Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 10839 CHAPTER 2 | THE AGING BR AIN Proxy Informants Bias arises in surveys when respondents decline or are unable to participate because they are too sick. This can result in underestimating the true prevalence of health conditions like dementia. To address this form of attrition bias, family members of partici- pants in the HRS and ADAMS are often called upon to provide survey information on behalf of participants, serving as proxy respondents. Approximately 10% of HRS interviews are obtained through proxies, and a large proportion of ADAMS respondents with dementia provide information through proxies. Weir et al. (2011) compare results from HRS to those from the English Longitudinal Survey of Ageing (ELSA), which is based on the HRS but uses proxies much less often. In the HRS, proxy respondents are asked a series of questions about the respondent’s change in memory for various types of information in the last two years. Use of proxies in the HRS leads to significantly higher overall response rates and virtually eliminates attrition bias in the estimation of cognitive function. Informant Reports Another source of information that can be used to improve the accuracy of dementia determi- nation is the informant report. ADAMS asks a close family member to complete an additional questionnaire about the main survey participant. The informant is most often a family member involved in caregiving. The informant also serves as the proxy respondent if one was needed. Potential racial bias in cognitive measures is a concern both for self-reported and proxy information. Potter et al. (2009) investigate this in ADAMS and find no evidence of racial bias in self-reported information. They also compare in- formant reports of African Americans and Whites in ADAMS. Results for dementia reveal no signif- icant racial differences. However, African Ameri- can informants are much less likely than Whites to identify symptoms corresponding to CIND in their family members with this condition. The First National Data Reliable data on dementia incidence and prevalence is critical for establishing benchmarks against which to measure population-wide changes over time. ADAMS provides the first national data on the prevalence of clinically diagnosed dementia and CIND. A random sample of 1,770 HRS participants aged 70 years or older in 2001 were invited to take part in ADAMS. The sample was stratified on five levels of cognitive func- tioning based on cognitive scores from the HRS. The cognitively normal group was further stratified by age (70 to 79, and 80 or older) and sex in order to ensure adequate numbers in each of these subgroups. A nurse and a neuropsychology technician conducted interviews and assessments in the homes of ADAMS participants. The information collected in the home was then reviewed by a board of qualified scientists and medical doctors to determine a diagnosis. The medical team deter- mined three general categories: normal cognition, CIND and dementia. Dementia often arises from different medical conditions, so dementia was further categorized as dementia, AD and vascular dementia (VaD). Using these landmark data, Plassman et al. (2007) report the first national estimates of the prevalence of dementia and dementia subtypes in individuals over the age of 70.