. 2007 Aug 1;22(10):1439–1446. doi: 10.1007/s11606-007-0288-z

Table 3.

ARIMA Regression Analysis Showing Seasonal and Meteorological Effects on Monthly DU Admission Rates, by Age Groups (≤19 and 20–34)

Age (yr)	Total (n = 160,510)		≤19 (n = 3,040)		20–34 (n = 20,196)
Independent variable	β	t value	â	t value	â	t value
Intercept	−39.7268	−0.60	−17.2793	−1.35	−15.8640	−0.22
AR1	−0.5833	−0.58	−0.5483	−1.69*	0.9241	10.57***
SAR12	−0.4921	−2.19*	−0.2610	−1.80*	−0.3460	−2.36**
MA1	1.2410	0.981	0.7727	3.17***	−0.6005	−3.58***
Atmospheric pressure	0.0480	0.75	0.0169	1.34	0.0204	0.29
Ambient temperature	−0.1575	−2.43*	0.0108	0.47	−0.1688	−1.51
Relative humidity	0.0664	2.78**	0.0093	1.51	0.0349	1.11
Rainfall	0.0003	0.45	0.0007	3.54***	0.0007	0.72
Hours of sunshine	0.0000	0.16	0.0004	2.80***	0.005	0.66
February	−1.0960	−5.03***	−0.2163	−4.45***	−0.8899	−4.41***
May	0.6822	2.27*
Oct
Nov
Dec
Comorbidities
Arthritis^a	0.4908	0.54
COPD^a	0.1837	0.51
Congestive heart failure^a	−0.2264	−0.98
Diabetes^a	−0.1092	−1.28
History of stroke^b	0.1649	0.95
History of myocardial infarction^b	0.5063	1.55
Trend	−0.0142	−2.14*	−0.0019	−3.08***	0.0010	0.07
AIC	1.5336		−1.5022		1.7693
Schwarz criterion (SC)	2.4330		−0.8330		2.4386
R²	0.876		0.565		0.547

Selection of the final parameters was based upon the lowest AIC and SC.

AR1 Autoregressive lag 1, MA1 moving average lag 1, SAR12 seasonal correlation lag 12

*p < 0.05

**p < 0.01

***p < 0.001

^aComorbidities that adversely impact DU exacerbations through pathophysiological mechanisms related to DU. The ARIMA model adjusts for the prevalence of the respective comorbidity among the admissions during each month. Age groups of <19 and 20–34 are not subjected to these adjusted variables due to almost nil or very few numbers of these comorbidities in these groups.

^bComorbitities that are adjusted for to account for possible long-term aspirin medication for stroke/myocardial infarction prophylaxis.