Stage 1 of the Campaign recognised that the scope and scale of a problem must be clearly known before its remedy could be envisaged.
When, early on, all existing data on the burden of headache were collated, Western Europe and North America were far better represented than elsewhere, and migraine far better than other headache disorders [
6]. What was then known of headache covered less than half the world’s population, among whom only half of the burden attributable to headache was estimated with any reliability.
Filling these large knowledge gaps was the first priority (Table
1), requiring a series of new population-based burden-of-headache studies. Most of these would be in low- and middle-income countries, and promised to be methodologically and financially challenging. Therefore, LTB brought together an international expert consensus group to establish standardised methodology and questionnaire [
28‐
32]. Adult studies using these have now been conducted in all world regions: African (Ethiopia [
33,
34] and Zambia [
35,
36], Benin, Cameroon and Mali [not yet published], and Malawi in a HIV-positive population [
37]); American (Brazil [
38] and Peru [not yet published]); Eastern Mediterranean (Pakistan [
39‐
41], Saudi Arabia [
42,
43] and Morocco [not yet published]); European (Georgia [
44‐
47], Lithuania [
48], Russia [
49‐
52] and, within the Eurolight project, eight countries of western Europe [
53‐
59]); South East Asia (India south [Karnataka State] [
60‐
64], Nepal [
65‐
74] and India north [Delhi and National Capital Territory Region] [not yet published]); Western Pacific (China [
75‐
81] and Mongolia [
82,
83]). Schools-based child and adolescent studies began later, again with development and testing of new methodology [
84,
85]. Studies have completed data collection in Austria [
86], Ethiopia [
87], Lithuania [
88,
89] and Turkey [
90], and in Benin, Iran, Mongolia, Serbia and Zambia [not yet published]. Others have commenced or are planned in Brazil, Cambodia, Cameroon, Estonia, Georgia, Nepal and Spain, but are interrupted by the SARS-CoV-2 pandemic.
These studies inform local policy as well as global knowledge. To the extent that they have been conducted in low- and middle-income countries, they have enhanced research capacity in these countries [
21] as a collateral benefit. Among other such benefits are a broader understanding of the full spectrum of headache-attributed burden, which goes far beyond symptom burden and disability [
10‐
12,
14,
22,
29,
30,
32,
51,
54,
58,
84,
85,
90‐
94].
Two databases under construction at NTNU are capturing the individual-participant data (ie, primary data) from all LTB population-based studies, with sub-datasets describing sampling and other methodology as attributes of the main datasets. Ultimately, following development and imposition of quality controls, these will be available as free goods for academic purposes, as are all Global Campaign products.