Background:
Smokers usually feel fine and accept the commonly cited risks. However, many smokers are unaware that they carry additional risks that would further shorten their lives.

Methods:
The cohort, 434,496, was recruited from participants in a health surveillance program between 1994 and 2008. Blood and urine were collected and analyzed. Mortality was followed up by matching with National Death file. Hazard ratios (HR) and loss of life expectancy were calculated, based on the reference group of those without the risk factor(s).

Results:
Male smokers as a group had their life expectancy shortened by 5.66 years. When smokers were inactive, life shortened by 8.92 years. When accompanied by proteinuria or diabetes, years of life shortened became 14.8 and 15.4 respectively. When smokers have both proteinuria and diabetes, life years lost became 23.85. Life years lost from 2or 3 risks were found to be additive.



[Years of life lost from multiple risk in male]



Conclusions:
The life-shortening effect of additional risk was surprisingly large, and could be used to motivate them to quit to extend their lives.