Mild cognitive impairment and progression to dementia

Dr. Roberts and colleagues(1) examined 2,719 elderly residents of Olmstead County, MN, every 15 months. The examinations showed that 534 persons had mild cognitive impairment, or MCI (see About MCI, following section). Some people had MCI when they were first seen. Others developed the condition later, so their problems were discovered during follow-up exams. The doctors knew from earlier studies that many people with MCI go on to develop dementia after a few years. But other people show little change over this time, while still others seem to recover or revert to appear cognitively normal when next examined. The doctors found that almost 40% of people with MCI reverted in this last way (a typical result). They wanted to know whether these reverters differed from other cognitively normal people in their risk of dementia. Over about 5 years of observation, they found that 65% of the reverters did go on to develop dementia. That was about 6 times the percentage of other cognitively normal people.