Infodemiology of cluster headache seasonality: A proof of concept by a Google Trends analysis.

BACKGROUND: Cluster headache is commonly reported to follow an annual pattern with a peak in the spring and a second peak in autumn. Patients with headache frequently use search engines, such as Google, to look for terms related to their disease, creating trend data that can be analyzed with Google Trends. Indeed, Google Trends has been used for surveillance studies and can provide indirect estimates of the burden of diseases and symptoms. The present cross-sectional study investigated the seasonality of searches for "cluster headache" in the northern and southern hemispheres using 10 years of Google Trends data. METHODS: The term "cluster headache" or its translation in the 10 most spoken languages in the world was searched on Google Trends to obtain relative search volumes (from 0 to 100), in order to compare variations in searches across periods. Twenty-eight countries were selected according to the following criteria: (1) a relative search volume of >40 for the term for cluster headache; and (2) a population of at least 5 million inhabitants. For statistical purposes, countries were grouped in relation to hemisphere (northern or southern). Relative search volumes were extracted from January 2012 to January 2022 and analyzed according to two subgroups based on meteorological seasons (summer and winter vs. spring and autumn). RESULTS: A seasonal trend for in searches for cluster headache was found worldwide exhibiting higher relative search volumes in spring and autumn compared with summer and winter (17 [0, 39] vs. 13 [0, 37]; p = 0.016). CONCLUSION: Higher search volumes for the term during the meteorological seasons of spring and autumn clearly reflect a circannual pattern of cluster headache occurrence, representing new evidence for its seasonality.

Headache Worsening after COVID-19 Vaccination: An Online Questionnaire-Based Study on 841 Patients with Migraine.

Vaccines have represented the breakthrough in the fight against COVID-19. Based on reported headache attacks after vaccination in randomized controlled trials, we focused on the effects of COVID-19 vaccine administration on the migraine population, using an online questionnaire published on Italian Facebook groups oriented to headache patients. We collected data about the demographics and clinical parameters of migraine severity, COVID-19 infection, vaccination, and characteristics of headaches following vaccination. Out of 841 migraine patients filling in the questionnaire, 66.47% and 60.15% patients experienced a headache attack (from 1 hour to 7 days) after the first and the second vaccine dose, respectively. The main finding concerns headaches perceived by 57.60% of patients: attacks following vaccination were referred to as more severe (50.62% of patients), long-lasting (52.80% of patients) and hardwearing (49.69% of patients) compared to the usually experienced migraine attacks. This could be related to the production of inflammatory mediators such as type Iß interferon. Considering the high prevalence of migraine in the general population, awareness of the possibility of headaches worsening following COVID-19 vaccination in these patients may allow both patients and clinicians to face this clinical entity with conscious serenity, and to reduce the waste of resources towards inappropriate health-care.