Serum creatinine/cystatin C ratio is a predictor of all-cause mortality for older adults over 80 years

Serum creatinine and serum cystatin C as an index of muscle mass in adults

PURPOSE OF REVIEW

Serum creatinine reflects both muscle mass and kidney function. Serum cystatin C has recently been recommended as an additional marker for estimating kidney function, and use of both markers together may provide an index of muscle mass. This review aims to describe the biological basis for and recent research examining the relationship of these markers to muscle mass in a range of adult populations and settings.

RECENT FINDINGS

This review identified 67 studies, 50 of which had direct measures of muscle mass, and almost all found relationships between serum creatinine and cystatin C and muscle mass and related outcomes. Most studies have been performed in older adults, but similar associations were found in general populations as well as in subgroups with cancer, chronic kidney disease (CKD), and other morbid conditions. Creatinine to cystatin C ratio was the measure examined the most often, but other measures showed similar associations across studies.

SUMMARY

Measures of serum creatinine and cystatin C together can be an index of muscle mass. They are simple and reliable measures that can be used in clinical practice and research. Further study is needed to determine actionable threshold values for each measure and clinical utility of testing and intervention.

Cystatin C and sarcopenia index are associated with cardiovascular and all-cause death among adults in the United States

OBJECTIVES

This study aimed to investigate the association of cystatin C, serum creatinine and sarcopenia index with cardiovascular and all-cause death in general population.

METHODS

Data of participants from the National Health and Nutrition Examination Surveys (NHANES) from 1999 to 2004 were used and all participants were followed up regularly until December 31, 2019. Multivariable Cox analysis was used to investigate the association of cystatin C, serum creatinine and sarcopenia index with cardiovascular and all-cause death. Restricted cubic spline was conducted to evaluate the nonlinear association.

RESULTS

A total of 9894 participants with a mean age of 45.64 years were enrolled and followed up for a mean duration of 15.62 ± 4.68 years. Approximately 50.3% were male and there were a total of 2681 all-cause deaths and 691 cardiovascular deaths recorded during the follow-up period. In final adjusted model, compared with the first quartile of cystatin C (< 0.659 mg/L), the risk of cardiovascular and all-cause death increased 2.36-fold and 1.71-fold for participants in the fourth quartile (≥ 0.877 mg/L) (HR: 3.36, 95% CI: 2.06-5.46, P < 0.001; HR: 2.71, 95% CI: 2.17-3.38, P < 0.001; respectively). Furthermore, a higher sarcopenia index (< 88.41 vs. ≥125.52) was associated with the reduced risk of cardiovascular death (HR: 0.41, 95% CI: 0.31-0.53, P < 0.001) as well as all-cause death (HR: 0.41, 95% CI: 0.35-0.49, P < 0.001). Additionally, restricted cubic splines showed that there was a nonlinear relationship between sarcopenia index levels and all-cause death while there was a linear relationship between sarcopenia index levels and cardiovascular death.

CONCLUSIONS

Higher sarcopenia index was associated with the decreased risk of cardiovascular and all-cause death in general population in the United States. Elevated cystatin C was positively associated with cardiovascular and all-cause death.

Associations of serum albumin and dietary protein intake with all-cause mortality in community-dwelling older adults at risk of sarcopenia

Objective

The Asian Working Group for Sarcopenia 2019 consensus emphasized nutritional assessment and intervention for community-dwelling older people with sarcopenia status. This study aimed to examine the association of serum albumin and dietary protein intake (DPI) with all-cause mortality among older adults at risk of sarcopenia.

Methods

We enrolled 1763 older adults at risk of sarcopenia in the Chinese Longitudinal Healthy Longevity Survey (2012-2018) using calf circumference and handgrip strength. Serum albumin concentrations were measured using bromocresol green methods, and DPI frequency was evaluated using a semi-quantitative questionnaire at baseline. Cox proportional hazards models were used to explore the association of serum albumin and DPI with all-cause mortality.

Results

During 5606.3 person-years of follow-up (median: 3.28 years), 802 older people died. After adjusting for socio-demographics, health behaviors, and clinical characteristics, we observed an inverse linear association between serum albumin and all-cause mortality (Pnon-linear = 0.429). Participants with low albumin levels (<40.0 g/L) had a 43 % higher risk of mortality than their counterparts (hazard ratio (HR) = 1.43, 95 % confidence interval (CI) = 1.22-1.66). There was no significant association between DPI and mortality (Ps > 0.05). Moreover, the association between low albumin and all-cause mortality remained significant in the lower DPI subgroup (HR = 1.47, 95 % CI = 1.18-1.85), but was not significant in the high DPI subgroup (HR = 1.15, 95 % CI = 0.92-1.39).

Conclusions

Serum albumin levels are inversely associated with all-cause mortality in community-based older adults at risk of sarcopenia. Sufficient dietary protein consumption may attenuate the effect of low serum albumin on increased mortality and potential mechanisms for the interaction warrant further exploration.

Value of Cystatin C-Based Sarcopenia Index in Patients Undergoing Surgery for Renal Tumors

INTRODUCTION

Sarcopenia is a condition of low muscle strength and quantity, severe if low physical performances. The sarcopenia index (SI), calculated by blood levels of creatinine and cystatin C, had been reported to be correlated with skeletal muscle mass and is a potential simple screening tool for sarcopenia. We hypothesized that patients with a low SI, meaning low muscle mass, would have an inflated estimated glomerular filtration rate (eGFR) value based on serum creatinine levels. We also tested the prognostic value of the SI in a cohort of patients who had surgery for renal malignancies.

PATIENTS AND METHODS

We conducted a retrospective, observational study of 322 patients that had surgery for renal tumors in National Cancer Center Hospital East (Kashiwa, Chiba) between April 2017 and June 2023. We assessed sarcopenia measuring psoas muscle index (PMI), psoas muscle density (PMD), and skeletal muscle area (SMA) by computed tomography. We assessed the association between SI and eGFR before and after surgery. We also assessed the association between SI and postoperative outcome, including overall survival.

RESULTS

Of the 322 patients, 211 (66%) were males, with a median age of 69 years. SI had a weak correlation with both PMI and PMD in males (PMI: ρ = 0.25; PMD: ρ = 0.21). In females, SI and PMD exhibited a low correlation (ρ = 0.26), while SI and PMI displayed an insignificant correlation (ρ = 0.19). The correlation between SMA and SI was moderate for both males and females (males: ρ = 0.51; females: ρ = 0.46). After radical nephrectomy, eGFR decreased in 98% of patients with high SI, compared to 69% of patients with low SI. We also demonstrated that low SI predicted poor prognosis.

CONCLUSIONS

Clinicians can recognize the possibility of overestimated eGFR in the low SI group by measuring SI around the surgery. Low SI may also help predict poor prognosis.