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How Using a CPAP Machine Changes Your Body

You may have been prescribed a CPAP machine if you’ve been diagnosed with obstructive sleep apnea (OSA). When someone has OSA, their airway collapses1 to the point that it can impact their breathing and oxygen levels, also leading to nighttime arousals. Not only can OSA result in more fragmented sleep, but experts warn that it can impact your cardiovascular and mental health, quality of life, and safety while driving.1 

CPAP machines are a form of treatment for this sleep disorder. They deliver a constant stream of pressurized air through tubing and a mask. This keeps the airway open, allowing you to breathe uninterrupted. In addition to helping you to breathe easier and sleep more soundly, CPAP therapy can have a huge impact on your overall health. We’ll review the changes you might notice – both good and bad – after starting CPAP therapy.

The Correlation Between CPAP Use and Bodyweight 

Individual needs vary, but most adults require seven to nine hours of quality sleep per night2 for optimal health. However, when you’re sleep deprived, this can lead to weight gain3. The reason for this is that the body craves food rich in fat and carbohydrates when it’s tired, which can cause an increase in calorie intake. Research shows that not getting enough sleep can reduce your levels of leptin4, the hormone that curbs appetite, and cause higher levels of ghrelin, the hormone that increases appetite.

The link between weight gain and OSA is bi-directional5; obesity can cause OSA, and OSA can, in some cases, lead to obesity. The reason for this is that fat deposits in obese people can narrow the airway6, leading to apnea episodes. Conversely, sleep apnea can lead to poor sleep, which can result in weight gain. 1, 4 

Poor sleep quality is also linked to a more sedentary lifestyle7, as feeling tired can make you less likely to exercise and exert energy. This can then lead to a vicious cycle8 of weight gain worsening sleep apnea, and sleep apnea exacerbating weight gain.

Will Using a CPAP Machine Help You Lose Weight? 

Considering that quality sleep can help you maintain a healthy weight and CPAP machines can improve sleep9, it would be easy to assume that CPAP therapy could aid weight loss. 

Sleep specialists originally hypothesized10 that patients who slept better thanks to CPAP would have more energy to be active during the day, which would then lead to weight loss. Some early research supported this theory, with one small 2011 study on 86 patients showing a link between CPAP therapy and decreased body mass index (BMI) and abdominal fat11. Researchers thought that this was because of the aforementioned benefits of quality rest – increased ability for physical exercise and balanced appetite hormones. However, research since then has been conflicting.

Will Using a CPAP Machine Cause You to Gain Weight?

Although initial research claimed that CPAP therapy could help patients lose weight, later data suggests otherwise.11 

Research from 201712 shows a link between long-term CPAP therapy and significant weight gain. Researchers suggest this could be due to the body not expending as much energy while sleeping since it doesn’t have to work as hard to breathe while on CPAP.12

A more recent meta-analysis from 202113 looked at the data of 6,954 patients from 39 randomized controlled trials. Researchers found a significant increase in BMI after CPAP therapy, especially in those who used their CPAP for less than five hours per night. However, researchers can’t agree on why this weight gain occurs as there are many factors involved in weight change, indicating that additional studies are needed. 

Additional Health Benefits of Using a CPAP Machine

Lower Blood Pressure

Obstructive sleep apnea has been linked to higher blood pressure (hypertension), especially in those with more severe apnea14. However, CPAP therapy can lead to modest improvements in blood pressure in hypertensive patients.14 

OSA patients can have higher levels of the amino acid cystine15 in their blood, which may be what causes the increase in blood pressure. CPAP therapy was found to reverse this increase, and therefore reduce the patient’s blood pressure.15

Decreased Stroke Risk

OSA can increase your risk of having a stroke16, and stroke patients with untreated OSA are more likely to continue experiencing strokes17. However, patients who use their CPAP as advised have been shown to have a lower risk of further strokes in cases where both stroke and OSA are present.16

Improved Alertness

Research reveals that people with OSA have lower levels of glutamate18, a neurotransmitter that’s essential for cognitive function19. Decreased levels of glutamate can lead to trouble concentrating and mental exhaustion.19 Glutamate levels can increase after CPAP therapy20, which could lead to improved alertness.

Reduced Symptoms of Depression and Anxiety

Sleep and mood are closely linked21; not getting adequate quality rest can lead to feelings of stress and irritability in the short term, while chronic sleep deprivation can increase your risk of developing anxiety or depression. 

People with obstructive sleep apnea are more likely to have depression22 than the rest of the general population, and researchers believe that sleep apnea may often be misdiagnosed as depression23  due to the conditions sharing multiple symptoms. 

It’s not completely understood why the two conditions are linked, though OSA leads to broken sleep, which can then lead to a worse mood.1, 21

OSA is also linked to higher feelings of anxiety. A recent 2022 study24 of 99 patients with moderate to severe OSA found that feelings of anxiety and depression were high among participants. After six months of CPAP therapy, depression and anxiety scores were significantly reduced, with researchers suggesting that CPAP could help avoid the use of psychiatric medication in depressed or anxious patients with OSA.24

Healthier Heart

Untreated sleep apnea carries an increased risk of cardiovascular diseases. It’s not entirely known why, but it’s thought that the pauses in breathing caused by OSA lower blood oxygen levels, which can damage the blood vessels leading to the heart25. Heart rate also increases every time you stop breathing, increasing blood pressure and putting a strain on the heart.25 There is conflicting evidence26 on CPAP’s heart health benefits, except in cases related to high blood pressure. 

However, longitudinal research presented in 2023 found that patients who continued to use CPAP long-term had an 18 percent lower risk27 of being hospitalized with cardiovascular disease. They also had a 36 percent lower risk of dying from it, compared to patients who stopped using CPAP.27

Fewer Headaches

People with obstructive sleep apnea sometimes report waking up with a headache28, and a 2020 study revealed that 29.5 percent of the 1,009 participants who had OSA experienced morning headaches. However, there was insufficient evidence to suggest that these headaches were specifically related to OSA, rather than other potential factors.

More recent research backs this up; in 116 patients with OSA, the severity of their headaches increased with the severity of OSA29. However, they found that three months of positive airway pressure therapy improved headache symptoms in patients with OSA, especially in those with severe OSA, in which symptoms improved by up to 72 percent.29

While there’s not enough research on the link between OSA, CPAP, and headaches, current data does suggest that CPAP may be a useful tool in lessening headaches in patients with OSA. 

Healthier Pregnancy

Pregnant women who have obstructive sleep apnea are at greater risk30 of gestational hypertension (pregnancy-related high blood pressure), pre-eclampsia, and gestational diabetes. Additionally, it may cause preterm delivery, a lower birth weight, and a higher risk of the baby needing intensive care after birth.30

Although more extensive research on treating OSA in pregnancy is needed, a recent systematic review of seven clinical trials suggests that treating OSA with CPAP during pregnancy may be linked to reduced blood pressure, lower risk of pre-eclampsia, less chance of premature delivery, and increased birth weight of the infant.30

Fewer Male Reproductive Issues 

OSA has been linked to male infertility31, though there’s a lack of research to help explain why. A small pilot study of 41 male patients32 found that those with OSA had lower semen quality, decreased testosterone levels, and increased erectile dysfunction. 

A larger study of 150 newly diagnosed male OSA patients revealed that 51 percent33 of them were experiencing erectile dysfunction. After 3 months of CPAP therapy, patients reported a significant increase in sexual satisfaction, but CPAP had no effect on the levels of sex hormones.33 

Other research suggests that CPAP therapy can help improve symptoms of erectile dysfunction in men with both severe erectile dysfunction and severe OSA34, as well as significantly increase levels of sex hormones like testosterone. However, a similar study found that while CPAP improved erectile function, it had no effect on testosterone levels35 after three months of treatment. 

Conflicting evidence shows that further research needs to be done in this area, but it’s worth speaking to your doctor if you suspect reproductive issues could be caused by sleep apnea.

Improved Diabetes Symptoms

Obstructive sleep apnea can worsen symptoms of diabetes36 as it causes interruptions in breathing, which increases levels of carbon dioxide in the blood. This, in turn, leads to insulin resistance, causing higher blood sugar.36

Treating sleep apnea can help diabetes patients with OSA manage their diabetes more efficiently. A recent systematic review and meta-analysis of 11 randomized clinical trials showed that continued CPAP therapy appears to improve long-term blood glucose levels37 in patients with both OSA and type 2 diabetes.

Signs You May Have Sleep Apnea 

Signs of obstructive sleep apnea38  can include feeling exhausted after waking up, extreme daytime fatigue, negative changes in mood, poor concentration, and sexual dysfunction. Other sleep apnea symptoms you may notice are loud snoring, frequent nighttime awakenings, and waking up gasping for breath. 

Untreated sleep apnea can lead to further health complications, so it’s important to visit your doctor if you suspect you might have OSA. They may refer you to a sleep center for further assessment, and you may be prescribed a CPAP machine upon diagnosis.

Frequently Asked Questions

What does CPAP do for the body?

A CPAP machine delivers a steady stream of pressurized air into the upper airway via a hose and mask. This forces the airway open in cases of obstructive sleep apnea where the airway collapses while sleeping, allowing the patient to breathe normally and get a better night’s sleep.

What happens to your body when you start using a CPAP machine?

Consistently using a CPAP machine can lead to better physical, mental, and cognitive health. Benefits of CPAP39 include better sleep, decreased snoring, more energy, improved cognitive function, and lower blood pressure.

How long does it take to see results from using a CPAP?

The time it takes to see results from CPAP differs from person to person. Consistent use of the machine is necessary to see results, and you should give yourself time to adjust to wearing a mask while sleeping, as this may initially feel uncomfortable.

You’ll get a sense that treatment is working when you start to notice positive impacts on your health and day-to-day vitality. If you’re struggling with your CPAP machine, reach out to your healthcare provider; they may be able to offer advice on ways to make sleeping with a CPAP easier, or they may even suggest an alternative to CPAP therapy.

Lisa Bowman

Lisa Bowman


About Author

Lisa is a content writer for Sleep Advisor, which combines two of her greatest passions – writing and sleeping. She can also be found writing about fitness, sustainability and vegan food.

Combination Sleeper