Older adults with low of vitamin D – especially those who are frail – may have a greatly increased risk of death, a new US study suggests.
The randomized, nationally representative trial, led by Ellen Smit of Oregon State University, USA, found that overall people who are frail are also more than twice as likely to die than those who were not frail. It reveals that older adults with low vitamin D levels are not only more frail than elderly who have higher levels, the researchers also found additive effects of serum 25(OH)D and frailty on all-cause mortality in older adults (hazards ratio 2.98; 95% CI: 2.01–4.42), tripling the risk of death.
For the first time, a study prospectively examined the combined effects of frailty and vitamin D status on mortality in older adults in the US. In past research, both frailty and low vitamin D levels have been separately associated with an increased risk of adverse health, but their joint effects on mortality had not been reported before.
In their study, the researchers examined more than 4,300 adults over 60 years of age using data from the Third National Health and Nutrition Examination Survey. They divided the participants into four groups. The low group had levels less than 50 nanograms per milliliter of vitamin D in the blood, measured as serum 25(OH)D. The highest group had vitamin D of 84 nanograms per milliliter or higher. The authors adjusted their analysis for gender, race, age, smoking, education, latitude and other comorbid conditions. In general they found that those who had lower vitamin D levels were more likely to be frail. However, due to the cross-sectional nature of the survey, the researchers could not determine if low vitamin D contributed to frailty, or whether frail people became vitamin D deficient because of health problems. But according to the researchers longitudinal analysis on death showed that it may not matter which occurred first, frailty or deficiency.