Headache Epidemiology

Headache epidemiology describes the who, where and how often of headaches.

If whole populations are studied, it is clear that virtually everybody in the world will experience a headache at some point of time. One English survey estimated that about 70% of the population would have at least one headache every three months. In women aged 18-35 this figure is almost 93%!

The most widely quoted surveys of headache come from Denmark, and I've created a chart to show that over 90% of men and over 95% of women will report some form of headache at some time in their lives.

The Point Prevalence chart answers the question "In the last year have you experienced a headache?"

You can see that headaches are extremely common, and that in Denmark, as in most countries, tension-type headache is the most frequent headache type.

Headache Epidemiology can be used in the emergency setting as it tells you the probability of certain diagnoses.

If you consider thunderclap headache, we know that this occurs about 40 times each year out of a population of 100,000 persons.

The 2 most common causes of thunderclap headache are primary thunderclap headache - which can be brought on by exertion i.e. a form of Exercise Induced Headache - or could also be due to a serious disorder like Subarachnoid Haemorrhage.

One estimate of the frequency of all exercise induced headaches is that it can happen to about 35% of people at some point in their lives 35,000 per 100,000.

If you assume an average life span of 70 years, then this is about 500 per 100,000 per annum.

If about one quarter of exercise headaches are thunderclap type, then this gives you an estimated annual incidence of exercise induced thunderclap headache of 125 per 100,000 per year.

It is known that subarachnoid haemorrhage occurs in about 10 people per 100,000 each year.

This means that epidemiology is telling you that for every 1 subarachnoid haemorrhages you get 12.5 primary, exercise induced thunderclap headaches.

Guess what?? Studies of thunderclap headache presenting to emergency departments will show that the risk of subarachnoid haemorrhage is also about 10%.

So all this number crunching is not in vain - it can help you make diagnoses at the front door of the hospital - you can use the statistics to inform you that for each thunderclap headache you see there is an approximately 10% chance that there is a serious cause like intracranial bleeding.

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