Age and Ageing Advance Access originally published online on January 25, 2007
Age and Ageing 2007 36(2):233; doi:10.1093/ageing/afl177
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Reply
Sir—As Dr Zeimer states, our randomised controlled trial of vitamin D supplementation was not double-blind [1]. However, a double-blind design is more important when the trial outcome is a subjective one (such as well-being or pain relief); its absence should not have been critical in our trial where the outcome measures (fractures and falls) were more objective. While the mean duration of follow-up in our trial was only 10 months, 1,233 participants continued in the trial for >12 months (up to 20 months) and Table 1 shows that there was no reduction in non-vertebral fractures or falls in participants allocated vitamin D even in the second year. Also, one would expect any effect of vitamin D in preventing non-vertebral fractures to be evident within the first year because most of the effect on bone density is attained within the first year. A two-year randomised trial of vitamin D in elderly women showed that femoral neck bone density was on average 1.7% greater in women allocated vitamin D than placebo by the end of the first year, and only 2.3% greater by the end of the second year [2] (most of the effect was therefore evident within the first year). Another such trial produced similar results [3]. Vitamin D might also prevent fractures by reducing the risk of a fall, and while our trial showed no reduction in falls, it is recognised that people with very low serum 25(OH) vitamin D concentration have impaired muscle function and power that predispose to falling [4], and a study of vitamin D supplementation in such women showed substantial improvement in muscle function and power after only 6 months, with much of the improvement apparent after 3 months [4]. Moreover, in the two trials of vitamin D supplementation (with or without calcium) showing the greatest reduction in incidence of non-vertebral fractures in treated patients, the proportional reduction in fractures in the first year was similar to that during the second and third year of the two trials [3, 5]. We conclude therefore that the failure of our trial to show the effect of vitamin D in preventing fractures was not attributable to short duration; rather, that it supports the results of larger recently published trials in showing no protective effect of vitamin D.
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Wolfson Institute of Preventive Medicine Barts & The London, Queen Mary's School of Medicine and Dentistry Charterhouse Square, London EC1M 6BQ, UK
* To whom correspondence should be addressed Tel: ++44 (0) 20 7882 6268; Fax: ++44 (0) 20 7882 6270. Email: m.r.law{at}qmul.ac.uk
References
- Law M, Withers H, Morris J, Anderson F. (2006) Vitamin D supplementation and the prevention of fractures and falls: results of a randomised trial in elderly people in residential accommodation. Age Ageing 35 482–86.
[Abstract/Free Full Text] - Ooms ME, Roos JC, Bezemer PD, van der Vijgh WJF, Bouter LM, Lips P. (1995) Prevention of bone loss by vitamin D supplementation in elderly women: a randomized double-blind trial. J Clin Endocrinol Metab 80 1052–8.[Abstract]
- Dawson-Hughes B, Harris SS, Krall EA, Dallas GE. (1997) Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med 337 670–6.
[Abstract/Free Full Text] - Glerup H, Mikkelsen K, Poulsen L, et al. (2000) Hypovitaminosis D myopathy without biochemical signs of osteomalacic bone involvement. Calcif Tissue Int 66 419–24.[CrossRef][ISI][Medline]
- Chapuy MC, Arlot ME, Duboeuf F, et al. (1992) Vitamin D3 and calcium to prevent hip fractures in elderly women. N Engl J Med 327 1637–42.[Abstract]
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