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.