Mild cognitive impairment: incidence and risk factors: results of the leipzig longitudinal study of the aged.

OBJECTIVES

To provide information on age- and sex-specific incidence rates of mild cognitive impairment (MCI) and risk factors for incident MCI.

DESIGN

Prospective longitudinal cohort.

SETTING

Leipzig Longitudinal Study of the Aged, a population-based German study of the epidemiology of dementia and mild cognitive impairment.

PARTICIPANTS

At baseline, 1,692 subjects aged 75 and older were included in the sample.

MEASUREMENTS

Trained psychologists and physicians conducted structured clinical interviews including neuropsychological assessment and questions about sociodemographics, familial history of dementia, activities of daily living, subjective memory impairment, and lifestyle (alcohol consumption, smoking) at participants' homes. Structured third-party interviews were conducted with proxies. Incidence was calculated according to the person-years-at-risk method. Cox proportional hazards models were used to examine the association between risk factors and incident MCI.

RESULTS

During an 8-year follow-up period, 26.4% (n=137) of the 519 study participants (population at risk) were identified as incident MCI cases (person-years=1,791.1). The overall incidence rate of MCI was 76.5 (95% confidence interval=64.7-90.4) per 1,000 person-years. Older age, subjective memory impairment, impairment in instrumental activities of daily living, and antecedent lower cognitive performance were found to be significantly associated with the development of future MCI.

CONCLUSION

MCI is highly incident in the elderly population. For the purpose of early detection of dementia, subjective memory impairment should be taken seriously as a possible prestage of MCI.