Researchers have been able to identify a specific physical trait in the blood of those who light up.
But it was not found in non-smokers.
Authors say this biomarker could be an early indication of emphysema.
The thought is that a test showing smokers are developing lung disease may be a stronger incentive to kick the habit than just the threat of being at risk.
There's more on this report in the American Journal of Respiratory and critical Care Medicine.
