Vitamine D en ouderen*
Uit een kleine Nederlandse studie onder 116 ouderen van gemiddeld 79 jaar blijkt dat vitamine D supplementatie goed kan zijn voor ouderen met al duidelijke balansproblemen. Aan het begin van de studie hadden alle ouderen een duidelijk
vitamine D tekort en was de gemiddelde bloedwaarde vitamine D 13,9 ng/ml. De helft van de ouderen kreeg 16 weken lang iedere week een supplement van 210 mcg vitamine D3, de andere helft een placebo. Na 16 weken bleek in de vitaminegroep de bloedwaarde gestegen te zijn tot gemiddeld 26,2 ng/ml en dat zonder bijwerkingen. Ouderen die al in het begin van de studie duidelijke balansproblemen hadden bleken duidelijk verbeterd te zijn. Bij de anderen werden geen verschillen vastgesteld.
Weekly Vitamin D3 Improves Vitamin D Insufficiency but Not Neuromuscular Function in Older Adults
Weekly treatment with 8400 IU of vitamin D3 raises serum 25-hydroxyvitamin D [25(OH)D] concentrations, but does not improve neuromuscular function in elderly, vitamin D–insufficient individuals, according to the results of a randomized controlled, double-blind trial reported online in the American Journal of Clinical Nutrition.
"Vitamin D insufficiency, which is prevalent in older individuals, is associated with bone and muscle weakness and falls," write Paul Lips, from Vrije Universiteit Medisch Centrum, Amsterdam, Netherlands, and colleagues. "We examined the effects of a weekly dose of 8400 IU vitamin D3 on postural stability, muscle strength, and safety."
Participants 70 years or older with 25(OH)D concentrations of 20 ng/mL or less but at least 6 ng/mL were randomly assigned to receive a weekly dose of 8400 IU of vitamin D3 or placebo. The main endpoint of the study was mediolateral body sway with eyes open, measured with use of the AccuSwayPLUS platform (Advanced Medical Technology Inc, Watertown, Massachusetts). The short physical performance battery and serum 25(OH)D concentrations were secondary outcomes. Safety and tolerability were evaluated, and treatments were compared by use of an analysis of covariance model.
Strength of Randomized Study Design
"An increasing number of studies report on significant associations between low serum levels of 25-hydroxyvitamin D (25-(OH)D) and a multitude of extra-skeletal diseases and pathological conditions," Meinrad Peterlik, PhD, MD, professor emeritus of pathophysiology at Medical University Vienna in Vienna, Austria, told Medscape Nutrition when asked for independent comment.
"However, these mostly observational studies are rarely controlled for potential confounders, and interventional trials that would prove a causative relation between a compromised vitamin D status and disease incidence are rare. The main strength of the study by Lips et al. thus lies in the fact that it was designed as a randomized controlled multicenter trial to evaluate the effect of vitamin D3 supplementation on a well defined neuromuscular functional parameter, i.e., body sway, in a group of elderly people with sub-optimal vitamin D supply."
In patients treated with 8400 IU of vitamin D3 (n = 114) but not in patients receiving placebo (n = 112), serum 25(OH)D concentrations increased significantly from 13.9 to 26.2 ng/mL (P < .001). Mediolateral sway and short physical performance battery at 16 weeks were not significantly different between treatment groups.
Treatment with 8400 IU of vitamin D3 was associated with significantly decreased sway vs treatment with placebo (P = .047) in patients with elevated baseline sway but not in patients with normal baseline sway, based on a post hoc analysis of patients subgrouped by baseline sway (≥ 0.46 vs < 0.46 cm).
"Weekly treatment with 8400 IU vitamin D3 raised 25(OH)D concentrations in elderly, vitamin D–insufficient individuals," the study authors write. "Treatment with 8400 IU vitamin D3 did not reduce mediolateral sway significantly compared with treatment with placebo in this population, although in post hoc analysis, treatment with 8400 IU vitamin D3 reduced sway in the subgroup of patients who had elevated sway at baseline. Weekly treatment with 8400 IU vitamin D3 was well tolerated."
Parathyroid hormone levels decreased significantly in the vitamin D3 group but not in the placebo group. Both groups had similar adverse events and incidences of hypercalcemia, hypercalciuria, and elevated creatinine levels.
Limitations of the Study
"Although the results are straightforward, their interpretation is hampered by a number of facts, most of which are appropriately addressed by the authors themselves," Dr. Peterlik told Medscape Nutrition. "However, they fail to discuss what impact the optimization of calcium intake in the entire study group could have had on the outcome of the study. It could well be that at high calcium intake levels vitamin D supplementation is only minimally effective. This would not be surprising since a recent study by one of the coauthors (Pfeifer et al., Osteoporosis Int. 20:315-322, 2009) shows a positive effect of combined vitamin D and calcium supplementation on parameters of muscle function in elderly people."
Limitations acknowledged by the study authors include small size and unusually healthy condition of the elderly participants. In addition, a substantial number of participants had mediolateral sway values at baseline that were consistent with participants who did not fall, suggesting that their balance as measured by sway was adequate. There may have been little room for improvement of sway and physical performance with treatment in these patients.
"It is clear that elderly individuals with an increased body sway will benefit from a daily dose of 1200 IU vitamin D3 in combination with intake of > 1000 mg calcium per day," Dr. Peterlik concluded. "Additional studies with fracture rates as endpoint are necessary to prove that the observed reduction of body sway actually has a substantial impact on the incidence of falls and osteoporotic fractures in elderly people."
Merck & Co Inc supported this study, employs 5 of the study authors, and provided research grants to 4 other study authors. Dr. Peterlik has disclosed no relevant financial relationships.
Am J Clin Nutr.
Clinical Context
Vitamin D insufficiency is common in older adults, and epidemiologic studies link vitamin D insufficiency with a higher risk for falls. A previous meta-analysis by Bischoff-Ferrari and colleagues, which was published in the April 28, 2004, issue of the Journal of the American Medical Association, examined the results of 5 randomized trials of vitamin D supplementation to prevent falls in older adults. The researchers concluded that vitamin D supplementation reduced the risk of falling by 22%, and this improvement was independent of the type of vitamin D administration or the duration of therapy.
Vitamin D may help to reduce the risk for falls by improving neuromuscular function in older adults. The current study uses a unique objective measure to evaluate this hypothesis.
Study Highlights
· Patients eligible for study participation were 70 years or older and had low, but not severely low, levels of serum 25(OH)D, a metabolite of vitamin D (levels between 6 and 20 ng/mL). All participants were ambulatory and mentally competent.
· Patients with hypothyroidism or uncontrolled chronic disease were excluded from the study protocol, as were those who had received treatment with vitamin D within 6 months of study evaluation.
· Participants were randomly assigned to receive vitamin D3 at a dose of 8400 IU weekly or placebo. The study was double-blinded, and the treatment duration was 16 weeks.
· Participants were instructed to maintain their regular diet and exercise as well as limit their sun exposure during the trial. Calcium supplementation was offered to subjects with a low dietary calcium intake.
· The main study outcomes were postural stability and lower extremity performance. Researchers used a device that objectively measured mediolateral body sway, which is a good marker of an individual's ability to maintain balance in an upright position. The Short Performance Physical Battery consists of a series of practical exercises and was used to measure lower extremity performance.
· 226 individuals participated in the trial. The mean age of the study cohort was 78 years, 15% of participants used walking devices, and 14% of participants lived in a nursing home. The mean 25(OH)D level at baseline was 13.9 ng/mL.
· Serum 25(OH)D levels increased appropriately, as did 24-hour urinary calcium excretion, in comparing the vitamin D group vs the placebo group. Serum parathyroid hormone levels decreased in the vitamin D group but increased in the placebo cohort.
· Mediolateral sway did not change from baseline in either the vitamin D group or placebo group, and there was no significant difference between treatment groups.
· Although baseline levels of 25(OH)D did not affect the relationship between the randomized groups and the change in mediolateral sway, vitamin D was significantly more effective than placebo in improving mediolateral sway among participants with a higher degree of sway at baseline.
· Vitamin D supplementation was not effective in improving lower extremity performance vs placebo.
· The incidence of adverse events was similar in the vitamin D and placebo groups.
Clinical Implications
· A previous meta-analysis demonstrated that vitamin D supplementation significantly reduced the risk of falling in older adults. This improvement was independent of the type of vitamin D supplement used or the duration of therapy.
· The current study finds that vitamin D supplements do not improve mediolateral sway or lower extremity performance vs placebo among older adults. Vitamin D did appear to improve mediolateral sway among individuals with elevated sway at baseline. (April 2010)
