Table 1. Negative binomial regression models for NMSC and MSC cancers by month of birth.

	NMSC (C44)				MSC (C43)
Variable	IRR	95% CI		P	IRR	95% CI		P
Months
January	1.18	1.09	1.28	<0.001	1.41	1.12	1.77	0.003
February	1.29	1.19	1.39	<0.001	1.15	0.90	1.47	0.25
March	1.30	1.20	1.40	<0.001	1.36	1.09	1.71	0.007
April	1.31	1.21	1.41	<0.001	1.15	0.90	1.45	0.26
May	1.14	1.05	1.23	0.002	1.15	0.90	1.46	0.26
June	1.02	0.93	1.11	0.70	1.41	1.11	1.77	0.004
Julya	Ref.				Ref.
August	1.04	0.96	1.13	0.32	1.12	0.88	1.43	0.36
September	1.09	1.00	1.18	0.04	1.14	0.90	1.46	0.28
October	1.08	1.00	1.17	0.06	1.10	0.86	1.40	0.45
November	1.20	1.11	1.31	<0.001	1.12	0.87	1.43	0.37
December	1.11	1.02	1.21	0.01	0.93	0.72	1.21	0.61
Gender
Males	Ref.				Ref.
Females	0.66	0.64	0.68	<0.001	0.95	0.86	1.04	0.25

Abbreviations: CI=confidence interval; IRR=incidence rate ratio; MSC=melanoma skin cancer; NMSC=non-melanoma skin cancer; Ref.=reference category.

^areference category is the month with the lowest date of birth.