I have a 96 year old aunt with dementia and in poor health. She sleeps a lot. Do I need someone to come in while I am gone?

I like both answers, it really depends on where you go and for how long and what she is capable of getting up to while she is alone. Would you like to share more details?

(I routinely left my mom at home in bed when I went for my daily jog, but I knew she couldn't get up on her own and I was never far away)

A slightly different answer-- If it is for a short time and your experience is that trying to get up is not on the cards for her, perhaps it's a call you can make. There are always 'what ifs' in life that we have to ignore. For example, how many times have we heard 'you could get killed today crossing the road'. Just do your best to be responsible, based on what you know is likely or very unlikely. I have a lot of respect for Ahmijoy's commonsense, and as she says it depends on how long and what are the risks.

Gone for how long? Like every day while you’re at work for maybe 10 hours or so? Or running up to Mickey D’s for 15 minutes for a Big Mac? Or gone on a long weekend?

Heck yeah you do. What if there was a fire? Or a break in? What if she fell out of bed? What if she woke up and wandered off? What if she had a health emergency? What if she woke up and went into a panic attack because she was alone?

Either hire a caregiver giver or find some way to place her in a facility. If, God forbid, something should happen and it was discovered that you’re leaving her alone in her condition, you could be charged with neglect.