Prognosis
Long-term effects
Although it has been assumed that airway inflammation and airway remodeling have a cause and effect relationship, longitudinal evidence suggests that remodeling is an independent parallel process, unresponsive to anti-inflammatory medication such as inhaled corticosteroids (ICS). Longitudinal follow-up of childhood asthma into adulthood suggests that in some asthma patients, remodeling commences early in the disease process leading to fixed airflow obstruction. These cohort studies from general populations in Australia and New Zealand have reproducibly shown that in children with persistent asthma symptoms, most deficits in lung function growth have already occurred by ages 6-9 years, with only a modest further effect of asthma on lung function thereafter.[189][190] This is consistent with adult data, where a longitudinal study of more than 9000 subjects found that asthmatic nonsmokers had reduced forced expiratory volume at 1 second (FEV₁) at age 19 years when compared with values in nonasthmatic nonsmokers, and showed only minimal additional decrease thereafter.[191] This suggests that airway remodeling with irreversible airflow obstruction occurs early with persistent childhood asthma, but is a stable physiological phenotype thereafter. However, an accelerated decline in lung function has also been observed in chronic severe asthma, particularly in association with frequent and severe exacerbations.[192][193]
Life expectancy
The life expectancy of people with controlled asthma is similar to that for the general population.
Male sex, single marital status, and hypertension were found to be correlated with a higher risk of all-cause mortality in a Danish cohort study of adults with incident asthma.[194] Conversely, greater levels of self-reported physical activity were associated with a lower all-cause mortality risk.[194]
Remission
Remission is possible either on treatment (ICS, biologics, allergen immunotherapies) or off treatment.[52][195] It has been proposed that patients meeting the following criteria over a 12-month period (including those receiving monoclonal antibody therapy) may be considered in remission:[196]
No exacerbations
No missed work or school
Stable and optimized pulmonary function results on ≥2 measurements
Continued use of controller therapies, only at low-medium dose of ICS, or less
Asthma Control Test >20, Asthma Impairment and Risk Questionnaire <2, or Asthma Control Questionnaire <0.75 on ≥2 measurements
Symptoms requiring 1-time reliever therapy no more than once a month
It should be noted that remission is not cure, and that asthma may recur later in life.[52]
This is a topic of ongoing debate.
Impact of corticosteroids
ICS provide clinical and laboratory improvement to the patient. If the corticosteroids are discontinued, symptoms recur and pulmonary function studies return to the initial abnormality. Treatment with ICS, although not disease modifying, provides an additional anti-inflammatory effect. In other words, the lung inflammation is reduced only while the patient is on the ICS, and once stopped, the inflammatory process returns. When optimally controlled, asthma attacks decrease in frequency. Some patients will have no asthma attacks, and others have continued attacks when exposed to precipitating agents. Long-term use (≥1 year) of low-dose ICS may also provide modest improvement in lung function, although these findings are currently limited to patients with mild asthma.[197]
See Complications for details of the adverse effects associated with long-term corticosteroid use.
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