Table 2.

Selected characteristics of the study population (n = 602,242) at enrollment by smoking (ever versus never) status and gender

Men n = 299,376Women n = 302,866
CharacteristicsEver smokers (n = 200,988)Never smokers (n = 98,388)PaEver smokers (n = 179,363)Never smokers (n = 123,503)Pb
Age at enrollment (mean, year)4443<0.00014445<0.0001
Age at diagnosis among cases (mean, year)6461<0.00016064<0.0001
Follow-up years(median)1412<0.00011312<0.0001
Education (n%)
≤10 years27132820
10–12 years55525752
≥13 years and more1835<0.00011528<0.0001
Physical activityc(n%)
BMI (kg/m2, mean)2526<0.00012425<0.0001
Age at smoking initiation ≤16 years (n%)5743<0.0001
Number of cigarettes smoked per day ≥20 years (n%)6931<0.0001
Smoking duration ≥40 years (n%)7228<0.0001
Number of pack-yearsd ≥20 years (n%)6832<0.0001
  • at test or χ2 test for differences between ever and never smokers in men.

  • bt test or χ2 test for differences between ever and never smokers in women.

  • cLevel of physical activity; sedentary(reading, watching television, and sedentary activity), moderate (walking, bicycling, or similar activities ≥4 hours/wk), and heavy (light sports or heavy gardening ≥4 hours/wk, heavy exercise or daily competitive sports).

  • dPack-years were calculated as numbers of cigarettes smoked per day, divided by 20, and multiplied by smoking duration in years.