Although people with cardiovascular conditions were previously discouraged from using sauna, it’s accepted that sauna is safe (and likely beneficial) for people with stable cardiovascular disease.[1] People with symptomatic, unstable, or unmanaged cardiovascular issues, such as unstable coronary artery disease, severe aortic stenosis, or recent myocardial infarction shouldn’t use sauna, however, because the physiological stress of sauna might precipitate a cardiac event. [2]
One of the biggest risk factors for adverse effects in the sauna is concurrent alcohol use: it both increases the risk of environmental injury (e.g., trauma from falling or heat injury from remaining in the sauna for too long) and can lower blood pressure to unsafe levels (sauna already has blood-pressure-lowering effects).[1]
A few papers have raised concerns about sauna use during pregnancy, but the practice is considered safe and is common in Finland.[3]
Overall, it’s worth appreciating that sauna is a low-risk but physiologically stressful activity. Individuals engaging in this practice should pay attention to how they feel and exit the sauna if they feel too uncomfortable.