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Sample Topic: Asthma

Asthma : Last revised in December 2013


Evidence on lifestyle interventions

The evidence for lifestyle interventions in asthma management is based on a few small studies. Most of the trial evidence is inconsistent, however smoking cessation (by the individual or parent of a child with asthma) and weight reduction (in obese people) improve asthma symptoms. Larger, more robust studies of allergen avoidance are needed to confirm benefit:

  • Smoking:
    • There is a direct causal relationship between parental smoking and lower respiratory tract illness in children up to 3 years of age. Infants whose mothers smoke are four times more likely to develop wheezing illnesses in the first year of life [GINA, 2006].
    • Exposure to tobacco contributes to the severity of childhood asthma. Average exposure is associated with a 30% increased risk of asthma symptoms. One small study suggests that, by stopping smoking, parents can decrease the severity of asthma in their children [SIGN and BTS, 2011].
  • Vaccinations:
    • A systematic review (search date August 2003, nine randomized controlled trials [RCTs]) concluded that evidence is insufficient to determine whether influenza vaccination prevents exacerbations in people with asthma, but influenza vaccination with inactive vaccine does not cause exacerbations [Cates et al, 2003].
    • A systematic review (search date 2001 September) including only one RCT (n = 30 children) of poor methodological quality (lack of blinding and inadequate allocation concealment), showed that pneumococcal vaccination decreased the incidence of acute asthma exacerbations per child (from ten to seven episodes per year) in those with asthma prone to recurrent episodes of otitis media [Sheikh et al, 2002].
  • Allergen avoidance:
    • Aero-allergen avoidance trials have shown inconsistent effects on asthma. Air pollution may provoke or aggravate an acute asthma attack, but this trigger is minimal compared with an infectious trigger [SIGN and BTS, 2011].
    • Two Cochrane reviews suggest that measures to control house dust mite allergens do not appear to be a cost-effective method of treating asthma. Studies were heterogeneous in terms of intervention, and allocation was not adequately concealed in some studies. At present, there is no clear benefit of house dust mite avoidance [Woodcock et al, 2003; GINA, 2006; SIGN and BTS, 2011].
    • Results of observational studies are conflicting and have not shown that removing a pet from the home improves asthma control [SIGN and BTS, 2011].
  • Weight reduction, diet, and exercise:
    • An open study of two randomized parallel groups of obese people with asthma found that a supervised weight-reduction programme significantly improved lung function, symptoms, morbidity, and health status [Stenius-Aarniala et al, 2000]. A smaller study found that weight loss reduces airways obstruction and peak flow variability in obese people with asthma [Hakala et al, 2000].
    • There is no convincing evidence from Cochrane reviews to support the use of fish oil supplements, salt restriction, or tartrazine exclusion in the management of asthma [SIGN and BTS, 2011].
    • A Cochrane review (13 RCTs, n = 455) showed that physical training increases cardiorespiratory capacity but has no effect on lung function and days of wheezing in people with asthma. Evidence is insufficient on the role of breathing exercises in the management of asthma to recommend any one particular technique [Ram et al, 2005]. Nevertheless, some small studies have suggested a possible benefit in asthma symptoms with the Buteyko [Cooper et al, 2003] and Papworth [Holloway and West, 2007] methods of breathing. These findings need further confirmation.
  • Associated conditions:
    • Rhinitis: one study showed that 76% of people with asthma had symptoms of rhinitis. Half of these people said their rhinitis made their asthma worse [Pinnock and Shah, 2007]. Rhinitis usually comes before asthma, and it is both a risk factor for asthma and is associated with increased severity of the disease [GINA, 2006]. The treatment of allergic rhinitis has not been shown to improve asthma control [SIGN and BTS, 2011].
    • Gastro-oesophageal reflux disease: the relationship of increased asthma symptoms, particularly at night, to gastro-oesophageal reflux remains uncertain, although the condition is three times more prevalent in people with asthma than in the general population [GINA, 2006]. A Cochrane review (12 RCTs) concluded that the treatment of gastro-oesophageal reflux in people with asthma had no effect on asthma symptoms or lung function. Dry cough improved, although this symptom was probably not due to asthma [SIGN and BTS, 2011].
    • Hay fever: there is a strong link between asthma and hay fever, and deaths from asthma in young adults peak during the pollen season [Pinnock and Shah, 2007].