Abstract: Objective To evaluate the conversion rates from mild cognitive impairment(MCI) to Alzheimer disease(AD) in elderly veterans during an average of 5 years follow-up.Methods This study was a prospective cohort study based on diagnosis.The study subjects were derived from a prevalence investigation of MCI in Shijiazhuang,China,in the year 2001.A total of 216 MCI subjects(mean age,74.2 years) and other 2 302 normal cognitive(NC) subjects(mean age,73.9 years) were followed up for an average of 5 years.The diagnosis of dementia and AD were assessed by neurologists using the DSM-IV and NINCDS-ADRDA criteria.The main outcome measures were the annual conversion rates of MCI and NC subjects to AD,the relative risks(RR) of MCI and NC developed AD and 95% confidence interval(95% CI).The conversion rates were calculated using the person-year method.Results After 5 years,the mortality of MCI subjects was 7.9%,and for NC subjects,3.4% respectively(P=0.001).After 3 years,the conversion rate of MCI subjects to AD was 16.8%,and after 5 years,the conversion rate of MCI subjects to AD was 33.7%.The annual conversion rate of MCI subjects to AD was 6.7(95% CI=5.4～8.0) per 100 person-year,and for NC subjects,0.8(95% CI=0.6～1.0) per 100 person-year respectively,but no difference was found between male and female(P=0.62).The conversion rates of MCI subjects to AD were decreased with the elevation in degree of education(P=0.03).The relative risk of MCI subjects to AD was 8.1(95% CI=6.1～10.6,P<0.0001) times as compared with NC subjects.Conclusion The conversion rates of MCI subjects to AD in elderly veterans is very higher than the normal cognitive subjects.There are sufficient data to recommend the evaluation and clinical monitoring of the elderly persons with mild cognitive impairment due to their increased risk for developing AD.

Key words: mild cognitive impairment, Alzheimer disease, cohort studies