After getting covid, I forgot things easily and could not focus, I went to the bathroom 3 to 4 times per night, I felt extremely tired even after a long night sleep. Doctors checked me up and could not find the reason. But after some months of getting enough oxygen level, I feel energized in the morning, my memory is getting better by 90% -95%, I am still trying to reach to 100% level. I now can work long hours without feeling tired. This is all that I have been doing: walking at least 6000 steps every morning, often practicing 4-7-8 breathing technique during day time (I read about this technique from CNN), use Medcline pillow (you can use an alternate brand, as long as it is elevated, it is good for you), humidifier for my bedroom, light salt water (after brushing teeth), neck/muscle stretching and I wear Oxygen ring monitor overnight. When you wear an oxygen ring monitor, you will know what position of sleeping can help to get the best oxygen level. To my knowledge, lacking oxygen makes our brain foggy, tired, all of our organs are affected dramatically since blood cannot be delivered to all parts of our body. A year ago, I myself thought I got Alhzeimer at an early age but now I am back to normal so I hope my info helps you too. Daily 4/7/8 Mindfulness breathing before bedtime truly helps. Good luck to you all!!!