Vitamin D Supplementation Efficacy and Its Relationship to Grip Strength and Gait Speed in the Oldest Olds with Functional Dependence

different ABSTRACT Vitamin D deficiency is common in older people and oral vitamin D supplementation is considered safe. The main aim of this study was to evaluate the efficacy of vitamin D supplementation and its relationship to muscle strength and function in the oldest of the olds with functional decline. A total of 44 nursing home residents (mean age 85.1 years) participated in the study. The serum concentrations of 25-hydroxycholecalciferol (25(OH)D) and parathyroid hormone were measured at the beginning of the study, at three months and at six months. Based on their initial 25(OH)D measurement, the subjects were divided into two subgroups: one with 21 patients with 25(OH)D <10 ng/ml and the other with 23 patients with 25(OH)D ≥10 ng/ml. All the participants followed a three-month oral calciferol supplementation schedule. At the beginning of the study and after three months of vitamin D supplementation, all the participants had their handgrip strength assessed and were administered the timed up and go test (TUGT). For the whole group, the mean (SD) 25(OH)D serum concentration at the beginning of the study was 10.10 (6.07) ng/ml (8.11 (1.01) ng/ml in the first subgroup and 15.92 (9.02) ng/ml in the other); after three months of calciferol supplementation it was 32.05 (6.61) ng/ml (p<0.001). No relationship was found between vitamin D status and handgrip strength nor TUGT. Vitamin D supplementation is effective to increase in 25(OH)D serum levels in elderly patients with functional decline. However, no relationship between vitamin D concentration and muscle strength and function was observed.


Introduction
Vitamin D is a well-known regulatory factor, not only in calcium and phosphorus homeostasis, but also in extraskeletal actions.
It contributes to tissue health, reduces telomere-shortening rate, reduces cancer risk and appears to influence the optimal ageing process [1,2]. Moreover, vitamin D deficiency is common amongst elderly people, is linked to many chronic illnesses and its receptor expression in muscles decreases with age [3,4]. 7-Dehydrocholesterol concentration, the substrate for UV-induced skin vitamin D synthesis, is significantly reduced in the elderly when compared to young adults [5]. In addition, nutrition intake, calcium absorption, renal 1-alpha-hydroxylase activity and vitamin D receptors in different tissues decline with advanced age [6,7]. Evidence from different countries has highlighted vitamin D deficiency as a prevalent public health problem, but data on the vitamin status in older adults are insufficient [8,9]. In clinical practice, measurement of the total serum 25-hydroxycholecalciferol (25(OH)D) level is recommended to determine vitamin D status.
Oral vitamin D supplementation is considered safe, well founded and recommended for use all over the world [10].

ARTICLE INFO ABSTRACT
Vitamin D deficiency is common in older people and oral vitamin D supplementation is considered safe. The main aim of this study was to evaluate the efficacy of vitamin D supplementation and its relationship to muscle strength and function in the oldest of the olds with functional decline. A total of 44 nursing home residents (mean age 85.1 years) participated in the study. The serum concentrations of 25-hydroxycholecalciferol (25(OH)D) and parathyroid hormone were measured at the beginning of the study, at three months and at six months. Based on their initial 25(OH)D measurement, the subjects were divided into two subgroups: one with 21 patients with 25(OH)D <10 ng/ml and the other with 23 patients with 25(OH)D ≥10 ng/ml. All the participants followed a three-month oral calciferol supplementation schedule. At the beginning of the study and after three months of vitamin D supplementation, all the participants had their handgrip strength assessed and were administered the timed up and go test (TUGT). For the whole group, the mean (SD) 25(OH)D serum concentration at the beginning of the study was 10.10 (6.07) ng/ml (8.11 (1.01) ng/ml in the first subgroup and 15.92 (9.02) ng/ml in the other); after three months of calciferol supplementation it was 32.05 (6.61) ng/ml (p<0.001). No relationship was found between vitamin D status and handgrip strength nor TUGT. Vitamin D supplementation is effective to increase in 25(OH)D serum levels in elderly patients with functional decline. However, no relationship between vitamin D concentration and muscle strength and function was observed. and handgrip strength, that identify and characterise sarcopenia [11]. The main aim of this study was to evaluate the efficacy of vitamin D supplementation and its relationship to muscle strength and function in the oldest of the olds with functional decline.

Materials and Methods
The study group consisted of 32 women and 12 men aged between 75 and 98 years with a mean age of 85.1 years. All the subjects were nursing home residents with similar levels of sun exposure and diets that contained about 700 mg of calcium.

Results
For the whole group, the first measurement of vitamin D status (taken at the beginning of the study) determined from the 25(OH) D serum concentration was 10.10 (6.07) ng/ml (mean (SD)).   [1], after three months of vitamin D supplementation [2], after another three months during which vitamin D supplementation was no longer administered [3]).   ng/ml, higher than in our study [16]. Taking into account the lower 25(OH)D concentration after three successive months without supplementation, sufficient vitamin D supplementation should be systematically applied to achieve permanent optimal blood 25(OH) D concentrations necessary for skeletal and extraskeletal actions.
Nonetheless, at the time this study was conducted, the Polish guidelines for vitamin D supplementation were not well established and as a consequence may be the main reason for the low compliance of the recommendations for vitamin D supplementation [17].
Moreover, optimal vitamin D blood concentration can be defined by several criteria, for example PTH. In a global study, certain correlation trends with PTH have been found in subgroups with an initial lower vitamin D status and significantly higher PTH [18].

Conclusion
Our study presents data indicating that vitamin D supplementation is effective amongst advanced age patients with

Declaration of Conflict of Interest
None.