Exploring the Potential Consortium of Migraine and Periodontitis

Table 1

Nature of association of migraine and periodontitis as elicited by The Bradford Hill criteria.

Criteria	Interpretation based on available data
Strength of association	for the strength of association between periodontitis and migraine ranges from 0.811 to 2.4 as evidenced by Davis et al.^a, Ameijeira et al.^b, Leira et al.^c, This is suggestive that there is a weak strength of association.
Consistency	The results are inconsistent as Ameijeira et al.^b, have given an of 2.4, while other authors such as Davis et al.^a and Leira et al.^c, have quoted to be in the range of 0.811–1.100.
Specificity	The occurrence of migraine is associated with the presence of various risk factors which is similar to the multifactorial oral disease—periodontitis. Hence, it would not be appropriate to say that only periodontitis specifically causes migraine.
Temporality	Huang et al.^d, in a Taiwanese population has noted an of 1.21 which suggests the temporarily of periodontitis over migraine.
Biological gradient	Davis et al.^a, showed that as the increased, there was an increase in the of developing migraine. However, this did not achieve statistical significance, this finding highlighted the biological gradient phenomenon.
Plausibility	The plausibility of periodontal disease-causing migraine and as a disease model has been studied by Ameijeira et al.^e. He stated that periodontal disease, a low-grade systemic inflammation, leads to higher expression of neurogenic markers due to interaction with bacteria causing endotoxemia and systemic spread of periodontitis that directly promotes the activation of the trigeminovascular system leading to migraine occurrence.
Coherence	The adjusted and unadjusted in Leira et al.^c, study was found to be 1.406 and 1.100, respectively. However, the adjusted did not gain any statistical significance thereby making this study noncoherent with the findings of other studies.
Experiment	Most of the studies done to explore the association between periodontitis and migraine are all RCT^# and biomarker-based studies. Only one available prospective cohort study is available done by Huang et al.^d,
Analogy	There have been no previous animal studies to examine the association between periodontitis and migraine. However, a case report by Watanabe et al.^f, has suggested that an association exists between apical periodontitis and migraine in humans.

- odds ratio, - hazard ratio, - Clinical attachment loss, ^# - randomized controlled trial, ^aDavis et al. [13], ^bAmeijeira et al. [47], ^cLeira et al. [48], ^dHuang et al. [49], ^eAmeijeira et al. [21], ^fWatanabe et al. [50].