What do we actually know about air pressure and the body?
Aneroid is built on a claim worth testing: that some people react to air pressure, that it varies from person to person, and that none of us are very good at working it out just by thinking about it. Here's what the research has actually measured — and where it stops knowing anything.
Every article has its sources at the bottom. They're real, and you can read them.
Pressure and headaches
What the research has actually measured — and how big it is.
979 studies, 14 left
A systematic review went through everything written about air pressure and migraine since 1973. The conclusion is more interesting than a yes or a no.
336,951 hours of headache
4,375 Japanese people logged their headaches hour by hour for a whole year. What the machine found in the data wasn't what people believed.
What happened six hours ago
The strongest single factor in one of the largest datasets wasn't the pressure right now. It was the drop six hours earlier.
Some people react to the opposite
The literature says falling pressure. But within the same studies sit patients who feel worse when pressure rises. They disappear into the average.
How big is the effect, really?
Odds ratio 0.962. That doesn't sound like much — and that's the point. Here's what the number means once you translate it into a day of your life.
What the weather doesn't do to you
Three studies have looked at whether air pressure prolongs an attack. All three found nothing. That's a result, not a shortfall.
The headache no one doubts
There is one pressure-triggered headache with its own diagnostic code. It strikes during landing, sits behind one eye, and is gone again within half an hour.
Nine out of ten were women
In the largest Japanese dataset, 89% of users were women. That's not a bias in the app. It's a bias in the disease.
The body
Where in the body is there even a pressure gauge?
You have a barometer in your head
The inner ear doesn't just measure which way is up. New experiments suggest it also registers what air pressure is doing.
The rats that felt the low pressure
You can't ask a rat to rate its pain on a scale. You can lower the pressure around it — and that's been done since 1999.
When the weather was changed indoors
Healthy volunteers in a pressure chamber, without knowing what was happening. Some of them felt something in their face.
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.
Four cavities that can't keep up
The sinuses are air locked inside bone. When outside pressure changes faster than they can equalise, you feel it.
When meteorology becomes cardiology
Blood clots have been counted against the barometer since the 1990s. The findings are small, but they keep turning up.
Weather and pain
Joints, muscles, arthritis — and the studies that contradict each other.
13,000 Britons and their pain
The largest study of weather and pain ever done was run through phones. It found a link — and was honest about how small it was.
Osteoarthritis: four studies, four answers
One found that rising pressure hurt. One found nothing. A third found the opposite. The fourth found a link and dismissed it as irrelevant itself.
The hands that were tracked for years
A French cohort has measured finger joints against weather data. Osteoarthritis in the hand is one of the most sensitive places to look.
Fibromyalgia: the link that only exists in the individual
A Dutch study found an effect of air pressure — but only individually, and only together with stress levels.
The variable that beat air pressure
In the largest dataset, the barometer didn't win. Humidity did. Here's why that doesn't actually change anything.
Why two good studies can give opposite answers
It's not sloppiness. It's what happens when you stack people with opposite reactions on top of each other and pull out an average.
Are more babies born in low pressure?
Midwives have said it for generations. There are actually studies. They're both better and worse than you think.
The feeling
Why you cannot trust your own memory of the weather.
The 18 patients who were wrong
Seventeen of eighteen were certain the weather controlled their arthritis. Fifteen months of measurements said otherwise. The study is from 1996 and is still uncomfortable.
The brain finds patterns in pure randomness
97 students were given two number sequences with no connection between them and asked to find one. They did.
Your triggers are a guess
48% believed stress triggered their headaches. 23% actually had elevated stress. And almost no one suspected the thing half of them were actually exposed to.
How were you feeling last Tuesday?
You can't answer correctly. It's not your fault — it's a well-documented flaw in human pain memory, and it has a name.
Why the app asks when nothing is happening
Three times a day, Aneroid asks without a trigger. It's the most boring feature in the app, and the only one that makes the rest trustworthy.
The trial with one participant
There's a type of trial where the subject and the entire population are the same person. Some consider it the strongest evidence there is — for you specifically.
The forecast as a painkiller — in reverse
The belief that weather hurts has itself been measured as a factor in how much it hurts. That's not imagination. It's worse than that.
"There is no link for you"
That's the answer no forecasting service can ever give you. And for many people, it's the most valuable one.
The instrument
The can from 1844, the sensor in your pocket, and what it can measure.
The can that did away with mercury
In 1844, a Frenchman patented an empty metal can with 33 springs. This app is named after it.
The man who weighed the air
Before anyone could measure air pressure, someone first had to prove that air weighs something. That took a glass tube, some mercury, and an argument over whether a vacuum can exist.
What is a hectopascal?
1013.25. The number appears on every weather chart in the world. Here's where it comes from, and why your grandfather's barometer showed something completely different.
The sensor you didn't know you had
There's a barometer in your iPhone. It was put there to count stairs — and meteorologists have written papers on what else it can be used for.
The number is unreliable. The change isn't
Two phones side by side rarely show the same pressure. Yet they show exactly the same drop. The whole app rests on that difference.
One hectopascal is four steps on a staircase
Walk up to the second floor, and the pressure drops as much as a weather change can. That's why the app can't do without knowing how high up you are.
Millions of barometers in free fall through the city
Meteorologists have fed pressure readings from ordinary phones into real weather models. The forecasts got better.
The forecast doesn't measure where you are
The weather station is at the airport. Your body is in a basement twelve kilometres away. The difference is bigger than you think.
The weather above you
Fronts, low pressure, and the hours it takes.
Meteorology also measures over three hours
Aneroid looks at the pressure change over three hours. That figure isn't made up — it's the world standard, and has been long before apps.
The anatomy of a weather change
Pressure falls, bottoms out, and rises again. That's a front passing over you — and it's the pattern the app looks for.
When the North Sea sends a low
Denmark sits where the Atlantic's low-pressure systems land. That's bad news for dry weather and good news for an experiment that needs pressure swings.
STORMY, RAIN, CHANGE, FAIR, VERY DRY
The words on a barometer dial are old, imprecise, and charmingly wrong. They're still there, on Aneroid's dial too. Here's why.
Why the app doesn't need to measure constantly
Air pressure changes over hours. That single fact is what makes the whole project technically possible — and the battery lasts the day.
Almost half a population
Germans have been asked since the 1950s. 46% say weather affects their health. Headaches are by far the most common complaint.
How many Danes have migraine?
Some of the world's most thorough headache studies were done in Copenhagen. The numbers are bigger than most people walk around believing.
Health apps lose people in four days
A Stanford study kept its participants for an average of 4.1 days. That's the real reason Aneroid only asks for one tap.
None of the articles here claim the app can help you
Aneroid is not medical equipment, doesn't predict attacks, and treats nothing. The connection between air pressure and symptoms is described in the literature, but it's disputed and far from universal — and that's a point of the product, not a caveat. Maybe the app finds no connection for you. That's also an answer.