Differences in abdominal and neck circumferences in patients with and without obstructive sleep apnoea

We have recently shown that patients with sleep apnoea have thicker necks than non-apnoeic snoring controls. However, it was not clear whether this difference simply reflects the fact that apnoeic patients are more obese than the non-apnoeic ones, or whether it represents a preferential distribution of fat over the neck region compared to the abnormal region. We therefore measured the neck and abdominal circumferences in a large group of 670 patients suspected of having sleep apnoea, all of whom had full nocturnal polysomnography, including measurement of snoring. We divided these patients into apnoeic and non-apnoeic groups based on the apnoea/hypopnoea index (AHI) of 10. Apnoeic patients had significantly higher body mass index (BMI), neck, and abdominal circumferences than non-apnoeic controls. We then matched apnoeic and non-apnoeic patients exactly, one-for-one for BMI and age; this procedure left us with 156 patients in each group. Abdominal circumferences were similar, but the neck circumference was significantly higher in apnoeic patients (41.2 +/- 3.5 cm vs 39.1 +/- 3.7 cm, p less than 0.0001). Multiple stepwise linear regression analysis revealed that neck circumference and BMI correlated significantly with apnoea (multiple R2 = 0.27, p less than 0.001) and snoring (multiple R2 = 0.19, p less than 0.001). We conclude that obese patients with sleep apnoea have fatter necks than equally obese non-apnoeic snorers, and that the neck circumference could be a significant determinant of apnoea and snoring.