Suffering From Huge Short Term Memory Loss. What Is The Best Possible Way To Improve Situation ?

Hello Doctor , My Grandfather is 85 Year old, suffering from huge short term memory loss . His memory is getting deteriorated from last 5 – 6 years more rapidly. He is not suffering / having any other problem. He is very mobile and active. Does his all personal work but very much confused. Gets irritated and angry very very quickly and many times uses foul language ( which he never use to do earlier). The biggest challenge is he just leaves homes and then it becomes impossible for him to come back by himself. In day time he don’t want stay at home, always interested in going out alone. He gives very easily many slips to family members. As the night falls, he feel very very scared, he just don’t feel comfortable in coming out of his room to attend even nature calls. What is the best possbile to way to improve the situation?