Aerobic exercise capacity is maintained over a 5-year period in mild-to-moderate chronic kidney disease: a longitudinal study.

BACKGROUND: Aerobic exercise capacity is reduced in non-dialysis chronic kidney disease (CKD), but the magnitude of changes in exercise capacity over time is less known. Our main hypothesis was that aerobic ExCap would decline over 5 years in individuals with mild-to-moderate CKD along with a decline in renal function. A secondary hypothesis was that such a decline in ExCap would be associated with a decline in muscle strength, cardiovascular function and physical activity. METHODS: We performed a 5-year-prospective study on individuals with mild-to-moderate CKD, who were closely monitored at a nephrology clinic. Fiftytwo individuals with CKD stage 2-3 and 54 age- and sex-matched healthy controls were included. Peak workload was assessed through a maximal cycle exercise test. Muscle strength and lean body mass, cardiac function, vascular stiffness, self-reported physical activity level, renal function and haemoglobin level were evaluated. Tests were repeated after 5 years. Statistical analysis of longitudinal data was performed using linear mixed models. RESULTS: Exercise capacity did not change significantly over time in either the CKD group or controls, although the absolute workloads were significantly lower in the CKD group. Only in a CKD subgroup reporting low physical activity at baseline, exercise capacity declined. Renal function decreased in both groups, with a larger decline in CKD (p = 0.05 between groups). Peak heart rate, haemoglobin level, handgrip strength, lean body mass and cardiovascular function did not decrease significantly over time in CKD individuals. CONCLUSIONS: On a group level, aerobic exercise capacity and peak heart rate were maintained over 5 years in patients with well-controlled mild-to-moderate CKD, despite a slight reduction in glomerular filtration rate. In line with the maintained exercise capacity, cardiovascular and muscular function were also preserved. In individuals with mild-to-moderate CKD, physical activity level at baseline seems to have a predictive value for exercise capacity at follow-up.

Gradual reduction in exercise capacity in chronic kidney disease is associated with systemic oxygen delivery factors.

BACKGROUND: The cause of reduced exercise capacity (ExCap) in chronic kidney disease (CKD) is multifactorial. The aim of this study was to investigate determinants of aerobic ExCap in patients with mild to severe CKD not undergoing dialysis. METHODS: We included 52 individuals with CKD stage 2-3, 47 with stage 4-5, and 54 healthy controls. Peak workload and peak heart rate (HR) were assessed by a maximal cycle exercise test. Cardiac function including stroke volume (SV) and vascular stiffness were evaluated by ultrasound at rest. Handgrip strength, body composition, haemoglobin level and self-reported physical activity were assessed. RESULTS: Peak workload (221±60, 185±59, 150±54 W for controls, CKD 2-3 and CKD 4-5 respectively), peak HR (177±11, 161±24, 144±31 beats/min) and haemoglobin level (14.2±1.2, 13.5±1.4, 12.2±1.3 g/dL) were all three significantly lower in CKD 2-3 than in controls, (p = 0.001, 0.001 and 0.03 respectively) and were even lower in stages 4-5 CKD than in CKD 2-3 (p = 0.01, 0.001 and <0.001 respectively). Resting SV and lean body mass did not differ between groups and handgrip strength was significantly lower only in CKD 4-5 compared to controls (p = 0.02). Peak workload was strongly associated with the systemic oxygen delivery factors: SV, peak HR and haemoglobin level. These three factors along with age, sex and height2 explained 82% of variation in peak workload. Peak HR contributed most to the variation; the peripheral variables handgrip strength and vascular stiffness did not improve the explanatory value in regression analysis. CONCLUSIONS: In this cross-sectional study of CKD patients not on dialysis, aerobic ExCap decreased gradually with disease severity. ExCap was associated mainly with systemic oxygen delivery factors, in particular peak HR. Neither muscle function and mass, nor vascular stiffness were independent determinants of aerobic ExCap in this group of CKD patients.

Initiation of erythropoiesis-stimulating agents and outcomes: a nationwide observational cohort study in anaemic chronic kidney disease patients.

BACKGROUND: In 2012, new clinical guidelines were introduced for use of erythropoiesis-stimulating agents (ESA) in chronic kidney disease (CKD) patients, recommending lower haemoglobin (Hb) target levels and thresholds for ESA initiation. These changes resulted in lower blood levels in these patients. However, there is limited evidence on just when ESA should be initiated and the safety of a low Hb initiation policy. METHODS: In this observational inception cohort study, Swedish, nephology-referred, ESA-naïve CKD patients (n = 6348) were enrolled when their Hb dropped below 12.0 g/L, and they were followed for mortality and cardiovascular events. Four different ESA treatments were evaluated applying dynamic marginal structural models: (i) begin ESA immediately, (ii) begin ESA when Hb <11.0 g/dL, (iii) begin ESA when Hb <10.0 g/dL and (iv) never begin ESA in comparison with 'current practice' [the observed (factual) survival of the entire study cohort]. The adjusted 3-year survival following ESA begun over a range of Hb (from <9.0 to 12.0 g/dL) was evaluated, after adjustment for covariates at baseline and during follow-up. RESULTS: Overall, 36% were treated with ESA. Mortality during follow-up was 33.4% of the ESA-treated and 27.9% of the non-treated subjects. The adjusted 3-year survival associated with ESA initiation improved for subjects with initial Hb <9.0 to 11 g/dL and then decreased again for those with Hb above 11.5 g/dL. Initiating ESA at Hb <11.0 g/dL and <10.0 g/dL was associated with improved survival compared with 'current practice' [hazard ratio (HR) 0.83; 95% confidence interval (CI) 0.79-0.89 and 0.90; 95% CI 0.86-0.94, respectively] and did not increase the risk of a cardiovascular event (HR 0.93; 95% CI 0.87-1.00). CONCLUSION: In non-dialysis patients with CKD, ESA initiation at Hb < 10.0-11.0 g/dL is associated with improved survival in patients otherwise treated according to guidelines.