Effect of mild hyperglycemia on autonomic function in obstructive sleep apnea.

INTRODUCTION: Obstructive sleep apnea (OSA) has been hypothesized to cause a hypersympathetic state, which may be the mechanism for the increased incidence of cardiovascular disease in OSA. However, there is a high prevalence of hyperglycemia in OSA patients, which may also contribute to autonomic dysfunction. METHODS: Thirty-five patients with OSA and 11 controls with average body mass index (BMI) of 32.0 ± 4.6 underwent polysomnography, glucose tolerance testing, autonomic function tests, lying and standing catecholamines, overnight urine collection, and baseline ECG and continuous blood pressure measurements for spectral analysis. A linear regression model adjusting for age and BMI was used to analyze spectral data, other outcome measures were analyzed with Kruskal-Wallis test. RESULTS: Twenty-three OSA patients and two control patients had hyperglycemia (based on 2001 American Diabetes Association criteria). Apnea-hypopnea index (AHI) correlated with total power and low frequency (LF) power (r = 0.138, 0.177, p = 0.031; and r = 0.013) but not with the LF/high frequency (HF) ratio (p = 0.589). Glucose negatively correlated with LF systolic power (r = -0.171, p = 0.038) but not AHI (p = 0.586) and was marginally associated with pnn50, total power, LF, and HF power (p ranged from 0.07 to 0.08). CONCLUSION: These data suggest that patients with OSA and mild hyperglycemia have a trend towards lower heart rate variability and sympathetic tone. Hyperglycemia is an important confounder and should be evaluated in studies of OSA and autonomic function.

Mortality by race among low-income adults with early-onset insulin-treated diabetes.

OBJECTIVE: To determine if long-term mortality rates in early-onset insulin-treated diabetes differ by race among adults of similar socioeconomic status. RESEARCH DESIGN AND METHODS: A total of 391 (299 African Americans, 92 whites) mostly low-income adults 40-79 years of age with insulin-treated diabetes diagnosed before 30 years of age were recruited from community health centers in the southeast U.S. Cox models were used to estimate hazard ratios (HRs) of all-cause mortality among African Americans compared with whites. Additionally, standardized mortality ratios (SMRs) were used to compare the mortality experience of the individuals with diabetes with both national and general community health center sex- and race-specific population norms. RESULTS: Mean age at diabetes diagnosis and cohort entry, respectively, was 21 and 50 years in African Americans and 19 and 51 years in whites. During an average of 6.7 years of follow-up, 29% of African Americans and 35% of whites died. In multivariable analysis, no significant mortality difference was observed among African Americans compared with whites (HR 0.83 [95% CI 0.53-1.30]; P=0.51). Compared with the race-specific U.S. general population, SMRs for those with diabetes were 5.7 in African Americans and 11.7 in whites. However, when compared with the same source population (i.e., the community health center population), SMRs were 3.5 and 3.7 in African Americans and whites, respectively. CONCLUSIONS: Elevated mortality persists in men and women with long duration of early-onset insulin-treated diabetes, but given survival to 40 years of age and similarly low economic status and access to health care, our data do not suggest a racial disparity in mortality.