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Age-period-cohort effects on the development of cognitive impairment among the elderly

Zhu, Xinmei (2017) Age-period-cohort effects on the development of cognitive impairment among the elderly. Master's Thesis, University of Pittsburgh. (Unpublished)

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The objectives of the study were to investigate the effects of age, calendar period, and birth cohort on the development of cognitive impairment among the elderly, and to identify factors possibly moderating these effects. Harmonized data were drawn from two community-based cohort studies. A total of 3,021 participants, born after 1895, age 65 years or older with normal cognitive capacities were recruited during 1987-2008 and followed for more than 10 years. Cognitive capability was evaluated periodically using the Clinical Dementia Rating (CDR) scale. Incident mild cognitive impairment (MCI) was defined as the CDR value reaching 0.5. Age-period-cohort (APC) modelling approach was used to evaluate three time-varying effects on the development of MCI. Confounding and moderating effects of gender, education, and ApoE4 allele were also examined. Our analysis results showed that age was the most significant time-dependent factor affecting the MCI incident rates. Within the same calendar period and birth cohort, the MCI rate in the older elderly was significantly higher compared with the younger elderly population. A significant period effect was observed in which the MCI incidence rates were decreasing from the period of 1990-1994 through 2015 after controlling for age and birth cohort. No significant cohort effect was found. Gender showed no significant confounding or moderating effects. The age effects on MCI incidence rate was not moderated or confounded by education, while the period effects were significantly confounded by education. The cohort effect was significantly moderated by education. The cohort effects on MCI incidence rates for individuals who received HS education or higher education were different depending on the levels of education. ApoE4 allele did not show a significant moderating effect.
Public Health Significance
The APC model shows advantages over the traditional modelling approaches as it dissects the independent effects of age, period, and cohort. For public health, chronic disease prevalence often reflects a combination of processes that vary by these three factors. Better understanding the impacts of these time-dependent factors on disease rates help to guide hypotheses about etiologic mechanisms, and more importantly, guides researchers in conducting and presenting surveillance with the best practices.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Zhu, Xinmeixiz40@pitt.eduxiz40
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairChang, Chung-Chou
Committee MemberKurland, BrendaBFK10@pitt.eduBFK10
Committee MemberLin,; yal2005@gmail.comYAL14
Committee MemberDodge,
Date: 25 September 2017
Date Type: Publication
Defense Date: 9 June 2017
Approval Date: 25 September 2017
Submission Date: 25 July 2017
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 73
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Biostatistics
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Cognitive Impairment, Age-Period-Cohort Model
Date Deposited: 25 Sep 2017 14:25
Last Modified: 01 Sep 2018 05:15


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