Hyperoxia improves autonomic function in individuals with long-duration type 1 diabetes and macroalbuminuria.

AIM: Acute oxygen inhalation and slow deep breathing improve measures of autonomic function transiently in individuals with short-duration type 1 diabetes. Our aims were to examine these interventions and changes in autonomic function in individuals with long-duration type 1 diabetes and to explore interactions with the presence of macroalbuminuria or existing cardiovascular autonomic neuropathy. METHODS: Individuals with type 1 diabetes (n = 54) were exposed to acute oxygen inhalation, slow deep breathing and a combination of both (hereafter 'the combination'). Primary outcomes were change in baroreflex sensitivity and heart rate variability. Associations between changes in outcomes were evaluated using mixed effects models. RESULTS: Mean age ± sd was 60 ± 10 years and diabetes duration was 38 ± 14 years. Changes are presented as per cent difference from baseline with 95% confidence intervals. Acute oxygen inhalation, slow deep breathing and the combination increased baroreflex sensitivity by 21 (10, 34)%, 32 (13, 53)% and 30 (10, 54)%, respectively. Acute oxygen inhalation trended towards increasing heart rate variability 8 (-1, 17)% (P = 0.056), and slow deep breathing and the combination increased heart rate variability by 33 (18, 49)% and 44 (27, 64)% respectively. Macroalbuminuria or cardiovascular autonomic neuropathy did not modify results. CONCLUSION: Autonomic function is improved transiently in individuals with long-duration type 1 diabetes and normoalbuminuria or macroalbuminuria by acute oxygen inhalation and slow deep breathing. There is a risk of survival bias. Autonomic dysfunction might be a reversible condition, and hypoxia might represent a target of intervention.

Association of anemia with the risk of cardiovascular adverse events in overweight/obese patients.

OBJECTIVE: Anemia is associated with increased cardiovascular risks. Obesity may cause anemia in several ways, for example, by low-grade inflammation and relative iron deficit. The outcomes associated with anemia in overweight/obese patients at high cardiovascular risk are however not known. Therefore, we investigated the cardiovascular prognosis in overweight/obese subjects with anemia. METHODS: A total of 9,687 overweight/obese cardiovascular high-risk patients from the Sibutramine Cardiovascular OUTcomes trial were studied. Patients were stratified after baseline hemoglobin level and followed for the risks of primary event (comprising nonfatal myocardial infarction, nonfatal stroke, resuscitated cardiac arrest or cardiovascular death) and all-cause mortality. Risk estimates (hazard ratios (HR) with 95% confidence intervals (CI)) were calculated using Cox regression models. RESULTS: Anemia was unadjusted associated with increased risk for the primary event, HR 1.73 (CI 1.37-2.18) and HR 2.02 (CI 1.34-3.06) for patients with mild or moderate-to-severe anemia, respectively, compared with patients without anemia. Adjusted for several confounders, anemia remained of prognostic importance. Increased risk of the primary events appeared to be driven by risk of cardiovascular death, adjusted HR 1.82 (CI 1.33-2.51) for mild anemia and adjusted HR 1.65 (CI 0.90-3.04) for moderate-to-severe anemia, and all-cause mortality, adjusted HR 1.50 (CI 1.17-1.93) for mild and adjusted HR 1.61 (CI 1.04-2.51) for moderate-to-severe anemia. While adding serum creatinine to the models, the increased risk of mild anemia was still a significant predictor for mortality (cardiovascular and all-cause), whereas moderate-to-severe anemia was not. For the primary events, anemia was no longer of independent prognostic importance when including serum creatinine. CONCLUSION: Anemia is associated with an increased risk of long-term adverse cardiovascular events and deaths among overweight/obese cardiovascular high-risk patients. The increased risk appeared to be driven by the risk of cardiovascular death and all-cause mortality, and renal impairments seemed to have a role in the increased risk.