Carpal Tunnel Syndrome is primarily caused by repetitive strain of the hands, usually due to performing a task frequently.
This syndrome is caused by the compression of the median nerve which is located in a "tunnel" in the forearm and wrist, called "carpal tunnel".
Here is a video that explains more about Carpal Tunnel Syndrome:
The article discusses the possibility of developing hand pain, numbness or tickling due to the abnormal wrist position in patients with sleep disorders. The researchers observed that:
CTS and sleep apnea increase in prevalence with the age of the person,
like sleep apnea, the CTS is more common in men than women,
obesity, which is a risk factor for sleep apnea, has also an influence on Carpal Tunnel Syndrome,
sleep position can affect sleep apnea and the development of CTS.
In sleep apnea, a person stops breathing in sleep by collapse of the tongue and obstruction of the airway. This happens mostly in that persons is sleeping in the supine position, and is exacerbated by increased body weight and by age.
Sleeping on a side rather than on your back can prevent sleep apnea evens, where almost 90% of normal weight people have a good response to this sleep position change.
However, there is a catch here! The article mentions that sleeping on the side is related to positioning the wrist in flexion or extension, which could be a casual pathway for nerve compression.
Bottom line... Sleep position has been suggested as a direct mechanism in nerve compression, which will cause Carpal Tunnel Syndrome.
People with sleep apnea can be at risk of developing hand pain, numbness or tickling (CTS) if they:
have a higher BMI - an obese or overweight person may search for comfort in the cervical spine or back causing him to sleep on his side,
sleeping on the side - people who sleep on their side more than other persons are more prone to Carpel Tunnel Syndrome,
As you can see, I didn't find any information that mentions a relationship between CPAP and CTS. The only explanation might be that you're spending more time in REM sleep recovering your sleep debt from sleep apnea. In REM sleep, your body doesn't move much.
I found that hand pain can also be caused by fibromyalgia, which is a syndrome that affects your soft tissues, muscles and tendons.
Many people with sleep apnea also have fibromyalgia. Unfortunately, it's hard to diagnose it, and though it may be suspected, it takes an average of five years to reach a diagnosis.
Although the onset of fibromyalgia can be gradual, it can sudden appear after a traumatic event in your life, such as severe ilness (severe sleep apnea) or injury.
For your hand pain or numbness, I recommend visiting a rheumatologist, your primary doctor and your sleep doctor.
You need an inspection from your doctor, because other surprising health problems can cause your hand pain. One of them that I'm thinking can be Gout.