Relationship between the population incidence of pertussis in children in New South Wales, Australia and emergency department visits with cough: a time series analysis

Table 3 Final model: Change in daily emergency department (ED) visits with cough associated with 10-unit increases in independent variables ^1,2

Independent variable	Category	Parameter estimate	Standard error of the estimate	Relative risk (RR)	RR confidence interval (95%)	p-value
Pertussis notifications		0.050	0.023	1.052	1.005-1.100	0.028
Influenza notifications		0.008	0.004	1.008	1.000-1.017	0.059
Bronchiolitis ED visits		0.047	0.018	1.048	1.012-1.086	0.009
Lag 1 cough ED visits		0.006	0.002	1.006	1.003-1.009	<.001
Day of week	Sunday (ref.)	0.000		1.000
	Monday	0.217	0.037	1.243	1.156-1.336
	Tuesday	−0.042	0.042	0.959	0.833-1.041
	Wednesday	−0.097	0.038	0.908	0.842-0.979	<.001
	Thursday	−0.064	0.038	0.938	0.871-1.011
	Friday	−0.109	0.038	0.896	0.832-0.966
	Saturday	−0.084	0.038	0.919	0.853-0.991
Public holiday	Not public holiday (ref.)	0.000		1.000		<.001
	Public holiday	0.287	0.061	1.333	1.182-1.502	<.001

1. Data sources: ED data were obtained from the New South Wales Emergency Department Data Collection. Disease notifications data were obtained from the New South Wales Notifiable Conditions Information Management System. Study period: 1 January 2007–31 December 2010. Study population: New South Wales children aged under 10 years.
2. Spline term for time not included in the Table. Only the following variables were scaled by a factor of 10: Pertussis notifications; Influenza notifications; and Bronchiolitis ED visits.

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