TABLE 4—

Associations Between an Increasing Number of Cold Days During the Hazard Period and the Odds of Out-of-Hospital Cardiac Arrest in Different Sex and Age Groups by Season: Helsinki, Finland, 1997–2018

Subgroup	Autumn, OR (95% CI)	Winter, OR (95% CI)	Spring, OR (95% CI)	Summer, OR (95% CI)	All Seasons,a OR (95% CI)
Age 18–64 y	1.08 (0.99, 1.18)	1.02 (0.93, 1.11)	1.05 (0.96, 1.15)	1.13 (1.01, 1.26)	1.06 (1.02, 1.12)
Age ≥ 65 y	1.05 (0.97, 1.13)	1.09 (1.02, 1.16)	1.10 (1.03, 1.18)	1.03 (0.94, 1.13)	1.07 (1.03, 1.11)
Male	1.05 (0.98, 1.12)	1.06 (0.99, 1.13)	1.02 (0.95, 1.09)	1.14 (1.04, 1.24)	1.06 (1.02, 1.10)
Female	1.09 (0.99, 1.19)	1.08 (0.98, 1.18)	1.20 (1.09, 1.31)	0.96 (0.85, 1.09)	1.09 (1.04, 1.15)

Note. CI = confidence interval; OR = odds ratio. All estimates were derived by using the absolute number of seasonally cold days (0–7) as a continuous predictor in the model.

^a Estimate for all seasons was derived by including all cases in the analyzed subgroup, irrespective of the season of occurrence, into the analysis.