In this study, Port and colleagues describe hemodialysis prevalence and patient characteristics by sex, compare men-to-women mortality rate with data from the general population, and evaluate sex interactions with mortality. The results show that women's survival advantage was markedly diminished in hemodialysis patients.
Please see later in the article for the Editors' Summary
A comprehensive analysis of sex-specific differences in the characteristics, treatment, and outcomes of individuals with end-stage renal disease undergoing dialysis might reveal treatment inequalities and targets to improve sex-specific patient care. Here we describe hemodialysis prevalence and patient characteristics by sex, compare the adult male-to-female mortality rate with data from the general population, and evaluate sex interactions with mortality.
Methods and Findings
We assessed the Human Mortality Database and 206,374 patients receiving hemodialysis from 12 countries (Australia, Belgium, Canada, France, Germany, Italy, Japan, New Zealand, Spain, Sweden, the UK, and the US) participating in the international, prospective Dialysis Outcomes and Practice Patterns Study (DOPPS) between June 1996 and March 2012. Among 35,964 sampled DOPPS patients with full data collection, we studied patient characteristics (descriptively) and mortality (via Cox regression) by sex. In all age groups, more men than women were on hemodialysis (59% versus 41% overall), with large differences observed between countries. The average estimated glomerular filtration rate at hemodialysis initiation was higher in men than women. The male-to-female mortality rate ratio in the general population varied from 1.5 to 2.6 for age groups <75 y, but in hemodialysis patients was close to one. Compared to women, men were younger (mean = 61.9±standard deviation 14.6 versus 63.1±14.5 y), were less frequently obese, were more frequently married and recipients of a kidney transplant, more frequently had coronary artery disease, and were less frequently depressed. Interaction analyses showed that the mortality risk associated with several comorbidities and hemodialysis catheter use was lower for men (hazard ratio [HR] = 1.11) than women (HR = 1.33, interaction p<0.001). This study is limited by its inability to establish causality for the observed sex-specific differences and does not provide information about patients not treated with dialysis or dying prior to a planned start of dialysis.
Women's survival advantage was markedly diminished in hemodialysis patients. The finding that fewer women than men were being treated with dialysis for end-stage renal disease merits detailed further study, as the large discrepancies in sex-specific hemodialysis prevalence by country and age group are likely explained by factors beyond biology. Modifiable variables, such as catheter use, showing significant sex interactions suggest interventional targeting.
Please see later in the article for the Editors' Summary
Throughout life, the kidneys filter waste products (from the normal breakdown of tissues and from food) and excess water from the blood to make urine. Chronic kidney disease—an increasingly common condition globally—gradually destroys the kidney's filtration units (the nephrons). As the nephrons stop working, the rate at which the blood is filtered (the glomerular filtration rate) decreases, and waste products build up in the blood, eventually leading to life-threatening end-stage kidney (renal) disease. Symptoms of chronic kidney disease, which rarely occur until the disease is advanced, include tiredness, swollen feet and ankles, and frequent urination, particularly at night. Chronic kidney disease cannot be cured, but its progression can be slowed by controlling diabetes and other conditions that contribute to its development. End-stage kidney disease is treated by regular hemodialysis (a process in which blood is cleaned by passing it through a filtration machine) or by kidney transplantation.
Why Was This Study Done?
Like many other long-term conditions, the prevalence (the proportion of the population that has a specific disease) of chronic kidney disease and of end-stage renal disease, and treatment outcomes for these conditions, may differ between men and women. Some of these sex-specific differences may arise because of sex-specific differences in normal biological functions. Other sex-specific differences may be related to sex-specific differences in patient care or in patient awareness of chronic kidney disease. A comprehensive analysis of sex-specific differences among individuals with end-stage renal disease might identify both treatment inequalities and ways to improve sex-specific care. Here, in the Dialysis Outcomes and Practice Patterns Study (DOPPS), the researchers investigate sex-specific differences in the prevalence and practices of hemodialysis and in the characteristics of patients undergoing hemodialysis, and investigate the adult male-to-female mortality (death) rate among patients undergoing hemodialysis. The DOPPS is a prospective cohort study that is investigating the characteristics, treatment, and outcomes of adult patients undergoing hemodialysis in representative facilities in 19 countries (12 countries were available for analysis at the time of the current study).
What Did the Researchers Do and Find?
To investigate sex-specific differences in hemodialysis prevalence, the researchers compared data from the Human Mortality Database, which provides detailed population and mortality data for 37 countries, with data collected by the DOPPS. Forty-one percent of DOPPS patients were women, compared to 52% of the general population in 12 of the DOPPS countries. Next, the researchers used data collected from a randomly selected subgroup of patients to examine sex-specific differences in patient characteristics and mortality. The average estimated glomerular filtration rate at hemodialysis initiation was higher in men than women. Moreover, men were more frequently recipients of a kidney transplant than women. Notably, although in the general population in a given age group women were less likely to die than men, among hemodialysis patients, women were as likely to die as men. Finally, the researchers investigated which patient characteristics were associated with the largest sex-specific differences in mortality risk. The use of a hemodialysis catheter (a tube that is inserted into a patient's vein to transfer their blood into the hemodialysis machine) was associated with a lower mortality risk in men than in women.
What Do These Findings Mean?
These findings show that, among patients treated with hemodialysis for end-stage renal disease, women differ from men in many ways. Although some of these sex-specific differences may be related to biology, others may be related to patient care and to patient awareness of chronic kidney disease. Because this is an observational study, these findings cannot prove that the reported differences in hemodialysis prevalence, treatment, and mortality are actually caused by being a man or a woman. Importantly, however, these findings suggest that hemodialysis may abolish the survival advantage that women have over men in the general population and that fewer women than men are being treated for end-stage-renal disease, even though chronic kidney disease is more common in women than in men. Finally, the finding that the use of hemodialysis catheters for access to veins is associated with a higher mortality risk among women than among men suggests that, where possible, women should be offered a surgical process called arteriovenous fistula placement, which is recommended for access to veins during long-term hemodialysis but which may, in the past, have been underused in women.
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001750.
More information about the DOPPS program is available
The US National Kidney and Urologic Diseases Information Clearinghouse provides information about all aspects of kidney disease; the US National Kidney Disease Education Program provides resources to help improve the understanding, detection, and management of kidney disease (in English and Spanish)
The UK National Health Service Choices website provides information for patients on chronic kidney disease and about hemodialysis, including some personal stories
The US National Kidney Foundation, a not-for-profit organization, provides information about chronic kidney disease and about hemodialysis (in English and Spanish)
The not-for-profit UK National Kidney Federation provides support and information for patients with kidney disease and for their carers, including information and personal stories about hemodialysis
World Kidney Day, a joint initiative between the International Society of Nephrology and the International Federation of Kidney Foundations, aims to raise awareness about kidneys and kidney disease
MedlinePlus has pages about chronic kidney disease and about hemodialysis