A total of 136 incident cases (61 females and 75 males) of pancreatic cancer were diagnosed during 560
666 person-years of follow-up, yielding a crude incidence rate of 24.3 per 100
000 person-years. The incidence rate was similar among women (24.1 per 100
000 person-years) and men (24.4 per 100
000 person-years). The mean (±s.d.) age of the participants at baseline in 1997 was 62 (9.3) years for women and 60 (9.7) years for men. The mean (±s.d.) age of the participants at time of diagnosis of pancreatic cancer was 72 (8.5) years for female cases and 72 (8.0) years for male cases. presents the baseline characteristics by BMI. The mean (±s.d.) baseline BMI was 25.0 (3.9)
among women and 25.8 (3.4)
among men. In all, 34% percent of the women and 46% of the men were overweight (BMI 25–29.9
); 11% percent of the women and 10% of the men were obese (BMI
). Compared with women and men with a BMI of 20–25
, obese women and men were less likely to have a post-secondary education and to be current smokers, but were more likely to have diabetes; they also exercised less and had lower alcohol consumption. BMI was strongly correlated with waist circumference (women, r
=0.76; men, r
=0.75). The proportions of never, past and current smokers, respectively, at baseline were 54, 27 and 19% among women and 36, 46 and 18% among men.
Age-standardised characteristics among women and men according to categories of body mass index at baseline
We observed a positive association between BMI and risk of pancreatic cancer (). After controlling for age and other potential risk factors for pancreatic cancer, women and men with a BMI of 30
or higher had an 81% increased risk compared with those with a BMI of 20–25
. When analysed as a continuous variable, an increment of 1 BMI unit (kg/m2
) was related to a 5% increased risk of pancreatic cancer among women and men combined (RR: 1.05; 95% CI: 1.00–1.10), a 4% increased risk among women (RR: 1.04; 95% CI: 0.97–11), and a 6% increased risk among men (RR: 1.06; 95% CI: 0.99–1.14). The findings for BMI did not change appreciably after excluding cases that occurred within the first year of follow-up. Waist circumference was also positively associated with risk of pancreatic cancer, and similar to the observed association for BMI; the risk was greater among men (). For a difference of 20
cm (approximately two standard deviations) in waist circumference, the multivariate RRs were 1.32 (95% CI: 0.73–2.37) among women and 1.74 (95% CI: 1.00–3.01) among men.
Rate ratios (95% confidence intervals) of pancreatic according to body mass index, waist circumference, and diabetes
A history of diabetes was associated with a statistically significant 1.9-fold elevated risk of pancreatic cancer (). This association remained after early follow-up cancers (i.e., those diagnosed within the first year) were excluded (RR: 1.97; 95% CI: 1.10–3.53). The association with diabetes seemed to be confined to men, but the number of diabetic women with pancreatic cancer was small (n=5).
Women and men who were current smokers at baseline had a significantly higher risk of pancreatic cancer compared with never smokers (). Past smoking was not related to a significantly increased risk, although women who had smoked in the past had a nonsignificant elevation in risk. Risk of pancreatic cancer increased with increasing number of pack-years of smoking. Current smokers of 40 or more pack-years had a fivefold elevated risk of pancreatic cancer compared to never smokers. An increment of 10 pack-years of smoking was associated with a multivariate RR of 1.36 (95% CI: 1.15–1.61; P value for trend=0.0003).
Rate ratios (95% confidence intervals) of pancreatic cancer according to cigarette smoking status and total number of pack-years of smoking
We also assessed the association between smoking cessation and risk of pancreatic cancer (). Compared with current smokers, the RR among past smokers diminished steeply and approached the RR for never smokers within 5–10 years following smoking cessation.
Figure 1 Multivariate rate ratios of pancreatic cancer in relation to time since quitting of smoking among women and men. Multivariate models were stratified by age in months at baseline and sex and were simultaneously adjusted for education (less than high school, (more ...)
shows the RRs of pancreatic cancer according to cross-classification of BMI and smoking status. High BMI and cigarette smoking were independently associated with increased risk of pancreatic cancer and there was no apparent effect modification between these variables (P
for interaction=0.74). Compared with nonsmokers (never and past) with a BMI of less than 25
, current smokers with a BMI of 30
or more, had a multivariate RR of 5.07 (CI: 1.93–13.30).
Figure 2 Multivariate rate ratios of pancreatic cancer according to body mass index (BMI) and cigarette smoking status among women and men. Multivariate models were stratified by age in months at baseline and sex and were simultaneously adjusted for education (more ...)