In this large-scale prospective community-based Korean cohort observed over 12 years, we investigated the relationship between the CRP/Alb ratio and the incidence of MetS among Korean adults. To the best of our knowledge, this study is the first to reveal a positive relationship between CRP/Alb ratio and the incidence of MetS regardless of baseline insulin resistance (such as HOMA-IR). This relationship was even present after adjusting for potentially confounding variables.
Our findings are consistent with previous results showing that those with a higher CRP at baseline had a higher risk of incident MetS.[7, 8] However, a cross-sectional study conducted in South Korea indicated that high serum albumin levels are also associated with MetS. The associated assumption is that high serum albumin reflects high protein dietary intake.[11] Similarly, a cross-sectional study in Japan had similar results but also emphasized that elevated serum albumin levels are associated with reduced risk of all-cause and cardiovascular mortality due to the anti-oxidative properties of serum albumin.[12] Also, a longitudinal study demonstrated an inverse relationship between changes in serum albumin levels and incident MetS, suggesting that an increase in serum albumin concentration represents an adaptive response to heightened oxidative stress demands.[13] While CRP serves as an indicator of participants’ inflammatory status, serum albumin levels seem to not only reflect nutritional status but also signify the potential anti-oxidative response to chronic inflammation. In this regard, we did not examine CRP or albumin alone; we considered the correlation between CRP and albumin and assumed that CRP/Alb ratio could be a novel marker able to predict incident MetS.
Cho et al. reported that CRP/Alb ratio is also positively related to incident type 2 diabetes among community-dwelling Korean adults without chronic disease.[21] These researchers suggested that CRP/Alb ratio reflects oxidative stress that is linked with the pathogenesis of type 2 diabetes, insulin resistance. Karabag et al. reported that elevated CRP/Alb ratio in stable coronary artery disease is associated with extent, severity, and complexity of coronary atherosclerosis.[22] This group mentioned that increased CRP/Alb ratio indicates a higher inflammatory status and may be superior to CRP and albumin alone in determining the prevalence and severity of coronary artery disease.
Besides insulin resistance, the specific mechanism by which high CRP/Alb ratio is related to the development of MetS remains unclear. MetS is associated with chronic low-grade inflammation, including oxidative stress. Individuals who are more responsive to inflammation are also more susceptible to developing MetS compared to those not at risk. During inflammation, serum albumin levels naturally exhibit an inverse correlation with CRP levels.[23] Conversely, individuals with high albumin levels, which act as protective proteins against inflammatory reactions[24], compensate for inflammatory conditions and may exhibit a lower CRP/Alb ratio. As a result, individuals with higher serum albumin levels, reflecting an anti-oxidative response to inflammatory conditions that may decrease due to inflammation, may have a reduced risk of developing MetS.
This study has several limitations that should be considered. Despite its large size, our study was conducted in a Korean population. Therefore, our results may not be generalizable to other ethnic/racial populations. Second, the study population may not represent the general Korean population as the participants were limited to specific geographic regions. Therefore, this study may be subject to selection bias. A third limitation is that the study did not show the effect of sequential change in the CRP/Alb ratio; we only considered the baseline measurement of the CRP and albumin. Despite these limitations, our findings have clinical implications regarding preventive public health strategies for East Asian patients at high risk of developing MetS.
In conclusion, a high CRP/Alb ratio predicts future incident MetS that is independent of other associated variables, such as insulin resistance, among community-dwelling Korean adults.