A longitudinal study of cognitive decline in rural Tanzania: rates and potentially modifiable risk factors

Heward, Jessica; Stone, Lydia; Paddick, Stella-Maria; Mkenda, Sarah; Gray, William K.; Dotchin, Catherine; Kissima, John; Collingwood, Cecilia; Swai, Bernadetha; Walker, Richard

doi:10.1017/s1041610217002861

Cited by 30 publications

(31 citation statements)

References 35 publications

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“…Our findings are consistent with cross-sectional studies associating low education and illiteracy with higher prevalence of cognitive impairment and dementia in South Africa and other sub-Saharan African countries but inconsistent with those identifying sex/gender-based disparities [7-9, 13, 27, 39-41]. Our results are mostly consistent with a longitudinal study of cognitive decline over 2 years among adults aged 65 and over in a rural Tanzania [42].…”

Section: Discussionsupporting

confidence: 74%

Incidence of Cognitive Impairment during Aging in Rural South Africa: Evidence from HAALSI, 2014 to 2019

Kobayashi

Farrell²,

Langa

et al. 2021

Neuroepidemiology

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Introduction: Despite rapid population aging, there are currently limited data on the incidence of aging-related cognitive impairment in sub-Saharan Africa. We aimed to determine the incidence of cognitive impairment and its distribution across key demographic, social, and health-related factors among older adults in rural South Africa. Methods: Data were from in-person interviews with 3,856 adults aged ≥40 who were free from cognitive impairment at baseline in the population-representative cohort, “Health and Aging in Africa: a Longitudinal Study of an INDEPTH Community in South Africa” (HAALSI), in Agincourt sub-district, Mpumalanga province, South Africa (2014–19). Cognitive impairment was defined as scoring <1.5 standard deviations below the mean of the baseline distribution of orientation and episodic memory scores. Incidence rates and rate ratios for cognitive impairment were estimated according to key demographic, social, and health-related factors, adjusted for age, sex/gender, and country of birth. Results: The incidence of cognitive impairment was 25.7/1,000 person-years (PY; 95% confidence interval [CI]: 23.0–28.8), weighted for mortality (12%) and attrition (6%) over the 3.5-year mean follow-up (range: 1.5–4.8 years). Incidence increased with age, from 8.9/1,000 PY (95% CI: 5.2–16.8) among those aged 40–44 to 93.5/1,000 PY (95% CI: 75.9–116.3) among those aged 80+, and age-specific risks were similar by sex/gender. Incidence was strongly associated with formal education and literacy, as well as marital status, household assets, employment, and alcohol consumption but not with history of smoking, hypertension, stroke, angina, heart attack, diabetes, or prevalent HIV. Conclusions: This study presents some of the first incidence rate estimates for aging-related cognitive impairment in rural South Africa. Social disparities in incident cognitive impairment rates were apparent in patterns similar to those observed in many high-income countries.

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Section: Discussionsupporting

confidence: 74%

Incidence of Cognitive Impairment during Aging in Rural South Africa: Evidence from HAALSI, 2014 to 2019

Kobayashi

Farrell²,

Langa

et al. 2021

Neuroepidemiology

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“…Education, to a point of being literate, seems to have a protective effect against progression to symptomatic HAND in our study. A previous study in the older general population by our team identified never having attended school as significantly associated with cognitive decline over 2 years, with school attendance for as little as 1 year being protective 44 . Greater social interaction is thought to be associated with increased “cognitive reserve” 45 in studies of neurodegenerative dementias 46 .…”

Section: Discussionmentioning

confidence: 91%

Risk factors for symptomatic HIV‐associated neurocognitive disorder in adults aged 50 and over attending a HIV clinic in Tanzania

Eaton

Lewis

Kellett-Wright

et al. 2020

Int J Geriat Psychiatry

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Objectives HIV‐associated neurocognitive disorder (HAND), although prevalent, remains a poorly researched cause of morbidity particularly in sub‐Saharan Africa (SSA). We aimed to explore the risk factors for HAND in people aged 50 and over under regular follow‐up at a government HIV clinic in Tanzania. Methods HIV‐positive adults aged 50 years and over were approached for recruitment at a routine HIV clinic appointment over a 4‐month period. A diagnostic assessment for HAND was implemented, including a full medical/neurological assessment and a collateral history from a relative. We investigated potential risk factors using a structured questionnaire and by examination of clinic records. Results Of the cohort (n = 253), 183 (72.3%) were female and the median age was 57 years. Fifty‐five individuals (21.7%) met the criteria for symptomatic HAND. Participants were at a greater risk of having symptomatic HAND if they lived alone [odds ratio (OR) = 2.566, P = .015], were illiterate (OR 3.171, P = .003) or older at the time of HIV diagnosis (OR = 1.057, P = .015). Age was correlated with symptomatic HAND in univariate, but not multivariate analysis. Conclusions In this setting, HIV‐specific factors, such as nadir CD4 count, were not related to symptomatic HAND. The “legacy theory” of early central nervous system damage prior to initiation of anti‐retroviral therapy initiation may contribute, only in part, to a multifactorial aetiology of HAND in older people. Social isolation and illiteracy were associated with symptomatic HAND, suggesting greater cognitive reserve might be protective.

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“…After reading through the texts, 7 articles were further excluded because they examined broadly defined cognitive impairment and did not provide information about participants with dementia (Figure 1). Of the Seven excluded articles, one each was from Senegal (15), Cameroun ( 16), South Africa (17), Tanzania (18), and Rwanda (19), while the remaining two were from Nigeria (20,21).…”

Section: Resultsmentioning

confidence: 99%

Dominant and Modifiable Risk Factors for Dementia in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

2021

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Background: Sub-Saharan Africa (SSA) is projected to have a rapid increase in the number of people living with dementia by 2050. Yet, there is currently no robust evidence on the risk factors for dementia in the sub-region that could inform context specific interventions.Methods: We conducted a systematic review and meta-analysis of observational studies to determine the dominant and modifiable risk factors for dementia in SSA. We searched MEDLINE, EMBASE, PsychINFO, and African Journals Online using keywords for dementia and Alzheimer's disease as well as the.mp operator for all 47 SSA countries or regions. We included peer-reviewed original studies with epidemiological designs, conducted random effect meta-analysis and determined the dominant and modifiable risk factors for dementia using the inverse of variance method.Results: A total of 44 studies out of 2,848 met criteria for syntheses. The pooled annual incidence of dementia from 5,200 cohort risk years was 2.0% [(95% Confidence Interval (CI) = 1.0–4.0%)]. The pooled prevalence was 5.0% (95% CI = 2.0–7.0%). Older age was the dominant risk factor for both prevalent [(Standard error (S.E = 0.3, weight = 25.2%)] and incident dementia (S.E = 0.02, weight = 95.8%), while low educational attainment (S.E = 0.19, weight = 32.6%) and poor predementia cognitive functioning at baseline (S.E = 0.2, weight = 20.5%) were the best ranked modifiable risk factor for incident dementia.Conclusion: Low formal educational attainment which, in SSA, may represent a stable index of low socioeconomic position and health disadvantage over the life course, was the most prominent modifiable risk factor for incident dementia. Findings have implications for deliberate policies targeted at access to education across the life course as a primary prevention strategy against dementia in SSA.

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A longitudinal study of cognitive decline in rural Tanzania: rates and potentially modifiable risk factors

Abstract: This is one of the first studies of cognitive decline conducted in SSA. Rates of decline at two years were relatively high. Future work should focus on identification of specific modifiable risk factors for cognitive decline with a view to developing culturally appropriate interventions.

Cited by 30 publications

References 35 publications

Incidence of Cognitive Impairment during Aging in Rural South Africa: Evidence from HAALSI, 2014 to 2019

Incidence of Cognitive Impairment during Aging in Rural South Africa: Evidence from HAALSI, 2014 to 2019

Risk factors for symptomatic HIV‐associated neurocognitive disorder in adults aged 50 and over attending a HIV clinic in Tanzania

Dominant and Modifiable Risk Factors for Dementia in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

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