Does CPAP Stop you from having a Heart Attack?

Continuous positive airway pressure (CPAP) therapy is often used to treat a condition called obstructive sleep apnoea (OSA). This condition causes temporary pauses in breathing during sleep and is associated with a higher risk of heart and blood vessel-related health problems. However, it is still unclear if using CPAP effectively reduces these heart-related risks.

I will go through the evidence for and against in this article:

---

CPAP for Prevention of Cardiovascular Events in Obstructive Sleep Apnoea

Published Aug 28, 2016 · R. Mcevoy et al.
The New England Journal of Medicine

This article was published in the world’s most prestigious medical journal. The authors studied 2,717 adults aged 45 to 75. All participants first tried a pretend CPAP machine (called "sham CPAP") for one week. After that, they were split into two groups: one group received CPAP treatment along with their normal care, and the other group just received normal care without CPAP.

Researchers kept track of events like deaths caused by heart problems, heart attacks, strokes, or hospital stays for serious issues like chest pain or heart failure. They also monitored things like quality of life, snoring, tiredness during the day, and mood.

After about 3.7 years, researchers found that serious heart problems occurred at nearly the same rate in both groups. CPAP therapy did not appear to reduce the risk of these events. However, CPAP did provide other benefits—it reduced snoring, improved daytime tiredness, enhanced mood, and boosted overall quality of life.

• In the CPAP group, 229 participants (17.0%) experienced one of these events.
• In the usual-care group, 207 participants (15.4%) experienced one of these events.
• The difference between the groups was not statistically significant. This means the results could have been due to chance rather than CPAP having an effect. The hazard ratio (a measure of risk) was 1.10, with a confidence interval (CI) of 0.91 to 1.32 and a p-value of 0.34. A p-value above 0.05 indicates statistical insignificance.

CPAP therapy did show benefits outside of heart health, such as:

• Reduced snoring.
• Improved daytime sleepiness, helping people feel less tired.
• Enhanced quality of life and mood.

Statistically, CPAP therapy did not significantly prevent major heart problems. However, it did improve general well-being, including sleep quality and daytime alertness.

---

Efficacy of Continuous Positive Airway Pressure (CPAP) in the Prevention of Cardiovascular Events in Patients with Obstructive Sleep Apnoea: Systematic Review and Meta-Analysis

Published: 14 March 2020
Author: Gonzalo Labarca et al.

The researchers reviewed multiple previous studies called randomised controlled trials (RCTs), which are carefully designed experiments to test the effects of treatments. Two independent reviewers searched various databases for relevant studies and assessed factors that could impact the reliability of the results, a process referred to as "assessing the risk of bias."

The researchers focused on several health outcomes related to the heart and blood vessels, including:

• Major cardiovascular events (MACEs): Serious heart-related problems like heart attacks or strokes.
• Cardiovascular (CV) mortality: Deaths caused by heart or blood vessel issues.
• Myocardial infarction: A heart attack.
• Unstable angina: Sudden chest pain due to reduced blood flow to the heart.
• Stroke: A disruption in blood supply to the brain.
• Atrial fibrillation (Afrib): An irregular and often fast heartbeat.
• Heart failure: When the heart struggles to pump blood effectively.

The researchers also analysed whether factors such as daytime sleepiness, CPAP adherence (how consistently patients used the therapy), or the severity of obstructive sleep apnoea (OSA) affected the outcomes. The reliability of the evidence was rated using the GRADE method (Grading of Recommendations Assessment, Development, and Evaluation).

• The researchers reviewed 8 RCTs involving a total of 5,817 participants.
• The results for relative risk (RR) were as follows:
  • Major cardiovascular events - MACEs: RR = 0.87 (CI: 0.70–1.10). No clear reduction in risk.
  • Cardiovascular mortality: RR = 0.94 (CI: 0.62–1.43). No significant reduction.
  • Heart attacks: RR = 1.04 (CI: 0.79–1.37). Risk was similar in both groups.
  • Unstable angina: RR = 1.05 (CI: 0.51–2.15). No clear difference.
  • Heart failure: RR = 0.92 (CI: 0.68–1.23). No strong effect observed.
  • Strokes: RR = 0.94 (CI: 0.71–1.26). No clear impact.
  • Atrial fibrillation (Afrib): RR = 0.94 (CI: 0.54–1.64). No significant benefit.

What do these numbers mean?

• The relative risk (RR) indicates how likely an event is to happen with CPAP therapy compared to without it.
  • An RR of 1 means no difference.
  • Values below 1 suggest a reduced risk.
  • Values above 1 indicate an increased risk.
• The confidence interval (CI) shows the range in which the true RR value might fall. If the CI includes 1, the result is statistically insignificant.

Additional analyses explored factors such as daytime sleepiness, CPAP adherence, and OSA severity. However, none of these factors significantly influenced the outcomes.

Conclusion

The study concluded that there is no strong evidence to show that CPAP therapy reduces the risk of major heart-related problems. However, factors such as study reliability (bias), patient adherence to therapy, and participant selection might have influenced the results. Further research is needed to understand these outcomes more fully.

---

Impact of Obstructive Sleep Apnea Treatment on Cardiovascular Disease Associated Mortality and Morbidity: A Systematic Review

Published: 18 October 2023 - Authors: Niyati Grewal et al.

The researchers carried out a detailed review of studies from three large databases: PubMed, Medline, and Scopus. They followed PRISMA guidelines, which are rules for conducting high-quality reviews, and included 25 studies in their final analysis.

Key Focus:

The main aim was to investigate how treatments for obstructive sleep apnoea (OSA) affect heart and blood vessel health (referred to as cardiovascular disease or CVD) in terms of:

• Morbidity: Being ill or having health problems related to CVD.
• Mortality: Death caused by CVD.

Types of Studies:

Out of the 25 studies:

• 10 were meta-analyses (these combine results from multiple studies to identify overall patterns).
• 8 were observational studies (these look at participants’ outcomes without interfering with their treatment).
• 7 were randomised controlled trials (RCTs) (these assign people to different treatment groups to compare results).

Treatments Studied:

• CPAP therapy (continuous positive airway pressure) was the main treatment in 23 studies. CPAP uses a machine to help people with OSA breathe more easily while sleeping.
• Two studies examined other treatments: noninvasive positive pressure ventilation (a type of breathing support) and oral appliance therapy (devices to keep airways open during sleep).

In 23 studies, the main goal was to look at secondary prevention, which refers to preventing heart problems in people who already have CVD.

Participants:

The review included a total of 165,775 people aged between 45 and 75, with most studies involving 60% to 90% men. The average Epworth Sleepiness Scale (ESS) score, which measures how sleepy someone feels during the day, ranged from 5 to 9 (lower scores indicate mild sleepiness).

Cardiovascular (CV) Outcomes:

The studies explored various CV health issues, including:

• Myocardial infarction (heart attack).
• Angina (chest pain caused by reduced blood flow to the heart).
• Heart failure (HF) (when the heart can't pump blood properly).
• Acute coronary syndrome (ACS) (a term for conditions where blood flow to the heart is suddenly reduced, like a heart attack).
• Coronary artery disease (CAD) (blockages in the heart's blood vessels).
• Ischaemic heart disease (caused by narrowed heart arteries).
• Cardiomyopathy (diseases that affect the heart muscle).
• Atrial fibrillation (AF) (an irregular, often fast heartbeat).
• Hypertension (high blood pressure).

Main Findings:

• In 4 studies, CPAP therapy was linked to fewer deaths caused by CVD.
• In 10 studies, CPAP showed improvements in illness (morbidity) related to CVD.
• However, the overall review did not find consistent evidence that CPAP or other OSA treatments improve CV health outcomes for all patients.

Gaps and Future Research:

The review pointed out important gaps in knowledge, such as:

• A lack of studies showing whether the benefits of OSA treatments depend on the dose (how often or how much treatment is used).
• Limited research on how OSA severity and gender affect results.
• The need for larger, long-term studies to explore these factors in greater detail.

In summary: While some studies suggested benefits from CPAP therapy, the overall evidence for improving heart and blood vessel health in OSA patients remains unclear. More research is needed to better understand these effects.

---

Potential Benefits with High Adherence:

Some evidence suggests that CPAP may reduce cardiovascular events in patients who adhere to the therapy for more than four hours per night.

---

Meta-Analysis of Cardiovascular Outcomes With Continuous Positive Airway Pressure Therapy in Patients With Obstructive Sleep Apnoea

Published Aug 15, 2017 · A. Abuzaid

The study analysed the impact of CPAP therapy (a treatment for obstructive sleep apnoea that helps with breathing during sleep) on heart-related health. It included four carefully designed experiments called randomised controlled trials (RCTs), involving a total of 3,780 patients.

Key Findings:

1. General Results: When comparing CPAP therapy alongside usual medical care to medical care alone, CPAP didn’t show a clear reduction in the risk of serious heart-related problems. These problems, also known as major adverse cardiac events (MACEs), include heart attacks, strokes, deaths caused by heart issues, and hospitalisations for heart-related emergencies.
   • Relative Risk (RR): The risk of these events was 0.94 (with a confidence interval [CI] of 0.78 to 1.15 and a p-value of 0.93). Since the confidence interval includes 1 and the p-value is high, this means there was no statistically significant difference between the groups.
   • I² = 0%: This means there was no variation in results across the different studies.
   
   
2. Subgroup Results: However, in the subgroup of patients who used CPAP for more than 4 hours per night:
   • There was a 30% reduction in the risk of MACEs (RR 0.70, CI 0.52 to 0.94, p = 0.02). This indicates that consistent use of CPAP for longer periods may provide some benefit.
   
   
3. Specific Heart Problems: CPAP therapy did not reduce the risk of individual heart-related issues such as:
   • Cardiac mortality (death from heart problems): RR 1.14 (CI 0.66 to 1.97, p > 0.36).
   • Heart attack (myocardial infarction): RR 0.96 (CI 0.64 to 1.44, p > 0.15).
   • Angina (chest pain): RR 1.16 (CI 0.90 to 1.50, p > 0.51).
   • Stroke: RR 1.01 (CI 0.73 to 1.38, p > 0.86).
   • Transient ischaemic attack (a “mini-stroke”): RR 1.36 (CI 0.69 to 2.68, p > 0.24).
   • Heart failure: RR 0.91 (CI 0.50 to 1.66, p > 0.55).
   
   For each of these outcomes, the p-values were high, and the confidence intervals included 1. This means CPAP therapy did not make a significant difference.
4. Type of Analysis:
   • The study used a fixed-effect model, which assumes the results from all included studies are similar.
   • For some subgroup analyses (e.g., CPAP usage over 4 hours), they used a random-effects model (DerSimonian and Laird’s model), which allows for differences across studies.
   
   

Conclusion:

Overall, using CPAP therapy alongside standard medical care in patients with obstructive sleep apnoea did not improve heart-related outcomes compared to standard care alone. However, patients who used CPAP for more than 4 hours per night showed a reduced risk of serious heart issues, highlighting the importance of consistent use. Further research is needed to explore this potential benefit.

---

Nonfatal and Fatal Cardiovascular Disease Events in CPAP-Compliant Obstructive Sleep Apnoea Patients

Published Mar 8, 2019 · Minna Myllylä

Overview:

The study looked at whether long-term CPAP (continuous positive airway pressure) therapy for obstructive sleep apnoea (OSA) could help reduce the risk of serious heart and blood vessel problems (cardiovascular disease or CVD). It compared two groups:

• CPAP-treated group: Patients who regularly used CPAP.
• Control group: Patients who did not receive CPAP treatment.

How the Study Was Done:

• The researchers reviewed patient data from a retrospective observational study (a study that looks at existing records to find patterns).
• They carefully matched the CPAP and control groups based on factors like gender, age, and apnoea-hypopnoea index (AHI), which measures how severe someone’s sleep apnoea is.
• The study tracked both fatal and nonfatal CVD events, such as heart attacks, strokes, or death caused by heart problems.

Key Details:

• Participants: A total of 2,060 patients were included:
  • 75.8% were men.
  • The average age was 56 years old.
  • 76.4% of participants had moderate-to-severe OSA.
  
  
• CPAP Use:
  • In the CPAP group (1,030 patients), the average use of CPAP was 6.4 hours per night, and patients were followed for an average of 8.7 years.
  • The control group (1,030 patients) was followed for an average of 6.2 years.
  
  

Results:

• The main outcome (serious heart-related problems) occurred in:
  • 14.4% (148 patients) of the CPAP-treated group.
  • 18.8% (194 patients) of the control group.
  • This difference was statistically significant (p = 0.006), meaning it is unlikely to have happened by chance.
  
  
• Using a Cox regression model (a statistical method that accounts for multiple factors), the researchers found that:
  • CPAP was linked to a 36% lower risk of serious heart problems compared to the control group.
  • Hazard ratio (HR): 0.64 (95% confidence interval: 0.5–0.8, p < 0.001). A hazard ratio below 1 means reduced risk, and the low p-value shows strong evidence for this result.
  
  

Conclusions:

The study concluded that long-term CPAP therapy is associated with a lower risk of serious heart problems, both fatal and nonfatal, in people with obstructive sleep apnoea (OSA). This benefit was observed even after considering other risk factors like age, gender, body mass index (BMI), existing heart problems, high blood pressure, type 2 diabetes, and chronic lung disease. Most of the patients in the CPAP group were consistent in using their treatment.

---

Subgroup Variability:

The effectiveness of CPAP may vary based on patient characteristics, such as the severity of OSA and adherence to therapy. Some studies suggest that patients with a heightened pulse rate response to apnoeas/hypopnoeas may be at increased risk of cardiovascular events, indicating a need for targeted treatment strategies.

---

The Sleep Apnea-specific Pulse Rate Response Predicts Cardiovascular Morbidity and Mortality

Published Jan 6, 2021 · A. Azarbarzin

Overview:

The study investigated whether the heart rate response to breathing interruptions during sleep—called ∆HR (change in heart rate)—can help predict the risk of heart problems or death in people with obstructive sleep apnoea (OSA). The researchers divided participants into categories based on their ∆HR to see if having a very high or very low heart rate response affected health outcomes.

What is ∆HR (Change in Heart Rate)?

∆HR measures how much a person's heart rate increases during apnoea (pauses in breathing) or hypopnoea (shallow breathing). For example:

• When someone stops breathing for a short time, their body reacts to the reduced oxygen by increasing the heart rate.
• A higher ∆HR means a stronger heart rate response to these events, while a lower ∆HR means a weaker response.

What are "Upper and Lower Quartiles"?

To analyse the data, the researchers ranked all participants based on their ∆HR and divided them into four equal groups:

• Lower quartile: The bottom 25% of people with the weakest (lowest) heart rate response.
• Upper quartile: The top 25% of people with the strongest (highest) heart rate response.
• The middle 50% (between the 25th and 75th percentiles) were grouped as mid-range ∆HR.

By comparing these groups, the researchers aimed to see if very high or very low ∆HR levels were linked to worse health outcomes compared to the mid-range group.

Findings in More Detail:

1. Early Signs of Heart Disease:
   • Using data from the MESA study, the researchers found that both the upper quartile (highest ∆HR) and lower quartile (lowest ∆HR) were associated with worse scores on early heart health indicators (biomarkers). This means:
     • People with very high or very low pulse rate responses during breathing interruptions might already have underlying heart problems.
     • A U-shaped relationship was observed. This means that having a very high or very low ∆HR was worse for heart health, while a mid-range ∆HR seemed to be the healthiest.
     
     
   
   
2. Heart Problems and Mortality:
   • Using data from the SHHS study, participants in the upper quartile (highest ∆HR) were at greater risk of:
     • Non-fatal cardiovascular disease (CVD): 1.60 times higher risk compared to those in the mid-range group.
     • Fatal CVD: 1.68 times higher risk.
     • All-cause mortality (death from any cause): 1.29 times higher risk.
     
     
   • These risks were particularly severe for people who also experienced significant oxygen level drops during breathing interruptions (high hypoxic burden):
     • Non-fatal CVD: Risk increased to 1.93 times.
     • Fatal CVD: Risk jumped to 3.50 times.
     • All-cause mortality: Risk rose to 1.84 times.
     
     
   
   

Why Do High or Low ∆HR Levels Matter?

• High ∆HR (upper quartile): A very strong heart rate response during breathing interruptions might indicate that the body is under significant stress. This could be linked to overactivation of the nervous system, which can strain the heart over time.
• Low ∆HR (lower quartile): A weak heart rate response could mean the body isn't reacting properly to low oxygen levels, which might suggest impaired cardiovascular or nervous system function.

In both cases, these extreme responses are thought to increase the risk of heart-related problems and death.

Conclusion:

The study found that people with OSA who fall into the upper quartile (highest ∆HR) are at significantly greater risk of serious heart issues and death. This risk is even higher if they experience severe oxygen drops during sleep (high hypoxic burden). The findings suggest that ∆HR could be used as a marker to identify high-risk patients and guide treatment or further research.

---

Positive airway pressure therapy and all‐cause and cardiovascular mortality in people with obstructive sleep apnoea: a systematic review and meta-analysis of randomised controlled trials and confounder-adjusted, non-randomised controlled studies

Published March, 2025: Author - Adam V Benjafield et al.

This is the most recent study which looks at the data so far. I have summarised the details below.

Findings for All-Cause Mortality:

1. 2 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.57 (CI: 0.34–0.95)
     • CPAP reduced the risk of death by 43% in this group (an HR of 0.57 means 43% lower risk compared to no CPAP).
     • The CI range (0.34–0.95) does not include 1, so this result is statistically significant.
     
     
   • RCTs: HR = 0.95 (CI: 0.60–1.50)
     • No meaningful reduction in risk, as the HR is close to 1 and the CI includes 1 (not statistically significant).
     
     
   
   
2. 4 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.50 (CI: 0.33–0.76)
     • CPAP reduced the risk of death by 50%.
     • The CI (0.33–0.76) does not include 1, so it’s statistically significant.
     
     
   • RCTs: HR = 0.84 (CI: 0.55–1.28)
     • Some reduction in risk (16% lower), but the CI includes 1, so it’s not statistically significant.
     
     
   
   
3. 6 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.44 (CI: 0.30–0.65)
     • CPAP reduced the risk of death by 56%.
     • The CI (0.30–0.65) is statistically significant.
     
     
   • RCTs: HR = 0.84 (CI: 0.46–1.19)
     • No significant difference, as the CI includes 1.
     
     
   
   

Cardiovascular Mortality Risk (Risk of Death from Heart-Related Causes):

This section looks at whether CPAP reduces deaths caused specifically by heart problems.

Findings for Cardiovascular Mortality:

1. 2 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.25 (CI: 0.06–1.09)
     • CPAP reduced risk by 75%, but the CI includes 1 (not statistically significant).
     
     
   • RCTs: HR = 0.79 (CI: 0.31–2.01)
     • No significant difference, as the CI is wide and includes 1.
     
     
   
   
2. 4 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.24 (CI: 0.10–0.60)
     • CPAP reduced the risk by 76%, and the CI does not include 1 (statistically significant).
     
     
   • RCTs: HR = 0.78 (CI: 0.44–1.35)
     • Some reduction (22% lower risk), but the CI includes 1 (not statistically significant).
     
     
   
   
3. 6 Hours of CPAP Use Per Night:
   • NRCS: HR = 0.24 (CI: 0.14–0.40)
     • CPAP reduced risk by 76%, and the CI is statistically significant.
     
     
   • RCTs: HR = 0.76 (CI: 0.36–1.63)
     • No significant difference, as the CI includes 1.
     
     
   
   

This meta-analysis examined data from both randomised controlled trials (RCTs) and non-randomised controlled studies (NRCSs) regarding the benefits of continuous positive airway pressure (CPAP) therapy on mortality and cardiovascular risk. Previous meta-analyses have demonstrated inconsistent findings on the efficacy of CPAP. Even the 2023 meta-analysis failed to show a clear benefit. However, this newer study from 2025 incorporated a substantial 2024 study involving 888,835 older adults, significantly increasing the total number of participants and potentially influencing the overall conclusions.

The large 2024 study was a retrospective analysis of CPAP users but did not account for whether participants had undergone surgery or received other treatments for their sleep apnoea. As a result, it is uncertain whether CPAP alone was the primary factor contributing to improvements in cardiovascular outcomes related to sleep apnoea.

Analysis of the sub-studies indicated that a statistically significant reduction in cardiovascular risk was observed only in the NRCSs, and this may have been influenced by the inclusion of the large 2024 study. Notably, these benefits were evident when patients used CPAP for more than four hours per night. By contrast, the RCTs demonstrated no significant benefit, even among patients who used CPAP for an average of six hours per night.

The number of participants in the NRCSs totalled 1,083,763 (888,835 of whom were from the large 2024 study), compared to only 5,612 participants in the RCTs. This disparity in participant numbers may have introduced bias, potentially skewing the results and raising questions about the reliability of the overall conclusion.

I am also concerned that the study was funded by ResMed, which has a significant conflict of interest in making CPAP appear better than it is. Furthermore, 4 of the authors are employed by ResMed, and 6 authors work for consulting companies (of a total of 17 authors).

I believe this study provides a solid analysis of the current literature. However, in my view, the way it has been presented on social media does not accurately reflect the conclusions outlined in the discussion.

Conclusion:

While CPAP therapy improves certain symptoms and quality of life in OSA patients, its impact on reducing cardiovascular morbidity is not consistently supported by current evidence. High adherence to CPAP may offer some cardiovascular benefits, but further research is needed to explore these effects and identify which patient subgroups might benefit most.

Read more

If you would like to know more, please use the links on this page to understand better what the treatment options for these conditions are.

If you would like more information please contact Prof Vik Veer via his team of secretaries:

Private secretary: 0207 458 4584

Email: Secretary@Consultant-Surgeon.co.uk