Table 4. The results of the sequentially built Negative-Binomial Generalized Linear Models (NB-GLM) with harmonic terms for heat-related hospitalizations (HH) for heatwave episodes in Boston MSA, 1991–2006 based on the proposed definition and four alternative definitions of a heatwave episode.

	Model 2			Model 3			Model 4
	Estimate	Std. Error	p-value	Estimate	Std. Error	p-value	Estimate	Std. Error	p-value
Proposed Definition
Intercepta	−2.46	0.20	<0.001	−2.76	0.20	<0.001	−2.88	0.20	<0.001
COS (1st)b	−1.58	0.11	<0.001	−1.38	0.10	<0.001	−1.38	0.10	<0.001
SIN (1st)	0.07	0.12	0.52	0.14	0.11	0.21	0.13	0.11	0.25
COS (2nd)	0.69	0.09	<0.001	0.59	0.09	<0.001	0.56	0.09	<0.001
SIN (2nd)	0.46	0.10	<0.001	0.21	0.10	0.03	0.23	0.09	0.02
WEEKEND-HDAYc	−0.23	0.12	0.06	−0.26	0.12	0.03	−0.29	0.12	0.01
HW Episode				1.93	0.18	<0.001
1st HW							2.59	0.30	<0.001
Later HW							1.32	0.22	<0.001
Definition A
HW Episode				2.26	0.14	<0.001
1st HW							2.48	0.28	<0.001
Later HW							2.20	0.15	<0.001
Definition B
HW Episode				2.52	0.19	<0.001
1st HW							2.63	0.34	<0.001
Later HW							2.46	0.22	<0.001
Definition C
HW Episode				1.70	0.15	<0.001
1st HW							2.20	0.20	<0.001
Later HW							1.21	0.19	<0.001
Definition D
HW Episode				2.84	0.44	<0.001
1st HW							3.01	0.53	<0.001
Later HW							2.21	0.77	<0.001

^aAll models are adjusted for the year effects as described in Method section (data not shown).

^bThe sin and cos terms for the first and second harmonics of seasonal components, respectively.

^cA term for weekend and holiday effects (WEEKEND-HDAY).