The dizziness and the barometer

Below 1013 hPa, the risk of a Ménière's attack rises. And a scan can show what the pressure drop does to the fluid in the ear.

Most of the links between weather and the body in this collection end in a cautious "maybe". Ménière's disease is an exception. Here there isn't just a statistical link — there's a picture of what air pressure actually does to an organ.

Ménière's disease causes attacks of severe dizziness, tinnitus and a feeling of pressure in the ear. The cause sits in the inner ear, in a system of fluid-filled spaces, where the amount of fluid — the endolymphatic space — appears to play a central role in when an attack occurs.

The threshold at 1013 hPa

1013 hPa is the figure every weather chart uses as normal pressure at sea level. A study that compared air pressure with Ménière's attacks found that the risk of an attack at pressure below this threshold was 1.3 times as high as at pressure above it. Lower pressure was also linked to a higher degree of dizziness, tinnitus and a feeling of pressure in the ear among those affected.

The finding doesn't stand alone. Another study, built as a repeated measures study — where the same patients are followed over time and held up against their own swings in the weather — similarly found that changes in air pressure were significantly associated with when Ménière's episodes occurred.

What you can normally only guess at, you can see here

What sets Ménière's disease apart from most of the other examples in this collection is that the link doesn't live in the statistics alone. A more recent study used imaging to measure the endolymphatic space in patients with moderate, one-sided Ménière's disease — affecting only one ear, so the healthy ear could be used as an internal reference. When air pressure fell, the researchers measured an increased volume of the endolymphatic space on the affected side.

That's a different kind of evidence than an odds ratio. It's a picture of the mechanism the numbers can otherwise only point to indirectly: less air pressure from outside, more fluid in a space that is already under pressure in a person with Ménière's disease.

Two different ways of asking the same question

It's worth noting how differently the three studies ask the question, and that they still point the same way. One counts attacks against a fixed threshold, 1013 hPa. One follows the same patients over time and holds their own fluctuations up against their own weather. One goes into the ear with imaging and measures a physical change directly. Statistics, repeated measures and anatomy end up at the same conclusion — that's rarer than you'd think, when three different methods agree.

What it doesn't mean

Being able to see a link on a scan doesn't make it a guarantee for any one individual. Not everyone with Ménière's disease reacts the same way to air pressure, and an attack usually has several contributing causes. The three studies here were done on different patient groups, with different methods, and none of them make it possible to predict a specific attack in a specific person on a specific day.