Cognitive impairment in the Amish: A four county survey

Background. The prevalence of probable dementia was determined in a rural, homogeneous community of Amish individuals in the Midwestern USA. The Amish are a genetically isolated group with a low level of formal education (≤ 8 years) and few exposures to modern life, who live in intergenerational settings and have strong social support networks. Methods. Using community directories, trained interviewers administered the Mini Mental State Examination (MMSE) and a medical history survey to all Amish over 64 years old in a four county area. Individuals with scores < 27 (out of a maximum of 30 points) were given additional neuropsychological tests. Results were reviewed by a neuropsychologist and subjects were classified with regard to probable cognitive impairment. Results. The MMSE scores were inversely related with age and directly with education. The Amish have higher MMSE scores than reported for the general US population. The overall prevalence of probable cognitive impairment for those over 64 years was 6.4%. The prevalence increased with age and lower education and was lowest among married individuals. Conclusions. The MMSE scores among the Amish were higher than the general population despite their low level of formal education. The lower level of cognitive impairment among the Amish could reflect a lack of inherited susceptibility to dementing diseases, or environmental factors characteristic of their traditional lifestyle. Even among this population with ≤ 8 years of formal education, education may protect against cognitive impairment.