Scientists have identified genetic variants that protect some smokers from developing cancer and dying early.
Smoking has been shown to have drastic consequences for lifespan and disease progression, and it has been suggested that cigarette exposure may impact the risk of death and disease via its acceleration of the ageing process.
Not all smokers experience early mortality, however, and a small proportion manage to survive to extreme ages.
Using long-lived smokers as their phenotype, researchers identified a network of SNPs (a DNA sequence variation occurring commonly within a population) that allow certain individuals to better withstand environmental damage (like smoking) and mitigate damage.
Collectively, these SNPs were strongly associated with high survival rates.
"We identified a set of genetic markers that together seem to promote longevity," said corresponding author Morgan E Levine, from the David Geffen School of Medicine at University in Los Angeles.
"What's more, many of these markers are in pathways that were discovered to be important for ageing and lifespan in animal models," Levine said.
"There is evidence that these genes may facilitate lifespan extension by increasing cellular maintenance and repair," Levine said.
"Therefore, even though some individuals are exposed to high levels of biological stressors, like those found in cigarette smoke, their bodies may be better set up to cope with and repair the damage," Levine said.
These findings suggest that longevity, rather than being entirely determined by environmental factors, may be under the regulation of complex genetic networks which influence stress resistance and genomic stability.
Therefore, there is reason to believe that long-lived smokers represent a biologically distinct group, endowed with genetic variants allowing them to respond differentially to environmental stressors.
Genomic instability also happens to be one of the hallmarks of cancer pathogenesis, and so the same genes that may promote survival among smokers may also be important for cancer prevention.
This is consistent with the findings of the study, which showed that the genes identified were associated with a nearly 11 per cent lower cancer prevalence.
The study was published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences.
