Fluctuations in episodic and chronic migraine status over the course of 1 year: implications for diagnosis, treatment and clinical trial design

Table 2 Unadjusted model for headache days per month for persons with EM and CM

Random-effect variance parameter estimates
	Estimate	Standard Error
Intercept	0.82	0.01
Linear trend	0.17	0.01
Quadratic trend	0.09	0.01
Scale	0.09	0.005
Fixed Effects
Label		RR (95% CI) ^a	DF	t	P value
Intercept		3.98 (3.82–4.15)	16,788	66.53	<0.0001
Linear trend		0.73 (0.72–0.75)	29,528	−28.49	<0.0001
Quadratic trend		1.09 (1.06–1.11)	29,528	7.90	<0.0001
Cubic trend		0.98 (0.97–1.00)	29,528	−1.51	0.1318
Headache status: CM vs. EM		4.45 (4.3–4.59)	29,528	89.36	<0.0001
Headache status by linear trend interaction		1.19 (1.13–1.26)	29,528	6.67	<0.0001
Headache status by quadratic trend interaction		1.03 (0.98–1.08)	29,528	1.26	0.2075
Headache status by cubic trend interaction		0.99 (0.95–1.03)	29,528	−0.72	0.4710

CM chronic migraine, DF degrees of freedom, EM episodic migraine, RR rate ratio, t t-statistic
^aStatistically significant RRs are bolded

ISSN: 1129-2377