Table 2.

Cox proportional hazard regression analysis for any new activation-related epileptiform abnormality in 449 people with epilepsy aged 1 year or older who had at least one EEG

Factors	N (%)	Crude HR (95% CI)	Adjusted HR* (95% CI)
Age at EEG**
1–19 years		2.3 (1.6– 3.4)	1.8 (1.1– 2.9)
≥20 years		1.0 (referent)	1.0 (referent)
Gender
Male	238 (53%)	1.0 (referent)	1
Female	211 (47%)	1.1 (0.9–1.5)
Sleep done**
No		1.0 (referent)	1.0 (referent)
Yes		1.8 (1.3– 2.7)	2.7 (1.8– 4.2)
Photic stimulation done**
No		1.0 (referent)	1.0 (referent)
Yes		0.9 (0.6– 1.4)	0.8 (0.5– 1.6)
Hyperventilation done**
No		1.0 (referent)	1.0 (referent)
Yes		1.0 (0.7– 1.4)	1.2 (0.7– 2.1)
Etiology^
Genetic	83 (18.5%)	1.0 (referent)	1.0 (referent)
Prenatal/developmental	55 (12.2%)	0.6 (0.4–0.9)	0.5 (0.3–1.02)
Postnatal symptomatic	104 (23.2%)	0.3 (0.2–0.5)	0.3 (0.1–0.5)
Unknown	207 (46.1%)	0.5 (0.4–0.7)	0.4 (0.3–0.7)
Status epilepticus
No	438 (97.6%)	1.0 (referent)	1
Yes	11 (2.4%)	0.4 (0.1–1.6)

^*accounting for the number of seizures during each of the first five years of follow up (categorized as none, one, two or more, or unknown).

^**Time–dependent variable The status of each EEG with regard to use of any activation technique (i.e., sleep, photic stimulation, hyperventilation). It is not possible to give the N for all the variables because the time dependent covariates change over time. Therefore, we provide the remaining variables that are not time dependent.

^{^}Genetic etiology includes epilepsy formerly classified as idiopathic (e.g. idiopathic generalized, N=67, 80.7%; idiopathic focal, N=16, 19.3%).

HR= Hazard Ratio; 95% CI= 95% Confidence Interval;

¹Factor not included in the model;