Asthma Management Handbook

Obesity and asthma

Recommendations

For obese patients with a previous diagnosis of asthma, perform or arrange spirometry to obtain objective measurement of lung function, and confirm the diagnosis by demonstrating variable airflow limitation.

Table. Confirming the diagnosis of asthma in a person using preventer treatment Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/9

How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Global Initiative for Asthma, 20121

Advise people with asthma who are obese that weight loss might help control their asthma.

How this recommendation was developed

Consensus following inconclusive literature search

Based on clinical experience and expert opinion, after systematic literature review yielded insufficient evidence for an evidence-based recommendation: studies that met the inclusion criteria were not suitable for consideration due to unreliability (e.g. small number of participants, inappropriate study design or unacceptable risk of bias).

Clinical question for literature search:

Does weight loss improve asthma control in overweight/obese patients with asthma?

  • Does a weight loss intervention or program (e.g. diet, exercise, physical activity) improve asthma outcomes in obese/overweight patients (adults/children) with asthma, compared with usual care?
  • Does surgically induced weight loss (e.g. gastric bypass, gastric banding, bariatric surgery) improve asthma outcomes in obese patients with asthma, compared with usual care?

Recommendation informed by the following source:

  • Adeniyi and Young, 20122

Support obese or overweight people with asthma to lose weight by following current national guidelines for the management of obesity and overweight, including referral for bariatric surgery, if indicated.

How this recommendation was developed

Consensus following inconclusive literature search

Based on clinical experience and expert opinion, after systematic literature review yielded insufficient evidence for an evidence-based recommendation: studies that met the inclusion criteria were not suitable for consideration due to unreliability (e.g. small number of participants, inappropriate study design or unacceptable risk of bias).

Clinical question for literature search:

Does weight loss improve asthma control in overweight/obese patients with asthma?

  • Does a weight loss intervention or program (e.g. diet, exercise, physical activity) improve asthma outcomes in obese/overweight patients (adults/children) with asthma, compared with usual care?
  • Does surgically induced weight loss (e.g. gastric bypass, gastric banding, bariatric surgery) improve asthma outcomes in obese patients with asthma, compared with usual care?

Recommendation informed by the following sources:

  • Adeniyi and Young, 20122
  • Jensen et al. 20133
  • Juel et al. 20124
  • Lombardi et al. 20115
  • Reddy et al. 20116
  • Scott et al. 20137

Advise patients that weight loss of as little as 5–10% in obese or overweight people with asthma may result in clinically important improvement in asthma control and quality of life.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Scott et al. 20137

In obese patients, monitor the effect of asthma treatment using objective measures of lung function (spirometry), to avoid escalating asthma treatment unnecessarily.

How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Global Initiative for Asthma, 20121

More information

Obesity links with asthma

Prevalence and mechanisms

Obesity (defined as BMI ≥ 30 kg/m2) is associated with an increased prevalence of asthma.8

Obesity could contribute to asthma development or worsening via mechanical, inflammatory and genetic/developmental factors.8 Increased rates of obstructive sleep apnoea or gastro-oesophageal reflux disease among obese people do not entirely explain the higher rates of symptoms and morbidity seen in obese people with asthma, compared people with asthma who have a normal BMI.9

Asthma in obese patients appears to be a specific phenotype810 associated with changes in lung function caused by breathing at low lung volumes, a systemic inflammatory process, and a reduced response to asthma medicines.8 Obesity reduces chest wall compliance, which results in reduced lung volumes, increased work of breathing and increased energy and oxygen costs of breathing.11

Considerations for diagnosis and assessment

Obese people with asthma report more dyspnoea and asthma-like symptoms than non-obese patients.11

Respiratory symptoms associated with obesity can mimic asthma.11

In obese patients it is especially important to confirm a previous diagnosis of asthma by objective measures of variable airflow limitation.1

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Definition of variable expiratory airflow limitation

Most of the tests for variable expiratory airflow limitation are based on showing variability in FEV1. While reduced FEV1 may be seen with many other lung diseases (or due to poor spirometric technique), a reduced ratio of FEV1 to FVC indicates airflow limitation.12 Normal FEV1/FVC values derived from population studies vary,1314 but are usually greater than:13

  • 0.85 in people aged up to 19 years
  • 0.80 in people aged 20–39 years
  • 0.75 in people aged 40–59 years
  • 0.70 in people aged 60–80 years.

In children, it is less useful to define expiratory airflow limitation according to a specific cut-off for FEV1/FVC ratio, because normal values in children change considerably with age.14

Some spirometers provide predicted normal values specific to age group. If these are available, a FEV1/FVC ratio less than the lower limit of normal (i.e. less than the 5th percentile of normal population) indicates airflow limitation.

Variable expiratory airflow limitation (beyond the range seen in healthy populations) can be documented if any of the following are recorded:

  • a clinically important increase in FEV1 (change in FEV1 of at least 200 mL and 12% from baseline for adults, or at least 12% from baseline for children) 10–15 minutes after administration of bronchodilator
  • clinically important variation in lung function (at least 20% change in FEV1) when measured repeatedly over time (e.g. spirometry on separate visits)
  • a clinically important reduction in lung function (decrease in FEV1 of at least 200 mL and 12% from baseline on spirometry, or decrease in peak expiratory flow rate by at least 20%) after exercise (formal laboratory-based exercise challenge testing uses different criteria for exercise-induced bronchoconstriction)
  • a clinically important increase in lung function (at least 200 mL and 12% from baseline) after a trial of 4 or more weeks of treatment with an inhaled corticosteroid
  • clinically important variation in peak expiratory flow (diurnal variability of more than 10%)
  • a clinically important reduction in lung function (15–20%, depending on the test) during a test for airway hyperresponsiveness (exercise challenge test or bronchial provocation test) measured by a respiratory function laboratory.

Notes

Patients referred to a respiratory function laboratory may be asked not to take certain medicines within a few hours to days before a spirometry visit.

A clinically important increase or decrease in lung function is defined as a change in FEV1 of at least 200 mL and 12% from baseline for adults, or at least 12% from baseline for children, or a change in peak expiratory flow rate of at least 20% on the same meter.1512 A clinically important increase in FVC after administering bronchodilator may also indicate reversible airflow limitation, but FVC is a less reliable measure in primary care because FVC may vary due to factors such as variation in inspiratory volume or expiratory time.

The finding of ‘normal’ lung function during symptoms reduces the probability that a patient has asthma, but a clinically important improvement in response to bronchodilator or inhaled corticosteroid can occur in patients whose baseline value is within the predicted normal range.

The greater the variation in lung function, the more certain is the diagnosis of asthma. However, people with longstanding asthma may develop fixed airflow limitation.

Reversibility in airflow limitation may not be detected if the person is already taking a long-acting beta2 agonist or inhaled corticosteroid.

Airflow limitation can be transient and does not necessarily mean that the person has asthma (e.g. when recorded during a severe acute infection of the respiratory tract). Ideally, airflow limitation should be confirmed when the patient does not have a respiratory tract infection. Reduction in lung function during a respiratory tract infection with improvement in lung function after its resolution, commonly occurs in people with asthma, but can also be seen in patients with COPD or in healthy people without either asthma or COPD.16,17

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Asthma management in obese patients

Effects of obesity on asthma control

Among people with asthma, BMI predicts asthma control, independent of airway inflammation, lung function and airway hyperresponsiveness.18

Obese people may have a reduced response to inhaled corticosteroids, compared with non-obese people.119, 20, 21 However, inhaled corticosteroids are still effective in obese people.22 Compared to people with normal BMI, people with BMI > 40 may take longer to achieve peak FEV1 after starting preventer treatment.21

There is also some evidence of a reduced response to montelukast among obese patients, but findings are not consistent.20, 21

Effects of weight loss interventions on asthma

The true effects of weight loss in people with asthma cannot be determined reliably, because many clinical trials assessing the effects of weight loss intervention on asthma have been poorly designed or reported, and have a high risk of bias.2

Systematic reviews of weight loss trials in people with asthma show that – regardless of the weight loss intervention – weight loss in people with asthma who are obese or overweight may improve asthma symptoms and reduce reliever requirement.24 However, weight loss has not been shown to achieve clinically important improvement in lung function.2

Some recent case series studies have found that adults who underwent bariatric surgery (various procedures) were able to reduce their inhaled corticosteroid dose.56

In an Australian clinical trial comparing a dietary intervention, an exercise intervention, and a combination of these for obese adults with asthma, asthma control improved in the diet and combination groups.7 Regardless of the method of weight loss, 5–10% weight loss was associated with a clinically important improvement in asthma control in 58% of patients, and improvement in quality of life in 83% of patients.7

In a small study in Australian children, a dietary weight loss intervention was associated with improvement in lung function, compared with baseline.3

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References

  1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. GINA, 2012. Available from: http://www.ginasthma.org
  2. Adeniyi FB, Young R. Weight loss interventions for chronic asthma. Cochrane Database Syst Rev. 2012; 7: CD009339. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD009339.pub2/full
  3. Jensen ME, Gibson PG, Collins CE, et al. Diet-induced weight loss in obese children with asthma: a randomized controlled trial. Clin Exp Allergy. 2013; 43: 775-84. Available from: http://www.ncbi.nlm.nih.gov/pubmed/23786284
  4. Juel CT, Ali Z, Nilas L, Ulrik CS. Asthma and obesity: does weight loss improve asthma control? a systematic review. J Asthma Allergy. 2012; 5: 21-6. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3392696/
  5. Lombardi C, Gargioni S, Gardinazzi A, et al. Impact of bariatric surgery on pulmonary function and nitric oxide in asthmatic and non-asthmatic obese patients. J Asthma. 2011; 48: 553-7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21707447
  6. Reddy RC, Baptist AP, Fan Z, et al. The effects of bariatric surgery on asthma severity. Obes Surg. 2011; 21: 200-6. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20393807
  7. Scott HA, Gibson PG, Garg ML, et al. Dietary restriction and exercise improve airway inflammation and clinical outcomes in overweight and obese asthma: a randomized trial. Clin Exp Allergy. 2013; 43: 36-49. Available from: http://onlinelibrary.wiley.com/doi/10.1111/cea.12004/full
  8. Boulet LP. Influence of comorbid conditions on asthma. Eur Respir J. 2009; 33: 897-906. Available from: http://erj.ersjournals.com/content/33/4/897.long
  9. Farah CS, Salome CM. Asthma and obesity: a known association but unknown mechanism. Respirology. 2012; 17: 412-21. Available from: http://onlinelibrary.wiley.com/doi/10.1111/j.1440-1843.2011.02080.x/full
  10. Dixon A. The treatment of asthma in obesity. Expert Rev Respir Med. 2012; 6: 331-40. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22788947
  11. Aaron SD, Vandemheen KL, Boulet LP, et al. Overdiagnosis of asthma in obese and nonobese adults. CMAJ. 2008; 179: 1121-1131. Available from: http://www.cmaj.ca/content/179/11/1121.full
  12. Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005; 26: 948-968. Available from: http://erj.ersjournals.com/content/26/5/948
  13. National Heart Lung and Blood Institute (NHLBI) National Asthma Education and Prevention Program. Expert Panel Report 3: guidelines for the diagnosis and management of asthma. Full report 2007. US Department of Health and Human Services National Institutes of Health, Bethesda, 2007. Available from: http://www.nhlbi.nih.gov/health-pro/guidelines/current/asthma-guidelines/full-report
  14. Quanjer PH, Stanojevic S, Cole TJ, et al. Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations. Eur Respir J. 2012; 40: 1324-43. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22743675
  15. Levy ML, Quanjer PH, Booker R, et al. Diagnostic Spirometry in Primary Care: Proposed standards for general practice compliant with American Thoracic Society and European Respiratory Society recommendations. Prim Care Respir J. 2009; 18: 130-147. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19684995
  16. Collier AM, Pimmel RL, Hasselblad V, et al. Spirometric changes in normal children with upper respiratory infections. Am Rev Respir Dis. 1978; 117: 47-53. Available from: http://www.ncbi.nlm.nih.gov/pubmed/619724
  17. Melbye H, Kongerud J, Vorland L. Reversible airflow limitation in adults with respiratory infection. Eur Respir J. 1994; 7: 1239-1245. Available from: http://www.ncbi.nlm.nih.gov/pubmed/7925901
  18. Farah CS, Kermode JA, Downie SR, et al. Obesity is a determinant of asthma control, independent of inflammation and lung mechanics. Chest. 2011; 140: 659-66. Available from: http://journal.publications.chestnet.org/article.aspx?articleid=1088127
  19. Boulet LP, Franssen E. Influence of obesity on response to fluticasone with or without salmeterol in moderate asthma. Respir Med. 2007; 101: 2240-7. Available from: http://www.resmedjournal.com/article/S0954-6111(07)00284-3/fulltext
  20. Peters-Golden M, Swern A, Bird SS, et al. Influence of body mass index on the response to asthma controller agents. Eur Respir J. 2006; 27: 495-503. Available from: http://erj.ersjournals.com/content/27/3/495.long
  21. Camargo CA, Boulet LP, Sutherland ER, et al. Body mass index and response to asthma therapy: fluticasone propionate/salmeterol versus montelukast. J Asthma. 2010; 47: 76-82. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20100025
  22. Sutherland ER, Camargo CA, Busse WW, et al. Comparative effect of body mass index on response to asthma controller therapy. Allergy Asthma Proc. 2010; 31: 20-5. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20167142