Oxidative stress
Cognitive impairment has been attributed to oxidative stress, inflammatory reactions and changes in the cerebral microvasculature. The exact impact of each of these mechanisms in affecting cognitive aging is unknown. Oxidative stress is the most controllable risk factor and is the best understood. The online Merriam-Webster Medical Dictionary defines oxidative stress as, "physiological stress on the body that is caused by the cumulative damage done by free radicals inadequately neutralized by antioxidants and that is to be associated with aging." Hence oxidative stress is the damage done to the cells by free radicals that have been released from the oxidation process.