Background: Nursing home residents are in high risk of vitamin D deficiency, which negatively affects bone health. Vitamin D and calcium supplements haves shown to increase bone density and reduce fracture risk. Therefore, The Danish Health Authority recommends all nursing home residents a daily supplement of 20 μg vitamin D and 800-1000 mg calcium. However, adherence to the recommendation and knowledge of it is unknown. The aims of this study were to investigate adherence, knowledge, and potential barriers to this recommendation in Denmark.

Methods: A cross-sectional electronic survey was conducted in May-June 2020 among 50 randomly selected nursing homes widely distributed in Denmark. Questions included degree of adherence to the recommendation at each nursing home as well as respondent's knowledge and attitudes towards it, and experienced barriers in relation to adherence.

Results: Respondents from 41 nursing homes answered the questionnaire, and these were mainly nurses (63%) or nursing home leaders (20%). Low adherence (≤ 40% of residents receiving both supplements) was reported at 35% of nursing homes, and only 8% of the nursing homes had a high adherence (> 80% of residents receiving both supplements). Most respondents (88%) had knowledge of the recommendation and 62% rated importance of increased implementation as high. Common explanations of low implementation were a lack of prescription by the general practitioner in the central electronic database (60%), resident-refusal to eat tablets (43%), chewing-swallowing difficulties (40%), and a high number of tablets given to the residents daily (34%).

Conclusions: The recommendation of daily vitamin D and calcium supplements to Danish nursing home residents is poorly implemented even though knowledge of the recommendation is relatively high. Barriers relate to an ambiguity of responsibility between the general practitioners and the nursing home staff, as well as the high number of tablets to be consumed in total by the residents. These barriers must be targeted to improve adherence in this vulnerable group of institutionalized older adults.