Nocturnal Dialysis is Better for Bone

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It results in less loss in bone mineral density than conventional dialysis, new findings suggest.

 

SAN FRANCISCO—Nocturnal hemodialysis (NHD) offers superior calcium-phosphate control when compared with conventional hemodialysis (CHD), suggesting that NHD could enhance bone protection, according to Canadian researchers.

 

“Bone disease in kidney disease patients, and in particular fractures in dialysis patients, represent major problems,” said lead investigator Darren Yuen, MD, a nephrology fellow at the University of Toronto. “We also know that dialysis patients with fractures have higher mortality rates. This is a significant clinical problem, and so any type of therapy that can limit bone loss would be very helpful for dialysis patients.”

 

Patients with end-stage renal disease are at increased risk for bone loss and fracture compared with the general population in part because of disruption in the calcium-phosphate balance. Dr. Yuen and supervisors Christopher Chan, MD, and Sophie Jamal, MD, theorized that since NHD is associated with less disruption of the calcium-phosphate balance, it may be associated with less bone loss than CHD.

 

They compared changes in bone mineral density (BMD) at the hip (femoral neck, total hip) and the spine (L1 to L4) over a 12-month period in patients on CHD and patients converted from CHD to NHD, with patients dialyzing five or six nights a week. The researchers measured BMD at study entry and again at 12 months. Baseline demographic and biochemical data were obtained at study entry for the CHD group and prior to NHD conversion in the NHD group. 

 

The observational study, which was presented here during Renal Week 2007, included 52 CHD patients (mean age 66 years, 71% male) and 36 NHD patients (mean age 43 years, 58% male). Besides being older, the CHD group had a lower baseline serum calcium level (2.3 vs. 2.4 mM). However, there were no significant differences in weight, dialysis vintage, serum phosphate, parathyroid hormone, or alkaline phosphatase between the two groups at baseline.

 

After adjusting for baseline age, weight, dialysis vintage, BMD, and markers of mineral metabolism, the researchers found that the patients in both groups had a decrease in BMD at the lumbar spine, femoral neck, and total hip over the 12-month study period, but the decrease was significantly greater in the CHD patients. Compared with NHD patients, CHD patients had a 1.6% greater BMD loss at the lumbar spine, a 1.3% greater loss at the femoral neck, and a 0.7% greater loss in the total hip.

 

In addition, serum phosphate levels decreased significantly in the NHD patients from 1.58 to 1.15 mM, whereas serum phosphate levels remained fairly steady in the CHD patients (1.50 mM at baseline and 1.54 mM at 12 months).

 

The findings provide sufficient information to justify development of larger trials, Dr. Yuen said. A larger trial could better identify the mechanisms that may be involved on bone physiology in uremia in patients on NHD, he said.

 

It is important to note, he said, that the study was limited by the small number of patients and its observational design. In addition, the study looked at two separate populations and there was a relatively short follow-up. The researchers also had no fracture data available.

 

“We are still looking at what the mechanism of action may be,” said Dr. Yuen said in an interview with Renal & Urology News. “Nocturnal hemodialysis may lead to improvements in mineral metabolism and that may translate into benefits in bone.  However, we need still need to investigate this further.”

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