What can be the cause of a swollen tongue? Does sleep apnea play a part and is there any treatment?

The simple answer. is that an enlarged tongue can occur with several conditions including obesity leading to an obstruction of the airway and OSA. Weight loss can sometimes result in remediation of "macroglossia" and help with OSA. The tongue will not shrink if the problem is due to some other condition like acromegaly, hypothyroidism, vascular malformation, neurofibromatosis, mucopolysaccaridosis, MEN or angioedema.