Friday, June 1, 2012
Newly reported research studies reiterate the benefits of vitamin D in older adults for helping to prevent falls, maintain mobility, and reduce age-related disability. However, optimal dosing strategies and blood levels of vitamin D in this population need further elaboration, and the quantity and quality of clinical research in this area has been disappointing.
Preventing Painful Falls in Older Adults
The United States Preventative Services Task Force (USPSTF) recently released updated clinical guidelines on the prevention of painful falls in community-dwelling older adults [access document here]. Two primary recommendations for fall prevention were vitamin D supplementation and exercise, as also reported in an early online edition of the Annals of Internal Medicine by Virginia Moyer, MD, MPH, on behalf of the USPSF [Moyer 2012, see ref below].
Moyer notes that falls are the leading cause of injury in adults aged 65 or older. For the USPSTF report, researchers reviewed more than 50 clinical trials and found good evidence that exercise and vitamin D supplementation were effective at reducing falls in this population, and were associated with few harms. Therefore, the report concludes that healthcare providers should prescribe both exercise and vitamin D to their elderly patients.
More specifically, the USPSTF reviewed 9 trials focusing on vitamin D supplementation and found a statistically significant 17% reduction in risk for falling during 6 to 36 months of follow-up and a number needed to treat of 10. That is, for every 10 persons treated with vitamin D there would be 1 less fall.
Benefits were greater in older adults who were deficient in vitamin D at the outset. A wide range of doses and durations for vitamin D supplementation were studied, with a median dose of 800 IU daily and a median treatment duration of 12 months. The data suggest that benefits from vitamin D supplementation occur by 12 months, but the efficacy of shorter treatment is still unknown and optimal vitamin D levels, measured as 25(OH)D, were not indicated in the report.
Effects on Mobility & Disability
Another new study, appearing recently in the Journal of Gerontology: Medical Sciences, reports that older adults who do not get enough vitamin D may be at increased risk of developing mobility limitations and disability [Houston et al. 2012, see ref below]. Researchers analyzed data during 6 years of follow-up in the Health, Aging, and Body Composition (Health ABC) study from the U.S. National Institute on Aging. Mobility limitation and disability were defined as any difficulty or inability to walk several blocks or climb a flight of stairs.
Approximately 2,100 community-dwelling persons aged 70 to 79, men and women, black and white, were included. Upon entering the study, eligible participants reported no difficulty walking one-fourth mile, climbing 10 steps, or performing basic, daily living activities, and they were free of life-threatening illness. Occurrences of mobility limitations and disability during the 6-year follow-up were assessed at annual clinic visits and telephone interviews every 6 months.
At baseline, 65% of all subjects had insufficient vitamin D levels <30 ng/mL 25(OH)D; the level was <20 ng/mL in 30% of those cases. Among all of these elderly persons there was about a 30% increased risk of mobility limitations, and almost a 2-fold greater risk of mobility disability in the lowest group (<20 ng/mL), compared with elderly study subjects having 25(OH)D levels ≥30 ng/mL.
In a press release [here], lead author Denise Houston noted that vitamin D plays an important role in muscle function, so it is plausible that low levels of the vitamin could result in the onset of decreased lower-muscle strength and physical performance. She said that vitamin D may indirectly affect physical function, since low vitamin D levels have also been associated with diabetes, high blood pressure, and cardiovascular and lung disease — conditions that are frequent causes of decline in physical function.
“Higher amounts of vitamin D may be needed for the preservation of muscle strength and physical function as well as other health conditions,” Houston continued, “however, clinical trials are needed to determine whether increasing vitamin D levels through diet or supplements has an effect on physical function.”
COMMENTARY: Encouragement & Disappointment
Vitamin D for pain has been extensively discussed in our evidence-based research papers [here] and an ongoing series of Pain-Topics UPDATES [here]. The latest two studies, discussed above, were of good quality and suggest encouraging benefits of vitamin D supplementation in older persons, but there also are some disappointments.
The USPSTF report noted a median 800 IU/day dose of vitamin D, without specifying vitamin D2 or D3, and considerable time (12 months) appeared necessary to realize beneficial outcomes in terms of reduced falls. The report also does not specify optimal blood levels of vitamin D, measured as 25(OH)D. The study by Houston et al. clearly suggests that 25(OH)D levels >30 ng/mL are optimal for maintaining mobility and moderating disability, both of which also might facilitate exercise and help to prevent falls. However, the recommended daily dose of vitamin D to achieve and sustain more adequate 25(OH)D levels is not defined.
The latest guidance from the U.S. Institute of Medicine recommended a daily allowance of 600 IU vitamin D for adults aged 51 to 70 years and 800 IU for adults older than 70 years [see discussion of IOM report here]. Similarly, the American Geriatric Society recommends 800 IU per day for persons at increased risk for falls. In either case, there is some controversy about he recommendations and those daily amounts are based on minimal requirements for maintaining bone health; they are most likely severely inadequate for persons with pain or in the elderly at risk for falls, which also might be influenced by limited mobility and/or disability.
As noted in prior Pain-Topics reports and UPDATES, most experts in the field believe that much larger daily doses of vitamin D, specifically D3 (cholecalciferol), are more optimal for achieving 25(OH)D levels above 30 ng/mL. Doses significantly larger than 800 IU of D3/day also might shorten the time to realize beneficial effects, although this has not been studied.
As Houston and colleagues suggest, additional prospective clinical trials are needed to assess beneficial effects of vitamin D supplementation as well as the optimal dosing protocols to achieve those desired outcomes. Why more and better studies have not been done is inexplicable and highly disappointing.
In a previous UPDATE [here] we reported on the only prospective, randomized, double-blind, placebo-controlled trial examining benefits of vitamin D supplementation on quality of life, functional mobility, and pain relief in the elderly. Nearly two-thirds of the subjects had vitamin D insufficiencies (<30 ng/mL) at baseline, similar to what Houston et al. found in their study, and supplementation with the vitamin was generally beneficial. However, the vitamin D dosing regimen tested — single, megadose administration of 300,000 IU — was inappropriate for producing sustainable and robust effect sizes.
Clearly, this is an area of pain management that is ripe for further investigation.
> Houston DK, Neiberg RH, Tooze JA, et al. Low 25-Hydroxyvitamin D Predicts the Onset of Mobility Limitation and Disability in Community-Dwelling Older Adults: The Health ABC Study. J Gerontol A Biol Sci Med Sci. 2012; online ahead of print [abstract here].
> Moyer VA. Prevention of Falls in Community-Dwelling Older Adults: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2012;157: online ahead of print [article here].