The long-term benefits of controlling your asthma

Managing asthma is a challenge, but keeping the condition under control as you get older is more important than ever.

A major study has found that effectively controlling asthma through monitoring and medication is among several variables that can affect whether someone develops chronic obstructive pulmonary disease (COPD) later in life.

COPD groups together a range of conditions that impair breathing - like emphysema, chronic bronchitis and chronic asthma.

Published in The Lancet Respiratory Medicine, the University of Melbourne-led study was the world’s first to characterise lung function trajectories that could lead to COPD in a large general population from early childhood into a person’s 50s.

The researchers found that later COPD risk could be minimised if immunisation was encouraged, mothers didn’t smoke and their children didn’t smoke when they got older, especially if they had smoking parents or low childhood lung function.

Led by Mr Dinh Bui and Professor Shyamali Dharmage at the University of Melbourne School of Population and Global Health’s Allergy and Lung Health Unit, the study used data from 2438 participants of the Tasmanian Longitudinal Health Study.

Involving a range of university departments and hospitals across Australia, it pinpointed six lung function pathways from childhood to middle age, including two new ones.

Professor Dharmage says the findings suggest that early life factors including allergic diseases, lung infections, parental asthma and maternal smoking influence the three unfavourable lung function trajectories.

If study participants didn’t smoke and controlled their asthma as an adult, they could possibly reduce the impact of what had happened as a child.

“Personal smoking might amplify the effect of maternal smoking and adult asthma might amplify the effect of childhood asthma to determine membership of the worst lung function trajectory,” Professor Dharmage says.

“Clinicians, and patients with asthma, should be made aware of the potential long-term implications of non-optimal asthma control for lung function trajectory throughout life, and this should be investigated in future intervention trials.”

The lung function pathways are:

• early below average trajectory, accelerated decline (those with lung function below average in childhood followed by an accelerated decline in adulthood)

• persistently low trajectory

• below average trajectory

• early low trajectory, accelerated growth, normal decline (those with low lung function in early childhood followed by a catch-up growth during adolescence and remain normal in adulthood)

• persistently high trajectory

• average trajectory

Three of those - early below average, accelerated decline, below average and persistently low - have increased risk of COPD by middle age and were associated with 75 per cent of the COPD burden. However, this burden could be modified.

The study identified early life predictors of the three adverse trajectories, including childhood asthma, bronchitis, pneumonia, allergic rhinitis, eczema, parental asthma, and maternal smoking.

The ‘early below average, accelerated decline’ trajectory was created due to childhood exposure to the above conditions, adult personal smoking and active asthma.

These could be modified if they didn’t smoke and controlled their asthma as an adult. Personal smoking and active adult asthma increased the impact of maternal smoking and childhood asthma.

The two new trajectories - ‘early below average, accelerated decline’ and ‘early low, accelerated growth, normal decline’ - both contradicted the notion that lung function established in childhood tracks through life.

The results indicated that for people in the three adverse categories, reducing maternal smoking, encouraging immunisation and avoiding smoking could minimise later COPD risk.

The ‘early low, accelerated growth, normal decline’ trajectory also suggested a somewhat surprising pathway, where some children with low lung function in childhood still had an opportunity to grow out of it.

Female and underweight children were more likely to follow this trajectory, which saw them recover some lung function as they grew bigger and stronger.

Mr Bui says childhood asthma and adult active asthma are important predictors of adverse lung function trajectories.

“Importantly, if childhood asthma persists to adult asthma, it will increase the risk of the worst lung function trajectory, - or ‘below average, accelerated decline’,” he says.

“This analysis is of considerable importance because understanding lifetime lung function trajectories is crucial for population-based interventions to promote healthy trajectories and prevent unhealthy ones.

“Most COPD, especially when more severe, is attributable to three trajectories exhibiting lower lung function in childhood with subsequent normal or accelerated decline.”

“We suggest that reducing maternal smoking, encouraging immunisation, and avoiding personal smoking, especially in those with smoking parents or low childhood lung function, might minimise COPD risk.”

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