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Courtesy of Yuning Wu
A new study led by researchers at Oxford Population Health has found that smoking creates a biological imprint in the blood that can be measured to predict the risk of smoking-related death and illness.
As smoking has become less socially acceptable in many societies, self-reporting has become an unreliable way of determining an individual’s smoking history and their risk from smoking-related diseases. The study, which is published in Nature Communications, addressed the need for a more objective and precise measure of smoking history that could be used to estimate health risks.
A smoking index
The researchers developed an index based on 51 proteins found in the blood that accurately distinguished current smokers from those who had never smoked and assigned a smoking impact score to each of the study’s 43,914 participants. Index scores were largely driven by smoking behaviour over time such as number of smoking years and number of cigarettes smoked per day. A higher index score was strongly associated with a higher risk of premature death and 18 out of 27 major diseases.
Among current smokers, the index score was significantly associated with six out of 15 major smoking-related health outcomes, including lung cancer, various types of heart disease, osteoporosis, and premature death. Interestingly, Parkinson’s disease was one of the few common disorders with a lower risk in smokers.
Among former smokers, the index score was associated with higher risks of 12 diseases (including lung cancer, and chronic obstructive pulmonary disease), although the longer the period of not smoking, the more the score declined. Even non-smokers who had experienced passive exposure to smoking had raised index scores.
Tracking recovery in former smokers
While the index could differentiate some previous smokers in as little as two years since cessation, it took at least ten years for more than 80% of the previous smokers studied to recover from the effects of smoking. Some former smokers were found to have a similar index score and lifetime risks to participants who had never smoked, demonstrating the benefits of quitting.
‘Smokers may change the type or amount of tobacco consumed, or attempt to stop smoking multiple times, making it hard to accurately assess disease risk’, said Cornelia van Duijn, St Cross Professor of Epidemiology at Oxford Population Health and senior author of the study. ‘As well as predicting smoking-related deaths and diseases, our smoking index could be used to objectively assess recovery from smoking-related damage among previous smokers, and across diverse populations.’
Environmental and lifestyle factors
Sociodemographic and lifestyle factors contributed most of the variance in index score for those who had never smoked, with air pollution, diet, and alcohol consumption having the biggest impact. Favourable socio-economic indicators such as higher levels of education and household income, as well as healthier lifestyle choices such as higher levels of activity, were associated with a lower index score while an unhealthy environment and lifestyle choices were associated with a higher index score.
The authors acknowledged that a high index score did not guarantee that someone was or had been a smoker but could be due to other factors. They also stressed the need for further research to explore the index’s potential use in primary care settings.
‘Our study provides a strong foundation for understanding the molecular signatures of smoking and its associations with disease risk’, said Sihao Xiao, lead author and former DPhil student at Oxford Population Health. ‘The smoking index opens up opportunities for clinicians to track a patient’s recovery from smoking and whether the risk of smoking-related illness is going down or staying the same.’
The researchers used a subset of UK Biobank participants with available protein plasma measurements. The results were validated using a subset of the China Kadoorie Biobank. The work was supported by the Centre of Artificial Intelligence in Precision Medicines, King Abdulaziz University.