There is an increasing amount of research into the medical benefits of Tai Chi and Qigong practice. Here are some links to sources of information and some items which give you an idea of the extent that Tai Chi's benefits are being measured.
Can Tai Chi help knee osteoarthritus? A 2017 study conducted by Tufts University showed that 12 weeks practice resulted in equal improvement as 12 weeks of physical therapy. In addition the Tai Chi group also showed significantly more improvement than the physical therapy group when it came to symptoms of depression and quality of life.
Elderly people are 37% less likely to be injured in a fall after exercises such as Tai Chi, and 67% less likely to suffer a fracture. (The British Medical Journal).
The Medical Research Library maintained by 'World Tai Chi Day' contains a comprehensive list of the results of research on different health conditions ranging from aches through Parkinsons to weight loss.
The Harvard Medical School has long been involved in designing research studies to measure and compare the practice of Tai Chi for health. Peter Wayne's excellent book The Harvard Medical School Guide to Tai Chi details many of the findings and describes some simple Tai Chi routines.
This article in the Nursing Times describes a rheumatology nurse's experience of how Tai Chi classes helped people with chronic inflammatory and autoimmune conditions.
This 2010 Comprehensive Review of Health Benefits of Qigong and Tai Chi compared research onTai Chi and Qigong with a range of control groups. It contains a good description of what each are and their differences. It found significant positive outcomes for caridopulmonary fitness, physical function, falls and balance, quality of life, psychological and patient reported outcomes ie. feeling better.
This 2018 research project reported in Medical News Today demonstrates that Tai Chi could be considered a viable alternative to standard treatement for COPD.
Trust Me I am A Doctor's Michael Mosely tries out Tai Chi for the first time. He found that Tai Chi had a positive effect on his heart rate, blood and blood vessels. All good.