Cluster headache : focus on sleep, treatment, and genetics

The main hypothesis of this thesis is that cluster headache (CH) has a genetic component and by investigating this genetic component we can get insights into pathophysiological mechanisms behind CH. Clinical data can help indicate which genes can be contributing to the disease. The genetic variants can in turn help us better understand the biological mechanisms which give rise to CH. In that way we lay a foundation for developing treatment which can alleviate the suffering of millions of people around the world. This thesis focused on three major areas within CH research: sleep, treatment usage/response, and genetic links to CH pathophysiology.

Sleep has long been studied in connection to CH due to the strikingly rhythmic nature of CH attacks which regularly disrupt sleep. In Paper I, we studied sleep patterns of CH participants using actigraph units to record sleep and wake times, complemented with sleep diaries. Actigraphy data showed that, although sleep time did not differ between CH participants and controls, sleep latency and time in bed was increased in CH participants. Participants with CH scored worse in almost all subjective sleep scores. Interestingly, in objective sleep measurements, CH participants in an active bout did not significantly differ to participants in remission.

In Paper II, a survey investigating sleep quality, dysfunctional beliefs regarding sleep, and insomnia symptoms was sent to >700 CH participants. The survey results further established that sleep is disturbed during an active bout as compared to participants in remission and even more so to the general population. The sleep scores were additionally correlated to years since last active bout, again indicating participants in remission are still disrupted by the disease. Paper III used a similar method to investigate extent of burnout in the CH cohort. As high as 67.6% of participants in an active bout were in the risk zone for burnout. Burnout symptoms were also present in remission, but to a lesser degree and correlated to the length of time since the last active bout.

To study possible biological links to the observed sleep patterns and circadian rhythm of attacks we studied genetic variants in biological clock genes. PER, CRY, BMAL1, and CLOCK are the core clock genes which drives the 24-hour rhythm. In Paper IV six genetic variants were genotyped in PER1, PER2, and PER3 which had previous links to diurnal preference or sleep. No significant difference between CH participants and controls was found. In Paper V, genetic variants in BMAL1, and NPAS2, a paralog to CLOCK, were investigated. Variants in BMAL1 (rs3789327) and NPAS2 (rs3768984) were associated with CH. Significant or trending genetic variants in the core clock genes from this study and previous studies were combined in a multi allele risk analysis. This analysis showed that CH participants carried more risk alleles than controls further strengthening the possible role of the biological clock in CH.

Treatment response can vary greatly between different individuals and treatment options, and is not fully understood. In Paper VI a survey was sent out to investigate treatment response in a Swedish CH cohort. It confirmed the previously reported wide range of treatment responses observed for CH. Surprisingly, a considerable number of CH participants didn’t take any preventative medication. Side effects were common and prevented some participants with continuing their otherwise effective treatment.

Since treatment response varied between participants, Paper VII investigated if genetics could partially explain this variation in the first line treatment, triptans. Five genetic variants which had previously been linked to triptan response in other diseases were genotyped and the allelic distribution was compared between triptan users and non-users. One single nucleotide polymorphism (SNP) previously linked to triptan response in migraine was significantly associated with CH triptan usage, meaning the mechanisms of action behind triptan non-response could be similar.

Anecdotally, some CH patients have reported taking vitamin D supplements to improve their CH. To investigate if this was reflected in genetics, a SNP in the VDR gene was genotyped in Paper VIII. We pooled the data from the genotyped SNP and two other VDR SNPs from our previous genome-wide association study (GWAS) with data from a Greek CH cohort into a meta-analysis. No significant associations were found to CH for any of the SNPs.

In the last few years genetics have increasingly shown to play an important role in CH pathology. In Paper IX, a meta-GWAS was performed on genetic material from 11 cohorts comparing CH participants to controls. When only including the 10 European cohorts, the four significant loci from previous CH GWAS were replicated, in proximity to the genes MERTK, DUSP10, FTCDNL1, and FHL5. Three new loci reached genome wide significance: WNT2, PLCE1, and LRP1.

The next step was to translate the genetic findings to possible biological pathways which can contribute to the disease. MERTK is a cell-surface receptor mostly present on immune cells which plays a role in immune suppression, efferocytosis, and a range of other functions. Paper X investigated its potential role in CH. Trigeminal nerves from rats were stained with MERTK antibodies. MERTK was found to be present in Satellite cells and in Schwann cells close to the nodes of Ranvier which would allow MERTK to bind to its ligands if they were released during neuronal activation. Additionally, the protein expression levels of three of MERTK’s ligands were measured in serum. Protein levels of Galectin-3 were significantly higher in CH participants compared to controls.

To further investigate a possible immunological mechanism in CH, in Paper XI cerebral spinal fluid (CSF) and serum samples were sent for an immunoassay which allowed us to look at concentrations of dozens of proteins. Eleven immune system related proteins were elevated in the CSF of CH participants compared to controls. Only two cytokines showed differentiated protein expression in the serum. These data indicate increased inflammatory markers in CH participants both in an active bout and in remission, mostly isolated to the central nervous system.

List of scientific papers

I. Ran C, Jennysdotter Olofsgård F, Steinberg A, Sjöstrand C, Waldenlind E, Dahlgren A, Belin AC. Patients with cluster headache show signs of insomnia and sleep related stress: results from an actigraphy and self-assessed sleep study. J Headache Pain. 2023 Aug 18;24(1):114.
https://doi.org/10.1186/s10194-023-01650-w

II. Jennysdotter Olofsgård F, Ran C, Steinberg A, Sjöstrand C, Waldenlind E, Lantz M, Sundholm A, Söderström M, Dahlgren A, Belin AC. Characterization of insomnia and sleep quality in a cluster headache population. [Manuscript]

III. Jennysdotter Olofsgård F, Ran C, Steinberg A, Sjöstrand C, Waldenlind E, Lantz M, Sundholm A, Söderström M, Dahlgren A, Belin AC. Evidence of High Rates of Burnout in a Cluster Headache Cohort. [Manuscript]

IV. Jennysdotter Olofsgård F, Ran C, Fourier C, Wirth C, Sjöstrand C, Waldenlind E, Steinberg A, Belin AC. PER gene family polymorphisms in relation to cluster headache and circadian rhythm in Sweden. Brain Sci. 2021 Aug 23;11(8):1108.
https://doi.org/10.3390/brainsci11081108

V. Deborgies Sanches C, Jennysdotter Olofsgård F, Fourier C, Sundholm A, Lantz M, Sjöstrand C, Waldenlind E, Steinberg A, Ran C, Belin AC. Genetic variability within molecular core clock genes in cluster headache. [Manuscript]

VI. Smedfors G, Jennysdotter Olofsgård F, Steinberg A, Waldenlind E, Ran C, Belin AC. Use of prescribed and non-prescribed treatments for cluster headache in a Swedish cohort. Brain Sci. 2024 Mar 31;14(4):348.
https://doi.org/10.3390/brainsci14040348

VII. Jennysdotter Olofsgård F, Ran C, Qin Y, Fourier C, Waldenlind E, Steinberg A, Sjöstrand C, Belin AC. Genetic and phenotypic profiling of triptan users in a Swedish cluster headache cohort. J Mol Neurosci. 2024 Apr 18;74(2):45.
https://doi.org/10.1007/s12031-024-02219-1

VIII. Jennysdotter Olofsgård F, Ran C, Qin Y, Fourier C, Sjöstrand C, Waldenlind E, Steinberg A, Belin AC. Investigating vitamin D receptor genetic markers in a cluster headache meta-analysis. Int J Mol Sci. 2023 Mar 21;24(6):5950.
https://doi.org/10.3390/ijms24065950

IX. Winsvold BS, Harder AVE, Ran C, Chalmer MA, Dalmasso MC, Ferkingstad E, Tripathi KP, Bacchelli E, Børte S, Fourier C, Petersen AS, Vijfhuizen LS, Magnusson SH, O'Connor E, Bjornsdottir G, Häppölä P, Wang YF, Callesen I, Kelderman T, Gallardo VJ, de Boer I, Jennysdotter Olofsgård F, Heinze K, Lund N, Thomas LF, Hsu CL, Pirinen M, Hautakangas H, Ribasés M, Guerzoni S, Sivakumar P, Yip J, Heinze A, Küçükali F, Ostrowski SR, Pedersen OB, Kristoffersen ES, Martinsen AE, Artigas MS, Lagrata S, Cainazzo MM, Adebimpe J, Quinn O, Göbel C, Cirkel A, Volk AE, Heilmann-Heimbach S, Skogholt AH, Gabrielsen ME, Wilbrink LA, Danno D, Mehta D, Guðbjartsson DF; HUNT All-In Headache, The International Headache Genetics Consortium, DBDS Genomic Consortium; Rosendaal FR, Willems van Dijk K, Fronczek R, Wagner M, Scherer M, Göbel H, Sleegers K, Sveinsson OA, Pani L, Zoli M, Ramos-Quiroga JA, Dardiotis E, Steinberg A, Riedel-Heller S, Sjöstrand C, Thorgeirsson TE, Stefansson H, Southgate L, Trembath RC, Vandrovcova J, Noordam R, Paemeleire K, Stefansson K, Fann CS, Waldenlind E, Tronvik E, Jensen RH, Chen SP, Houlden H, Terwindt GM, Kubisch C, Maestrini E, Vikelis M, Pozo-Rosich P, Belin AC, Matharu M, van den Maagdenberg AMJM, Hansen TF, Ramirez A, Zwart JA; International Consortium for Cluster Headache Genetics. Cluster headache genomewide association study and meta-analysis identifies eight loci and implicates smoking as causal risk factor. Ann Neurol. 2023 Oct;94(4):713-726.
https://doi.org/10.1002/ana.26743

X. Edvinsson JCA, Ran C, Jennysdotter Olofsgård F, Steinberg A, Edvinsson L, Belin AC. MERTK in the rat trigeminal system: a potential novel target for cluster headache? J Headache Pain. 2024 May 23;25(1):85.
https://doi.org/10.1186/s10194-024-01791-6

XI. Ran C, Jennysdotter Olofsgård F, Wellfelt K, Steinberg A, Belin AC. Elevated cytokine levels in the central nervous system of cluster headache patients in bout and in remission. J Headache Pain. 2024 Jul 23;25(1):121.
https://doi.org/10.1186/s10194-024-01829-9