Why a Low Barometer Causes Aches and Pains
Some people say they can forecast an approaching storm by the aches and pains in their body. Some will say it is going to rain because their trick knee is hurting and others can forecast the weather because they are a human barometer. A low barometer can cause some people to have more aches and pains.
The Barometer and Air Pressure
Air pressure is the force exerted on us by the weight of the air. The air is made up of molecules and these molecules have weight to them. It is the weight of these air molecules that puts pressure on us and that is air pressure. The US National Weather Service defines air pressure as the amount of pressure exerted on a surface by the weight of the air. There is 14.7 pounds of air pressure per square inch pressing on your body or one ton (1,000 kg) of air molecules pressing down on the square foot cross section of your body. We are not crushed because we have air inside of us that equalizes this pressure .
Air pressure is measured by a barometer and gives us the barometric reading. The air pressure is measured in inches or millibars, inches is what we normally hear on the weather reports. A normal air pressure is 29.92 inches or 1013.25 millibars.
The lower the barometer reading, the lower the air pressure is. Low pressure means fewer molecules, less weight to the air and the air is less dense. The higher in elevation you are, the less dense the air is and the lower the pressure. When you notice your ears pop when in an airplane or driving through the mountains, this is the way our body equalizes the pressure outside of us with the air pressure inside of us.
Those who have been in the eye of a hurricane or when a tornado passes over them, notice that their ears pop. The center of both hurricanes and tornadoes are very low pressure areas with a rapid pressure change.
Low Barometer Readings and Aches and Pains
There have not been many scientific studies as to why some people with arthritis, osteoarthritis or fibromyalgia feel more pain when the barometer is low. One fact that confuses this is that some people say they can tell when a storm is coming while others say they have more aches and pains once the storm is already there.
Before a storm arrives, the barometer or the air pressure will fall. After the cold front or low pressure passes is when the rainy, chilly and damp weather starts.
In many places, once the cold front or low pressure passes and the damp and chilly weather occurs, the barometer will usually start to rise to a normal air pressure reading or higher. In other places, for example the eastern United States, it can be chilly and wet with a continued low pressure reading.
It is well known that damp, chilly and humid weather can cause more aches and pains. So it seems there are two causes for aches and pains that are aggravated by the weather. It is documented that many with arthritis will ache more when it is damp and cold but not very well documented that a falling barometer causes more aches and pains.
This is the area of scientific interest, when some people notice their aches and pains before the storm arrives, when the barometer shows the air pressure is falling.
Why A Low Barometer Cause Aches and Pains
As the air pressure drops, the air molecules and gasses in the atmosphere expand. This can be shown when an inflated balloon is put into a vacuum and the air pressure is lowered, the balloon will expand.
The same thing happens in our body when the barometric pressure falls, gases and fluids surrounding our joints expand, which causes pressure against nerves and this is what might cause the aches and pain when the barometer is falling.
Not only do people with arthritis or fibromyalgia feel the falling air pressure, but also those with old injuries. An old knee or shoulder injury can cause scar tissue, when the air pressure falls; it is the injured area that aches.
Low barometric pressure can also cause headaches and migraines in some people. The changing air pressure can cause the capillaries to expand or contract causing headaches.
Low Barometer Studies
There have not been many studies pertaining to barometric pressure and aches and pains. The few studies that have been conducted have found that lower air pressure can cause aches and pains in people with various forms of arthritis including rheumatoid arthritis.
In 2003, Japanese scientists using rats found that foot joint pain increased with lower temperatures and lower air pressure. 
A 2007 study conducted at Tufts University had 200 participants with knee osteoarthritis keep a diary of pain and weather conditions for three months. It was found that there was a consistent association between changes in air pressure as measured by a barometer and severity of pain .
Robert Jamison, who is assistant professor of anesthesia and psychiatry at the Brigham and Women's Hospital's Pain Management Center at Harvard Medical School, believes that it is the change in air pressure that leads to pain. In his book Learning to Master Your Chronic Pain, he wrote “this leads me to conclude that changes in barometric pressure are the main link between weather and pain”. 
Skeptics of Low Pressure Causing Aches and Pain
Some doctors believe that it is all in the patients head, that when you know a storm is coming, your mind then tells you that your arthritis will start to act up and you will have aches and pains.
Other doctors point out that people just feel worse when the weather is damp, humid and cold. But that does not explain how and why certain people can feel aches and pains before the humid and cold weather arrives as the low pressure system approaches.
If you wonder how low air pressure affects your aches and pains, you should record the barometer readings when you feel more aches and pains. You should also note every time the barometer is low and how you feel. A low barometer reading is about 29.70 and lower. If you suffer from migraines, you might also find out that either very low or very high barometer readings trigger your migraines.
Copyright © Sam Montana February 2012
References and Resouorces
 International Journal of Biometeorology Volume 47, Number 2, 55-61, DOI: 10.1007/s00484-002-0156-9
 American Journal of Medicine Changes in Barometric Pressure and Ambient Temperature Influence Osteoarthritis Pain.
 The HarvardUniversity Gazette