Prevalence estimates of dementia in older adults in rural Kilimanjaro 2009–2010 and 2018–2019: is there evidence of changing prevalence?

Abstract

Introduction Although limited, existing epidemiological data on dementia in sub‐Saharan Africa indicate that prevalence may be increasing; contrasting with recent decreases observed in high‐income countries. We have previously reported the age‐adjusted prevalence of dementia in rural Tanzania in 2009–2010 as 6.4% (95% confidence interval [CI] 4.9–7.9) in individuals aged ≥70 years. We aimed to repeat a community‐based dementia prevalence study in the same setting to assess whether prevalence has changed. Methods This was a two‐phase door‐to‐door community‐based cross‐sectional survey in Kilimanjaro, Tanzania. In Phase I, trained primary health workers screened all consenting individuals aged ≥60 years from 12 villages using previously validated, locally developed, tools (IDEA cognitive screen and IDEA‐Instrumental Activities of Daily Living questionnaire). Screening was conducted using a mobile digital application (app) on a hand‐held tablet. In Phase II, a stratified sample of those identified in Phase I were clinically assessed using the DSM‐5 criteria and diagnoses subsequently confirmed by consensus panel. Results Of 3011 people who consented, 424 screened positive for probable dementia and 227 for possible dementia. During clinical assessment in Phase II, 105 individuals met DSM‐5 dementia criteria. The age‐adjusted prevalence of dementia was 4.6% (95% CI 2.9–6.4) in those aged ≥60 years and 8.9% (95% CI 6.1–11.8) in those aged ≥70 years. Prevalence rates increased significantly with age. Conclusions The prevalence of dementia in this rural Tanzanian population appears to have increased since 2010, although not significantly. Dementia is likely to become a significant health burden in this population as demographic transition continues.

Patient and caregiver experiences of living with dementia in Tanzania

“…All 14 people with dementia who took part in the psychosocial intervention, and all but two caregivers, consented to a qualitative interview, which reduces selection bias from the initial sample. Additionally, the mean age of people with dementia in our sample (72.6 years) and predominance of Chagga tribe origin was comparable to a recent study showing an increasing prevalence of dementia over the last 10 years in the Kilimanjaro region (Yoseph et al, 2021).…”

Dementia Prevalence and Risk Factors

“…Community-based studies may report higher rates than hospital-based studies as they include individuals who live rurally or with very severe disease who may not be able to travel to the hospital. Our rate is lower than the 2013 estimate of Longdon et al 12 (6.4%), however, slightly higher than the 2021 estimate of Yoseph et al 16 (4.6%) who conducted community-based studies in the Hai District in Tanzania, using DSM-IV and DSM-V criteria respectively (Fig. 2).…”

“…7 In 2021, the same authors estimated prevalence to be 4.6% (95% CI: 2.9-6.4) using The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) criteria. 16 One further estimate was reported by Mubangizi et al 10 who found the prevalence of probable dementia to be 20% in rural Uganda when using the Community Screening Interview for Dementia (CSI-D).…”

“…In 2013 a cross-sectional community-based study was conducted in the Hai District in Tanzania of 1198 people over 70 years old, reporting age-adjusted prevalence of 6.4% (95% CI: 4.9-7.9) using The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria 12 and 21.6% (95% CI: 17.5-25.7) using 10/66 Dementia Research Group criteria 7 . In 2021, the same authors estimated prevalence to be 4.6% (95% CI: 2.9-6.4) using The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) criteria 16 . One further estimate was reported by Mubangizi et al 10 who found the prevalence of probable dementia to be 20% in rural Uganda when using the Community Screening Interview for Dementia (CSI-D).…”

Dementia in Africa: Current evidence, knowledge gaps, and future directions

“…Hence, more epidemiological studies are needed in Africa that will accurately track the secular trends of cognitive impairment and dementia and dementia subtypes in Africa. Community‐based studies in Tanzania have reported worsening cognitive decline over 2 years of follow‐up 161 and increased prevalence of dementia from 6.4% to 8.9% in a rural cohort of older persons > 70 years over a 9‐year interval and using the same methods of cognitive assessment 162 . This is in contrast to declining trends of dementia reported in high‐income countries.…”