Abstract
Dear Sir As I browsed through the sections of the paper ‘Prevalence of cluster headache in a population-based sample in Germany’ published in Cephalalgia 2007 (1), the interest that led me to read it in the first place gave way to puzzlement. I will explain why:
Firstly, the author's choice to evaluate 1-year prevalence for cluster headache. (Incidentally, why not to hint at that in the title as well?) Unlike other primary headaches, cluster headache has a periodic time pattern. What can be the scientific and clinical relevance of evaluating 1-year prevalence rates for this form of headache? Is it really important to know how many patients with cluster headache living in the town of Essen happened to have an active cluster period between December 2002 and November 2003? What is the impact of this finding on healthcare?
We know from the literature that 27% of cluster headache patients referred to headache centers (2) have less than one active period per year. The analysis of the clinical features of the cluster headache sufferers found in the study on the San Marino general population (3) shows that 11 cluster headache patients out of 15 had been free from headache for at least two years. Therefore, it is reasonable to assume that the 1-year prevalence rate of 119/100 000 (95% confidence interval: 3238/100 000) reported in the German population is certainly an underestimate of the actual figure.
Secondly, I do not think that the phrase ‘an acceptable response rate of 56%’ included in the second paragraph of the Discussion section is correct (1). As any investigator concerned with epidemiology knows well, the percentage of responders in a general population study must be at least 70%. In this survey, the studied population (n = 3336) cannot be considered representative of the initial population (n = 6000).
Based on the above considerations, the results of this study do not provide any significant evaluation of cluster headache prevalence in the German general population. In my opinion, a prestigious journal like Cephalalgia should publish only data of some significance.
P.S. The reference item #2 is inaccurate. The year of publication is 2007, not 2006.