CBD at doses of 10-20mg usually helps with sleep but it’s THC that improves sleep apnea. Everyone responds differently to cannabis so its best to start low, with THC dose of 1-2 mg and increase nightly by 1-2 mg, as indicated by your quality of sleep and the number of hypoxic episodes that occur as indicated on your CPAP machine. Care must be taken for those who have never used cannabis before, have risk of falling, or who have severe heart disease but THC doses up to 10 mg should be fine if increased gradually, allowing the body to become accustomed to it. Tinctures, gummies or chocolates usually last 5-8 hours. If using CBD for sleep, start at 10mg and increase by 5 mg every night until sleeping through the night. CBD can interfere with the metabolism of some medications so be sure to space it apart by 2-3 hours if you're taking bloodthinners, anticonvulsants, GERD medication, or statins; and it can increase intraocular pressure so patients with glaucoma should have their pressures monitored while using CBD.