In this cross-sectional study, we found a positive relation between Migraine and HTN in participants, especially in controlled and uncontrolled HTN of short duration groups. On the other hand, compared with Migraine, CDH had more positive relation with HTN and all of its categories. The prevalence of HTN, Migraine, and CDH was 22.5, 29.07, and 7.45%, respectively. In our cohort study, there were also general questions about Migraine and CDH without mentioning to their types. Therefore, observed Migraine prevalence higher than what we expected might have been due to the fact that our definition involved probable Migraine headaches as well. Other studies have reported the prevalence rates of Migraine and CDH to be 10-20% and almost 3%, respectively (3, 16).
Another reason for higher frequency of the headaches, especially Migraine in our study may be due to more social and economic tensions and psychological stress in our society as global burden of disease (GBD)2016 emphasized that primary headache disorders are an important health priority (27).
Frequent Migraine attacks were revealed by women and the most Migraine’s outbreak was observed among unemployed followed by participants with high BMI. Furthermore, 38.48% of Migraineurs reported a family history of Migraine. According to a population based-study in Spanish, the prevalence of Migraine in females was twice than that of males (R: Migraine and demography 2).
In Iran, the prevalence of Migraine was reviewed in 16 studies from 1998 to 2014by Sadeghi et al., who reported the highest prevalence of Migraine (18.11%). The difference between our study and that study conducted in (28) could be accounted for by our extended Migraine definition, which involved probable Migraine cases ( at least two attacks)in our cohort. Farhadi et al. also reviewed 30 studies and found far lower prevalence (about 14 %) than ours obtained from Rafsanjan as a part of kerman province. In Farhadi’s et al. study, the overall distribution of Migraine in some provinces of Iran was presented as follows; 23% in Tehran province , 26% in Hrmozgan, 35% in Lorestan and East Azarbayejan (29). They did not examine completely the central part of Iran (as our study area) from which 11% prevalence has been reported. As none of the above-mentioned works was done in a cohort study, their results could not be compared with ours.
In addition to female predominance in Migraine, our results, like studies, showed a female-male ratio of about 3:1 in CDH and Migraine with a mild higher proportion of CDH (7).
Despite the uncertainty about the correlation between Migraine and HTN, there was a unifying view suggesting that Migraine is positively correlated with diastolic blood pressure, while being negatively correlated with systolic blood pressure and pulse pressure (8, 30). In another study, it was argued that poor control of blood pressure may exacerbate the frequency and severity of Migraine and other types of headaches (18).
In these studies, blood pressure and its correlation with Migraine was considered. We also found different results on the HTN-Migraine association. For instance, we found changing of HTN with headache in many cases and these results may point to these changes in HTN during headaches but the causal relationship was not approved in these situations. Some studies did not show any relationship between headache and HTN (31).
Furthermore, in our study, the prevalence of HTN in CDH patients was 31.95%, which is far higher than other studies such as Huang’s et al. study in which HTN was 27.96% prevalent in CDH patients (16). Also, the prevalence of HTN among the cohort population (22.5%) was also less than it’s frequency in CDH group (31.98%), while it had a prevalence rate of 24.58% in Migraine group. These findings are consistent with other studies (18, 32). Additionally, in consistence with 42 other studies reviewed systematically by Mirzaei et al. to obtain the pooled prevalence of HTN, we observed a HTN prevalence of 22% in RCS population (30, 33).
An epidemiological studies carried out in Nord-Trondelag Health Survey also revealed a strong negative relation between HTN and Migraine, while the Northern Manhattan study described a strong correlation between HTN and Migraine in controlled and uncontrolled HTN of long duration groups as well as in short duration uncontrolled , a weaker correlation (7).The prevalence of Migraine in a study performed in the Northern Manhattan was 20.40% which is less than what we found in the present work. Unlike the current research, the Northern Manhattan study found a strong HTN-Migraine correlation in controlled and uncontrolled HTN of short duration groups of cases.
Race could be an effective factor, which has led to these differences. For example, Hispanics have shown stronger long duration HTN correlation with Migraine than Caucasian. Environmental factors, life styles, and occupational factors have also proved to be able to influence hypertension and Migraine.
Moreover, in HTN categories, prolonged use of some antihypertensive drugs, such as angiotensin converting enzyme inhibitors and angiotensin receptor blockers may have been the reason for reducing Migraine in long duration HTN cases.
In line with our findings, an Italian cohort study presented that young females had a higher chance to catch Migraine. This Italian study also verified that Migraine is associated with HTN and tension-type headaches. However, they reported a strong association between tension-type headaches and myocardial ischemia. Furthermore, some studies have described an association between chronic kidney disease (CKD) and Migraine so that older patients with Migraine showed higher incidence of CKD. Furthermore, using non-steroid anti-inflammatory drugs (NSAIDs)and prophylaxis drugs in Migraineurs have shown a high risk of HTN (7). In addition, our findings about HTN categories matched with CDH cases but not with Migraine cases in Gardner’s et al. study (7).
The findings of the present research work might have been influenced by different kinds of bias, such as sample selection, imprecise response about previous headache or diagnosis of Migraine, and wrong recall of subject's Migraine information.