I always heard that there can be night sweating with untreated sleep apnea. But your question prompted me to search more about it, some.
There isn't much explanation. Stanford describes it as a function of movements during sleep for people with sleep apnea. I found parts of the American Academy of Family Medicine (AAFM) interesting, some of it quoted below. I would imagine that some sweating can be due to more than one cause for untreated sleep apneacs, if suffering from other things such as thyroid problems. The AAFM article lists hyperthyroidism as one cause for night sweats. I developed some thyroid problems during my untreated apnea (with cpap therapy my thyroid levels returned to normal). And the article mentions acid reflux, and I know many who have OSA have this condition as well. And I do know that your heart rate can go way up during the night with untreated apnea. I would guess those experiencing a racing heart at night, as I had, is not unlike jogging and sweating. That ticker is working overtime to jumpstart your breathing. So who knows, maybe there is more happening in addition to the movements.
Click here for article from American Academy of Family Physicians
Click here for link to a physician's comments
Click here for Stanford article
Night sweats are a common outpatient complaint, yet literature on the subject is scarce. Tuberculosis and lymphoma are diseases in which night sweats are a dominant symptom, but these are infrequently found to be the cause of night sweats in modern practice. While these diseases remain important diagnostic considerations in patients with night sweats, other diagnoses to consider include human immunodeficiency virus, gastroesophageal reflux disease, obstructive sleep apnea, hyperthyroidism, hypoglycemia, and several less common diseases. Antihypertensives, antipyretics, other medications, and drugs of abuse such as alcohol and heroin may cause night sweats. Serious causes of night sweats can be excluded with a thorough history, physical examination, and directed laboratory and radiographic studies. If a history and physical do not reveal a possible diagnosis, physicians should consider a purified protein derivative, complete blood count, human immunodeficiency virus test, thyroid-stimulating hormone test, erythrocyte sedimentation rate evaluation, chest radiograph, and possibly chest and abdominal computed tomographic scans and bone marrow biopsy. (Am Fam Physician 2003;67:1019-24. CopyrightÂ© 2003 American Academy of Family Physicians.)
Thanks for helping me to learn more about it too.