Factors Associated with the Intention to Use Vitamin D Supplements: Quantitative Study among a Sample of Elderly People in a Medium-Sized Town in the Netherlands

The objective of this study was to assess which factors are related to the intention of elderly people to use vitamin D supplements. A questionnaire that was based on several theories, feedback of experts, and personal interviews with members of the target group was distributed among a random sample of 497 elderly people in a medium-sized town in the Netherlands (response 46%). Variables measured included perceived susceptibility, severity and control with respect to developing a vitamin D deficiency or getting a bone fracture, and beliefs, perceived social norms, modeling, self-efficacy, and intention with respect to the use of vitamin D supplements. Univariate analyses of variance, chi-square tests, stepwise multiple regression, and stepwise logistic regression analysis were performed. Respondents reporting a high intention had more positive attitudes and normative beliefs, higher self-efficacy expectations with respect to using vitamin D supplements, and more often used other supplements than respondents with a low intention. Subjects who already used vitamin D supplements were more often female and already familiar with the advice and had more positive attitudes and normative beliefs than nonusers. It was concluded that many elderly people have high intentions to start using vitamin D supplements as soon as they hear about the advice. A health promotion campaign to promote the use of vitamin D supplements should aim at making elderly people familiar with the Health Council of the Netherlands' advice. Furthermore, the campaign should place emphasis on changing attitudes, perceived social norms, and self-efficacy expectations toward vitamin D supplement use.