Exercise May Blunt the Deadly Toll of a Racing Heart in Kidney Disease

For the roughly 700 million people worldwide living with chronic kidney disease, the heart is the most vulnerable organ after the kidneys themselves. Cardiovascular mortality runs ten to twenty times higher in this population than in the general public, and even as clinicians tighten control of blood pressure and diabetes, a substantial share of deaths remains unexplained by the classic risk factors. A new multicohort study published in iScience adds two deceptively simple vital signs to the risk-assessment toolkit: resting heart rate and physical activity. Analyzing more than 12,000 patients across three prospective cohorts in China and the United States, researchers report that a fast resting pulse independently predicts early death in kidney disease, but that the danger is far from fixed. Patients who move more appear to substantially blunt, and in some analyses effectively neutralize, the mortality penalty carried by an elevated heart rate.

The research team, led by Guisen Li and colleagues, drew on an unusually broad evidence base. The Chinese Cohort Study of Chronic Kidney Disease, or C-STRIDE, contributed 3,700 patients with a mean age of 50 and a mean estimated glomerular filtration rate of about 42 mL/min/1.73 m². The China Health and Retirement Longitudinal Study, CHARLS, added 1,130 community-dwelling patients with kidney disease, averaging 66 years old. Finally, ten cycles of the US National Health and Nutrition Examination Survey from 1999 to 2018 yielded 7,212 American adults with kidney disease, followed for an average of more than ten years through linkage with the National Death Index. Chronic kidney disease was defined consistently across cohorts as either reduced filtration capacity or significant protein in the urine, and mortality was classified using the International Classification of Diseases, tenth revision.

The headline finding concerns resting heart rate. In the C-STRIDE cohort, patients whose resting pulse exceeded 100 beats per minute faced roughly 2.6 times the all-cause mortality risk and 3.2 times the cardiovascular mortality risk of those below 80 beats per minute. In the much larger NHANES sample, where the investigators used a finer six-category classification, risk climbed in a graded fashion: compared with a reference group below 60 beats per minute, patients in the 90 to 99 range carried a 50 percent higher risk of dying from any cause, and those at or above 100 beats per minute carried a 77 percent higher risk. Restricted cubic spline analyses confirmed that the relationship was essentially linear, with no threshold or plateau, meaning that every incremental rise in resting pulse translated into additional risk.

Because single cohorts can mislead, the team pooled fully adjusted hazard ratios from all three studies in a meta-analysis. The combined estimates were striking: compared with patients whose resting heart rate was below 80 beats per minute, those above 100 beats per minute had roughly double the all-cause mortality risk, with a pooled hazard ratio of 2.02, and an 83 percent higher cardiovascular mortality risk. Subgroup analyses suggested the excess risk was especially pronounced among women, younger patients, and those without diagnosed hypertension. The authors note that the association only emerged after careful statistical adjustment for age, sex, kidney function, comorbidities, and lifestyle factors, implying that crude comparisons can mask the true signal because confounders such as age and smoking distort the apparent relationship.

Why would a fast resting heart rate be so dangerous in kidney disease? The mechanistic case is well developed in the cardiovascular literature. A persistently elevated pulse promotes left ventricular remodeling, accelerates arterial stiffening, and worsens endothelial dysfunction, all of which feed atherosclerosis. Kidney disease compounds these insults: declining renal function brings chronic inflammation, oxidative stress, and electrolyte disturbances that amplify the wear and tear of a heart beating too quickly. Heightened sympathetic nervous system activity, a well-documented feature of uremia, is thought to be a key driver of the elevated pulse itself, which is why the authors argue that heart rate control may deserve particular attention in this population rather than being treated as a secondary vital sign.

Physical activity, by contrast, emerged as a powerful protective factor in every cohort examined. In CHARLS, patients reporting moderate activity levels had an 88 percent lower all-cause mortality risk than sedentary participants, and highly active patients had a 79 percent lower risk. In NHANES, even insufficiently active patients enjoyed a 35 percent reduction compared with those reporting no activity, while the most active group saw a 43 percent reduction, with parallel benefits for cardiovascular death. Notably, the dose-response curve was nonlinear. Two-piecewise Cox regression identified inflection points, around 7.4 units on the log-transformed activity scale for all-cause mortality and 7.6 for cardiovascular mortality, beyond which each additional unit of activity yielded a markedly larger benefit, cutting cardiovascular risk by 27.5 percent per unit. This suggests a threshold effect: modest movement helps, but crossing a certain activity level appears to unlock disproportionately greater survival gains.

The study’s most original contribution is a composite metric the authors call the RHR/PA ratio, calculated by dividing resting heart rate by the logarithm of weekly physical activity expressed in metabolic-equivalent minutes. The ratio captures the balance between autonomic stress and habitual movement, and it proved to be a robust predictor: in NHANES, each one-unit increase was associated with a 3 percent rise in both all-cause and cardiovascular mortality. The relationship with all-cause death was nonlinear, with a steep escalation in risk below a ratio of about 8.2 and a gentler climb above it, suggesting that early movement of the ratio into higher territory serves as an early-warning signal of a transition toward a high-risk physiological state. Crucially, the ratio predicted risk consistently across nearly every subgroup tested, including strata defined by age, blood pressure, diabetes status, and medication use, hinting at genuine clinical utility for risk stratification.

When the investigators crossed the two variables directly, a clear synergy emerged. Patients combining a high resting heart rate with low physical activity fared worst of all, facing a 70.8 percent higher risk of all-cause mortality and a 51.8 percent higher risk of cardiovascular death compared with the low-heart-rate, high-activity reference group. Yet the combination of high heart rate and high activity was not associated with elevated mortality at all. Within the high-heart-rate stratum, active patients cut their all-cause mortality risk by about 35 percent and their cardiovascular mortality risk by nearly 44 percent relative to their sedentary counterparts. Conversely, an elevated pulse only predicted death among inactive patients. The pattern echoes findings from Norway’s HUNT study in the general population and suggests that regular activity can, to a meaningful degree, buffer the cardiovascular system against the harms of autonomic overdrive.

Causal mediation analysis offered a glimpse into how that buffering works. Higher physical activity lowered resting heart rate, and this pathway accounted for 4.6 percent of the total reduction in all-cause mortality risk and 2.7 percent for cardiovascular mortality. The remainder of the benefit flowed through routes independent of heart rate, consistent with exercise’s established effects on inflammation, endothelial function, insulin sensitivity, and the renin-angiotensin-aldosterone system. Regular activity also improves heart rate variability, a marker of autonomic flexibility that fast resting pulses tend to erode. The authors are careful about causality: the data are observational, physical activity was self-reported and thus vulnerable to recall bias, and the new ratio still requires validation in additional independent cohorts with standardized activity measurements. Intervention trials that raise activity or lower heart rate will be needed to confirm that modifying these factors directly improves survival.

Even with those caveats, the practical implications are hard to ignore. Chronic kidney disease already causes 1.2 million deaths annually, with another 1.4 million cardiovascular deaths attributed to impaired kidney function, and its prevalence continues to climb. Resting heart rate costs nothing to measure, and the finding that a pulse above 100 beats per minute roughly doubles mortality risk gives clinicians a cheap, immediate flag for patients who need closer cardiovascular surveillance. Pairing that number with a simple activity questionnaire, and combining them in the RHR/PA ratio, could identify high-risk patients early in disease progression, when intervention still has time to change the trajectory. For patients, the message is arguably more empowering: a racing heart is not a fixed sentence, and the evidence suggests that getting moving, ideally past a meaningful activity threshold, may be one of the most effective ways to quiet it and extend life.

Subject of Research: The joint effects of resting heart rate and physical activity on mortality in chronic kidney disease

Article Title: Physical activity attenuates mortality risk associated with elevated resting heart rate in chronic kidney disease

Article References: Zhan, Y., He, B., Pu, L., Bi, W., Wei, G., & Li, G. (2026). Physical activity attenuates mortality risk associated with elevated resting heart rate in chronic kidney disease. iScience, 29(10), Article 117648. https://doi.org/10.1016/j.isci.2026.117648

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117648

Keywords: chronic kidney disease, resting heart rate, physical activity, mortality, cardiovascular risk, RHR/PA ratio, NHANES, CHARLS, C-STRIDE, mediation analysis, meta-analysis, risk stratification