Longitudinal Studies of Aging in Sub-Saharan Africa: Review, Limitations, and Recommendations in Preparation of Projected Aging Population

Background and Objectives

The United Nations has projected a 218% increase in older people in Sub-Saharan Africa (SSA) between 2019 and 2050, underscoring the need to explore changes that would occur over this time. Longitudinal studies are ideal for studying and proffering solutions to these changes. This review aims to understand the breadth and use of longitudinal studies on aging in the SSA regions, proffering recommendations in preparation for the projected aging population.

Research Design and Methods

This paper is the third of a four-part series paper of a previous systematic mapping review of aging studies in SSA. We updated the search (between 2021 and 2023) and screened the titles/abstracts and full-text articles by a pair of independent reviewers. Data were extracted using a standardized data-charting form, identifying longitudinal studies in SSA.

Results

We identified 193 studies leveraging 24 longitudinal study data sets conducted at 28 unique sites. The World Health Organization's Study on Global AGEing and Adult Health (WHO-SAGE) (n = 59, 30.5%) and Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa (HAALSI) (n = 51, 26.4%) were the most used longitudinal data sets. Four studies used more than one longitudinal study data set. Eighteen of the longitudinal study data sets were used only in 1-4 studies. Most (n = 150, 77.7%) of the studies used a cross-sectional analytical approach.

Discussion and Implications

Longitudinal studies on aging are sparingly being utilized in SSA. Most analyses conducted across the longitudinal data set were cross-sectional, which hindered the understanding of aging changes that occurred over time that could better inform aging policy and interventions. We call for funding bodies, such as WHO-SAGE, to develop funding competitions that focus on conducting longitudinal analyses, such as structural equation modeling, highlighting changes occurring among the aging population in SSA.

A longitudinal study of incident hypertension and its determinants in Indian adults aged 45 years and older: evidence from nationally representative WHO-SAGE study (2007-2015)

Objectives

Hypertension (HT) is a leading cause of mortality and morbidity in developing countries. This study aimed to estimate the incidence of HT among adults aged 45 years and older in India and its associated risk factors.

Methods

This study used longitudinal data from the Indian sample of the first and second waves of the World Health Organization Study on Global Ageing and Adult Health (WHO-SAGE). A bivariate analysis using Pearson's chi-square test was done to examine the associations of individual, lifestyle, and household characteristics with HT status reported in Wave 2. Incident HT changes were analyzed by adjusting for various covariates in the generalized estimating equation (logit link function) with an exchangeable correlation matrix and robust standard errors.

Results

The study found that during the 8-year period from 2007 to 2015, the incidence of HT in individuals aged 45 years and over was 20.8%. Pre-hypertensive individuals had an overall incidence rate of 31.1 per 1,000 [95% confidence interval (CI): 26.20-35.9] and a 2.24 times higher odds ratio: 2.24 (95% CI: 1.65-3.03) of developing incident HT compared to those who were normotensive. Adults aged 45 years and older, overweight/obese individuals, and women were more at risk of incident HT.

Conclusion

One in five individuals had developed HT over 8 years, with a greater risk of incident HT among women than men. Pre-hypertensive individuals were at a greater risk of developing incident HT compared to normotensive individuals. The study recommends comprehensive and effective management of pre-HT to tackle the burden of HT.

COVID-19 optimal vaccination policies: A modeling study on efficacy, natural and vaccine-induced immunity responses

About a year into the pandemic, COVID-19 accumulates more than two million deaths worldwide. Despite non-pharmaceutical interventions such as social distance, mask-wearing, and restrictive lockdown, the daily confirmed cases remain growing. Vaccine developments from Pfizer, Moderna, and Gamaleya Institute reach more than 90% efficacy and sustain the vaccination campaigns in multiple countries. However, natural and vaccine-induced immunity responses remain poorly understood. There are great expectations, but the new SARS-CoV-2 variants demand to inquire if the vaccines will be highly protective or induce permanent immunity. Further, in the first quarter of 2021, vaccine supply is scarce. Consequently, some countries that are applying the Pfizer vaccine will delay its second required dose. Likewise, logistic supply, economic and political implications impose a set of grand challenges to develop vaccination policies. Therefore, health decision-makers require tools to evaluate hypothetical scenarios and evaluate admissible responses. Following some of the WHO-SAGE recommendations, we formulate an optimal control problem with mixed constraints to describe vaccination schedules. Our solution identifies vaccination policies that minimize the burden of COVID-19 quantified by the number of disability-adjusted years of life lost. These optimal policies ensure the vaccination coverage of a prescribed population fraction in a given time horizon and preserve hospitalization occupancy below a risk level. We explore "via simulation" plausible scenarios regarding efficacy, coverage, vaccine-induced, and natural immunity. Our simulations suggest that response regarding vaccine-induced immunity and reinfection periods would play a dominant role in mitigating COVID-19.

Association of life course socioeconomic status and adult height with cognitive functioning of older adults in India and China

BACKGROUND

Cognitive functioning is an important measure of intrinsic capacity. In this study, we examine the association of life course socioeconomic status (SES) and height with cognitive functioning among older adults (50+) in India and China. The age pattern of cognitive functioning with measures of life course socioeconomic status has also been examined.

METHODS

Cross-sectional comparative analysis was conducted using the WHO's Study on global AGEing and adult health (SAGE) data for India and China. Multilevel mixed-effect linear regression analysis was used to examine the association of life course socioeconomic status and adult height with cognitive functioning.

RESULTS

In both India and China, parental education as a measure of childhood socioeconomic status was positively associated with cognitive functioning. The association between adult socioeconomic status and cognitive functioning was positive and significant. Height was significantly and positively associated with improved cognitive functioning of older adults in India and China. Furthermore, the age-related decline in cognitive functioning score was higher among older adults whose parents had no schooling, particularly in China. The cognitive functioning score with age was much lower among less-educated older adults than those with higher levels of education in China. Wealthier older adults in India had higher cognitive functioning in middle ages, however, wealth differences narrowed with age.

CONCLUSIONS

The results of this study suggest a significant association of lifetime socioeconomic status and cumulative net nutrition on later-life cognitive functioning in middle-income settings.

Height and quality of life among older adults (50+) in India: a cross-sectional study

Adult height is a summary measure of health and net nutrition in early childhood. This study examines the association between height and quality-of-life outcomes in older adults (50+) in India. Cross-sectional data from Wave 1 of the World Health Organization (WHO) Study on global AGEing and adult health (SAGE) conducted in 2007 were analysed. The association between height and quality of life was assessed using bivariate and multivariate logistic and linear regression models. The mean WHO quality-of-life score (WHO-QoL) increased from 45.2 among the older adults in the lowest height quintile to 53.2 for those in the highest height quintile. However, the prevalence of self-rated poor quality of life declined from 16.4% in the lowest height quintile to 6.1% in the highest height quintile. In the fully adjusted regression model, height was found to be positively associated with quality-of-life outcomes among both men and women, independent of socioeconomic and physical health confounders. The association was particularly strong for women. Women in the highest height quintile had a 2.65 point higher WHO-QoL score than those in the lowest height quintile. Similarly, the likelihood of reporting a poor quality of life was lower among women in the highest height quintile. Furthermore, measures of economic status, handgrip strength, cognitive ability and poor self-rated health were significantly associated with WHO-QoL and self-rated poor quality of life. Overall, this study revealed a significant association between height and quality of life among older adults in India, suggesting a significant role of childhood circumstances in quality of life in later life.

Predictors of public and private healthcare utilization and associated health system responsiveness among older adults in Ghana

BACKGROUND

Previous studies investigating factors associated with healthcare utilization by older Ghanaians lack distinction between public and private health services. The present study examined factors associated with public and private healthcare service use, and the resulting perceived health system responsiveness.

OBJECTIVES

To identify factors associated with public and private healthcare utilization among older adults aged 50 and older in Ghana; and to compare perceived differences in health system responsiveness between the private and public sectors.

METHODS

Cross-sectional data was analyzed from the World Health Organization Study on global AGEing and adult health (SAGE) Wave 1 in Ghana. Using Andersen's conceptual framework, public and private outpatient care utilization was examined using multinomial logistic regression to estimate and identify predictor variables associated with the type of outpatient healthcare facility accessed. Health system responsiveness was compared using chi-square tests.

RESULTS

Of 2517 respondents who used outpatient care in the 12 months preceding interview, 51.7% of respondents used a public facility, 17.8% a private facility, and 30.5% used other facilities. Older age group, higher education and higher wealth were associated with the use of private outpatient healthcare services. Using public outpatient care facilities was associated with having health insurance. Respondents with two or more chronic conditions were more likely to use public and private outpatient care than other facilities. Perceived health system responsiveness was better in private for-profit than in public and private not-for-profit healthcare facilities.

CONCLUSIONS

This study suggested that higher wealth and multimorbidity were significant predictors of public and private outpatient healthcare utilization; however, health insurance was a predictor only for the use of public facilities. Future mixed-method studies could further elucidate factors influencing the choice of public and private outpatient healthcare use.

Association Between Body Mass index and Prevalence of Multimorbidity in Low-and Middle-income Countries: A Cross-Sectional Study

Background

Chronic diseases are increasingly becoming a health burden in terms of both morbidity and mortality in low and middle-income countries (LMICs). The role of body mass index (BMI) especially overweight and obesity in the prevalence of multimorbidity, the occurrence of two or more chronic conditions, is understudied in LMICs where two thirds of the world’s obese individuals reside. We estimated the association between BMI and prevalence of chronic non communicable disease multimorbidity in six LMICs.

Methods

Cross-sectional data of total of 40,166 participants from China (n=13,970), India (10,915), Mexico (2,4 26), Russia (3,892), South Africa (4,000) and Ghana (4,971), aged 18 years and above included in the WHO Study on Global Ageing and adult health (SAGE), 2007–2010 were analyzed. Multimorbidity was measured as the simultaneous presence of two or more of the nine chronic conditions including angina pectoris, arthritis, asthma, chronic lung disease, diabetes mellitus, hypertension, stroke, depression, and vision impairment. Multivariable logistic regression models were fitted to test for associations between overweight/obesity and prevalence of non communicable multimorbidity after adjusting for age, sex, rural/urban residence, education, marital status, occupation, household wealth, tobacco smoking, alcohol drinking, fruits and vegetable intake and health insurance status. Data were analyzed country wise as well as pooled together to give overall LMIC estimates.

Results

The mean BMI was 24.4 [±7.3SD] in the pooled countries, being as low as 20.8 [±8.0 SD] in India to 23.4 [±6.3 SD] in Ghana, 23.9 [±4.9 SD] in China, 28.4 [±5.4 SD] in Mexico, 28.6 [±6.3 SD] in Russia, to as high as 30.5 [±12.0 SD] in South Africa. The prevalence of overweight was 13% and obesity was 24% in the pooled sample. The prevalence of non communicable disease multimorbidity was 23% in the pooled sample of six countries–the highest being in Russia (50%), followed by Mexico (27%), India (24%), Ghana (23%), South Africa (32%) and China (22%). The prevalence of multimorbidity was 37% among obese population and 27% among overweight population in the pooled sample–highest prevalence was in Russia (59% among obese; 45% among overweight) and lowest in Ghana (28% among obese; 23% among overweight). Being obese (OR:5.78;95%CI:3.55–9.40;p<0.0001) was associated with significantly higher likelihood of having multimorbidity as compared to normal weight category in the pooled sample. The likelihood of multimorbidity among obese were almost ten times higher in Russia (OR:9.90;95%CI:3.90–25.17;p=<0.0001), seven times higher in China (OR:7.06;95%CI:2.47–20.21;p=0.003), six times higher in Ghana (OR:5.61;95%CI:1.21–26.02;p= 0.007) and five times higher in South Africa (OR:4.66;95%CI:2.16–10.08;p=0.005). Non-significant but positive association were also observed in case of India and Mexico. The likelihood of multimorbidity was more than two times higher among overweight population in India (OR:2.33;95%CI:1.35–4.02;p=0.003) and pooled countries (OR:1.47;95%CI:1.05–2.07;p=0.004) while non-significant but positive association were also observed in case of China, Russia, and Ghana.

Conclusions

The prevalence of non communicable disease multimorbidity in the LMICs is high, one and half times higher in obese than in normal weight individual. Obesity was independently associated with the occurrence of multimorbidity in the six LMICs. These findings may be vital for public health surveillance, prevention and management strategies for non communicable disease multimorbidity in the LMICs.