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Smoking initiation was found to be associated with adverse childhood events and with measures of personality whereas smoking cessation was associated predominantly with socio-demographic and tobacco use-related factors.

Summary The association between the intake of nitrate or nitrite and gastric cancer risk was investigated in a prospective cohort study started in 1986 in the Netherlands, of 120 852 men and women aged 55-69 years. At baseline, data on dietary intake, smoking habits and other covariates were collected by means of a setf-administered questionnaire. For data anatysis, a case-cohort approach was used, in which the person-years at risk were estimated from a randomly selected subcohort (1688 men and 1812 women). After 6.3 years of follow-up, 282 microscopicalty confirmed incident cases of stomach cancer were detected: 219 men and 63 women. We did not find a higher risk of gastric cancer among people with a higher nitrate intake from food [rate ratio (RR) highest/lowest quintile = 0.80, 95% Cl 0.47-1.37, trend-P = 0.18], a higher nitrate intake from drinking water (RR highestAowest quintile = 0.88, 95% Cl 0.59-1.32, trend-P = 0.39) or a higher intake of nitrite (RR highestAowest quintile = 1.44, 95% Cl 0.95-2.18, trend-P = 0.24). Rate ratios for gastric cancer were also computed for each tertile of nitrate intake from foods within tertiles of vitamin C intake and intake of beta-carotene, but no consistent pattem was found. Therefore, our study does not support a positive association between the intake of nitrate or nitrite and gastric cancer risk. Both ascorbic acid and beta-carotene may act as scavengers for free radicals. thus preventing oxidative damage in gastric mucosa and mutations in DNA (Kyrtopoulos. 1987). Furthermore, the conversion of nitrate to nitrite may be inhibited by storage of foods in the refrigerator or freezer (Boeing. 1991 ). Other factors such as smoking habits, socioeconomic status. family history of stomach cancer and prevalence of stomach disorders may confound the association between nitrate or nitrite intake and gastric cancer risk (Boeing et al. 1991: Palli et al, 1994: Kono and Hirohata. 1996: van Loon et al. 1998. Numerous epidemiological studies which have been undertaken on the association between nitrate intake and gastric cancer risk show a lack of consistency (Jensen. 1982: Clough. 1983: Gilli et al. 1984: Beresford. 1985: Risch et al. 1985: Buiatti et al. 1990: Boein, et al. 1991: Leclerc et al. 1991: Palli et al. 1992: Rademacher et al. 1992: Xu et al. 1992: Gonzalez et al. 1994: Hansson et al. 1994: La Vecchia et al. 1994: Pobel et al. 1995 However. in most of these studies high nitrate consumption via ingested food showed no association with gastric cancer risk or even an inverse association. This finding might result from the fact that vegetables -the main source of nitrate -also contain vitamin C and beta-carotene. which appear to be protective factors for gastric cancer. Therefore, intake of nitrate from foods must be studied separately from intake of nitrate from drinking water. which does not contain protective substances.So far. epidemiological studies on nitrate intake and gastric cancer risk have been ecological or case-control in design. in which problems arise with co...