CWRU just published a study on the impact of caregiving on the adult child. This study was conducted by nurse researchers at Case Western Reserve University. If you are or have been a caregiver you are well aware the problems caregivers face such as back problems, fatigue, and depression. The study supports this and especially focuses on the higher levels of depression.
Previous studies done at The Ohio State University focused on the physical impact. They found that the caregiver actually shortened their life expectancy for 3 years. The caregiver is often called the "hidden patient". The primary caregiver of an Alzheimer's patient, often dies before the patient. This probably just documents what you are already feeling!
As a caregiver it is important to find time to take care of yourself. Take 1 hour per day to revive with a good book, gardening, and meeting friends for coffee. Try eating a well-balanced diet and exercising most days. Keep your stress levels as low as possible by prioritizing, making lists, establishing routines, and delegating tasks to other people. Find a support group online or better yet, locally. Most importantly ask for and accept help.