Well you can focus on dementia (like me!) if you so wish! Not many psychiatrists want to work with this patient population. You could focus on working in geriatric psychiatry, consultation-liaison psychiatry, or neuropsychiatry if you are interested in dementia. You could work on an inpatient geropsych or neurobehavioral unit, in a day hospital program, in a memory clinic, or in nursing homes (or some combination of the above). If you are interested in research there is plenty to research and lots of unanswered questions and it is relatively well funded compared to some other diseases. If you are interested in teaching, all the cool cases come to the academic medical centers so you could be heavily involved in teaching students, residents and fellows. Neurology is another potential avenue to working with dementia patients. Most of your psychiatry residency training is not going to be in dementia though, so you should also have an interest in mood disorders, psychosis, substance use disorders and so on as well. Given that behavioral and psychological symptoms are so common in dementia (and this is mainly where psychiatrists get involve), being interested in disturbances in emotion and behavior in general would suggest psychiatry is a good fit for you.
If you want to learn more about geriatric psychiatry, the AAGP annual meeting is in Hawaii next year and they have all expenses paid travel awards for med students to attend!
AAGP Scholars Program Information for Applicants