BMJ  2006;332 (15 April), doi:10.1136/bmj.332.7546.0-e

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Vitamin D plus calcium prevents falls in older women but not older men

Research question Which subgroups of older people benefit most from vitamin D plus calcium?

Answer The supplements help to prevent falls in women but not men. Older women who are less active than average benefit most.

Why did the authors do the study? These authors had already shown that taking extra vitamin D (cholecalciferol) can reduce falls in older people by 20%. They wanted to find out whether the benefits were different for men, women, and other subgroups defined by physical activity or baseline serum concentration of 25-hydroxyvitamin D (25-hydroxycholecalciferol).

What did they do? They analysed data on falls from a previous randomised trial examining the effects of vitamin D plus calcium on bone mineral density in older people living in the community. Falls were a secondary outcome in this trial, which had one author in common with the current analysis. The trial was double blind and included 199 men and 246 women aged over 65 who took 700 IU of cholecalciferol plus 500 mg of calcium or a placebo of identical appearance once a day for three years. Participants recorded falls on a card, which they posted to the research team, who obtained further details at follow-up visits every six months.

The current authors used multiple logistic regression analysis to estimate the impact of supplements on the risk of falling at least once. The main analyses were intention to treat and controlled for 12 possible confounders, including age, body mass index, dietary calcium intake, and smoking.

What did they find? 54% of the women (134/246) and 49% of the men (97/199) fell at least once during the three years. Vitamin D plus calcium did not prevent falls overall, or in men. But it did reduce the risk of at least one fall in the subgroup of 229 older women (odds ratio 0.54; 95% CI 0.30 to 0.97), particularly those who were less active than average (n = 130; 0.35 (0.15 to 0.81)). The supplements did not preferentially benefit women with a low serum concentration of 25-hydroxyvitamin D at the start of the trial. Nor did they reduce the total number of falls reported by women or men.

The benefits for women appeared after about a year of treatment and persisted for the rest of the three year follow-up period.

What does it mean? These findings are from subgroup analyses so should be treated with caution. They are also from a trial that was designed to look primarily for the effects of supplements on bone mineral density, not on falls. So the current analyses are likely to be underpowered. They do suggest, however, that older women, but not older men, fall less when they are taking extra calcium and vitamin D. It's still unclear exactly why, although we do know that vitamin D deficiency causes proximal muscle weakness, and that human muscle contains receptors for 1,25-dihydroxyvitamin D that promote protein synthesis and decline with age.

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Bischoff-Ferrari HA, et al. Effect of cholecalciferol plus calcium on falling in ambulatory older men and women Arch Intern Med 2006;166: 424-30[Abstract/Free Full Text]

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