Comparison of risk-adjusted surgical outcomes during winter and control seasons between the mountain and control areas.

a “Control season” was the reference group in both groups. b The ratio of odds ratio compare the change in the complication and the mortality rates between two groups. A ratio of odds ratios greater than 1 suggests that the increase of complication and mortality from the “winter season” to control was greater in the “mountain area” group than in the “control area” group. c Adjusted for age, sex, comorbidities, patient’s residence, surgical procedures and type of facility. d Interpretation of hazard ratio and ratio of hazard ratio is the same than odds ratio and ratio of odds ratio. Comparison of risk-adjusted surgical outcomes during winter and control seasons between the mountain and control areas.