Table 1 Selected previous studies of comorbidity in cluster headache

200 consecutive male and female CH patients from Italian headache clinic

Cross-sectional survey study

60% were current, 21% former, 19% never smokers.

No change in headache noted in those who had stopped smoking.

140 male and female CH patients vs. controls from a California headache clinic and healthy outpatients

Cross-sectional chart review

Men with CH had a statistically significantly higher prevalence of peptic ulcer disease compared with controls. No increased risk of coronary artery disease was demonstrated.

200 male CH patients and 200 migraine controls from Italian headache clinic

Cross-sectional chart review

Prevalence of traumatic head injuries 38.5% in those with CH vs. 23% in controls (OR 2.0 (95% CI 1.3 to 4.9). Prevalence of alcohol use was 74.5% and cigarette smoking 75% in those with CH.

Only males included in this study.

673 male and female CH patients from a Taiwanese National Health Database

Retrospective cohort study with 2.5 year median follow-up duration

3.6% developed depression over study period. Adjusted HR 5.6% vs. controls but not different from those with migraine; number of bouts/year of CH a risk factor for depression.

Study limited to patients diagnosed by neurologist and prescribed standard CH drugs; excluding those with previous psychiatric diagnoses (104 of original 777; 13%).

60 consecutive male and female CH patients seen at an Italian headache center

Cross-sectional, based on study examination

35% had hypertension, defined as blood pressure ≥ 140/90 on average of 3 blood pressure readings.

The authors concluded that the prevalence of hypertension in this group was within expected range given age and sex.

49 consecutive male and female CH patients seen in a New York headache clinic over a 3.5 year period

Cross-sectional chart review

Prevalence of depression (PHQ ≥ 1 0) was 6.3% in episodic CH, 11.8% in chronic CH; Anxiety (GAD-7 ≥ 10) prevalence was 15.6% in episodic CH and 11.8% in chronic CH. Prevalence of hypertension was 14%, current or former cigarette smoking was 65.3% and GERD was 8%.

210 consecutive male and female CH patients from two Italian headache centers

Cross-sectional interview and anonymous survey data

92.5% of male CH patients and 85.4% of female CH patients reported current or past use of tobacco, statistically significantly higher than prevalence in general population.

Self reported data on substance use.

1134 US male and female CH patients responding to an internet survey

Cross-sectional survey (internet)

Prevalence of depression was 24%, suicidal ideation was reported by 55%, sleep apnea by14%, restless leg syndrome by 11%, asthma by 9%. 73% were current or former smokers; 51% had been smoking at the time CH began. 65% used alcohol but only 3% reported a history of alcohol abuse. The prevalence of coronary problems was low: 1% had a history of myocardial infarction, 0.3% bypass surgery and 1% stent placement. Peptic ulcer disease was reported by 5%, diabetes by 3% and epilepsy by 1%.

Unlikely to be a representative sample of patients with CH due to self-selected nature of participants. Diagnosis not medically verified. Respondents compared with the US population in general rather than matched controls. Data should be interpreted cautiously.

85 male and female CH patients from 4 Belgian neurology clinics

Cross-sectional chart review

45% had been diagnosed with migraine, 23% with sinusitis, tooth/jaw problems 23%, trigeminal neuralgia 16%.

Average diagnostic delay was reported to be 44 months.

144 male and female Italian and Eastern European patients with episodic cluster headache

Cross-sectional (diagnostic interview and survey)

16% of CH patients had previously been diagnosed with sinusitis; 4.2% with dental disorders.

Average delay between onset of symptoms and diagnosis in this sample was 5.3 years. 10.4% had consulted an otolaryngologist and 2.8% a dentist.

26 male and female CH patients identified by survey in tertiary Chinese headache clinic

Cross-sectional (diagnostic interview)

14/26 (54%) were current smokers, 19.2% former and 26.9% nonsmokers.

The reported prevalence of smoking in those with CH is in line with that in the general population of Chinese men. According to 2010 data, 53% of Chinese men and 2.4% of women are smokers.

130 consecutive male and female CH patients and 982 with migraines in a specialty headache clinic

Cross-sectional chart review

Prevalence of anxiety or depression in CH was 4.6%, chronic sinusitis 3.6% diabetes mellitus 3.8%.