This is indeed an excellent question. What are the health effects of an untreated mild sleep apnea?
Consider the sleep apnea syndrome as being mild when the apnea – hypoapnea index (AHI) is between 5 and 15 events per hour. In 2006, the American Academy of Sleep Medicine (AASM) published a literature review with recommendations on the use of CPAP for treating sleep apnea. The review concluded that the scientific data were insufficient to recommend a systematic use of a CPAP for mild sleep apnea treatment.
One study compared changes in blood pressure following the treatment of mild sleep apnea syndrome and showed no difference compared to placebo. The impact of a CPAP in preventing cardiovascular risk in these patients remains unclear, possibly not significant.
A medical or conservative treatment is often recommended for a mild sleep apnea diagnosis. Such measures may include weight loss, positional therapy or the use of intranasal corticosteroids. Alternatives may also be considered before a CPAP such as the use of a mandibular advancement device which is effective in most cases of mild to moderate apnea.
Overall, the CPAP is not very beneficial for improving sleep apnea symptoms, such as daytime fatigue, cardiovascular risk and life quality in patients with mild sleep apnea. Not wearing your CPAP from time to time should not affect your long term health. A follow up with your doctor or specialist is recommended to ensure that your apnea remains stable over the years.