May 9, 2007 — Head and neck injury (HANI) is a significant risk
factor for the occurrence of chronic daily headaches (CDH), with a
dose-response relationship between the 2 conditions, results of a
large, population-based study indicate.
The research was conducted by James R. Couch, MD, PhD, a
professor of neurology at the University of Oklahoma Medical School,
in Oklahoma City, and colleagues and was presented here at the
American Academy of Neurology 59th Annual Meeting.
These results suggest that head injury is a significant risk
factor for chronic daily headache, and the risk is cumulative, Dr.
Couch concluded. "So the effect of a head injury doesn't really go
away," he said. "It's not like in the movies, where the private
investigator gets a lick on the head, then runs off and catches the
bad guy. In real life, there is continued risk after a serious head
injury."
Frequent Headaches
"Studies have shown that 50% to 80% of patients with head injury
have headaches immediately after the head injury, and 2 years later,
20% to 30% of these people still have headaches," Dr. Couch told
meeting attendees. "However, the reverse situation — head injury as
a risk factor for chronic daily headache — has not been studied in a
controlled population," he said.
To evaluate HANI as a risk factor for CDH, the researchers
analyzed data from the Frequent Headache Epidemiology Study, which
surveyed 53,000 subjects in the Baltimore and Atlanta areas by
telephone interview.
Subjects who reported having frequent headaches were asked
whether they ever had an injury to the head or neck and, if so,
whether the injury was followed by fainting or loss of
consciousness. "The fainting or loss-of-consciousness question was
meant to try to differentiate between those who had a more severe
[injury] and [those who had a] less severe injury," Dr. Couch
explained.
Subjects experiencing more than 180 headaches per year were
classified as having CDH, whereas individuals with 2 to 102
headaches per year were classified as episodic headache controls.
"This is the first study to look at head and neck injury as a risk
factor for chronic daily headache using a control population," Dr.
Couch noted.
Injuries were classified as potentially precipitating injuries if
they occurred within 2 years of CDH onset (cases) or in an
equivalent randomly generated 2-year period in controls.
The investigators found that after adjustment for age, sex, and
headache type, CDH cases were more likely to have experienced HANI
than episodic headache controls, and the odds of CDH in association
with a potentially precipitating injury were also elevated.
Risk for Chronic Daily Headaches (CDH) Associated with Any
Head and Neck Injury (HANI) or Potentially Precipitating Injuries
(PPI) vs Episodic Headache Controls
| Group |
Attributable Fraction (%) |
Odds Ratio (95% CI) |
| CDH with any HANI |
15 |
1.7 (1.1 – 2.4) |
| CDH in association with PPI |
5 |
2.3 (1.1 – 4.5) |
The researchers also evaluated the cumulative effect of HANI and
found that there was a significant linear trend (P < .001)
for increasing risk for CDH with increasing numbers of lifetime
HANI. People with 3 or more HANIs were at increased risk for CDH
(odds ratio, 3.6), compared with those without HANI.
"In this population sample, the estimated proportion of CDH cases
theoretically due to HANI was 15% for all HANI and 5% for HANI
within 2 years of CDH onset," the authors concluded. "HANI and
cumulative HANI are significant contributors to risk for CDH."
The study was supportedby GlaxoSmithKline, the Migraine Trust,
and the American Headache Society.
American Academy of Neurology 59th Annual Meeting: Session
S05.002. Presented May 1, 2007.
