Full-length ArticleChildhood socioeconomic status and inflammation: A systematic review and meta-analysis
Section snippets
Mechanisms of childhood SES effects on health
The pathogenic mechanisms that mediate the relationship between SES and disease are not fully understood, especially since lack of exercise, smoking, body mass index (BMI) and other factors that are also associated with SES do not completely account for these associations (Miller et al., 2011). In the past decade, researchers have become increasingly interested in the possibility that low-grade, chronic inflammation is the underlying mechanism linking risk factors like low childhood SES and
Empirical studies on childhood SES and inflammation
Research on the relationship between childhood SES and inflammation is equivocal. Some studies find no significant relation; others find a small but significant inverse relationship. In some studies, these associations persist after controlling for demographic and health factors, but in others, associations become non-significant after controlling for covariates. In addition to socio-demographic variables such as age, sex, and race, research has also shown that health related factors that are
Current study
We build on results from one systematic review (Nazmi and Victoria, 2007) and a recent meta-analysis (Liu et al., 2017). Nazmi and Victoria (2007) primarily reviewed studies of adult SES and CRP and found that most of these reported an inverse relationship. This review included few studies of childhood SES and CRP. A recent meta-analysis using 14 studies examining childhood SES and adult CRP found that participants from the least advantaged families had 25% higher CRP levels than participants
Search strategy and selection
A systematic review of the literature was performed using Pub Med and PsycINFO using the search criteria: “(socioeconomic OR SES) AND (inflammation OR inflammatory OR C-reactive OR CRP OR IL-6 OR IL-1 OR tumor necrosis factor OR tnf OR cytokines OR interleukin OR fibrinogen) AND (child* OR youth OR adolescen* OR early life)”. Search criteria were restricted to original peer-reviewed papers, in the English language, using human subjects. The literature search was performed between 4 March and 14
Systematic review
The initial search produced 998 papers in Pub Med and 166 in PsycINFO total. After screening and removal of duplicates (N = 28), 72 papers were chosen for in-text analysis including three additional studies that were included after an updated search. Following an in-text analysis, 37 were excluded (9 no childhood SES; 8 no inflammatory markers; 4 no individual SES; 5 an acute response; 2 a medical population; 7 duplicate cohorts; 2 no effect size available for either unadjusted or adjusted
Discussion
Our results showed a small but inverse relationship between childhood socioeconomic status and markers of chronic inflammation that remained significant across adjusted analyses, type of inflammatory markers, and type of SES measures utilized. In addition, for both unadjusted and adjusted analyses, the effect remained significant in both cross-sectional and longitudinal studies, even after only including studies that controlled for BMI. However, the effect between SES and inflammation was
Limitations
There are several caveats that should be considered in the interpretation of these results. Studies of SES and inflammation employ a range of statistical methodologies that produce many types of effect sizes (odds ratios, path coefficients from structural equation models, relative risk ratios, standardized and unstandardized regression coefficients, means, etc). For this meta-analysis, only a handful of studies used similar statistical techniques and effect sizes. Although the unadjusted
Conclusion
The present meta-analysis found a small but significant inverse association between childhood SES and chronic inflammation that remained significant across different inflammatory markers, SES measures, study designs, and after controlling for BMI. Results showed that the concurrent effect of childhood SES on childhood inflammation could be consistently and reliably detected in cross-sectional data suggesting immediate versus more long-term effects on inflammatory mechanisms. However, the
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