Effect of prolonged standardized bed rest on cystatin C and other markers of cardiovascular risk

Compared to baseline values there was a statistically significant increase in cystatin C in both groups after bed rest (P < 0.001). Glomerular filtration rate (GFR), calculated by both cystatin C and Cockcroft-Gault equation, decreased after bed rest while there were no differences in creatinine or creatine kinase levels. CRP did not change during bed rest in the exercise group, but there was an increase of CRP in the control group during recovery compared to both the baseline and the bed rest periods. The apo-B/apo-Ai ratio increased during bed rest and decreased again in the recovery period. Subjects experienced a small but statistically significant reduction in weight during bed rest and compared to baseline weights remained lower at day 8 of recovery.During and following prolonged standardized bed rest the concentrations of several clinically relevant cardiovascular risk markers change.Sedentary lifestyle is associated with inflammation in population-based studies [1,2] and increases cardiovascular risk [3].Bed rest causes muscle atrophy, which in turn leads to lower creatinine levels and decreased glomerular filtration rate (GFR), when calculated by the Modification of Diet in Renal Disease (MDRD) formula or Cockcroft-Gault formula dependant on creatinine [4]. Cystatin C is also a marker of GFR but is unaffected by muscle mass. However, age, sex, weight, smoking and high concentrations of CRP affect the plasma level of cystatin C [5]. Because bed rest and cystatin C levels are both cardiovascular risk factors we found it of interest to investigate how cystatin C, together with other risk markers, are affected by prolonged standardized bed rest.It has been proposed that elevated cystatin C levels are directly correlated to both inflammation and atherosclerosis [6]. High cystatin C levels are independently associated with cardiovascular risk factors such as BMI, low HDL cholesterol and smoking even in patients without chronic kidney disease or microalbuminuria [7