Obstructive Sleep Apnea and the Metabolic Syndrome

Jamie C.M. Lam; Mary S.M. Ip

Disclosures

Expert Rev Resp Med. 2009;3(2):177-186. 

In This Article

OSA and Dyslipidemia

Obesity is associated with increased plasma lipids, and adipose tissue distribution is a significant correlate of plasma lipoprotein concentrations.[78] The American Sleep Heart Health Study reported that HDL-cholesterol levels were inversely related to AHI levels, independent of obesity, in younger men and women, but not in older men; and triglycerides levels were positively associated with AHI also in younger men and women only.[79] Sleep clinic subjects with OSA demonstrated a higher prevalence of dyslipidemia compared with those without OSA, after adjustment for BMI.[80,81,82]

A few observational studies reported that nasal CPAP treatment improved lipid parameters.[45,80,83] However, to date, there are no consistent data from randomized, controlled studies to support that treatment of OSA can modify dyslipidemia. Pooled data from two randomized, controlled trials demonstrated that the group receiving CPAP treatment had a 15% reduction in total cholesterol leveL, but the between-group difference failed to achieve statistical significance.[84] Another randomized, crossover study was also negative, but the treatment period of 6 weeks was probably insufficient for changes in circulating lipid levels to occur.[36]

Low-density lipoprotein (LDL)-cholesterol, when modified by oxidation (oxidized LDL), is more injurious to endothelial cells and underlying smooth muscle cells, and is thus more atherogenic.[85] OSA was associated with enhanced lipid peroxidation, which improved with CPAP treatment.[86,87] Furthermore, we showed that HDL-cholesterol in OSA subjects, compared with that in non-OSA subjects, was unable to prevent the formation and inactivation of oxidized lipids, and the degree of HDL dysfunction was predicted by AHI, 8-isoprostane and the levels of oxidized LDL.[88]

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