The emigration of early humans from Africa to colder parts of Europe saw them develop a gene that made them more susceptible to migraines, researchers in the German city of Leipzig have discovered.
Around a billion people worldwide are estimated to suffer from migraine attacks. In Germany, some 1 million people are affected every day, while in the US roughly 13 percent of adults say they regularly suffer from severe headaches.
According to the World Health Organization (WHO), migraine attacks are the sixth-most debilitating disease in the world. As well as severe throbbing pain that can last for days on end, sufferers will often also experiences visual disturbances, nausea, dizziness and light sensitivity.
Read more: Headaches - What causes the throbbing pain?
However, look to Africa and Asia, and the number of sufferers is notably lower, according to the WHO.
Migraines have long been viewed as a hereditary disease, passed on by parents to their children. However, genetic researchers from the Max Planck Institute for Evolutionary Anthropology in the German city of Leipzig suggest the link may reach far further back.
Climate and migraines
A newly-released study led by Felix-Michael Key, a researcher in evolutionary genetics at the Max Plank Institute, found that a genetic mutation with a known link to migraines is significantly more prevalent among people in Europe or of European descent.
"We wanted to analyze human adaptation to different environmental factors and wanted to focus on the effect of temperature," Key told DW. By studying genetic patterns of the TRPM8 gene, a receptor through which humans sense cold temperatures and the cooling effects of menthol, Key and his team found that certain mutations were far more prevalent across various regions and geographical latitudes.
Using genome data to look back through tens of thousands of years of genetic evolution, the study found that the farther north towards colder climates one looks, the more prevalent the genetic mutation linked to migraines becomes. For example, according to Key's findings, only around 5 percent of people with Nigerian ancestors have the gene variant, while 88 percent of people with Finnish ancestors have it.
"Usually you observe something in some frequency in a population somewhere and you expect that those frequencies should be largely the same across all populations," Key said. "But here you have a near 80 percent frequency shift — that is something very unusual."
This suggests, therefore, that as early humans traveled north from Africa, they adjusted to colder temperatures but in doing so also made themselves more susceptible to migraines.
"The colonization could have been accompanied by genetic adaptations that helped early humans cope with lower temperatures," said geneticist Aida Andres of University College London, who supervised the study.
Read more: Can the weather make us ill?
Why do migraines and the chills share the same gene?
However, the findings don't cast light on why susceptibility to migraines and cold temperatures are genetically linked. That still remains a mystery, according to Key.
"We can speculate, however, that there is a functional overlap in the receptor that can mediate migraines along with the perception of pain and cold," he said. "So the cooling of the menthol receptor causes effects that go in a similar direction even though they are not directly related to one another."
Of course, next to climate, there are several other migraine symptoms to consider, both genetic and environmental. But researchers will welcome a deeper understanding into genetic development of migraines, above all when it comes to developing new drugs and medicines.