The Environment and Headache: a Narrative Review

PURPOSE OF REVIEW

In this narrative review, we summarize the peer-reviewed literature published between 2017 and 2022 that evaluated ambient environmental risk factors for primary headache disorders, which affect more than half of the population globally. Primary headache disorders include migraine, tension-type headache (TTH), and trigeminal and autonomic cephalalgias (TAC).

RECENT FINDINGS

We identified 17 articles that met the inclusion criteria via PubMed or Google Scholar. Seven studies (41%) relied on data from US populations. The remaining studies were conducted in China, Taiwan, Germany, Ghana, Japan, the Netherlands, South Korea, and Turkey. Air pollution was the most frequently assessed environmental risk factor. Most studies were cross-sectional and focused on all-cause or migraine headaches; one study included TTH, and none included TAC. Short-term exposure to fine particulate matter (PM2.5) was not consistently associated with headache endpoints, but long-term exposure to PM2.5 was associated with migraine headache prevalence and severity across multiple studies. Elevated ambient temperature, changes in weather, oil and gas well exposure, and less natural greenspace, but not noise pollution, were also associated with headache. No studies considered water pollution, metal exposure, ultrafine particulate matter, or wildfire smoke exposure. There is a need for ongoing research focused on headache and the environment. Study designs with the greatest explanatory power may include longitudinal studies that capture the episodic nature of headache and case-crossover analysis, which control for time-invariant individual-level confounders by design. There is also a clear need for research that considers comorbid psychiatric illness and socioeconomic position as powerful modifiers of the effect of the environment on headache.

Migraine Attacks Triggered by Ingestion of Watermelon

INTRODUCTION

Ingesting some foods can trigger headache attacks in migraine patients. Diet-sourced citrulline activates the l-arginine-nitric oxide pathway, acting on the pathophysiology of migraine.

METHODS

The study was a clinical trial, interventional, controlled, and with group comparison. The sample was non-random, composed of 38 volunteers with migraine and 38 without headache (control). Both groups ingested a portion of watermelon to determine the onset of headache attacks. Before and after ingesting watermelon, they underwent blood collections to determine serum nitrite levels.

RESULTS

There were 38 volunteers diagnosed with migraine without aura and 38 controls, whose mean age was, respectively, 22.4 ± 1.5 and 22.9 ± 3.1 years (p = 0.791). Headache was triggered by watermelon ingestion after 124.3 ± 20.5 min of ingestion in 23.7% (9/38) of the migraine volunteers and in none of the controls (p = 0.002). There was an increase in serum nitrite levels, both in migraine volunteers (23.4%) and in the control group (24.3%), after watermelon ingestion. This difference was significant (p < 0.001).

DISCUSSION

Watermelon ingestion triggered headache attacks in migraine patients and increased serum nitrite levels, attesting to a possible activation of the l-arginine-nitric oxide pathway.

Classification of odors associated with migraine attacks: a cross-sectional study

Migraine, a common primary headache disorder, is associated with various factors such as stress, hormones in women, fasting, weather, and sleep disturbance as well as odors. We aimed to categorize odors associated with migraine and explore their relationships with clinical characteristics. A total of 101 migraineurs answered a questionnaire to determine the odors associated with migraine attacks. We performed factor analysis to explore the common factors of the odors and the relationship between these factors and the clinical characteristics. The factor analysis estimated six common factors: factor 1, fetid odor; factor 2, cooking products; factor 3, oil derivatives and others; factor 4, shampoo and conditioner; factor 5, cleaning products; factor 6, perfumes, insecticides, and rose. Factor 5 also included hair styling preparations, laundry detergent, and fabric softener, usually those with floral fragrances, and factor 5 was more likely to be associated with migraine attacks in patients with chronic migraine than in those with episodic migraine (P = 0.037). Our study showed that odors associated with migraine attacks could be categorized into six groups and suggested that some chemicals were more likely associated with migraine attacks in patients with chronic migraine than in those with episodic migraine.

Migraine with aura: less control over pain and fragrances?

BACKGROUND

Accumulating data emphasizes the importance of olfaction in migraine pathophysiology. However, there are only a few studies evaluating how the migraine brain processes olfactory stimulation, and virtually no studies comparing patients with and without aura in this context.

METHODS

This cross-sectional study recorded event-related potentials from 64 electrodes during a pure olfactory or pure trigeminal stimulus in females with episodic migraine with aura (n = 13) and without aura (n = 15), to characterize the central nervous processing of these intranasal stimuli. Patients were tested in interictal state only. Data were analyzed in the time domain and in the time-frequency domain. Source reconstruction analysis was also performed.

RESULTS

Patients with aura had higher event-related potentials amplitudes for left-sided trigeminal and left-sided olfactory stimulations, and higher neural activity for right-sided trigeminal stimulation in brain areas related to trigeminal and visual processing. Following olfactory stimulations patients with aura displayed decreased neural activity in secondary olfactory structures compared to patients without aura. Oscillations in the low frequency bands (< 8 Hz) differed between patient groups.

CONCLUSIONS

Altogether this may reflect hypersensitivity to nociceptive stimuli in patients with aura relative to patients without aura. Patients with aura have a bigger deficit in engaging secondary olfactory-related structures, possibly leading to distorted attention and judgements towards odors. The cerebral overlap between trigeminal nociception and olfaction might explain these deficits.

Pathophysiology and Therapy of Associated Features of Migraine

Migraine is a complex and debilitating disorder that is broadly recognised by its characteristic headache. However, given the wide array of clinical presentations in migraineurs, the headache might not represent the main troublesome symptom and it can even go unnoticed. Understanding migraines exclusively as a pain process is simplistic and certainly hinders management. We describe the mechanisms behind some of the most disabling associated symptoms of migraine, including the relationship between the central and peripheral processes that take part in nausea, osmophobia, phonophobia, vertigo and allodynia. The rationale for the efficacy of the current therapeutic arsenal is also depicted in this article. The associated symptoms to migraine, apart from the painful component, are frequent, under-recognised and can be more deleterious than the headache itself. The clinical anamnesis of a headache patient should enquire about the associated symptoms, and treatment should be considered and individualised. Acknowledging the associated symptoms as a fundamental part of migraine has permitted a deeper and more coherent comprehension of the pathophysiology of migraine.

Interictal osmophobia is associated with longer migraine disease duration

Background

Sensitization to sensory stimuli is an essential feature of migraine attacks. The relationship between the clinical course of migraine and increased sensitivity to olfactory stimuli has been little studied so far.

Methods

We analyzed the frequency and quality of osmophobia depending on the phase of migraine in patients with episodic and chronic migraine treated in an tertiary headache center with regard to gender, age, medical history and migraine disability assessment score (MIDAS). Standardized diagnostic questions were used for the assessment of osmophobia.

Results

In our cross-sectional investigation (n = 113), 38.1% of the patients showed an increased preictal hypersensitivity to odors, whereas 61.9% described ictal and 31.9% interictal hypersensitivity to odors, odor-triggered migraine was described in 30.1%. Median migraine disease duration has been statistically significantly longer in patients who suffered from interictal hypersensitivity to odors (28.5 years vs. 20 years; p = 0.012). There was a significant correlation between interictal hypersensitivity and higher age (54.50 vs. 45; p = 0.015). Patients with higher migraine disability in MIDAS experienced more frequently preictal and interictal olfactory sensitization and odor triggered migraine attacks.

Conclusions

In patients with longer migraine disease duration and higher migraine-related impairment, osmophobia was more frequently observed. These results might support the hypothesis of increasing sensitization with increasing burden of migraine.

Cranial autonomic symptoms in migraine are related to central sensitization: a prospective study of 164 migraine patients at a tertiary headache center

Background

Cranial autonomic symptoms (CASs) during migraine attacks are reported to be quite common regardless of ethnicity. In our previous study investigating 373 migraineurs, we found that 42.4% of them had CASs. The patients with CASs more frequently had cutaneous allodynia than did those without CASs, and we speculated that CASs were associated with central sensitization. The present study searched for substantial evidence on the relationship between CASs and central sensitization in migraine patients.

Methods

This was a prospective cross-sectional study. We studied a new independent cohort of 164 migraineurs who presented to the Tominaga Hospital Headache Center from July 2018 until December 2019. The clinical features of CASs according to the criteria in ICHD-3 (beta) were investigated. We also evaluated central sensitization based on the 25 health-related symptoms utilizing the validated central sensitization inventory (CSI), and each symptom was rated from 0 to 4 resulting a total score of 0–100.

Results

The mean age was 41.8 (range: 20 to 77) years old. One hundred and thirty-one patients (78.9%) were women. Eighty-six of the 164 (52.4%) patients had at least 1 cranial autonomic symptom. The CSI score of the patients with ≥3 CASs reflected a moderate severity and was significantly higher than in those without CASs (41.9 vs. 30.7, p = 0.0005). The score of the patients with ≥1 conspicuous CAS also reflected a moderate severity and was significantly higher than in those without CASs (40.7 vs. 33.2, p = 0.013). The patients in the CSI ≥40 group had lacrimation, aural fullness, nasal blockage, and rhinorrhea, which are cranial autonomic parasympathetic symptoms, significantly more frequently than those in the CSI < 40 group.

Conclusions

Migraine patients with CASs showed significantly greater central sensitization than those without such symptoms. In particular, cranial parasympathetic symptoms were more frequent in centrally sensitized patients than in nonsensitized patients, suggesting that cranial parasympathetic activation may contribute to the maintenance of central sensitization.

Trial registration

This study was retrospectively registered with UMIN-CTR on 29 Aug 2020 (UMIN000041603).

Olfactory acuity based on Brief Smell Identification Test (BSITⓇ) in migraine patients with and without aura: A cross-sectional, controlled study

OBJECTIVE

The aim of this study was to evaluate olfactory acuity in migraine patients with and without aura (MwA and MwoA) MATERIAL AND METHODS: The study included 30 MwA patients, 30 MwoA patients, and 30 age- and gender-matched controls. Demographic features and odor-related symptoms (osmophobia, odor offensiveness, and odor-triggered attack status) were noted. Olfactory acuity was measured using the Brief Smell Identification Test (BSIT®), a 12-item derivative of the University of Pennsylvania Smell Identification Test (UPSIT®). BSIT® scores were compared between the migraine patients and controls.

RESULTS

The mean BSIT® score did not differ significantly between the MwA patients (8.7 ± 0.9) and MwoA (9.17 ± 0.9) patients (P = 0.094); however, the mean score in the control group was higher (10.4 ± 0.6) than in the MwA and MwoA patients (P < 0.001). The mean BSIT® score did not differ significantly between patients with and without odor-triggered migraine attacks (9 ± 0.9 and 8.8 ± 0.8, respectively) (P = 0.4). Osmophobia and odor-triggered attacks were more common in the MwA patients than in the MwoA patients (odor-triggered attacks: 66% vs. 40% [P = 0.04]; osmophobia: 76.6% vs. 60% [P = 0.16]) CONCLUSION: Olfactory acuity is lower during attack-free periods in migraine patients, as compared to controls. Migraine aura status does not affect olfactory acuity. Odor-triggered attacks, osmophobia, and offensive odors between attacks were more common in the MwA patients than in the MwoA patients.

Approach to Headache

There is a very high prevalence of headache in both outpatient and inpatient settings, in the United States and worldwide, due to an abundance of possible causes. Having a practical and systematic approach to evaluating and treating headache is, therefore, key to making the correct diagnosis, or possibly overlapping diagnoses. Taking a thorough and methodical headache history is the mainstay for diagnosis of both primary and secondary headache disorders. Evaluation and workup should include a complete neurological examination, consideration of neuroimaging in specific limited situations, and serum or spinal fluid analysis if indicated. Adopting a diagnostic approach to headache ensures that cannot-miss, or potentially fatal, headache syndromes are not overlooked, while resource-intensive tests are performed only on an as-needed basis.

Physical inactivity and headache disorders: Cross-sectional analysis in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

BACKGROUND

Physical inactivity has been linked to headache disorders but estimates based on the current World Health Organization physical activity guidelines are unknown.

OBJECTIVE

To test the associations between headache disorders and physical inactivity in the ELSA-Brasil cohort.

METHODS

In a cross-sectional analysis, linear (continuous variables) and logistic regression models (categorical variables) tested the associations of physical activity levels in the leisure time, commuting time, and combined leisure time physical activity + commuting time physical activity domains with headache disorders, adjusted for the effects of sociodemographic data, cardiovascular risk variables, psychiatric disorders, and migraine prophylaxis medication.

RESULTS

Of 15,105 participants, 14,847 (54.4% women) provided data on physical activity levels and headache. Higher physical activity levels (continuous values) in the leisure time physical activity domain associated with lower migraine and tension-type headache occurrence and lower headache attack frequency, while in the commuting time physical activity domain it associated with more frequent headache attacks. Compared to people who met World Health Organization physical activity levels in the leisure time physical activity or combining leisure time physical activity + commuting time physical activity domains (i.e. ≥150 min.wk^-1 of moderate and/or ≥75 min.wk^-1 of vigorous physical activity), physical inactivity associated with higher migraine occurrence, while somewhat active (i.e. not meeting World Health Organization recommendations) associated with higher migraine and tension-type headache occurrence. Physical inactivity in the commuting time physical activity domain associated with higher tension-type headache in men and lower migraine in women. Physical inactivity within vigorous leisure time physical activity intensity, but not moderate leisure time physical activity, associated with higher migraine, mostly in women. Finally, physical inactivity associated with higher headache attack frequency regardless headache subtype.

CONCLUSION

Physical inactivity and unmet World Health Organization physical activity levels associate with primary headaches, with heterogeneous associations regarding headache subtype, sex, physical activity domain/intensity, and headache frequency in the ELSA-Brasil study.

Watermelon and others plant foods that trigger headache in migraine patients

Background: Food is already recognized as a trigger for migraine, but its mechanism of action has not been fully clarified. There is evidence that they act on the pathogenesis of migraine, interfering with meningeal inflammation, vasodilation and cerebral glucose metabolism.Aim: The aim of this study was to know which plant foods are triggers for migraine and the latency time for the onset of pain.Method: We interviewed patients with migraine and tension-type headache about plant foods that trigger headache and onset time of the headache. We studied 3,935 migraine patients and 1,163 with tension-type headache.Results: There were headaches triggered by plant foods after 90.5 ± 7.9 minutes of ingestion in 40.3% (1,584/3,935) of migraine patients and none with tension-type headache. Headaches triggered by plant foods intake are distributed in the following order of frequency: watermelon (29.5%), passion fruit (3.73%), orange (2.01%), pineapple (1.52%), grape (0.51%), banana (0.46%), cucumber (0.43%), acerola (0.25%) and papaya (0.25%).Conclusions: Many plant foods, especially watermelon, may trigger headache attacks in migraine patients within a few minutes.

Headache and Osmophobia in Gas Station Workers Exposed to Gasoline Odor

INTRODUCTION

Headache attacks may be triggered by several factors, among them odors, especially in migraine patients.

OBJECTIVES

The aim of this study wasto determine the association between gasoline odor and headache attacks in patients with migraine or tension-type headache (TTH).

SUBJECTS AND METHODS

The study was prospective, cross-sectional, with comparison of groups, using nonrandom sample and convenience. Fifty-two gas station workers diagnosed with migraine or TTH according to ICHD-3 criteria were interviewed on the relationship between gasoline odor and headache.

RESULTS

Of the 52 gas station workers with headaches, there were 39 (75%) with migraine without aura and 13 (25%) with TTH. The age ranged from 19 to 50 years, with a mean of 29.5 ± 7.2 years. Osmophobia during headache attacks predominated in workers with migraine (29/39; 74.4%). The onset of headache due to odor exposure occurred in 23/39 (60%) of the workers with migraine and in 2/13 (15.4%) in TTH. These differences were statistically significant (χ2 = 7.4; p = 0.016). Osmophobia in the absence of pain (period between attacks) predominated in workers with migraine (17/39, 43.6%), but with no statistical value.

CONCLUSIONS

Gas station workers diagnosed with migraine or TTH may experience osmophobia and headache triggered by the odor of gasoline.

Association Between Occupational Physicochemical Exposures and Headache/Eyestrain Symptoms Among Korean Indoor/Outdoor Construction Workers

Background

Headache/eyestrain symptoms are common health problems that people experience in daily life. Various studies have examined risk factors contributing to headache/eyestrains, and physicochemical exposure was found to be a leading risk factor in causing such symptoms. The purpose of this study was to examine the relationship of headache/eyestrain symptoms with physicochemical exposure among Korean construction workers depended on worksite.

Methods

This study used data from the 4th Korean Workers Conditions Survey and selected 1,945 Korean construction workers as participants. Multivariable logistic regression analysis was used to determine the relationship.

Results

Exposure to vibrations among all construction workers affected the moderate exposure group [odds ratio (OR) 1.53, 95% confidence interval (CI) 1.01–2.32], the high exposure group (OR 1.77 95%CI 1.17–2.67), and the indoor high exposure group (OR 1.61, 95%CI 1.02-2.55) and among outdoor construction workers, the moderate group (OR 6.61, 95%CI 15.4–28.48) and the high group (OR 6.61, 95%CI 1.56–27.98). When exposed to mist, dust, and fumes, the indoor high exposure group was significantly affected (OR 1.63, 95%CI 1.07–2.47). All construction workers exposed to organic solvents were affected, high exposure group (OR 1.69, 95%CI 1.15–2.49) and indoor high exposure group (OR 1.77, 95%CI 1.08–2.89). The high exposure group in all construction worker (OR 1.70, 95%CI 1.20–2.42) and the indoor high exposure group (OR 1.83, 95%CI 1.17–2.89) also were affected by secondhand smoking exposure.

Conclusion

Many physicochemical exposure factors affect headache/eyestrain symptoms among construction workers, especially indoor construction workers, suggesting a deficiency in occupational hygiene and health environments at indoor construction worksites.

The persistence versus interchangeability of migraine and tension-type headaches in a 5-year population-based validated survey

OBJECTIVE

The aim of this population-based validated study was to determine the course of tension-type headache and migraine and to evaluate the predictors of persistence.

METHODS

We evaluated the course of headache in a large population from the first assessment in 2008 through a second assessment in 2013. Then we examined the factors associated with persistent migraine and persistent tension-type headache.

RESULTS

Our study in 2013 revealed that only 42.9% of definite migraineurs in 2008 received the same diagnosis again, and of the remaining migraineurs 23.3% were newly diagnosed as definite tension-type headache; 11.6% evolved into probable tension-type headache, 6.4% changed to probable migraine, and 15.8% were headache free. The 17.7% of patients with definite tension-type headache in 2008 were newly diagnosed as having probable tension-type headache, 14.7% as having definite migraine, 6.4% as having probable migraine, and 28.9% as headache free in 2013, and only 32.3% received the definite tension-type headache diagnosis again. Binary logistic regression analysis showed nausea, throbbing and severe headache were the significant parameters for persistent migraine. A multiple regression analysis model with stepwise variable selection revealed that nausea, throbbing and severe headache and osmophobia remained in the final model as predictors of migraine persistence. We found no predictive factor for persistent tension-type headache.

CONCLUSION

Migraine and tension-type headache did not seem to show a simple bidirectional linear worsening from headache-free state to definite migraine or vice versa, hence the transitions between them are more chaotic, reflecting that there are still unknown modifiers and modulators. Certain headache characteristics of migraine might predict persistent migraine.

Role of intraganglionic transmission in the trigeminovascular pathway

Migraine is triggered by poor air quality and odors through unknown mechanisms. Activation of the trigeminovascular pathway by environmental irritants may occur via activation of transient receptor potential ankyrin 1 (TRPA1) receptors on nasal trigeminal neurons, but how that results in peripheral and central sensitization is unclear. The anatomy of the trigeminal ganglion suggests that noxious nasal stimuli are not being transduced to the meninges by axon reflex but likely through intraganglionic transmission. Consistent with this concept, we injected calcitonin gene-related peptide, adenosine triphosphate, or glutamate receptor antagonists or a gap junction channel blocker directly and exclusively into the trigeminal ganglion and blocked meningeal blood flow changes in response to acute nasal TRP agonists. Previously, we observed chronic sensitization of the trigeminovascular pathway after acrolein exposure, a known TRPA1 receptor agonist. To explore the mechanism of this sensitization, we utilized laser dissection microscopy to separately harvest nasal and meningeal trigeminal neuron populations in the absence or presence of acrolein exposure. mRNA levels of neurotransmitters important in migraine were then determined by reverse transcription polymerase chain reaction. TRPA1 message levels were significantly increased in meningeal cell populations following acrolein exposure compared to room air exposure. This was specific to TRPA1 message in meningeal cell populations as changes were not observed in either nasal trigeminal cell populations or dorsal root ganglion populations. Taken together, these data suggest an important role for intraganglionic transmission in acute activation of the trigeminovascular pathway. It also supports a role for upregulation of TRPA1 receptors in peripheral sensitization and a possible mechanism for chronification of migraine after environmental irritant exposure.

Olfactory bulb atrophy in migraine patients

OBJECTIVE

Osmophobia and headache triggered by odors are commonly seen in migraine, and these are symptoms that differentiate migraine from other primary headaches. Since these odor-related symptoms are disease-specific, we aimed to measure the volume of olfactory bulb and depth of olfactory sulcus in migraine patients.

PATIENTS AND METHOD

A total of 93 subjects, consisting of 62 episodic migraine (32 with osmophobia, 30 without osmophobia) patients and 31 healthy controls, were included in this study. Diagnosis and classification of migraine were performed according to the beta version criteria of International Classification of Headache Disorders (ICHD-3 Beta version). Beck depression and beck anxiety inventory were applied to the patients, and the measurement of bilateral olfactory bulb volume (OBV) and olfactory sulcus depth (OSD) was performed manually in the brain magnetic resonance imaging (MRI).

RESULTS

More significantly in the left OBV, low OBV has been determined in migraine patients compared to the control group (p < 0.001, p = 0.020). When migraine patients with or without osmophobia were compared to the control group; OBV was determined to be the lowest in migraine group with osmophobia, and left-weighted bilateral OBV was determined to be low (p < 0.001, p = 0.046). No statistically significant difference was determined between groups in OSD measurements (p = 0.646, p = 0.490).

CONCLUSION

Left-weighted bilateral OBV atrophy determined in migraine patients may be guiding for the clarification of migraine pathophysiology and enlightening of the relation between migraine and odor.

Induction of chronic migraine phenotypes in a rat model after environmental irritant exposure

Air pollution is linked to increased emergency department visits for headache and migraine patients frequently cite chemicals or odors as headache triggers, but the association between air pollutants and headache is not well understood. We previously reported that chronic environmental irritant exposure sensitizes the trigeminovascular system response to nasal administration of environmental irritants. Here, we examine whether chronic environmental irritant exposure induces migraine behavioral phenotypes. Male rats were exposed to acrolein, a transient receptor potential channel ankyrin-1 (TRPA1) agonist, or room air by inhalation for 4 days before meningeal blood flow measurements, periorbital cutaneous sensory testing, or other behavioral testing. Touch-induced c-Fos expression in trigeminal nucleus caudalis was compared in animals exposed to room air or acrolein. Spontaneous behavior and olfactory discrimination was examined in open-field testing. Acrolein inhalation exposure produced long-lasting potentiation of blood flow responses to a subsequent TRPA1 agonist and sensitized cutaneous responses to mechanical stimulation. C-Fos expression in response to touch was increased in trigeminal nucleus caudalis in animals exposed to acrolein compared with room air. Spontaneous activity in an open-field and scent preference behavior was different in acrolein-exposed compared with room air-exposed animals. Sumatriptan, an acute migraine treatment blocked acute blood flow changes in response to TRPA1 or transient receptor potential vanilloid receptor-1 agonists. Pretreatment with valproic acid, a prophylactic migraine treatment, attenuated the enhanced blood flow responses observed after acrolein inhalation exposures. Environmental irritant exposure yields an animal model of chronic migraine in which to study mechanisms for enhanced headache susceptibility after chemical exposure.