Cognitive Functioning and Associated Factors in Older Adults in South Africa

Article excerpt

Cognition can be divided into domains of ability including orientation, memory, executive function and language. (1) Cognitive function is influenced by many factors such as genes, home environment in childhood, education and occupation. (1) Cognitive decline is first detectable in the fifth decade of life, with age-related decline from this point onwards. (2)

There is little research on cognitive functioning and variability among older adults in South Africa. In various cross-sectional and longitudinal studies, better cognitive performance in older adults has been found to be associated with: (i) socioeconomic status (younger age, female or male gender, higher education, greater wealth, population group); (3-5) (ii) illness conditions and health status (fewer depressive symptoms, no hypertension, no cardiovascular disease, particularly heart failure, no type 2 diabetes, no insomnia, no malnourishment, better quality of life (QoL) and life satisfaction); (6-13) (iii) social coherence and contact (attendance at religious gatherings); (4,14) and (iv) healthy behaviour (physical activity, no smoking and moderate alcohol use). (15-20)

We aimed to investigate cognitive functioning and associated factors in a national probability sample of older South Africans who participated in the Study of Global AGEing and Adult Health (SAGE) in 2008.

Methods

In 2008 we conducted a national population-based cross-sectional study with a sample of 3 840 South African adults aged [greater than or equal to] 50 years. The SAGE two-stage probability sample design yielded national and sub-national estimates to an acceptable precision at provincial level, by locality type (urban and rural) and population group (black, coloured, Indian/Asian and white). The individual response rate among adults aged [greater than or equal to] 50 years was 77%.

We administered a questionnaire surveying socio-demographic characteristics and health variables, and conducted anthropometric and blood pressure measurements. The questionnaire was translated into the major languages of the participants (Afrikaans, Northern Sotho, Southern Sotho, Tsonga, Tswana, isiXhosa and isiZulu). Simultaneous translation was used for respondents who were interviewed in a language for which a formal translated version had not been produced, with emphasis on consistent translation of keywords and phrases. To ensure the quality of translation, a list of keywords and phrases provided by the World Health Organization (WHO) for translation and back-translation were translated from English into vernacular languages by the original translator, then back-translated into English by an independent translator who provided all possible interpretations. The back-translations were cross-checked with the original English version. If no match was found, both translator and back-translator were consulted to reach a final agreement on the best solution and changes to the translated questionnaire were made where necessary. The interview commenced with filter questions about memory, to allow the interviewer to assess whether the respondent was cognitively and physically able to complete the interview. If unable to do so, the interviewer attempted to administer the proxy respondent questionnaire, and the respondent was excluded from the sample. The SAGE survey was carried out in partnership between the National Department of Health (DoH), the Human Sciences Research Council (HSRC) and the WHO. The study was approved by the HSRC Research Ethics Committee and the DoH.

Cognitive capacity

Cognitive tests were used to measure cognitive performance and to measure objective indicators of various aspects of cognition. The tests, which together measured concentration, attention and immediate memory, and were intended to measure the cognitive domains most affected by impairment and the early stages of dementia, included:

* Verbal fluency (executive function). …