The annual cost of systematic vitamin D supplementation versus assessment of S-25(OH)D status and supplementation only for those with insufficient levels (<50 nmol/L) in individuals aged ≥75 years living in Kalmar County is shown in Table 2. The net economic benefit of systematic vitamin D supplementation in all elderly individuals was estimated at €303,679, whereas that of supplementing only those with insufficiency was estimated at €858,826 (including the cost of assessment). Among nursing-home residents, these net economic benefits were estimated at €753,136 and €738,313, respectively.

The total annual cost of hip fractures (n = 378) among older adults (aged ≥75 years; n = 25,545) in Kalmar County was estimated at €7,776,902. Approximately 40% of the total hip fracture cost stemmed from nursing-home residents (Table 2).

The provision of systematic vitamin D supplementation to nursing-home residents would provide a substantial net economic benefit to society, and assessment of the vitamin D status before starting supplementation does not seem to be necessary in this high-risk group for vitamin D deficiency.

The intervention with the largest net economic benefit (Table 2) was assessment of the vitamin D status in all individuals aged ≥75 years in Kalmar County followed by supplementation of those who had insufficient S-25(OH)D levels (<50 nmol/L). The economic benefit associated with this intervention was approximately 80% larger than that associated with supplementing all individuals aged ≥75 years without previous assessment of the vitamin D status, but it was only 14-16% larger than either of the interventions in residents of nursing homes (Table 2). However, the true proportion of individuals with insufficient vitamin D levels in the population is uncertain.

Among nursing-home residents, who are a known risk group for vitamin D insufficiency, the annual net economic benefit of the two interventions was similar. Thus, in the nursing-home group, assessment of the vitamin D status prior to vitamin D supplementation does not seem to be necessary. An expert group from the French Group of Geriatrics and Nutrition has also suggested that, given the probable cost-effectiveness and safety of the intervention, a population-based rather than an individual-based approach to vitamin D supplementation, without the need of preliminary monitoring of S-25(OH)D levels, would be acceptable for nursing-home residents 38. Furthermore, the American Geriatrics Society has recently revised its recommendations, stating that routine laboratory testing for 25(OH)D levels before starting supplementation is not necessary in nursing-home populations 8, which also supports our findings.

While the results for the total elderly population were somewhat uncertain, the data for nursing-home residents were more robust. Thus, limiting systematic vitamin D supplementation to known risk groups such as the elderly and individuals who have limited exposure to the sun might be preferable. However, in addition to the economic aspects, there is also an ethical point of view. Assessment of the vitamin D status among all individuals aged ≥75 years would reach a larger population, leading to prevention of a higher number of hip fractures with associated reduced pain and suffering, and this would also affect the quality of life of this population. On the other hand, elderly citizens who consider themselves to be in good health may not need vitamin D supplementation 15. It appears that further studies are needed to determine the actual vitamin D status in the general population.

The calculations include some key figures and altering these figures would alter the outcome. The major cost driver was the 30% risk reduction of hip fracture. If this risk reduction was lower 16 the net benefit would also be lower. In the control group of the main study, only 13% had insufficient vitamin D levels 15. As a sensitivity analysis, we doubled this percentage to 25% in our calculations. There are several known risk groups in the general population who are predisposed to insufficient vitamin D levels 9, and the control group consisted of community dwelling elderly who considered themselves healthy. Hypothetically, if 50% of the individuals aged ≥75 years had insufficient vitamin D levels, the net benefit would be halved (approximately €385,000). Furthermore, in real life non-adherence to medication can also influence the outcome.

Among the nursing-home residents, as many as 76% had a S-25(OH)D level <50 nmol/L 15. A high prevalence of insufficient vitamin D in nursing-home residents has been reported previously 38. In addition, a Swedish study examining the vitamin D status of the elderly in nursing homes found that this highly prevalent vitamin D deficiency was associated with increased mortality 7.

Our decision to use 50 nmol/L as the cut-off point for insufficient S-25(OH)D levels 4111314 is further supported by the findings of a Swedish study showing that elderly women who maintain 25(OH)D levels above 50 nmol/L between the ages of 75 and 80 years have a lower incidence of both hip and major osteoporotic fractures during the following 5 years (age 80-85 years). However, over a 10-year period, a reduction in the incidence of hip fractures was only seen at serum levels above 75 nmol/L 39. Therefore, a higher target level of vitamin D (75 nmol/L) has been suggested for older, more fragile adults 813.

The calculations were based on a vitamin D dose of 800 IU daily, which is in accordance with the Nordic Nutrition Recommendations 4. A study from the United Kingdom found that treating all adults aged ≥65 years with vitamin D 800 IU daily reduced the incidence of hip fractures and the number of deaths. From a health economic perspective, the greatest savings were seen following the treatment of individuals aged ≥70 years, with similar reductions in mortality 22. Another study showed that treatment of the elderly population (aged ≥60 years) with vitamin D3 800 IU daily was associated with reductions in mortality and substantial cost-savings through fall prevention 21.

Supplementation with vitamin D and calcium has been shown to reduce the risk of hip fractures 16. However, the elderly are often already taking many medications and the addition of yet another pharmaceutical to be taken daily could meet resistance among both physicians and patients.

The protective effect of vitamin D is most often seen in those with low basal 25(OH)D levels. The evidence for improvements in bone health, total mortality, and the risk of falling is only conclusive for treatment with vitamin D combined with calcium 4. In general, treatment with oral vitamin D alone does not seem to be associated with serious harm 12. However, there appears to be a small increased risk of gastrointestinal symptoms and renal disease for vitamin D plus calcium 16. It is recommended that calcium supplementation should not be systematically prescribed, but should only be given to those who do not reach desirable calcium levels despite diet modification 38. Since some individuals, especially among the elderly, may not be able to take vitamin D supplementation that includes calcium because of these adverse events, a proportion of the elderly are treated with vitamin D alone. This was taken into account in our calculations, as the cost of the pharmaceuticals included a weighted average of the costs of vitamin D and vitamin D plus calcium supplementation.

In the United States, no primary care professional organisation currently recommends population-wide screening for vitamin D deficiency. One of the problems associated with screening is that some people may be misclassified as having vitamin D deficiency because of uncertainty about the cut-off point for defining deficiency and variability in the available 25(OH)D assay results. Misclassification can result in over-diagnosis (which may lead to non-deficient people receiving unnecessary treatment) or under-diagnosis (which may lead to deficient people not receiving treatment) 12. Another disadvantage associated with screening (assessment) is that it is a burden on the healthcare organisation with respect to personnel time and resources, which otherwise could be used in more prioritised healthcare areas.