Does the FTO rs9939609 AT genotype modestly increase obstructive sleep apnea risk?

The claim is scientifically supported as a modest, indirect susceptibility pathway: rs9939609 AT is associated with slightly higher body mass and waist circumference, and adiposity can promote obstructive sleep apnea (OSA) through anatomically plausible mechanical effects. It is not an individual-level prediction of obesity, visceral fat, or OSA.

Genetic and adiposity evidence

• In large mixed-ancestry data, each rs9939609 A allele was associated with approximately +0.4 kg/m² BMI, +1.3 kg body weight, and +0.8 cm waist circumference—estimates broadly applicable to AT versus TT under an additive model.
• Pooled evidence associated each A allele with higher odds of obesity (OR 1.31, 95% CI 1.26–1.36).
• The central-adiposity signal is less definitive than the BMI signal: some adjusted studies found no association with visceral or abdominal fat, suggesting that any waist effect may often track overall body mass rather than preferential visceral-fat deposition.
• A plausible upstream mechanism is altered central appetite, satiety, and food-reward signaling in A-allele carriers, including weaker satiety and greater intake of energy-dense foods.

OSA mechanisms

• Obesity-associated fat deposition in the tongue, soft palate, lateral pharyngeal walls, and parapharyngeal tissues narrows the pharyngeal lumen and raises surrounding tissue pressure. Reduced dilator-muscle activity during sleep then increases airway collapsibility; the clinical association between larger neck circumference and OSA supports this pathway.
• Abdominal loading elevates the diaphragm, reduces chest-wall compliance and functional residual capacity, and increases transdiaphragmatic pressure. Lower end-expiratory lung volume reduces caudal tracheal traction, further destabilizing the upper airway.

Bottom line

• AT genotype confers a small population-level tendency toward higher body mass, and possibly waist size; if clinically meaningful adiposity develops, especially in neck/upper-airway or abdominal compartments, it can increase OSA risk through established mechanical pathways.