Table 4.

Incidence Rate Ratios with 95% Confidence Interval Calculated by Poisson Regression

	P Value of Year/Study Period	Year/Study Period IRR	Month IRR	Day IRR
Overall	<0.001∗	0.553 (0.478–0.641)	1.035 (0.949–1.128)	1.010 (1.002–1.018)
Elective procedures	<0.001∗	0.500 (0.417–0.598)	1.028 (0.926–1.141)	1.009 (0.999–1.018)
Emergency procedures	0.002∗	0.675 (0.524–0.870)	1.036 (0.890–1.207)	1.013 (0.999–1.027)
Trauma	0.015∗	0.635 (0.440–0.915)	1.025 (0.824–1.275)	1.003 (0.984–1.024)
Oncology	0.005∗	0.600 (0.419–0.858)	0.899 (0.727–1.113)	1.008 (0.989–1.028)
Spine	<0.001∗	0.539 (0.438–0.664)	1.177 (1.041–1.330)	1.015 (1.004–1.027)
Vascular	0.062	0.574 (0.357–1.066)	0.903 (0.682–1.195)	1.017 (0.992–1.044)
Congenital	1.000	1.00 (0.062–15.98)	1.00 (0.183–5.459)	0.885 (0.719–1.090)
Hydrocephalus	0.372	0.571 (0.167–1.952)	1.523 (0.715–3.244)	0.965 (0.902–1.033)
Infection	0.014∗	0.315 (0.126–0.790)	0.941 (0.582–1.522)	0.998 (0.955–1.042)
Others	0.083	0.363 (0.115–01.141)	0.737 (0.391–1.390)	0.975 (0.920–1.032)
Complications	0.323	0.600 (0.218–1.650)	0.828 (0.452–1.517)	1.010 (0.956–1.067)

Number of daily admissions as the response variable; month, day, and year as the independent variables. Year variable represents the COVID-19 and pre–COVID-19 periods.

IRR, incidence rate ratio.

^∗Indicates statistically significant (P <0.05).