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1. Introduction
Migraine is the most prevalent and incapacitating neurovascular disorder worldwide, affecting approximately one billion people, exerting a considerable impact on quality of life, and representing a significant socioeconomic burden [1,2,3]. Speculated origins of pain are cortical neuronal hyperexcitability [4], modulatory dysfunction of brainstem and diencephalic systems [5], and peripheral activation [6], all of which lead to the release of vasoactive neuropeptides in the trigeminovascular system to process pain [7,8].
Although many hypotheses regarding migraine triggers have been proposed, the significance of causal relationships between the triggers is obscured [9,10]. Among these triggers, cervical pathologies may initiate the sequence of events that results in migraine symptoms. The extensive functional convergence of upper cervical spinal cord from the descending fibers in the trigeminal nucleus caudalis, which terminates within the trigeminocervical nucleus, and the afferent fibers from the upper cervical roots, which communicate in this region, accounting for the bi-directional pathway of pain between the neck and head. This interaction refers the cervical pathologies to the head, which is the activity also proposed to cause cervicogenic headache [11]. Constantly noxious cervical afferent irritation via this pathway is a possible key element in causing migraines.
Neck pain and muscle tension are common migraine symptoms and both could be sequelae of neck injuries, according to the musculoskeletal anatomy [11,12]. Moreover, administering multiple injections in targeted head and neck regions is sometimes considered important for the management of migraines, cervicogenic headaches, and myofascial referred pain [11,13,14,15,16], indicating that headache and neck pain may share some common pathways.
Although a previous report indicated that cervical spondylosis (CS) accounts for 15.9% of migraineurs [17], until now epidemiological evidence of a link between CS and the risk of migraine is minimal. Therefore, we conducted this nationwide retrospective cohort study to investigate the longitudinal causal relationship between CS and migraines and CS severity in relation to the risk of developing a migraine.
2. Methods
2.1. Data Source
The data used in this retrospective study was retrieved from the Longitudinal Health Insurance Database 2000 (LHID2000) of Taiwan, a subdataset of the National Health Insurance Research Database (NHIRD) that comprises 1,000,000 randomly selected people from the NHIRD. The NHIRD of Taiwan contains the detailed health care data of more than 99% of the Taiwanese population...