From the Journals

Cluster headache tied to high risk of mental and neurologic disorders



Cluster headache is associated with a significantly increased risk for comorbid conditions, including mental disorders and other neurologic disease, leading to significant disability and absenteeism, new research shows.

Results from a Swedish register-based study also showed that patients with cluster headache had a sixfold increased risk for central nervous system disorders and a twofold increased risk for musculoskeletal disorders.

Although cluster headaches are often more prevalent in men, researchers found that multimorbidity rates were significantly higher in women. In addition, rates of external injuries were significantly higher among individuals with cluster headache than among persons without cluster headache.

“The findings very clearly indicate that cluster headache patients suffer from other health issues as well and that they are at risk of having longer periods of times when they cannot work,” said lead investigator Caroline Ran, PhD, a research specialist in the department of neuroscience at the Karolinska Institutet, Stockholm.

“It’s really important for clinicians to look at cluster headache from a broader perspective and make sure that patients are followed up so that they don’t risk ending up in a situation where they have several comorbidities,” Dr. Ran added.

The findings were published online in Neurology.

‘Striking’ finding

Cluster headache is one of the most severe and debilitating types of headache. It causes intense pain behind the eyes, which has been described as being worse than pain associated with childbirth or kidney stones.

Attacks can occur multiple times in a single day and can last up to 3 hours. Cluster headache is rare, occurring in about 1 in 1,000 individuals, and is more common in men. Underdiagnosis is common – especially in women.

The study drew on two Swedish population-based registries and included 3,240 patients with cluster headache aged 16-64 years and 16,200 matched control persons. The analysis covered medical visits from 2001 to 2010.

Results showed that 91.9% of participants with cluster headache had some type of multimorbidity. By comparison, 77.6% of the control group had some type of multimorbidity (odds ratio, 3.26; P < .0001).

Prior studies have shown a higher incidence of mental health and behavioral disorders among patients with cluster headache. However, when the researchers removed those conditions along with external injuries from the dataset, patients with headache were still significantly more likely to have multiple co-occurring illnesses (86.7% vs. 68.8%; OR, 2.95; P < .0001).

The most common comorbid conditions in the overall cluster headache group were diseases of the nervous system (OR, 5.9; 95% CI, 5.46 -6.42); 51.8% of the cluster headache group reported these disorders, compared with just 15.4% of the control group.

Diseases of the eye, the respiratory, gastrointestinal, and musculoskeletal systems, and connective tissue were also significantly more common among patients with cluster headache.

“For each diagnosis that we investigated, we found a higher incidence in the cluster headache group, and we thought this was a very striking finding and worth discussing in the clinical setting that these patients are at risk of general ill health,” Dr. Ran said.

Risky behavior?

Another novel finding was the higher rate of external injuries among the cluster headache group, compared with the control group. The finding seems to back up the theory that patients with cluster headache are more likely to engage in risky behaviors, the researchers noted.

In the cluster headache group, external injuries were reported by 47.1% of men and 41% of women, versus 34.9% and 26.0%, respectively, in the control group.

“Now we can also show that cluster headache patients have more injuries and that is totally unrelated to the biological health of the individuals, so that could also indicate higher risk taking,” Dr. Ran said.

Overall multimorbidity rates and diagnoses in each medical category except external injury were higher among women with cluster headache than men with headaches. In addition, the mean number of days on sick leave and disability pension was higher among women with cluster headache than among men with cluster headache (83.71 days vs. 52.56 days).

Overall, the mean number of sickness absence and disability pension net days in 2010 was nearly twice as high in the cluster headache group as in the control group (63.15 days vs. 34.08 days).

Removing mental and behavioral health disorders from the mix did not lower those numbers.

“Our numbers indicate that the mental health issues that are related to cluster headache might not impact their work situation as much as the other comorbidities,” Dr. Ran said.

Struggle is real

Commenting on the findings, Heidi Schwarz, MD, professor of clinical neurology at the University of Rochester (N.Y.) Medical Center, called the study a “valuable contribution” to the field and to the treatment of cluster headache.

“It’s a good study that addresses factors that really need to be considered as you take care of these patients,” said Dr. Schwarz, who was not involved with the research.

“The most salient features of this is that cluster headache is quite disabling, and if you add a comorbidity to it, it’s even more disabling,” she said.

Dr. Schwarz noted that cluster headache is often misdiagnosed as migraine or is overlooked altogether, especially in women. These data underscore that, although cluster headache is more common in men, it affects women too and could lead to even greater disability.

“This has a direct impact on patient quality of life, and in the end, that really should be what we’re looking to enhance,” Dr. Schwarz said. “When a patient with cluster comes in and they tell you they’re really struggling, believe them because it’s quite real.”

The findings also fill a gap in the literature and offer the kind of data that could not be collected in the United States, she noted. Sweden provides paid sick time for all workers aged 16 and older and offers a disability pension to all workers whose ability to work is temporarily or permanently inhibited because of illness or injury.

“You will never get this kind of data in the United States because this kind of data comes from two datasets that are extremely inclusive and detailed in a society, Sweden, where they have a social support system,” Dr. Schwarz said.

The study was funded by the Swedish Research Council, the Swedish Brain Foundation, and Mellby Gård, Region Stockholm, Märta Lundkvist stiftelse and Karolinska Institutet research funds. Dr. Ran and Dr. Schwarz report no relevant financial relationships.

A version of this article first appeared on

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