Objectives:

Studies attempting to assess the association between the neck circumference (NC) and the apnea-hypopnea index (AHI) gave inconsistent results. We aimed to assess the effect modification of gender in the association between the NC and the AHI in stroke-free older adults living in Atahualpa (rural Ecuador).

Methods:

The study included 190 stroke-free Atahualpa residents aged ≥60 years who underwent brain MRI, polysomnography, assessment of cardiovascular risk factors, the NC and nasal septum deflection.

Results:

The mean age of the study population was 71.1±7.6 years, and 64% were women. The mean NC (37.4±2.6 versus 34±2.5 cm; p<0.001) as well as the mean AHI (14.4±14.5 versus 10.5±11.1 episodes per hour; p=0.039) were greater in men than in women. A fully-adjusted generalized linear model showed significant main effects for NC, gender, and a significant interaction between gender and NC over the AHI (dependent variable). Average AHI increased significantly as NC enlarged, but this change was different in men and women. Men started with lower AHI margins at the 10th percentile of the NC, and while both significantly increased, men had a much larger rate of change in the average AHI. Therefore, at the 90th percentile of NC, men had a larger average AHI than women.

Conclusions:

This study shows a significant effect modification of gender in the association between NC and AHI. Differences in cervical fat tissue distribution between men and women probably accounted for such effect.