Socioeconomic Disparities in Cardiovascular Health in South Korea: A Systematic Review

Overadjustment bias in systematic reviews and meta-analyses of socio-economic inequalities in health: a meta-research scoping review

BACKGROUND

Overadjustment bias occurs when researchers adjust for an explanatory variable on the causal pathway from exposure to outcome, which leads to biased estimates of the causal effect of the exposure. This meta-research review aimed to examine how previous systematic reviews and meta-analyses of socio-economic inequalities in health have managed overadjustment bias.

METHODS

We searched Medline and Embase until 16 April 2021 for systematic reviews and meta-analyses of observational studies on associations between individual-level socio-economic position and health outcomes in any population. A set of criteria were developed to examine methodological approaches to overadjustment bias adopted by included reviews (rated Yes/No/Somewhat/Unclear).

RESULTS

Eighty-four reviews were eligible (47 systematic reviews, 37 meta-analyses). Regarding approaches to overadjustment, whereas 73% of the 84 reviews were rated as Yes for clearly defining exposures and outcomes, all other approaches were rated as Yes for <55% of reviews; for instance, 5% clearly defined confounders and mediators, 2% constructed causal diagrams and 35% reported adjusted variables for included studies. Whereas only 2% included overadjustment in risk of bias assessment, 54% included confounding. Of the 37 meta-analyses, 16% conducted sensitivity analyses related to overadjustment.

CONCLUSIONS

Our findings suggest that overadjustment bias has received insufficient consideration in systematic reviews and meta-analyses of socio-economic inequalities in health. This is a critical issue given that overadjustment bias is likely to result in biased estimates of health inequalities and accurate estimates are needed to inform public health interventions. There is a need to highlight overadjustment bias in review guidelines.

Trends in Regional Disparity in Cardiovascular Mortality in Korea, 1983–2019

Mortality from cardiovascular diseases (CVDs) had been significantly improved in several decades. However, the recent reduction was slowed down, and the burden remained high. Understanding regional disparity in cardiovascular deaths would help facilitate the improvement. Thus, we investigated geographic variation in CVD mortality and its spatiotemporal trend in Korea between 1983 and 2019. The findings showed higher mortality in the southeastern regions, while the regional disparity converged over time. It suggested that these regions call for action in terms of prevention and management of CVDs, in addition to an effort to reduce the death rates in other regions.

Background and Objectives

Despite remarkable reduction in cardiovascular disease (CVD) mortality, the burden has remained the leading cause of death. Since little research has focused on regional disparity in CVD mortality, this study aims to investigate its spatiotemporal trends in Korea from 1983 to 2019.

Methods

Using the causes of death statistics in Korea, we analyzed the geographic variation in deaths from CVDs from 1983 to 2019. The sex and age-standardized mortality rate was calculated according to the 17 administrative regions. The analyses include all diseases of the circulatory system (International Classification of Diseases-10 codes, I00–I99), along with the following 6 subcategories which were not mutually exclusive: total heart disease (I00–I13 and I20–I51), hypertensive heart disease (I10–I13), ischemic heart disease (I20–I25), myocardial infarction (I21–I23), heart failure (I50), and cerebrovascular disease (I60–I69).

Results

Overall, heart failure death rate increased across all regions, and other CVD death rates showed a decreasing trend. Regional disparity in mortality was substantial in the early 1980s but converged over time. In all types of cardiovascular mortality, Busan, Ulsan and Gyeongnam remained the highest, although they showed a downward trend like other regions. Jeju continued to have a relatively low CVD mortality rate.

Conclusions

The regional disparity substantially decreased compared to the 1980s. However, the relatively high burden of CVD mortality in the southeastern region has not been fully resolved.

Socioeconomic Classes among Oldest-Old Women in South Korea: A Latent Class Analysis

Oldest-old women are known to live at the intersection of multiple socioeconomic disadvantages in South Korean society. This study classified oldest-old Korean women into several socioeconomically homogeneous classes based on various socioeconomic status (SES) risks and compared health characteristics among the identified classes. This cross-sectional study utilized the 2019 Korean Community Health Survey, including data from 11,053 women (≥80 years). Latent class analysis determined the number of underlying socioeconomic classes based on nine selected SES variables. Four distinct socioeconomic classes were identified: “Urban, living alone, recipient of NBLSS, moderate education, leisure activity” (Class 1), “Rural, traditional house, living with others, not financially deprived, low education, employed” (Class 2), “Urban, living with family, financially affluent, not employed, no barriers to healthcare” (Class 3), “Rural, traditional house, living alone, financially deprived, uneducated, employed, barriers to healthcare” (Class 4). Depressive symptoms, subjective stress, and the prevalence of sleep disorder and diabetes were higher in Class 1 compared to other classes. Health-related quality of life, perceived health, and self-rated oral health were the poorest in Class 4. Class 3 reported the best health status. Understanding the intersecting SES risk factors in this group can aid in developing targeted interventions.

A 9-Year Comparison of Dementia Prevalence in Korea: Results of NaSDEK 2008 and 2017

BACKGROUND

In many high-income Western countries, the prevalence of dementia had been reduced over the past decades.

OBJECTIVE

We investigated whether the prevalence of all-cause dementia, Alzheimer's disease, vascular dementia, and mild cognitive impairment (MCI) had changed in Korea from 2008 to 2017.

METHODS

Nationwide Survey on Dementia Epidemiology of Korea (NaSDEK) in 2008 and 2017 was conducted on representative elderly populations that were randomly sampled across South Korea. Both surveys employed a two-stage design (screening and diagnostic phases) and diagnosed dementia and MCI according to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders and the consensus criteria from the International Working Group, respectively. The numbers of participants aged 65 years or older in the screening and diagnostic phases were 6,141 and 1,673 in the NaSDEK 2008 and 2,972 and 474 in the NaSDEK 2017, respectively.

RESULTS

The age- and sex-standardized prevalence of all-cause dementia and Alzheimer's disease showed nonsignificant decrease (12.3% to 9.8%, odds ratio [OR] = 0.89, 95% confidence interval [CI] = 0.54-1.48 for all-cause dementia; 7.6% to 6.8%, OR [95% CI] = 0.91 [0.58-1.42] for Alzheimer's disease). Vascular dementia decreased in the young-old population aged less than 75 years (2.7% to 0.001%, OR [95% CI] = 0.04 [0.01-0.15]) and in women (1.9% to 0.5%, OR [95% CI] = 0.27 [0.10-0.72]) while MCI remained stable (25.3% to 26.2%, OR [95% CI] = 1.08 [0.67-1.73]).

CONCLUSION

We found that the prevalence of dementia in Korea showed a nonsignificant decrease between 2008 and 2017.

Self-care status in patients with heart failure: Systematic review and meta-analysis

Aim

To systematically review the status of self‐care in patients with heart failure through the Self‐Care of Heart Failure Index scale.

Design

A systematic review and meta‐analysis.

Methods

Following national and international databases were searched to retrieve eligible studies: PubMed, Web of Science, Embase, Google Scholar, Scientific Information Database and Magiran. The studies were screened and selected by two researchers. Data analysed through the random‐effects model, and the I² index was used to assess heterogeneity. Stata software version 12.0 was used for analysis. The PRISMA statement was used to report systematic review and meta‐analysis.

Results

Of the 5,953 articles initially identified, 39 studies were included. The average score was estimated at 58.16 (CI: 54.39–61.94) for self‐care maintenance, 53.11 (CI: 49.17–57.05) for self‐care management and 58.66 (CI: 54.32–63.00) for self‐care confidence. Despite the high heterogeneity of the studies, the results indicated that self‐care practice is inadequate in all the three dimensions of self‐care (maintenance, management and confidence).

A 10-year trend in income disparity of cardiovascular health among older adults in South Korea

Objectives

Although cardiovascular disease (CVD) risk has lessened in Korea, it is unclear whether older adults in all socioeconomic strata have benefited equally. This study explored trends in income disparities in CVD risk among older adults in Korea.

Methods

This was a secondary analysis of Korean National Health and Nutrition Examination Survey data (2008–2017), targeting 14,836 older adults (≥65 years). Socioeconomic position, defined as income and use of welfare benefits, was the primary indicator. The outcome was binary for predicted CVD risk (<90th vs. ≥ 90th). The Slope Index of Inequality (SII) and Relative Index of Inequality (RII) were used to assess trends in disparities.

Results

The percentage of older adults with a predicted CVD risk of 90% or more declined over time, but this was due to a decrease among the more affluent. Disparities have persisted since 2012, with a worsening trend seen for Medicaid recipients. We found significant absolute and relative disparities among men over 75 years of age in recent years (SII > 0.19, RII > 7).

Conclusions

These results may inform and improve policies regarding income disparity reduction and cardiovascular health.

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Income disparities in CVD risk have persisted since 2012, with a worsening trend seen for Medicaid recipients.

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Our results highlight the need to improve CVD risk management services offered to the economically disadvantaged.

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It is important to consider both the absolute and relative terms when examining the disparity trends.