How can a person know if they have sleep apnea if they sleep alone?

Sleep study. Talk to your doctor about a sleep study. Symptoms of sleep apnea include non refreshing sleep, waking at night gasping for air, sleepiness during the day, dry mouth in the morning, feeling of paralysis while falling asleep or waking from sleep. Also look up epsworth sleepiness scale.
Fatigue. If you are chronically tired and wake up each morning feeling like you want to sleep for several more hours and if you fall asleep easily and can nap during the day you may have sleep apnea. If you are overweight the likelihood is even higher. You should discuss this with your doctor and if there is concern have a sleep study.
Sleep Study. The only sure way to know is to get an overnight sleep study. I favor a study in the lab - you can also do a take home study as well. A very useful questionaire is the stop-bang questionaire. Also check my health guide: https://www.Healthtap.Com/health_guide/254.