Chicago—Too little and poor quality sleep are associated with a greater risk of kidney failure, according to results from the Chronic Renal Insufficiency Cohort Study (CRIC) presented at Kidney Week 2016.
While sleep disorders are common in patients with chronic kidney disease (CKD), how poor sleep may affect disease progression is not clear, according to the study’s lead author Ana C. Ricardo, MD, MPH, an assistant professor in the division of nephrology at the University of Illinois College of Medicine at Chicago.
So Ricardo and her colleagues conducted a prospective study of 432 adults enrolled in the CRIC study at 2 centers. The CRIC study is a longitudinal, multicenter study that has followed nearly 4000 people with CKD for several years. Participants in the sleep study wore a wrist activity monitor for 5–7 days to record their sleep duration and sleep quality. They also filled out questionnaires about their sleep quality, daytime sleepiness, and risk of sleep apnea. The participants were then followed for an average of 5 years during which 70 developed end stage renal disease (ESRD) and 48 died.
An average night of sleep for participants in the study was 6.5 hours, and about 1 in 5 participants experienced sleep interruptions. For every extra hour of sleep, the researchers found a 19% lower risk of developing ESRD when they controlled for several factors, including body mass index, blood pressure, baseline kidney function and cardiovascular disease (HR 0.81, 95% CI 0.67–0.99 per hour increased sleep length). Patients who had more interrupted sleep also had increased risk of developing ESRD with a 4% increase in risk for every 1% increase in sleep fragmentation (HR 1.04, 95% CI 1.01–1.07 per 1% increase in sleep fragmentation). More fragmented sleep was also linked to declines in eGFR (-0.17 mL/min/1.73 m2/year, p=0.016).
“Short sleep and fragmented sleep are significant, yet unappreciated risk factors for CKD progression,” Ricardo said. “Our research adds to the accumulating knowledge regarding the importance of sleep on kidney function, and underscores the need to design and test clinical interventions to improve sleep habits in individuals with CKD.”
Earlier this year, another study that followed 4238 participants in the Nurses’ Health Study for 11 years found that nurses who reported sleeping less were at higher risk for more rapid declines in their estimated glomerular filtration rate (McMullan CJ, et al. Kidney Int 2016; 89:1324–1330).
While the previous study suggested a link between shorter sleep duration and earlier stages of CKD, the Ricardo study strengthens the evidence by linking sleep duration to ESRD, said Mark J. Sarnak, MD, MS, Director of Research in the Division of Nephrology at Tufts Medical Center. The CRIC Study also used more objective measures of sleep duration and quality than the previous study.
How reduced or poor quality sleep might contribute to declining kidney function is less clear, Sarnak noted.
“A valid question is whether quantity or quality of sleep is a causal risk factor for kidney function decline or have we not sufficiently adjusted for covariates that may be associated with both poor sleep and kidney function decline,” Sarnak said.
Larger studies that adjust for such factors as well as additional mechanistic studies may help answer these questions and lay the groundwork for studies of potential interventions that improve sleep quality and slow progression of kidney disease, he said.
Although there is not yet enough evidence to definitively say that sleeping better will reduce the progression of kidney disease, there is sufficient evidence to show that sleep is important for overall health, Sarnak noted.
“Clinicians should be asking questions about sleep and educating patients about healthy sleep hygiene,” he said.
“The Association of Sleep Duration and Quality with Chronic Kidney Disease Progression” (Abstract 3754).