Fall Risk in Hemodialysis Patients Linked to Vitamin D Metabolite
DENVER—Hemodialysis (HD) patients who suffer from vitamin D deficiency may be at increased risk of falls and fractures, data suggest.
According to a study conducted at the University of Western Australia in Perth, suboptimal levels of 25-hydroxyvitamin D (25[OH]D) are associated with reduced quadriceps muscle strength and an increased risk of falls, independent of 1,25 dihydroxyvitmain D (1,25-[OH]2D) or intact parathyroid hormone (iPTH), according to researchers at the University of Western Australia in Perth.
“No one has studied this group before, and in view of their high rates of falls, high rates of fractures, and increased mortality we thought it was a good idea to investigate,” said lead researcher Paul Glendenning, PhD, MBChB, Clinical Associate Professor in the university's Department of Medicine and Clinical Consultant Pathologist at Royal Perth Hospital in Perth. “The traditional focus in end-stage renal failure has been on the active metabolite of vitamin D: 1,25 dihydroxyvitamin D. We believe there are data to substantiate that the other less active metabolites, including 25-hydroxyvitamin D, are equally important.”
He presented study findings here at the 31st annual meeting of the American Society for Bone and Mineral Research.
Vitamin D deficiency is common among HD patients, who are at increased risk for hip fracture and fall compared to non-uremic individuals. Clinical trials show that supplementation with calcium and cholecalciferol reduces the risk of hip and other non-vertebral fractures in older patients with intact renal function. However, the relationship between 25-(OH)D and the risk for falls has not been investigated in dialysis populations.
In a study of 25 HD patients, Dr. Glendenning and his colleagues obtained pre-dialysis measurements of 25-(OH)D, 1,25-(OH)2D, and intact parathyroid hormone (iPTH). They assessed fall risks using the FallsScreen, Berg Balance Scale (BBS) and Timed “up and go” (TUG) test.
FallsScreen is a falls risk calculator that helps measure visual edge contrast, proprioception, reaction time, quadriceps strength, and balance. The BBS helps determine a patient's ability to balance, and the TUG test is a measure of balance and muscle strength. The mean age of the subjects was 69.8 years and the median time on dialysis was 3.1 years (range 0.5 to 15.3 years). Muscle strength correlated positively with 25-(OH)D levels, but not 1,25-(OH)2D levels or iPTH.
“We saw a clear association between surrogate measures of fall risk and 25-(OH)D, but not 1,25-(OH)2D,” Dr. Glendenning said. “We believe this may be relevant as vitamin D could have a para-autocrine effect in muscle independent of it's traditional endocrine role. There was a large and meaningful difference between muscle strength in those patients with a 25-(OH)D level below 50 nmol/L and those with 25-(OH)D level above 50 nmol/L, which translated into big differences in the FallsScreen test.”
He suggests that clinicians should measure 25-(OH)D in HD patients and start using calciferol (unactivated sterols) in patients who are deficient in 25-(OH)D in HD patients.
As he states, “we are not advising clinicians to stop using calcitriol or alpha-calcidol (activated sterols) in HD patients as the activated sterols have an important effect on suppressing PTH. In contrast, unactivated sterols such as cholecalciferol or ergocalcifierol have weak effects on PTH suppression but may have strong effects on muscle strength.”