Research Submission Vitamin D Deficiency in Patients With Chronic Tension-Type Headache: A Case-Control Study Sanjay Prakash, DM (Neurology); Chaturbhuj Rathore, DM (Neurology); Prayag Makwana, DM (Neurology); Ankit Dave, DM (Neurology); Hemant Joshi, DM (Neurology); Haresh Parekh, DM (Neurology) Objective.—To see the interrelation between chronic tension-type headache (CTTH) and serum vitamin D levels. Background.—Several studies have suggested an association between chronic pain and vitamin D deficiency. Anec- dotal evidence suggests that vitamin D deficiency may be associated with tension-type headache and migraine. Methods.—This case-control study was carried out to examine the association between CTTH and serum 25-hydroxy vitamin (25(OH) D) levels. One hundred consecutive adult (>18 years) patients with CTTH and 100 matched healthy con- trols were enrolled. Results.—The serum 25(OH) D levels were significantly lower in CTTH patients than in the controls (14.7 vs 27.4 ng/ mL). The prevalence of vitamin D deficiency (serum 25 (OH) D < 20 ng/mL) was greater in patients with CTTH (71% vs 25%). CTTH patients had a significantly high prevalence of musculoskeletal pain (79% vs 57%), muscle weakness (29%vs 10%), muscle tenderness score (7.5 vs 1.9), and bone tenderness score (3.0 vs 0.8) in comparison to controls. CTTH patients with vitamin D deficient group (<20 ng/mL) had a higher prevalence of musculoskeletal pain (58% vs 31%), mus- cle weakness (38%vs 7%), muscle and bone tenderness score, associated fatigue (44% vs 17%) and more prolonged course (15.5 months vs 11.2 months). A strong positive correlation was noted between serum vitamin D levels and total muscle tenderness score (R 2 5 0. 7365) and total bone tenderness score (R 2 5 0. 6293). Conclusion.—Decreased serum 25(OHD) concentration was associated with CTTH. Intervention studies are required to find out if supplementation of vitamin D is effective in patients with CTTH. Key words: tension-type headache, chronic-tension-type headache, migraine, generalized pain, osteomalacia, vitamin D (Headache 2017;00:00-00) INTRODUCTION Several observations have suggested a link between chronic pain and vitamin D deficiency. 1-3 A few recent observations indicate that low serum vitamin D levels may be related to a few headache disorders, especially migraine and tension-type headache (TTH). 4-7 Muscular factors are very important in the gen- eration of TTH. Pericranial muscular tenderness From the Department of Neurology, Smt. B. K. Shah Medi- cal Institute and Research Centre, Sumandeep Vidyapeeth, Piparia, Waghodia, Vadodara, Gujarat 391760, India. Address all correspondence to S. Prakash, Department of Neurology, Smt B. K. Shah Medical Institute and Research Centre, Piparia, Waghodia, Vadodara, Gujarat 391760, India, email: drprakashs@yahoo.co.in Accepted for publication March 27, 2017. Previous Presentation: This manuscript was not presented at any meeting or published, nor is being considered for publi- cation elsewhere. Conflict of Interest: The authors declare that they have no competing interests. Source of Support/Funding: This study was supported by grants from the Sumandeep Vidyapeeth University, Piparia, Vadodara, India (SVRC/ON/2015/15268). The funder did not play any role in study design, data collection and analy- sis, or preparation of the manuscript. 1 ISSN 0017-8748 Headache doi: 10.1111/head.13096 V C 2017 American Headache Society Published by Wiley Periodicals, Inc.