Table 1 Odds ratio for the development of duodenal ulcer in day‐time workers and shift workers after adjustment for possible confounding factors.

Variable	OR*	95% CI
Age	0.98	0.96–1.01
Sex	1.38	0.82–2.30
Smoking	1.63	0.97–2.76
Familial history	1.02	0.55–3.41
Prevalence of duodenal ulcer	3.96	2.10–7.47

*ORs are adjusted with each other.