Cognitive function and cardiometabolic disease risk factors in rural South Africa: baseline evidence from the HAALSI study

DNA Methylation Mediates the Association Between Cardiometabolic Risk Factors and Cognition: Findings From the Health and Retirement Study

The association between cardiometabolic risk factors and cognitive function has been well documented, but the underlying mechanisms are not fully understood. This longitudinal study aimed to investigate the potential mediating role of DNA methylation in this association. We conducted the analyses in 3 708 participants (mean [standard deviation {SD}] age: 67.3 [9.5], women: 57.9%) from the Health and Retirement Study who were assessed in the 2014-2020 waves, had Infinium Methylation EPIC BeadChip methylation assays from the 2016 Venous Blood Study, and had cognitive assessment between 2016 and 2020. Causal mediation analyses were used to test the mediation role of DNA methylation in the associations between cardiometabolic risk factors and cognition, adjusting for demographic, socioeconomic, and lifestyle factors. Hypertension (-0.061 in composite cognitive z-score; 95% confidence interval [CI: -0.119, -0.004]) and diabetes (-0.134; 95% CI: [-0.198, -0.071]) were significantly associated with worse cognitive function while abnormal body weight and hypercholesterolemia were not. An increased number of cardiometabolic risk factors was associated with worse cognitive function (p = .002). DNA methylation significantly mediated the association of hypertension (mediated effect on composite cognitive z-score: -0.023; 95% CI: -0.033, -0.014), diabetes (-0.022; 95% CI: -0.032, -0.014), and obesity (-0.021; 95% CI: -0.033, -0.011) with cognitive function, whereas the mediation effect was not observed for having hypercholesterolemia. The estimated proportions mediated were 37.4% for hypertension and 16.7% for diabetes. DNA methylation may be an important mediator linking cardiometabolic risk factors to worse cognition and might even provide a potential target for dementia prevention.

The impacts of social determinants of health and cardiometabolic factors on cognitive and functional aging in Colombian underserved populations

Global initiatives call for further understanding of the impact of inequity on aging across underserved populations. Previous research in low- and middle-income countries (LMICs) presents limitations in assessing combined sources of inequity and outcomes (i.e., cognition and functionality). In this study, we assessed how social determinants of health (SDH), cardiometabolic factors (CMFs), and other medical/social factors predict cognition and functionality in an aging Colombian population. We ran a cross-sectional study that combined theory- (structural equation models) and data-driven (machine learning) approaches in a population-based study (N = 23,694; M = 69.8 years) to assess the best predictors of cognition and functionality. We found that a combination of SDH and CMF accurately predicted cognition and functionality, although SDH was the stronger predictor. Cognition was predicted with the highest accuracy by SDH, followed by demographics, CMF, and other factors. A combination of SDH, age, CMF, and additional physical/psychological factors were the best predictors of functional status. Results highlight the role of inequity in predicting brain health and advancing solutions to reduce the cognitive and functional decline in LMICs.

The path between socioeconomic inequality and cognitive function: A mediation analysis based on the HAALSI cohort in rural South Africa

Background

Socioeconomic position (SEP) strongly predicts late-life cognitive health, yet the pathways between SEP and cognitive function remain unclear. This study assessed whether and to what extent the association between SEP and cognitive function in the adult population in rural South Africa is mediated by some health conditions, behavioral factors, and social capital factors.

Methods

In this cross-sectional study, we used data from the 2014–15 “Health and Aging Africa: A Longitudinal Study of an INDEPTH Community in South Africa” (HAALSI) cohort, including 5,059 adults aged 40+ years from the Agincourt sub-district in Mpumalanga Province, South Africa. SEP, the independent variable, was measured based on ownership of household goods. Cognitive function, the dependent variable, was assessed using questions related to time orientation and immediate and delayed word recall. We used the multiple-mediation analysis on 4125 individuals with complete values on all variables to assess the mediating roles of health conditions (hypertension, diabetes, obesity, and disability), behavioral factors (leisure physical activity, alcohol consumption, and tobacco smoking), and social capital factors (community's willingness to help, trust, sense of safety, and social network contact) in the association between SEP and cognitive function.

Results

Compared to adults in the poorest wealth quintile, those in the richest wealth quintile had better cognition (β = 0.903, p < 0.001). The mediation analysis revealed that health conditions mediated 20.7% of the total effect of SEP on cognitive function. In comparison, 3.3% was mediated by behavioral factors and only 0.7% by social capital factors. In the multiple-mediator model, 17.9% of the effect of SEP on cognitive function was jointly mediated by health conditions, behavioral factors, and social capital factors.

Conclusion

Low socioeconomic position is a significant factor associated with poor cognitive function among adults aged 40 years and above in South Africa. Health conditions mainly mediate the effects between SEP and cognitive function. Therefore, actions to prevent and control chronic health conditions can serve as the entry point for intervention to prevent poor cognitive function among people with low socioeconomic status.

Early Stage and Established Hypertension in Sub-Saharan Africa: Results From Population Health Surveys in 17 Countries, 2010-2017

BACKGROUND

Multiple studies have reported a high burden of hypertension in sub-Saharan Africa, but none have examined early stage hypertension. We examined contemporary prevalence of diagnosed, treated, and controlled stage I (130-139/80-89 mm Hg) and II (≥140/90 mm Hg) hypertension in the general population of sub-Saharan Africa.

METHODS

We analyzed World Health Organization STEPwise Approach to Noncommunicable Disease Risk Factor Surveillance surveys from 17 sub-Saharan Africa countries including 85 371 respondents representing 85 million individuals from 2010 to 2017. We extracted demographic variables, blood pressure, self-reported hypertension diagnosis/awareness, and treatment status to estimate prevalence of stage I and II hypertension and treatment by country. We examined diagnosis and treatment trends by national sociodemographic index, a marker of development.

RESULTS

Stage I hypertension prevalence (regardless of diagnosis/treatment) was >25% in 13 of 17 countries, highest in Sudan (35.3% [95% CI, 33.7%-37.0%]), and lowest in Eritrea (20.2% [18.8%-21.6%]). Combined stages I and II hypertension prevalence was >50% in 13 countries; <20% were diagnosed in every country. Treatment among those diagnosed ranged from 26% to 63%, and control (<140/90 mm Hg) from 4% to 17%. In 8 of 9 countries reporting on behavioral interventions (eg, salt reduction, weight loss, exercise, and smoking cessation), <60% of diagnosed individuals received counseling. Rates of diagnosis, but not treatment, were positively associated with sociodemographic index (P=0.008), although there was substantial variation between countries even at similar levels of development.

CONCLUSIONS

Hypertension is common in sub-Saharan Africa but rates of diagnosis, treatment, and control markedly low. There is a large population with early stage hypertension that may benefit from behavioral counseling to prevent progression. Our analyses suggest that success in population hypertension care may be achieved independently of socioeconomic development, highlighting a need for policymakers to identify best practices in those countries that outperform similar or more developed countries.

Obesity and Neurocognitive Performance of Memory, Attention, and Executive Function

Background: Obesity has been linked to an increased risk of dementia in the future. Obesity is known to affect core neural structures, such as the hippocampus, and frontotemporal parts of the brain, and is linked to memory, attention, and executive function decline. The overwhelming majority of the data, however, comes from high-income countries. In undeveloped countries, there is little evidence of a link between obesity and neurocognition. The aim of this study was to investigate the effects of BMI on the key cognitive functioning tasks of attention, memory, and executive function in a South African cohort. Methods: A total of 175 females (NW: BMI = 18.5–24.9 kg/m2 and OB: BMI > 30.0 kg/m2) aged 18–59 years (M = 28, SD = 8.87 years) completed tasks on memory, attention, and executive functioning. Results: There was a statistically significant difference between the groups. The participants who had a BMI corresponding with obesity performed poorly on the tasks measuring memory (p = 0.01), attention (p = 0.01), and executive function (p = 0.02) compared to the normal-weight group. Conclusions: When compared to normal-weight participants, the findings confirm the existence of lowered cognitive performance in obese persons on tasks involving planning, decision making, self-control, and regulation. Further research into the potential underlying mechanism by which obesity impacts cognition is indicated.

Association between the Erythrocyte Membrane Fatty Acid Profile and Cognitive Function in the Overweight and Obese Population Aged from 45 to 75 Years Old

Dietary fatty acid intake is closely related to the cognitive function of the overweight and obese population. However, few studies have specified the correlation between exact fatty acids and cognitive functions in different body mass index (BMI) groups. We aimed to explain these relationships and reference guiding principles for the fatty acid intake of the overweight and obese population. Normal weight, overweight, and obese participants were recruited to receive a cognitive function assessment and dietary survey, dietary fatty acids intake was calculated, and the erythrocyte membrane fatty acid profile was tested by performing a gas chromatography analysis. The percentages of saturated fatty acids (SFAs) in the obese group were higher, while monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) were lower than in the normal weight and overweight groups. In the erythrocyte membrane, the increase of n-3 PUFAs was accompanied by cognitive decline in the overweight group, which could be a protective factor for cognitive function in the obese group. High n-6 PUFAs intake could exacerbate the cognitive decline in the obese population. Dietary fatty acid intake had different effects on the cognitive function of overweight and obese people, especially the protective effect of n-3 PUFAs; more precise dietary advice is needed to prevent cognitive impairment.

The Association of Reproductive Aging with Cognitive Function in Sub-Saharan African Women

Life expectancy in sub-Saharan African women is increasing, and by the late 2020s an estimated 76% of postmenopausal women globally will be living in developing countries. Menopause transition has been associated with cognitive decline in a wide range of studies, but data on cognition and reproductive aging are lacking in sub-Saharan African women. Approximately 72 million people in the region are expected to suffer from dementias and neurocognitive decline by 2050. Studies show that compromised cognitive health in low-income countries has significant implications for adult quality of life and socioeconomic development. There is now an urgent need to further examine risk factors for cognitive decline in these aging women and to understand the ability of public health programs to diagnose and treat cognitive dysfunction. This review examines studies assessing cognition and aging in sub-Saharan African adults, while addressing the significant research gaps. It examines data on the association of the menopause transition with cognitive function and describes how validated tools should be available to assess both menopausal stage and symptoms. Culturally appropriate and validated neurocognitive measures are required to better understand the relationship of reproductive aging with cognition. Longitudinal population-based studies are needed to assess the effect of lifestyle interventions, such as diet and exercise, on cognitive health in sub-Saharan African populations, with an emphasis on women as they transition into menopause.

Association of Physical Activity With Cognitive Function Among Older Adults in Rural Sichuan, China

The purpose of this study was to explore the relationship between total physical activity and different dimensions of cognitive function (orientation, attention, and memory) among older adults in rural Sichuan, China. This cross-sectional study involved 715 older adults (average age of 72 years). Total PA was measured by the Physical Activity Scale for the Elderly, and cognitive function was assessed by the Telephone Interview for Cognitive Status (TICS) questionnaire. The multivariate linear regression analysis indicated that total PA and household PA were significantly associated with the overall Telephone Interview for Cognitive Status score (β = 0.143, p < .001; β = 0.115, p = .002, respectively), the orientation dimension (β = 0.142, p < .001; β = 0.131, p = .001, respectively), and the memory dimension (β = 0.179, p < .001; β = 0.134, p = .001, respectively). The study showed a positive association between total PA, household PA, and cognitive function in older adults, especially in the orientation dimension and the memory dimension of cognitive function.

Apolipoprotein E Genetic Variation and Its Association With Cognitive Function in Rural-Dwelling Older South Africans

Apolipoprotein E (APOE) 𝜀4 allele carrier status is well known for its association with an increased likelihood of developing Alzheimer’s disease, but its independent role in cognitive function is unclear. APOE genetic variation is understudied in African populations; hence, this cross-sectional study in a rural South African community examined allele and genotype frequencies, and their associations with cognitive function. Cognitive function was assessed using two different screening methods to produce a total cognition score and four domain-specific cognition scores for verbal episodic memory, executive function, language, and visuospatial ability. Cognitive phenotype and APOE genotype data were used to determine whether APOE variation was significantly associated with cognitive function in this population. Observed allele frequencies for 1776 participants from the HAALSI study [age 40–80years (mean=56.19); 58.2% female] were 58.1% (𝜀3), 25.4% (𝜀4) and 16.5% (𝜀2). Allele distributions were similar to the African super population, but different from all non-African super populations from the 1,000 Genomes Project. The 𝜀3 homozygous genotype was most common (34.9%) and used as the base genotype for comparison in regression models. Four models were tested for each of the five cognitive phenotypes to explore association of APOE variation with cognitive function. In the first model assessing association with all genotypes for all individuals, marginally significant associations were observed for 𝜀2 homozygotes where executive function scored higher by ~0.5 standard deviations (p=0.037, SE=0.23), and for 𝜀3/𝜀4 heterozygotes where visuospatial ability scores were lower (p=0.046, SE=0.14). These did not survive correction for multiple testing. Regional African population differences were observed at the APOE locus. Marginally, significant associations between APOE genotype, and executive function and visuospatial ability indicate the need for larger studies to better examine these associations in African populations. Furthermore, longitudinal data could shed light on APOE genetic association with rate of change, or decline, in cognitive function.

The Longitudinal Association Between Cardiovascular Risk and Cognitive Function in Middle-Aged and Older Adults in China: A Nationally Representative Cohort Study

Objective: China has the largest population living with dementia, causing a tremendous burden on the aging society. Cardiovascular disease (CVD) may trigger a cascade of pathologies associated with cognitive aging. We aim to investigate the association between cardiovascular risk (CVR) factors and cognitive function in the nationally representative cohort in China. Methods: Participants were recruited from 150 counties in 28 provinces via a four-stage sampling method. The outcomes included several cognitive tasks. The independent variable was a composite score of cardiovascular risk calculated from sex-specific equations. We fitted the time-lagged regression to model the association between CVR and cognition. Besides, we performed cross-group analyses to test for model invariance across sex and age. We thus constrained path coefficients to be equal across each grouping variable (e.g., sex) and compared the fit of this constrained model with an unconstrained model in which the path coefficients were allowed to vary by group. Results: A total of 3,799 participants were included in the final analyses. We found that the CVR had a negative linear association with global cognition (β = -0.1, p < 0.01). Additionally, CVR had inverse linear associations with domain-specific measurements of memory and learning, calculation, orientation, and visual-spatial ability (all values of p < 0.01). Regarding sex and age moderation, males had a more pronounced association between higher CVR and worse general cognition, immediate recall, orientation, calculation, and visual-spatial ability (all values of p < 0.0001). In contrast, females exhibited a slightly larger negative association in delayed recall. Older participants (>65 years old) had a more pronounced association between higher CVR and worse calculation ability (p = 0.003). Conclusion: CVD are risk factors for lower global cognition and cognitive subdomains in middle-aged and older adults in China.