133 7 smaller tumors (stage I and II). Therefore, the association found between the WST outcome and treatment is also caused by tumor site and tumor stage. Unfortunately, because of the low number of patients in this study, no interactions between treatment, tumor stage, and tumor site could be explored in the linear mixed-effects model. Clinical relevance In order to improve swallowing function, promising results were found using swallowing exercises during the course of radiation treatment.26 These exercises are designed to improve swallowing safety, i.e., reduce penetration or aspiration, and increase efficiency of swallowing.27 The results found in the current study suggest that especially older patients and patients after surgery may benefit from preventive swallowing exercises, because they had a worse swallowing function. It is unknown how many patients received swallowing exercises during or after treatment. Especially in patients treated with surgery, performing swallowing exercises before, during and/or after (adjuvant) treatment may prevent dysphagia, or reduce its severity.28 Also in older patients, who are at a higher risk of aspiration due to a decrease in eating and swallowing function, swallowing exercises can help maintain or improve the oral function.29-31 In addition to providing swallowing exercises, patients can be informed about expected swallowing difficulties after treatment. It is important to set realistic expectations, so patients can cope with the effects of treatment on daily functioning.32 Information about expected difficulties can reduce distress and anxiety during treatment, and can increase active patient participation and satisfaction with provided care.32 In conclusion, in patients with head and neck cancer swallowing function changes over time from diagnosis up to 2 years after treatment, with the worst scores 3 months after treatment. A higher age and being treated with surgery are factors associated with the course of swallowing function over time. It is estimated that swallowing dysfunction occurs in 14-22% of patients with head and neck cancer before or after treatment.