There is evidence of a genetic basis for smoking behavior and lung disease.
The study, carried out by Prof. Ian Hall of Queen's Medical Centre at the University of Nottingham and colleagues, has sought to understand the genetic basis of airflow obstruction and smoking behavior, which they believe is key to determining what causes chronic obstructive pulmonary disease (COPD). It examines the "genetic architecture of smoking behavior and lung function phenotypes."
While smoking and indoor air pollution are known to be risk factors for COPD, there is also believed to be a strong genetic component in both smoking behavior and risk of COPD and other lung diseases.
The report presents evidence that between heavy smokers and people who have never smoked, there are shared genetic causes of lung deficiency. It also suggests that smoking and genetic effects act separately to cause COPD.
Moreover, it argues that there are shared genetic causes of airflow obstruction between participants with asthma, whether or not the asthma is diagnosed by a doctor.
A major genetic study
The study sampled individuals from the UK Biobank with the best, average or the poorest lung function among heavy smokers and never smokers.
- COPD is number three killer in the US
- Smoking causes up to 9 of every 10 COPD-related deaths
- However, up to 1 in 6 people with COPD have never smoked.
The project involved 152,030 people of white, European ancestry, who were either heavy smokers (46,758 people) or never smokers (105,272).
They were chosen from the extremes of lung function distribution, according to whether they had high or low forced expiratory volume (FEV) - FEV being an indicator of lung health. The scientists then investigated whether there were shared genetic causes between different phenotypes defined by extremes of FEV.
FEV is the measure of how much air a person can exhale during a forced breath and is captured through spirometry. If the amount of air exhaled is measured during the first second, this is FEV1. A low FEV indicates impaired pulmonary function, while high FEV suggests healthy lungs. For this study, FEV1 was measured.
A new genotyping array was used, which measures over 800,000 genetic variants in each UK Biobank participant, and new methods of analysis of genetic data. In this way, they were able to compare lung health and smoking behavior with both common and rare genetic variations across the whole human genome.
New genetic variants and links discovered
The team discovered six independent genetic variants associated with lung health and COPD. They also found genetic variants associated with COPD in people who had never smoked.
The team found that the numbers of copies of duplicated sequence of the genome on chromosome 17 were associated with lung health in heavy smokers and also in those who had never smoked. This implies widespread effects on gene regulation and, in turn, protein production.
Five independent genetic variants were discovered which were associated with heavy smoking. This could be useful in the prevention of COPD and other smoking-related diseases.
The findings provide new insight into the specific mechanisms underlying airflow obstruction, COPD and tobacco addiction. They reveal novel genetic causes of lung function and smoking behavior and provide evidence of shared genetic architecture underlying airflow obstruction across individuals, regardless of smoking behavior and other airway diseases.
In terms of methodology, the researchers commend the usefulness of sampling from the Biobank data in order to identify novel genetic signatures that may underlie phenotypes that are important in the development of airway disease and smoking behavior. They recommend further study of genetic factors, to expand and consolidate the work done so far.In the authors' words:
"These findings, taken together with previous findings, will help define pathways underlying predisposition to development of COPD and smoking behaviors.
A full understanding of the biological mechanisms underlying these genetic associations will improve our understanding of the pathophysiology of COPD and smoking behavior, and potentially give rise to novel therapeutic strategies for the management of airway disease and prevention of nicotine addiction."
The authors are optimistic that the study will ultimately lead to new and improved approaches for helping people to stop smoking and for prevention and treatment of COPD.Earlier this year, Medical News Today reported that certain proteins lead to overproduction of mucus in diseases such as COPD and asthma.