Prevalence and correlates of neurocognitive impairment among older persons in rural Eastern Uganda – npj Dementia
In multivariable regression analyses, we found that completion of primary school or higher, being overweight or obese, using firewood or other fuels, being Pentecostal or other religion, or being currently married were protective factors against probable neurocognitive impairment. Age 80 years or older was a significant risk factor for probable neurocognitive impairment. These protective factors were still statistically significant after removing the socio-demographic covariates (Table 3, Fig. 1).
This study aimed to estimate the prevalence and the correlates of dementia among older people in rural eastern Uganda. We present the first study on neurocognitive impairment and dementia prevalence in a rural eastern Ugandan population, and one of the only indoor-to-door prevalence studies among community-dwelling older adults in Uganda using a regionally validated cognitive screening tool for illiteracy or low literacy levels. The prevalence of possible or probable dementia was 12%, a finding higher than what has been reported from an earlier systematic review of dementia in Africa. Though other studies conducted in Uganda reported a prevalence of 20%, this difference could be accounted for by the instruments used that may not have assessed how functional impairment accompanies dementia.
Our study identified several key protective factors that may lower the risk of neurocognitive impairment, including higher formal education, higher BMI, and being currently married, after controlling for covariates that were statistically significant in the bivariate comparison. We did not find that known risk factors, such as hypertension, hyperglycemia, obesity, social isolation, or depression, were statistically significant in the multivariable regression analyses. However, we found that important risk factors, such as female sex, depression, being underweight, and currently or formerly smoking, were associated with significantly higher frequency of neurocognitive impairment.
Our results suggest that having a normal weight or being obese, compared with being underweight, could be protective of dementia. According to the 2024 Lancet Commission on dementia, obesity is a modifiable risk factor for dementia, which, when eliminated, could lead to a 1% reduction in cases of dementia. In the United States, however, longitudinal associations indicated that an obese BMI was associated with a less steep decline in motor function in men with HIV, whereas in HIV-negative men, obesity was associated with a greater decline in motor function, learning, and memory. WC, or central obesity, showed similar patterns of associations. Other data suggest that inadequate nutrition can influence the progression of Alzheimer's disease. In older adults, malnutrition often reflects a trajectory of declining health and reduced quality of life, characterized by inadequate dietary intake, muscle wasting, poor appetite, and unintentional weight loss, and is often driven by social and physical factors such as loss, dependency, loneliness, and chronic illness.
In sub-Saharan Africa, prevalence estimates of malnutrition among older adults range from 6% to 48%, and pooled estimates show rates of undernutrition as high as 18%. In some low socio-economic settings, prevalence may reach up to 28.4%, with the highest rates often reported in rural and economically disadvantaged communities. In this context, a higher body mass index in this setting could indicate better nutrition and greater resilience among older adults. The doubling of overweight and obesity prevalence in Ugandan men and women from 2011 to 2022 further highlights changing nutritional patterns that may influence dementia risk. These findings underscore the importance of considering both overnutrition and undernutrition for dementia risk, particularly in regions where malnutrition remains prevalent among older adults.
Social engagement is a critical determinant of cognitive health, yet older adults in Uganda often experience reduced social contact due to widowhood and family migration patterns. Loneliness and social isolation have been linked to dementia in various studies. Loneliness can be categorized as emotional loneliness, which involves a lack of an attachment figure and feelings of isolation even when not alone, and social loneliness, which refers to the absence of a social network or community belonging. For instance, a meta-analysis involving 51 longitudinal cohort studies and 102,035 participants aged 50 and older found that high social contact was associated with better cognitive function. Some studies suggest the relationship may be mediated by depressive symptoms, which account for approximately 75% of this connection. Another UK-based 28-year follow-up study of 10,308 people showed that frequent social contact at age 60 reduced dementia risk over 15 years, independent of socioeconomic and lifestyle factors. Individuals with limited social networks, low frequency of social contact, or inadequate social support are at higher risk for cognitive decline and dementia. One US-based study found that loneliness was associated with poorer cognitive performance in executive function and processing speed among older people with HIV. In Uganda, where traditional family structures are increasingly disrupted, promoting social engagement could serve as a protective factor against dementia. Our study found that being currently married and being Pentecostal were each protective factors lowering risk of neurocognitive impairment, but living alone and being socially isolated were not statistically significant, demonstrating that strong bonds, such as those in marriage, help lower neurocognitive risk in this population.
Religious affiliation is known to provide regular social interaction, which leads to cognitive stimulation, which has been shown to be associated with better cognitive function in older adults. Religious participation can also strengthen social support networks and foster a sense of belonging and purpose, which may be factors protecting against life stressors and promote emotional well-being, which may protect against cognitive impairment. Regular involvement in faith activities also offers structured routines and complex mental engagement that can build cognitive reserve over time. Pentecostals may have higher religiosity and more frequent engagement in communal worship compared with other religions, which may influence the relationship between religion and cognition seen in our study.
Although depression was not a significant risk factor in multivariable regression analyses, we found that 26.7% of those with neurocognitive impairment had moderate to severe depression (compared with 13.1% of those without neurocognitive impairment), highlighting that depression may be a significant risk factor. Recently, global research has identified depression as a potential risk factor for dementia, with substantial evidence linking late-life depressive symptoms to increased dementia risk. A meta-analysis of 32 studies, encompassing 62,598 participants, found that depression nearly doubles the risk of dementia over follow-up periods ranging from 2 to 17 years. A 14-year longitudinal study of 4,922 older men also found that depression increased the incidence of dementia by 1.5 times. However, this relationship was strongest among those who developed dementia within five years of experiencing depression, suggesting that depression may be an early symptom of dementia rather than solely a risk factor. In Uganda, the impact of depression on dementia risk is of particular concern, given the high prevalence of underdiagnosed and undertreated mental health conditions.
Another known risk factor for neurocognitive impairment found in our study was having no formal education compared with primary school or higher. Lower levels of formal education represent a significant and modifiable risk factor for neurocognitive impairment. Numerous studies, including hospital-based surveys of older Ugandan adults, have demonstrated that having no formal education is strongly associated with greater odds of cognitive impairment and dementia. One study in a tertiary care hospital reported that lower education was significantly linked to severe neurocognitive impairment among adults aged 60 years and older. Community surveys also highlight this relationship. For example, in a cohort of older Ugandans, individuals with any formal schooling were about 46% less likely to be at risk of dementia compared to those with no education. Moreover, a systematic review across sub-Saharan Africa showed that low educational attainment is among the most prominent modifiable risk factors for incident dementia in the region. The concept of "cognitive reserve" is thought to protect against age-related neurodegeneration, delaying the onset of clinical decline. In Uganda, where formal schooling may be inaccessible in rural areas and particularly among older adults, a lack of formal education contributes to low cognitive reserve, increasing risk of neurocognitive impairments. These findings emphasize the potential of educational interventions, such as late-life or adult-education programs, which have been demonstrated in other studies to be protective against neurocognitive impairments.
Our study also found that using firewood, compared with paraffin lamp or electricity, was a protective factor for neurocognitive impairment. Exposure to household and ambient air pollution is known to be a risk factor for dementia. For example, studies in India, China, and Mexico have consistently found that using polluting cooking fuels is linked with poorer cognitive function and greater cognitive decline. Firewood use may be a proxy for more active lifestyles, such as farming or fishing, which may be protective against cognitive impairment. Paraffin lamps may be a source of indoor air pollution (particulate matter 2.5), which is known to be a risk factor for dementia. For example, one study in rural Uganda reported that use of open-wick kerosene lamps generated about twice as much PM2.5 and nearly five times as much black carbon in living rooms compared with cleaner options like solar lighting, even when controlling for household income. Moreover, there may be variables that are highly associated with firewood use that were not captured in this study.
Despite these findings, our study has some strengths and limitations. First, our study was a cross-sectional and door-to-door population-based study, limiting applicability to clinic or hospitalized populations. Second, our primary outcomes, neurocognitive impairment or dementia, were based on brief cognitive screening tools and not on a complete battery of neuropsychological tests. However, the tool utilized had been validated for low literacy and illiterate populations from neighboring Tanzania, strengthening its applicability to our population, but it has not been validated in rural eastern Uganda. Third, our study was limited to two rural districts of eastern Uganda, limiting generalizability to other regions of Uganda or other countries. Next, the CAGE questionnaire does not capture overall alcohol consumption patterns, and future studies may use a more detailed questionnaire. Moreover, although we adjusted for risk factors significant in the bivariate comparisons, there may have been unmeasured covariates, such as adverse social determinants of health, that were unmeasured.
This was the first large cross-sectional door-to-door population-based study of older community-dwelling adults in two rural eastern Uganda districts. Second, our study demonstrated important protective factors, including being currently married, being underweight, and having a higher education, as factors that reduced dementia risk. These factors are important because they highlight the need to improve the nutrition of older adults in the region in order to prevent long-term neurodegenerative consequences. Other factors such as implementing a late-life education program, may help mitigate the onset of cognitive decline. Cognitive stimulation therapy (CST), a structured psychosocial group intervention for people with dementia, has been adapted and piloted in sub-Saharan African settings, and has been followed by significant improvements in cognition. Lastly, forming strong emotional bonds, such as through a healthy marriage, may also help prevent the onset of cognitive decline. Future studies would propose piloting interventions in the community to address these factors and mitigate cognitive decline in these rural regions of sub-Saharan Africa.
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