CKD Severity Is Associated with Likelihood of Vitamin D and Balance Deficits

Approximately 15% of the US population is affected by chronic kidney disease (CKD), creating a significant and costly health problem. In 2014, 118,000 individuals with end-stage renal disease (ESRD) initiated dialysis and 662,000 individuals were receiving chronic dialysis or had undergone kidney transplantation.

The risk of fracture is increased in patients with ESRD. Treatment of fractures in this patient population contributes to the total cost of care. Patients with CKD are at increased risk of fracture at all stages of disease, but the risk is exacerbated with disease progression, with the highest incidence among patients with ESRD receiving maintenance dialysis. Mortality and morbidity rates are high after fracture; a recent study found a 1-year mortality rate of 64% following hip fracture. Risk factors for fracture in these patients include older age, female sex, Caucasian ethnicity, and lower body mass index. Due to its effects on bone and balance, low vitamin D status may also be a contributing factor to the increased risk of fracture.

Fractures typically occur after a fall in this patient population; there is a correlation between increased rate of falls and increased risk of fracture. The relative risk of falls in patients at all stages of CKD is four to five times higher than that in the general population. In addition to fracture, falls are associated with head injury, wounds, and an enhanced fear of falling, leading to subsequent inactivity.

Vitamin D deficiency, measured by 25(OH)D, is estimated to be as high as 70% to 90% in the dialysis population. A meta-analysis suggested that vitamin D supplementation results in a decrease of 14% in the risk of falls in the general elderly population. Supplementation also improved gait speed in individuals >70 years of age.

Jordan F. Wickstrom, MS, and colleagues, recently conducted a study designed to examine data from the 1999-2004 National Health and Nutrition Examination Study (NHANES) to assess the prevalence of balance deficits and describe the relationships between stage and severity of CKD and vitamin D status, self-reported balance and falling problems, and measured gait speed in the CKD sample. Results of the study were reported in the Journal of Renal Nutrition [29(6):490-497].

The primary outcome measures were measured 25(OH)D levels, timed 20-feet walk, Romberg standing balance task, and self-reported balance and falling issues. The study included 8554 subjects >40 years of age. Participants were categorized into CKD stages based on glomerular filtration rate; participants with normal kidney function and CKD stages 1 and 2 served as the control group, those with CKD stages 3 and 4/5 served as the CKD groups.

In the Romberg standing balance test, following adjustment for age, in the measure when standing on a firm surface with eyes open, failure rates increased with severity of kidney disease: those in the control group failed 0% of the time, those in the CKD stage 3 a/b group failed 1% of the time, and those in the CKD stage 4/5 group failed 3% of the time. Compared with the 0% failure rate in the control group, the 3% failure rate in the stage 4/5 group was a significant increase (P=.02). In the most difficult measure (standing on a foam surface with eyes closed), the rates of failure again increased with severity of kidney disease: the control group failed 54% of the time, the CKD stage 3 a/b group failed 76% of the time, and the CKD stage 4/5 group failed 85% of the time. The stage 4/5 group has a statistically significant increased fail rate compared with that of the control group (P=.02).

The amount of time to complete the walking test increased with kidney disease severity, indicating slower gait speed. The mean times to complete the 20-feet walk for the control group, the CKD stage 3 a/b group, and the CKD stage 4/5 groups were 6.8 seconds, 8.3 seconds, and 9.8 seconds, respectively. The stage 4/5 mean time was significantly longer than the mean time for the control group and for the stage 3 a/b group (P<.001 for both). The stage 3 a/b group took significantly longer than the control group to complete the walk (P=.003).

Compared with controls, the odds of self-reporting of dizziness, difficulty in balance, or difficulty with falling in the past year were higher in the stage 3 a/b group (odds ratio [OR], 1.54; 95% confidence interval [CI], 1.29-1.83) and the stage 4/5 group (OR, 2.07; 95% CI, 1.26-3.40). The ORs in older subjects versus younger subjects were 1.02 (95% CI, 1.01-1.03); in females versus males, 1.73 (95% CI, 1.52-1.98); in former smokers versus never smokers, 1.35 (95% CI, 1.17-1.56); in current smokers versus never smokers, 1.53 (95% CI, 1.28-1.82); in those with lower levels of 25(OH)D versus higher levels, 0.99; (95% CI, 0.98-1.00); and in those with lower levels of albumin versus higher levels, 0.79; (95% CI, 0.65-0.98).

Increased odds of taking longer than 8 seconds to complete the 20-feet walk were seen in the stage 4/5 group (OR, 3.39 vs controls); older subjects (OR, 1.12 vs younger subjects); females (OR, 1.35 vs males); those with lower levels of 25(OH)D (OR, 0.97 vs those with higher levels); and those with lower levels of albumin (OR, 0.38 vs those with higher levels).

Study limitations cited by the authors included utilizing cross-sectional data resulting in a limited scope in examining the relationships between CKD severity and impairments in 25(OH)D levels, balance, and gait speed; using subjective measures to test balance and falling problems; and the possibility that patients receiving dialysis were included in the analysis.

In conclusion, the researchers said, “The unique finding of this study is that the likelihood of reporting more balance and falling issues (both perceived and measured) and having slower gait is higher in persons with increased CKD severity and those with lower 25(OH)D levels. Patients with moderate-to-severe CKD may benefit from screening and treatment of both balance and vitamin D status.”

Takeaway Points

1. Patients with chronic kidney disease (CKD) face a high risk of fracture at every stage of their disease; the risk is exacerbated with disease progression, with the highest incidence rates in those with end-stage renal disease on dialysis.
2. Researchers conducted an analysis of 1999-2004 NHANES data to examine the prevalence of balance deficits and the relationships between severity of CKD and vitamin D status, self-reported balance and falling issues, and measured gait speed in the CKD sample.
3. The likelihood of more reporting of balance and falling issues (both perceived and measured) and having slower gait was higher in those with increased severity of CKD and in those with lower 25(OH)D levels.