What Underlies Sex Differences in CKD Cardiovascular Risk?

Older men with chronic kidney disease (CKD) show higher resting muscle sympathetic nerve activity, but not vascular stiffness, compared with older women, offering clues to the underlying reasons why men with CKD have a higher cardiovascular risk than to women with the disease.

"Although it is well established that sympathetic nerve system activity is chronically elevated in patients with impaired kidney function, we show for the first time that males with CKD have higher resting muscle sympathetic nerve activity compared with females with CKD," report the authors on research published in the American Journal of Physiology-Renal Physiology.

"For clinicians, the key takeaway is the importance of recognizing sex-specific differences in sympathetic activity and vascular function when assessing cardiovascular risk in CKD patients," first author Matias G. Zanuzzi, MD, of the Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, told Medscape Medical News.

In the general population, cardiovascular risk is lower in younger women vs men, but their risks converge in older age as women develop similar levels of sympathetic overactivity, vascular stiffness, and cardiovascular risk.

However, an exception to that pattern is seen in the CKD population, where men continue to have a higher cardiovascular mortality risk vs women even in older age.

Studies evaluating the reasons for that have been conflicting, with some reporting a tendency of higher muscle sympathetic nerve activity in older women compared with men and others suggest the opposite finding — lower activity vs men.

To further investigate, Zanuzzi and colleagues enrolled 129 participants, including 96 men and 33 women with stage III or IV CKD.

The mean age of the study participants was 64 years for men and65 years for women. Most had obesity, and importantly, more than 80% of participants in each group was Black. There were no significant differences between the groups in terms of body mass index or comorbidities, including smoking, diabetes, or hypertension.

At two separate study visits, vascular stiffness was assessed with carotid-femoral pulse wave velocity measurement, and resting muscle sympathetic nerve activity was measured using microneurography. 

The results showed that men with CKD had significantly higher resting muscle sympathetic nerve activity compared with women with CKD (68 vs 55 bursts per 100 heartbeats; P = .005), whereas no differences in vascular stiffness were observed between the genders (P = .248).

"The findings suggest that the higher cardiovascular disease risk observed in older males with CKD may be influenced by elevated sympathetic activity," Zanuzzi explained.

"However, the lack of significant differences in vascular stiffness between genders implies that additional factors beyond vascular remodeling may contribute to the observed sex-specific differences in cardiovascular risk," he said.

Of note, resting vascular stiffness was not associated with muscular sympathetic nerve activity in either men or women, which was surprising to the authors, Zanuzzi noted.

"This underscores the multifactorial nature of vascular pathophysiology in CKD and underscores the need for further research to unravel the underlying mechanisms."

In other findings, although prior studies have shown a positive correlation between age and resting muscle sympathetic nerve activity in White, healthy women and men without obesity,, no similar relationship was observed in men or women with CKD.

"These findings suggest that the protective effect of younger age on sympathetic function may not be present in the setting of decreased kidney function in both males and females," the authors note.

In addition, whereas previous research has shown a clear association between sympathetic overactivity and a wide variety of measures of obesity, in the current study, that association was only observed in men with CKD. 

Important limitations of the study include the cross-sectional design and that the population was predominantly Black, Zanuzzi noted.

"Generalizability to other demographic groups may be limited, and future longitudinal studies are needed to validate these findings and explore potential causal relationships," he said.

The findings underscore "the need for novel therapeutic approaches targeting sympathetic overactivity and vascular stiffness in CKD patients, especially considering the observed sex-specific differences," Zanuzzi added. 

"Potential interventions may include pharmacological agents that modulate sympathetic tone or vascular remodeling pathways," he said.

"Lifestyle modifications focusing on stress reduction and cardiovascular health promotion could also play a crucial role in mitigating cardiovascular risk."

Zanuzzi concluded that "tailoring treatment strategies to address these differences may lead to more personalized and effective management approaches, ultimately improving clinical outcomes in this high-risk population."

The authors had no disclosures to report.