The Ibadan Study Of Aging

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METHODS Sample selection, recruitment and follow-up The Ibadan Study of Aging (ISA) has been previously described (Gureje et al., 2007); we provide only a brief overview. Individuals were selected using stratified multistage cluster sampling from eight neighbouring states of the Yoruba-speaking region of Nigeria, representing approximately 25 million or about 22% of the total Nigerian population at the time of the study. From 15 strata, based on state and urban versus rural location, 43 Local Government Areas were selected as the primary sampling units (PSUs). Four secondary sampling units (SSUs) defined by numeration units of 50 to 70 housing units were systematically selected from each PSU (172 SSUs in total). A census was conducted within each of the selected SSUs and a random sample of 17 households with individuals aged 65 years or over selected from each SSU. One individual from each household was approached to participate in the study. For households with multiple eligible individuals (aged 65 years or over and fluent in Yoruba – the local language), one individual was selected using a Kish grid (Kish L, 1949). Up to five calls were made to contact the selected individual; and there was no replacement for those who could not be contacted or who refused to participate in the study. Baseline assessment was conducted between November 3, 2003, and August 27, 2004. Three annual follow-up waves were implemented in 2007, 2008 and 2009 Measures and Procedure Information on
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