What Causes Fatigue, Forgetfulness And Chronic Insomnia In An Elderly Patient?
I read your question carefully and I understand your concern.
The answer is not straight forward as those symptoms are not that specific, meaning that they can be caused by many different causes, perhaps there may be more than one cause at play. May be due to small vessel disease in the brain (more common with age and diabetes), stroke, diabetic neuropathy, altered liver and kidney function, non adequate control of blood glucose, thyroid dysfunction, nutritional deficiencies, chronic infections, anemia etc.
So some tests need to be done. To start with some routine blood tests (perhaps you've already had some of those recently) such as blood count, HbA1c, liver and kidney function, electrolyte panel, thyroid function, vitamin B12 deficiency. If any of the above issues are found of course should be addressed accordingly.
If no major anomalies are revealed then a neurological exam would be indicated for neurological signs (reflexes and sensory changes, motor weakness, mental state test to check for cognition etc) which could indicate peripheral neuropathy or neurological deficits due to a minor stroke which should then be further explored through peripheral nerve studies and/or brain imaging.
I remain at your disposal for other questions.