AstraZeneca along with researchers from the Swedish Medical University Karolinska Institutet designed a series of studies of COPD in pairs of Twins to determine the contribution of environmental factors and inherited genes in the development of the disease.
Because identical twins have the same genetic makeup, and fraternal twins share ~50 per cent of their genes, twin studies provide an interesting opportunity to study the interplay of genetic and environmental causes of disease in COPD. Both chronic bronchitis and emphysema are surrogates for COPD.
The first study in the series was a Twin study of self-reported bronchitis1. The publication from this study was highlighted by the American Thoracic Society (ATS) as a major advance in knowledge, prompting an ATS press release2. The Twin study showed that heritability (genetics) did play an important role in bronchitis, and was independent of smoking. Heritability for chronic bronchitis was 40 per cent. Genes common to both smoking and bronchitis accounted for only a small part (14 per cent) of the 40per cent (i.e. ~6 per cent of the total variance). Non-shared environmental factors (smoking and others) contributed 60 per cent of the variance for chronic bronchitis.
To explore this further, a Twin study is currently underway to understand genetic effects in emphysema. Preliminary data were presented as a poster at the recent American Thoracic Society international conference in Toronto, Canada3. Demographics and smoking patterns in more than 190 pairs of twins were evaluated to identify the underlying genetic basis for emphysema. Twins with lung capacity below 90 per cent of predicted had a CT (quantitative computed-tomography) lung scan performed and emphysema index was calculated. To our knowledge, this is the first Twin study where heritability for emphysema has been investigated. The study findings so far indicate that genetics does play a role in the development of emphysema, and this data supports the findings in the Twin study of bronchitis. In the final analysis, further CT scans for both twins in each pair will be performed.
COPD is a mostly environmentally-driven disease, with smoking a very powerful factor in causing the disease. The above studies are the first to quantify that chronic bronchitis/COPD genetics are largely independent from smoking genetics, and that genetics also seems to play a role in emphysema.
References:
1. American Journal of Respiratory Critical Care Medicine, Vol 177, 2008; p486-490. Interaction between Smoking and Genetic Factors in the Development of Chronic Bronchitis. J. Hallberg, A. Dominicus, U. Eriksson, M. Gerhardsson de Verdier, N. Pedersen, M. Dahlback, U. Nihlen, T.Higenbottam and M. Svartengren
2. American Thoracic Society (ATS) release: 29th February 2008; Genetic factors in smoking also increase risk of chronic bronchitis
3. American Thoracic Society International Conference. May 21st 2008: Poster #H54: CT Findings in Relation to Lung Function and Smoking Profile in MZ and DZ Twins. G. Edula, J. Hallberg, M. Gerhardsson de Verdier, M. Dahlback, T. Fehniger, C. Lindberg, U. Nihlen, M. Anderson and M. Svartengren
Notes to Editors
About AstraZeneca
AstraZeneca is a major international healthcare business engaged in the research, development, manufacture and marketing of prescription pharmaceuticals and the supply of healthcare services. It is one of the world's leading pharmaceutical companies with healthcare sales of $29.55 billion and leading positions in sales of gastrointestinal, cardiovascular, neuroscience, respiratory, oncology and infection products. AstraZeneca is listed in the Dow Jones Sustainability Index (Global) as well as the FTSE4Good Index.
For more information about AstraZeneca please visit: www.astrazeneca.com
About COPD
COPD is a leading cause of morbidity and mortality worldwide. It is predicted to be the third biggest cause of death worldwide by 2020. It is the only major cause of death that has increased significantly in recent years. An estimated 210 million people have COPD, and 3 million people died of COPD in 2005 (2007 World Health Organisation data). COPD is a preventable and treatable disease that is characterised by airway inflammation and chronic airflow limitation.
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