Weight loss is the single most important factor for improving cardiovascular health in obese obstructive sleep apnoea (OSA) patients, claim researchers from a multidisciplinary team at the Perelman School of Medicine at the University of Pennsylvania.
Writing in the New England Journal of Medicine, they state that obesity and OSA tend to co-exist and are associated with a variety of cardiovascular risk factors, including inflammation, insulin resistance, abnormal cholesterol, and high blood pressure.
“We performed this study to find out to what degree obesity and OSA contribute to the burden of cardiovascular risk factors and to quantify the reduction in these risk factors achieved by weight loss, therapy for sleep apnoea, weight loss surgery, or the combination of both” said lead study author, Dr Julio Chirinos, assistant professor of Medicine at Penn.
The investigators randomly assigned 181 participants with obesity, moderate-to-severe OSA and high C-reactive protein levels (CRP) (an inflammatory marker associated with heart disease) for 24 weeks to either weight loss therapy, CPAP therapy, or the combination of weight loss and CPAP.
The authors then evaluated the incremental effect of combination therapy with CPAP and weight loss over each therapy alone, on subclinical inflammation, insulin resistance, dyslipidemia and blood pressure in obese subjects with OSA.
Among the 146 participants for whom there were follow-up data, those assigned to weight loss only and those assigned to the combined interventions had reductions in CRP levels, insulin resistance, and serum triglyceride levels.
None of these changes were observed in the group receiving CPAP alone. Blood pressure was reduced in all three groups and no significant incremental effect on CRP levels was found for the combined interventions, compared with either weight loss or CPAP alone.
Reductions in insulin resistance and serum triglyceride levels were greater in the combined-intervention group than in the group receiving CPAP only, but there were no significant differences in these values between the combined-intervention group and the weight-loss group.
In per-protocol analyses, which included 90 participants who met pre-specified criteria for adherence, the combined interventions resulted in a larger reduction in systolic blood pressure and mean arterial pressure than did either CPAP or weight loss alone.
“These data argue against an independent causal relationship between obstructive sleep apnoea and these cardiovascular risk factors in this population and suggest that CPAP is not an effective therapy to reduce the burden of these particular risk factors,” said Chirinos. “These findings also indicate that weight loss therapy should be a central component of strategies to improve the cardiovascular risk factor profile of obese patients with OSA. The design of this trial allowed us to conclude that both obesity and sleep apnoea are causally related to high blood pressure.”
In addition, the results suggest that adhering to a regimen of weight loss and CPAP therapy will result in larger reductions in blood pressure as compared with either therapy alone. Future research should assess how to best deliver effective weight loss programmes for these patients, as well as research on strategies to enhance CPAP adherence or to identify subjects that are most likely to demonstrate an important reduction in blood pressure with CPAP would be desirable.