Tai Chi started life as a martial art in China in the 13th century. Now, it is practised as a health-promoting exercise. It is ideal for older people because it is a low impact exercise
A recent report suggests that Tai Chi may improve balance and reduce falls amongst Parkinson's sufferers. 195 people with Parkinson's met twice a week for six months. They split into three groups doing strength building exercises or stretching or Tai Chi. After six months, those doing Tai Chi were stronger and better balanced than the others. They also had significantly less falls and slower rates of decline in motor control.
Source: Tai Chi and Postural Stability in Patients with Parkinson's Disease. Fuzhong et al Feb 2012
However, some doubt has been expressed over the validity of this study.
Overall, the present consensus appears to confirm that tai chi may do some good and it is very likely that it will not do any harm.