The results obtained in the present review mainly found an association between sleep disorders and migraine attacks during the social isolation in the COVID-19 pandemic. Eating habits and physical activity were the other most studied factors in relation to headache attacks during the health crisis. In addition, studies originating mainly from Europe (50%) were reviewed. The propensity for research on the subject can be justified by the fact that in that continent, headaches are the second cause for “years lived with disability”, according to data from the Global Burden of Disease Study (GDB), which is capable of having a major impact on public health [23].
Discussing GBD data, it was reported that, in relation to age, young adult women (15-49 years) are the most affected by migraines. In the aforementioned research, the disease occupied the second place related to disability, only behind gynecological diseases. Such data are close to those seen in this review, where the studies that provided the mean age of the sample group showed values from 42.3 to 45.2 years for the age group, and in the analyzed populations, women also predominated. Young adults and women appear to be more prone to migraines [24-27]. Through a literature review, Delaruelle Z, et al. [27] observed that primary headaches occur more frequently in females of reproductive age. For the authors, headache patterns evolve over time and are correlated with hormonal changes throughout life, since sex hormones have effects on the nervous system and affect important brain areas.
Sleep disorders were evaluated by 90% of the studies that composed the current work, and it was possible to find positive relationships between these disorders and the frequency and intensity of migraines. In this aspect, Buse DC, et al. [28] observed that migraine subjects had a triple chance of insomnia through a prospective longitudinal cross-sectional study. Likewise, the intensity of the headache was related to a greater risk for the disorder.
According to Souza LFF, et al. [29], the COVID-19 pandemic, with the imposition of social isolation, contributed as a risk factor related to mental health, which directly impacts sleep quality. In this way, the state of reclusion and the public health situation may have acted as drivers for this factor related to migraines, in view of the occurrence of an association between migraines, anxiety, and sleep disorders [30]. As exposed by Korabelnikova EA, et al. [31], migraines and sleep disorders have a complex bidirectional relationship, both as a cause and aggravation, which is due to the sharing of neurobiological pathways. The authors reinforce that anxiety worsens this relationship, resulting in a decrease in quality of life. Thus, diagnosing and treating sleep-related comorbidities should be part of the goals included in the treatment of migraines, since better sleep quality is crucial for reducing the severity and recurrence of headache attacks [32,33].
Most studies (70%) also evaluated the association between eating habits and worsening of migraines, due to the idea that food is a trigger of migraine episodes, in addition to the context of the pandemic that influenced the emotional eating developed by some individuals in situations of stress and anxiety. This leads to an increase in the consumption of foods considered palatable and often chosen in an attempt to seek comfort, which are also known as potential triggers for migraine attacks [22]. However, only three studies identified a positive association between these food triggers and migraine attacks, which can be explained by the low methodological quality and high risk of bias in the publications included that may have contributed to the absence of further associations.
According to Finkel AG, et al. [34], dietary changes can cause chronic implications in almost all migraine subtypes regardless of the nutrient, and the characteristics in the individual’s behavior can make it possible to make choices, conscious or not, that reduce or provoke the ability of migraine triggers. Work by Di Stefano V, et al. [18] showed increased consumption of carbohydrate-rich foods and sweets in all groups of migraine patients during social distancing but also a positive correlation between increased consumption of dairy or fruit in the general group and subgroup of patients who reported a stable headache. According to the authors, the lockdown may have contributed to a lower sensitivity of migraine patients in relation to food triggers, making it difficult for migraines to worsen.
Among the food triggers, caffeinated beverages, including coffee, were the most studied in this review. Alcoholic and sugar-rich drinks were also evaluated as triggers. In most of the included articles that evaluated caffeinated beverages as migraine triggers [6,16,22], coffee consumption was not associated with pain duration, intensity, impact, or frequency of migraine attacks. However, the study by Toghaet M, et al. [21] showed a positive association between migraine attacks and consumption of caffeinated beverages. Headaches caused by vasodilation have symptom relief with caffeine, which has the property of constricting blood vessels [35]. According to Zhang, caffeine may exhibit antinociceptive actions by blocking adenosine receptors, inhibiting the synthesis of the cyclooxygenase-2 enzyme or by changing the emotional state [36].
Given the complexity of triggers for migraine attacks, including food, complementary non-pharmacological strategies or treatment alternatives aim to improve migraine control and, consequently, functional capacity with minimized adverse effects, compared to prophylactic pharmacological treatment [37]. In this context, moderate-intensity aerobic exercise is also suggested for pain modulation in prophylactic treatment, with a possible short- and long-term analgesic effect at the central and peripheral levels [37,38].
In a study by Di Stefano V, et al. [18], a significant decrease in physical activity levels during COVID-19 quarantine was observed in the entire study sample, due to the isolation imposed by the pandemic. During the period of social distancing, 28% of patients reported worsening headache, 33% reported improvement, and 39% reported a stable headache frequency. The study by Cola et al. reported that the negative impact of the pandemic on migraines implied a change in the daily routine of individuals, causing physical inactivity and irregularity of meals [17].
As for the study of Togha M, et al. [21], the reduction in physical activity was significantly more reported by individuals who had increased migraine attacks during the pandemic, and decreased hours of sleep, consumption of caffeinated beverages, and regularity of meals were also reported. Regarding the latter, prolonged fasting is one of the most cited triggers of migraines [5,39,40]. Therefore, 40% of the studies in this current review evaluated the association between migraines and meal regularity, obtaining findings of a positive association [16,17,21].
In a cross-sectional study, Curró CT, et al. [16] found that individuals who reduced the regularity of meals during social isolation had a longer duration of migraines. It is known that eating at regular times, avoiding fasting, and maintaining adequate food in quantity and quality is important to avoid migraines [41-43]. This may be related to hypoglycemia, which causes the brain to not function properly, as the organ is dependent on glucose for energy and to fulfill its functions. Unfavorable conditions increase blood flow to obtain more glucose, leading to vasodilation, which can cause headaches [39,40,43].
A higher frequency of migraine days is associated with irregular meals [17,21]. According to Cola et al., those patients who modified their eating habits during social isolation, avoiding fasting and binge eating, were in the group that had improved migraine attacks compared to the others [17]. It is already established that the modification of eating habits and behaviors, aimed at improving migraine attacks, can have a significant effect on both the reduction of days and the severity of pain, thus promoting a better quality of life for these patients [40,42], since triggering factors of the disease are associated with metabolic disorders and oxidative stress [43].
Although the investigation of this relationship was present in a small portion of the analyzed studies (30%), with an association absent in all, alcohol consumption is reported as one of the 10 biggest triggers for migraines [44], and the period of the pandemic seems to have increased its consumption, mainly related to anxiety [10,45,46]. Recent literature reviews on food triggers for migraines point to alcohol consumption as a common triggering factor for increased frequency of attacks [42,47,48]. Alcoholic beverages, especially red wine, are described as triggers for the onset of migraine attacks [49-52]. According to the scientific literature, the relationship involves the action of biogenic amines, sulfites, and phenolic flavonoids present in such beverages, their vasodilating effects, and mechanisms linked to 5-hydroxytryptamine [49,51]. In a review, Martins et al. observed that alcohol-induced headache can be immediate or delayed, and the doses needed to trigger the attacks are variable [53].
In this review, only three articles performed the analysis between migraines and smoking, with two studies reporting that smoking had no association with migraine [6,17], in disagreement with Curró CT, et al. [16], who showed a positive association with an increase in days of migraine attacks, corroborating other findings in the literature [54-57]. There are some factors that can trigger migraines in smokers and worsen the pattern of pain compared to non-smokers, such as high levels of carboxyhemoglobin in smokers. In addition, nicotine can accelerate the metabolism of some drugs, such as caffeine, propranolol, and imipramine, as well as influence the neuroendocrine increase and serotonin turnover. However, it is worth mentioning that nicotine withdrawal can also lead the individual to have headaches [54-56].
Although a migraine is a primary headache and the mechanisms of relationship between headaches and water intake are multifactorial and variable and its pathophysiology is not completely understood [7], a correlation has already been found between increased water intake and improvement in migraine severity, pain intensity, frequency, and duration of attacks. Some hypotheses are suggested, including the fact that some triggers for migraine, such as alcohol intake, sleep disturbances, and stress, are possibly affected by water balance. In addition to increasing water consumption, it reduces osmolarity and balances electrolyte concentration [58]. It is also speculated that water scarcity can cause dural venous stretching and hypertonicity, leading to traction on vascular structures and pain-sensitive meninges, and that the pain threshold in dehydrated people is lower [7]. However, in the two studies evaluated by the present review, it was not possible to identify the level of dehydration or hypohydration of the individuals, considering that the range to consider low water intake was large (between 0 and 1.5 L) and did not address other signs and symptoms of dehydration.
In summary, sleep disorders and eating habits were the main evaluated factors for the worsening of migraine attacks. Therefore, better identifying these migraine triggers, as well as others (alcohol consumption, dehydration, fasting, physical exercise) from detailed and up-to-date notes of these triggers, can help to avoid or modify them to some extent [59]. However, to assess migraines, Granato A, et al. [6], Curró CT, et al. [16] and Suzuki K, et al. [20] were the only studies that used validated instruments that are useful to measure the disability impact that migraine has on quality of life, such as the Headache Impact Test (HIT-6) and the Migraine Disability Assessment Scale (MIDAS) [60-62].
Regarding the non-association between migraine and factors such as alcoholism, smoking and water consumption, observed in some studies included in the present review, but with an association present in other studies in the scientific literature, this can be explained by the small number of studies that analyzed such correlations. In addition, it should be noted that the studies had gaps in methodological quality and a high risk of bias in terms of information, selection, and representativeness of the sample. It is also known that cross-sectional studies are limiting for identifying causal relationships and have not ensured that confounding factors are equally distributed between groups. In addition, some studies have associated a reduction in the duration of pain in the period of confinement, less contact with stressors, and the possibility of resting at the time of the migraine attack, due to being at home. Therefore, these are limitations to the evidence produced by the current review.
Other studies with greater methodological rigor that investigate triggers related to lifestyle and migraines, especially during and after the COVID-19 pandemic, investigating the repercussions generated by the quarantine period, should be encouraged so that more effective measures are formulated for the treatment of migraines. However, the importance of the findings of this review is highlighted because it is unprecedented and has fulfilled all the steps described in the methodology to avoid bias. Selection, data extraction, and quality and bias assessment were performed independently by the researchers.
