Table 4.

Most common traumatic brain injury (TBI) international classification of diseases, ninth revision (ICD-9) codes at hospitalizations.

	Exposed	Unexposed	RR	95% CI
First 12 months	n = 41	n = 26
Concussion	43.90%	38.46%	1.14	0.63–2.07
Head injury, unspecified	21.95%	23.08%	0.95	0.38–2.36
Fracture of base of skull	9.76%	11.54%	0.84	0.21–3.48
Years 2–7	n = 143	n = 76
Concussion	59.44%	50.00%	1.19	0.91–1.55
Intracranial injury nos	17.48%	10.53%	1.66	0.79–3.50
Fracture of base of skull	10.49%	15.79%	0.66	0.33–1.35
Years 8–14	n = 13	n = 3
Post-concussion syndrome	38.46%	0.00%	–	–
Concussion	23.08%	100.00%	0.23	0.09–0.62
Intracranial injury nos	23.08%	0.00%	–	–

Categories are not mutually exclusive.