06.02.12. What risk factors have been associated with dementia? | South Africa
06.02.12. What risk factors have been associated with dementia? | South Africa
15 Aug 2022
In line with international research, dementia risk in South Africa was associated with older age (De Jager et al., 2017; Kalula & Petros, 2011). The landscape of age-associated risk of dementia with older age is however changing. HIV-associated dementia (HAD) is considered to be the most common cause of dementia among adults 40 years and younger (Rowland and Pedley, 2010 as in Robbins et al., 2011; Kalaria et al., 2008). Emerging research in South Africa on developing appropriate screening for HIV-associated dementia (HAD) has found that 80% of the study’s 65 participants were on average 40 years of age (range 19-68 years; SD 9.26) and screened positive for HAD (Robbins et al., 2011). Therefore, the expected risk of dementia with older age is changing with the sequelae of the high HIV/AIDS prevalence in South Africa.
Depending on the progression of the disease, 30-60% of people living with HIV (PLWH) will manifest some degree of neurocognitive disturbance, whereas an estimated 50% will develop a HIV-associated neurocognitive disorder (HAND) (Fogel et al., 2014; Grant, 2008). HIV-associated dementia (HAD) is recognised as the most severe form of HAND and identified as the most common neurocognitive consequence of untreated HIV infection (Robbins et al., 2011).
In a study validating the International HIV Dementia Scale in South Africa, a sample of 96 HIV-positive individuals who are not receiving ART, displayed greater impairment on a range of neuropsychological tests (including HAD) when compared to HIV-negative controls (Joska et al., 2011). Another study examining the rates of positive HIV-associated dementia (HAD) screens at a general medical clinic in the Western Cape Region found that in a sample of 65 HIV-positive participants, 80% (n=52) were at risk for having HAD (Robbins et al., 2011). These participants have been diagnosed with the HIV virus for just over 5 years and have been on ART for more than 3 years, with less than 90% adherence. Majority of participants were female (65%) and ranged between the ages of 19 and 68 (mean 40 yrs, SD 9.26). Significant relationships were found with known associated risk factors for HAD such as low CD4 count, the presence of an alcohol disorder, and a current alcohol dependence disorder (Robbins et al., 2011). Therefore, suggesting that HIV-positive South Africans on ART, with low CD4 count and adherence issues may be at a very high risk for developing HAD.
- Family history
The aetiology of AD/dementia are not fully understood yet; however, generic factors such as the apolipoprotein E (APOE) epsilon 4 (e4) allele) and having a family history of dementia has been linked to the development of the disease (Kowall et al., 2018; Meyer et al., 2016). It is believed that where there is a first degree relative with dementia, the risk in developing AD increases by 10-30% (Meyer et al., 2016). Genetic links to dementia in the African region is inconclusive as research in Sub-Saharan Africa on aetiology of dementia and AD has not supported these genetic associations found elsewhere (Olayinka & Mbuyi, 2016).
The incidence and prevalence of Alzheimer’s disease (AD) or dementia is not conclusively associated with sex, but research in developing countries suggest that it is more prone amongst women with increasing age (Kalaria et al., 2008; Meyer et al., 2016). However, the largest prevalence study in a South African rural community, to date, found no association between being female and screening positive for dementia, despite 68.6% of participants being female (De Jager et al., 2017). Given the known increased risk with increasing age, women are more likely to develop dementia as they tend to have longer life expectancies.
- High prevalence of stroke and associated risk factors
Stroke is a major cause of long term mortality and disability in developing countries (Kalaria et al., 2008). However, there is no compelling evidence that controlling for or modifying vascular risk factors can prevent dementia (Ramlall et al., 2013). However, clinical factors such as hypertension and cardiovascular diseases are commonly associated with dementia risk (Olayinka & Mbuyi, 2016). Although international prevalence research on developing countries suggest that vascular dementias are low, Kalula et al., (2010) found that vascular dementia (VaD) (28%) and mixed dementia (15%) had a higher prevalence in South Africa. This finding suggests that a high prevalence of stroke and associated risk factors (e.g., hypertension and cardiovascular diseases) require improved management within health care practices. A study describing the clinical and risk profile of a sample of older participants in Durban (Kwazulu-Natal) (n=140) who were assessed for dementia and mild cognitive impairment (MCI), found that vascular risk factors were most prevalent (Ramlall et al., 2013). Thirty-six point four (36.4%) percent of those who screened positive for dementia (n=38) had a history of stroke and 66.4% had hypertension (i.e. 36.7% in dementia and 57.9% in MCI) (Ramlall et al., 2013). Therefore, in the absence of specific, accessible treatment of dementia, researchers call for the optimum and aggressive management of vascular risk factors such as hypertension, diabetes, weight, and use of substances (e.g., smoking) (Ramlall et al., 2013; Wilson et al., 2011).
- Low levels of education and literacy
Globally, as well as in Sub-Saharan Africa, low literacy levels has been identified as a risk factor for dementia (Olayinka & Mbuyi, 2016). In certain communities in South Africa more than 80% of older persons people do not read or write (Kalaria et al., 2008). Low literacy is often linked to poverty or lower socio-economic status and therefore associated with constrained access to health care, poorer health, and increased risk of dementia (Kalaria et al., 2008). A cross-sectional community prevalence study has found a negative association between increasing education level and dementia, thus supporting the notion that formal education, cognitive reserve and resulting informed lifestyle choices, are protective against cognitive decline (De Jager et al., 2017). In fact, 69.8% of the 1394 participants had less than 7 years of education. The educational qualifications and better remuneration of caregivers in rural context in Kwazulu-Natal was also found to play a protective role in the care for persons with dementia, as it was found to guard against caregiver burden (Gurayah, 2015), and promote access to care resources.
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