (UK) between 1950 and 1956, and is derived from 15 thousand subjects who took part in the Aberdeen Child Development Survey, a cross-sectional study of 'mental subnormality' (learning disability) in a population of all children who were attending Aberdeen primary schools in December 1962. Data collection included information on birthweight, gestational age, childhood height and weight, tests of cognition and behavioural disorder, and a range of multilevel socio-economic indicators. In 1998 we began the process of revitalising this cohort (now termed the Aberdeen Children of the 1950s study). We have been successful in ascertaining the current vital status and whereabouts of 98.5% of a target population of 12 150 subjects (6276 males, 5874 females) with full baseline data. The large majority (81%) of study participants still reside in Scotland and many (73%) have remained in the Grampian region which incorporates Aberdeen. At the present time, a total of almost 500 subjects are known to have died. Linkages to hospital admissions and other health endpoints captured through the Scottish Morbidity Records system have been completed. This includes an intergenerational linkage to approximately eight thousand deliveries in Scotland occurring to female members of the study population. A postal questionnaire to all traced surviving cohort members has also been distributed.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Wheezy bronchitis in childhood: a distinct clinical entity with lifelong significance?

BACKGROUND

Historically, clinicians have recognized the existence of the clinical syndrome of childhood wheezy bronchitis. In the late 1960s, children with this syndrome were relabeled as having asthma, and the term wheezy bronchitis was abandoned. In a 1989 study of a cohort that originally had been studied in 1964, we reported that those who had childhood wheezy bronchitis had as adults attained lung function similar to that of healthy control subjects and had less significant symptoms than did those who had experienced childhood asthma, in whom lung function was reduced. In this study, we reexamined these subjects 12 years later to determine whether the improved outcome of the wheezy bronchitis group had been maintained.

METHODS

In 2001, we followed up the 283 participants of the 1989 study, who were now aged 45 to 50 years. In interviews, respiratory symptoms and smoking status were assessed. Spirometry was measured.

RESULTS

One hundred seventy-seven subjects (63%) completed the study. After adjusting for age, height, gender, socioeconomic status, smoking status, and number of pack-years smoked, the current FEV(1) in the childhood asthma group (mean, 2.45 L; 95% confidence interval, 2.29 to 2.62) was significantly lower than the wheezy bronchitis group (2.78 L, 95% confidence interval, 2.64 to 2.91; p < 0.01) and the control group (2.96 L; 95% confidence interval, 2.83 to 3.1; p < 0.01). The difference between the wheezy bronchitis group and the control subjects was not significant (p = 0.06). Between 1989 and 2001, both the childhood wheezy bronchitis group (p < 0.01) and the childhood asthma group (p = 0.01) had greater declines in FEV(1) than did the control group (asthma group decline, - 0.75 L [95% confidence interval, - 0.66 to - 0.84]; wheezy bronchitis group decline, - 0.75 L [95% confidence interval, - 0.68 to - 0.83]; control group decline, - 0.59 L [95% confidence interval, - 0.52 to - 0.67]). In 2001, the asthma group had more symptoms than did the wheezy bronchitis group (p < 0.01), who were more symptomatic than the control group (p < 0.01).

CONCLUSION

Those with childhood wheezy bronchitis, having achieved normal lung function in earlier adulthood, now show a more rapid decline in lung function than did control subjects. If this rate of decline persists, these subjects may develop obstructive airways disease in later life.

Long-term outcome of childhood asthma

What we know: The outcome of childhood asthma is dependent on the pattern of asthma through childhood. Episodic asthma in childhood tends to resolve in adolescence and through mid-adult years, with no impairment of lung function. Persistent asthma in childhood is more likely to persist into adult years, with modest impairment of lung function. The impairment of lung function occurs early in the disease process and is not progressive, despite continuing symptoms. What we need to know: Are there clearly identifiable phenotypes of childhood asthma that have different aetiologies, response to treatment, genotypes and natural history? Does early treatment with anti-inflammatory agents prevent impairment of lung function? Can an algorithm be developed to predict the likelihood of persistent asthma on first presentation?

Genetic/environmental determinants of adult chronic obstructive pulmonary disease and possible links with childhood wheezing

Epidemiological evidence and similarities in underlying inflammatory mechanisms suggest that childhood respiratory conditions and adult onset chronic obstructive pulmonary disease (COPD) may have a common aetiology. The prevalence of COPD in the UK has been estimated to be 10% in males and 11% in females, and like asthma, is thought to have a polygenic contribution with a complex interplay between genetic and environmental factors. The only proven genetic factor so far identified in its pathogenesis is alpha1-antitrypsin deficiency, although this accounts for less than 1% of individuals with disease. Environmental exposures are significant but the observation that only 15% of smokers develop COPD and only some young children exposed in utero develop recurrent wheezing points to as yet undefined contributory genetic factors. The similarity in response to medication also suggests some features in common and a central question must be whether those adults who develop COPD had transient viral-associated wheeze (VAW) or non-specific bronchial hyperresponsiveness (BHR) in childhood? Similarities between some of the childhood wheezing syndromes and adult onset COPD invites a re-examination of possible links between the two conditions.