The studies reviewed in this article seem to suggest that type O has the least amount of health risks compared to the other types. However, these findings, excluding those relating to malaria, are meant to serve as associations and not as a means of evidential proof for cause and effect.
There is a significant amount of research needed to be conducted in order to determine the exact link between the effect of blood type and risks of diseases. Until such research is available, it is advised that you work towards more practical lifestyle changes such as regular exercise, maintaining a healthy diet and not smoking in order to maintain good health and avoid illness.
It is also suggested that you go for regular screening tests with your doctor and always check any health issues and concerns you may have with a healthcare professional.