Wern Yew Ding, MBChB
Obstructive sleep apnea (OSA) is common in morbidly obese patients and has been linked to the initiation and maintenance of atrial fibrillation (AF), which in turn predisposes patients to an increased risk of ischemic stroke. The benefits of gastric banding in patients with and without AF have previously been demonstrated. However, there is a lack of studies examining the effects of OSA in such patients.
In this study by Dalmar and colleagues, the authors sought to determine whether incident AF and stroke rates after gastric banding are influenced by OSA using a single-centre retrospective analysis of 853 morbidly obese patients (defined as body mass index ≥35 kg/m2 with obesity-associated comorbidity or body mass index ≥40 kg/m2) who failed conservative treatment for weight loss and were selected for laparoscopic adjustable gastric banding by a multidisciplinary team approach. Most patients were females (84%) with a mean age of 44 years old, body weight of 136kg and body mass index of 48.6 kg/m2. OSA was present in 27% of this cohort. Over a follow-up period of 6 years, it was reported that new-onset AF and incident stroke were significantly higher in the OSA group than in the non-OSA group (new-onset AF: 1.7% vs 0.5%, incident stroke: 2.1% vs. 0.5%). The findings persisted after propensity score matched analysis to account for differences in baseline characteristics between the groups. Furthermore, OSA was found to be an independent risk factor for new-onset AF and incident stroke after adjustment for other risk factors.
There are a few issues to consider with this study. First, the presence of OSA was determined from medical records — it was unclear how many of these patients had been appropriately investigated and whether or not they were receiving treatment for their OSA, which may have influenced the results. Second, the fact that laparoscopic adjustable gastric banding led to sustained weight loss was reassuring. However, though the degree of weight loss was comparable between the groups at 3 years, it should be noted that gradual weight gain was observed in patients with OSA at 4 years after the procedure (but not in the non-OSA group). This is an important confounder as the timing coincides with the divergence of Kaplan-Meier curves for the incidence of stroke or transient ischaemic attack between the groups. Third, the diagnosis of AF may have been underestimated given the apparent lack of continuous cardiac monitoring. Overall, it remains unclear whether gastric banding has a beneficial role for the prevention of AF and stroke in morbidly obese patients with OSA, though the results of this study are interesting and provide further evidence on the negative impact of OSA in cardiovascular and cerebrovascular disease. It also highlights the need for OSA screening and aggressive intervention among these patients.
