Summary

Background & aims
Vitamin D deficiency is a condition with different causes. It is associated with numerous comorbidities such as autoimmune diseases, bone diseases, cancer, cardiovascular diseases, neurodegenerative diseases, psychiatric diseases, and respiratory infections like COVID-19. Due to its high prevalence all over the world, it is a major task for health care systems worldwide. Through a combination of low sunlight exposure, insufficient nutrition, and age-related changes in skin, liver, and kidney function, especially seniors and nursing home residents, in particular, have a significantly increased risk of developing a vitamin D deficiency.

Methods
This retrospective study analyzed the prevalence of vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] < 12 ng/ml) amongst selected Austrian nursing home seniors. It also examined whether demographic data and other laboratory values like calcium correlate with vitamin D levels by using the Pearson correlation coefficient. This correlation was graphically illustrated with a scatter plot and regression line. A total of 478 patients admitted to a nursing home in Vienna between January 3, 2017, and August 31, 2020, were included.

Results
A total of 106 seniors (22,2%) suffered from a manifest vitamin D deficiency. The vitamin D level of the men was significantly lower than the level of the women (22.9 ± ۱۲٫۶ ng/ml vs. 26.2 ± ۱۴٫۸ ng/ml, p = 0.027). The vitamin D serum levels significantly correlated with the serum calcium levels of the participants (r = 0.19, p < 0.001). 39.5% (189 out of 478) of the nursing home residents had inadequate serum vitamin D levels.

Conclusions
In summary, it can be said that the prevalence of vitamin D deficiency among nursing home residents is considerably high. Inadequate vitamin D levels were often associated with reduced calcium levels. Given the high prevalence, the numerous negative health consequences of inadequate levels, and the large therapeutic index, this risk group should get a general supplementation with a dose of 25 μg (1000 IU) vitamin D3 per day. In addition, a blood examination should be performed as early as three months after the start of the supplementation therapy. If some residents do not achieve an adequate vitamin D concentration, the substitution has to be adapted to the individual needs to treat them as precisely as possible.

Introduction

More than 100 years ago, it became apparent that an adequate vitamin D supply is essential for bone health and physical development [1]. In addition to the well-known effects on calcium and phosphate metabolism, numerous immunomodulatory properties have also been detected [2]. Therefore, the consequences of a vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] < 12 ng/ml) are extensive, from mineralization disorders with accelerated bone turnover and reduced bone density (osteopenia and osteoporosis) to extraskeletal consequences such as reduced muscle strength, acute respiratory infections, and even cancer [[3], [4], [5]]. In addition, vitamin D deficiency could also be linked with neurodegenerative diseases, psychiatric disorders, and autoimmune diseases such as diabetes mellitus, multiple sclerosis, psoriasis, and rheumatoid arthritis [[6], [7], [8], [9], [10]]. Furthermore, an association between vitamin D levels and the risk of developing cardiovascular disease could also be found [11].

Despite the numerous diseases associated with vitamin D inadequate levels, more than 40% of the European population show insufficient vitamin levels (below 20 ng/ml). Also, more than 13% have an acute deficiency (less than 12 ng/ml) [12]. Especially the elderly often suffer from low vitamin D levels in their blood serum, and several studies have already demonstrated that nursing home residents, particularly, have a significantly increased risk [13]. On the one hand, the concentration of the vitamin D3 precursor 7-dehydrocholesterol in the blood decreases with advancing age; on the other hand, the ability of the skin to synthesize vitamin D3 under UV radiation declines. A little sunlight exposure, a poor diet, and age-related changes in the skin, liver, and kidney function predispose this population group to develop a vitamin D deficiency [14]. In addition, medication such as antiepileptics and glucocorticoids can affect the vitamin D status [12].

Conclusions

In conclusion, it can be summarized that there was a high prevalence of vitamin D deficiency in the examined nursing home residents. The vitamin D serum level significantly correlated with the calcium level of the participants, and females had slightly lower vitamin D concentrations than men.

Given the numerous adverse health consequences and because a vitamin D deficiency can be easily treated, all nursing home residents should get a general supplementation of a dose of 25 μg (1000 IU) vitamin D3 per day. This dosage is considered safe, and therefore neither the kidney function nor the calcium needs to be monitored regularly. A blood test should be used no earlier than three months after starting the vitamin D supplementation therapy to check whether a sufficient serum concentration has been reached. If this is not the case, the vitamin D substitution must be adapted to individual needs and treated precisely.

In addition, further action is needed to make health workers aware of the high incidence and risks associated with vitamin D deficiency. Further research is required to establish clear, evidence-based guidelines for the prophylaxis, detection, and treatment of vitamin D deficiency in nursing homes.