The impact of nocturnal hemodialysis on sexual function
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Sexual dysfunction is common in patients with end stage renal disease (ESRD) and treatment options are limited. Observational studies suggest that nocturnal hemodialysis may improve sexual function. We compared sexual activity and responses to sexual related questions in the Kidney Disease Quality of Life Short Form questionnaire among patients randomized to frequent nocturnal or thrice weekly conventional hemodialysis.
We performed a secondary analysis of data from an RCT which enrolled 51 patients comparing frequent nocturnal and conventional thrice weekly hemodialysis. Sexual activity and responses to sexual related questions were assessed at baseline and six months using relevant questions from the Kidney Disease Quality of Life Short Form questionnaire.
Overall, there was no difference in sexual activity, or the extent to which people were bothered by the impact of kidney disease on their sex life between the two groups between randomization and 6 months. However, women and patients age < 60 who were randomized to frequent nocturnal hemodialysis were less bothered by the impact of kidney disease on their sex life at 6 months, compared with patients allocated to conventional hemodialysis (p = 0.005 and p = 0.024 respectively).
Our results suggest that frequent nocturnal hemodialysis is not associated with an improvement in sexual activity in all patients but might have an effect on the burden of kidney disease on sex life in women and patients less than 60 years of age. The validity of these subgroup findings require confirmation in future RCTs.
KeywordsNocturnal hemodialysis Sex Sexual function Frequent hemodialysis
Sexual dysfunction is common in men and women with end stage renal disease (ESRD) [1, 2, 3, 4, 5], contributed to by both the diseases that cause ESRD, as well as the consequences of kidney failure [4, 6]. Recently, Vecchio et al. published a systematic review examining the treatments available to ESRD patients with sexual dysfunction . Their report highlights the limited treatment options available, noting that phosphodiesterase-5 inhibitors improve erectile dysfunction in men with ESRD, with little research available to guide therapy in women with ESRD.
Frequent nocturnal hemodialysis (NHD) has gained popularity recently as a form of renal replacement therapy, and among other reported benefits, some studies have reported improved sexual function. Published literature however shows conflicting results, although these are based mainly on small observational studies comparing pre-NHD to post-NHD quality of life scores, usually compared with patients on conventional hemodialysis (CvHD) [8, 9, 10, 11, 12]. Ting et al. followed 42 patients and noted that sexual function improved after conversion to NHD  while Lockridge et al. observed an increase in sexual desire after NHD initiation in 40 patients . However, other studies have not documented improvement, including a recent prospective observational study of 63 patients which demonstrated no improvement in sexual function scores after conversion to NHD .
Our group has previously reported a randomized controlled trial in which we examined the effects of NHD on both left ventricular mass as well as quality of life [13, 14, 15]. One of the quality of life tools used was the kidney disease quality of life: short form (KDQOL-SF) questionnaire , containing specific questions assessing sexual arousal and sexual enjoyment. These questions have not been analyzed nor reported previously. Herein we report the results of a post hoc analysis to determine if frequent NHD was associated with an improvement in sexual activity and responses to sexual related questions listed in the Kidney Disease Quality of Life Short Form questionnaire compared to thrice weekly conventional hemodialysis.
The methods of this study have previously been reported in detail . Patients were recruited from 10 hemodialysis centers in Alberta, Canada. Patients were considered eligible if they were 18 years old and they were receiving in-center, self-care or home CvHD 3 times a week. In addition to being interested in NHD, patients had to be willing to train and start NHD. Exclusion criteria included physical or mental impediment to training for NHD. Ethics approval was obtained from the Conjoint Health Research Ethics Board at the University of Calgary and informed consent was obtained from all participants.
Fifty-one patients were randomized to either frequent NHD or CvHD in a two group parallel design. Patients randomized to frequent NHD were trained to perform NHD at home for 5-6 nights per week at a minimum of 6 hours, while those randomized to CvHD continued thrice weekly conventional hemodialysis . For the majority of patients treated with CvHD, dialysis was delivered in-centre. Quality of life questionnaires were administered prior to randomization, at the baseline study visit (corresponding to the first day of NHD training for the NHD group), and at study end at 6 months.
Description of Contemporary Measures of Quality of Sexual Function in comparison to the KDQOL-SF
Number of items
Kidney Disease Quality of Life Short Form (KDQOL-SF) ***Present Study
SR/male and female
Sexual activity, satisfaction, arousal, burden of kidney disease on sex life
Arizona sexual experience scale (ASEX)
SR/male and female
Drive, arousal, penile erection/vaginal lubrication, orgasm, satisfaction
Center for Marital and Sexual Health Sexual Functioning questionnaire (CMASH-SFQ)
SR/male and partner
Sexual frequency, sexual satisfaction, orgasm, erectile function
Derogatis interview for sexual functioning (DISF-SR)
CI and SR/male and female
Cognition, arousal, behaviour, orgasm, drive/relationship, overall total score
Female sexual function index (FSFI)
Desire, arousal, lubrication, orgasm, satisfaction, pain
Index of premature ejaculation
Sexual satisfaction, control, distress
International index of erectile function (IIEF)
Erectile function, orgasm, desire, intercourse satisfaction, overall total score
Profile of female sexual function (PFSF)
Desire, arousal, orgasm, pleasure, concerns, responsiveness, self-image
Sexual function questionnaire (SFQ)
Desire, arousal–sensation, arousal–lubrication, enjoyment, orgasm, dyspareunia, partner relationship, overall total score
Sexual interest and desire inventory
Overall total score
Short scale to measure female sexual functioning (SPEQ)
Feelings for partner, sexual responsivity, sexual frequency, libido, dyspareunia, partner problems
Female sexual distress scale (FSDS/FSDS-R)
Unidimensional scale measuring sexually related personal distress. 'R' version has an additional desire item
Have you had any sexual activity in the past 4 weeks? (yes / no)
If yes, then how much of a problem was each of the following in the past 4 weeks?
A.) Enjoying sex?
B.) Becoming sexually aroused?
Burden of kidney disease on sex life question (answered by all participants):
Some people are bothered by the effects of kidney disease on their daily life, while others are not. How much does kidney disease bother you … with respect to…Your sex life?
The responses to the two sexual enjoyment and arousal questions and the burden of kidney disease on sex life question were recorded on a five point Likert scale, ranging from 1 to 5 (1 representing no problem or not bothered and 5 indicating a severe problem or extremely bothered). For the secondary outcomes, we chose to examine the proportion of patients who reported improvement. The burden of kidney disease on sex life question was answered and analysed in all patients, while the sexual enjoyment and arousal questions were answered and analysed only in patients who had sexual activity in the prior 4 weeks.
To confirm the reliability of the sexual arousal and enjoyment question, Cronbach’s alpha was calculated on these questions in patients who declared that they had engaged in sexual activity. In addition, to verify the validity of analyzing the burden of kidney disease on sex life question alone, Pearson’s R correlation coefficient was determined between this question and the sexual enjoyment and arousal question in those participants who had engaged in sexual activity. A Cronbach’s alpha was also calculated between the three questions together to determine if taken together, they demonstrate reliability in measuring sexually related concerns.
All analyses used the intention to treat principle and all enrolled patients were included in the analysis. For the primary outcome (sexual activity), we first assessed whether there was a higher proportion of patients reporting sexual activity using Chi square tests. We next compared changes in burden of kidney disease scores from randomization to study end (6 months) between patients allocated to frequent NHD and conventional hemodialysis. Since there is no requirement in the KDOQL-SF for a patient to be engaged in sexual activity to answer the burden of kidney disease on sex life question, and since we were interested in whether NHD reduced the burden of kidney disease on sex life – an outcome that is relevant, irrespective of sexual activity, we chose to analyze all patients irrespective of sexual activity. Given that we were testing differences in proportions, we used chi-square tests and applied the Yates continuity correction for analyses that did not meet the 5 items expected per cell criteria. For missing data at six months (n = 3; due to death or loss to transplantation), we used the last value carried forward approach .
Among the subgroup of patients reporting sexual activity, we next categorized patients based on whether they experienced an improvement for both the domains “enjoying sex”, or “becoming sexually aroused”. This was chosen because it is considered a clinically significant change . Statistical significance was defined as a p-value < 0.05.
Since the causes and prevalence of sexual dysfunction differs across patients with ESRD, we performed exploratory analyses to determine if there was any subpopulation of patients who might benefit from nocturnal hemodialysis with respect to sexual function. All subgroups were conceived prior to analyzing the data. These included women, patients <60 years of age, patients without vascular disease, and patients without diabetes. It was not possible to analyze any subgroups for the sexual activity question due to the small numbers of patients who were sexually active. However, we chose to do subgroup analysis on the burden of kidney disease question since there was no requirement to be sexually active to answer the question. All statistical analyses were performed using STATA software package version 11.
Baseline characteristics at study initiation by dialysis modality
Nocturnal hemodialysis (n = 26)
Conventional hemodialysis (n = 25)
55.1 ± 12.4
53.1 ± 13.4
Male gender (%)
Time on dialysis (years)
5.5 ± 5.3
4.8 ± 3.8
Median (interquartile range)
Baseline dialysis modality (%)
Home or self-care hemodialysis
Cause of ESRD (%)
Polycystic kidney disease
Comorbid illnesses (%)
Ischemic heart disease
Congestive heart failure
Peripheral vascular disease
β-Blocker usage (%)
Married, Common-law or in
Responses to relevant sexual questions
Proportion with Sexual Activity in Last 4 Weeks
Proportion of patients very much or extremely bothered on burden of Kidney Disease on Sex Life
Proportion of patients having sex who reported very much or severe problems enjoying Sex*
Proportion of patients having sex who reported very much or severe problem becoming Sexually Aroused*
The Cronbach’s alpha of the sexual arousal and enjoyment questions was 0.97 in patients who had engaged in sexual activity indicating excellent reliability of these questions. The Pearson R correlation coefficient of the burden of kidney disease on sex life question was 0.61 (p = 0.01) with both the sexual enjoyment and arousal questions indicating a strong correlation between these questions. The Cronbach’s alpha of all three questions analyzed together was 0.89 suggesting good reliability.
In this post-hoc analysis of a randomized controlled trial we observed no improvement in sexual activity or or self-reported arousal, enjoyment or burden of kidney disease on sex life between patients on NHD versus CvHD overall. Consistent with prior reports of sexual activity on hemodialysis, only 43 percent of patients indicated that they were sexually active in the 4 weeks prior to either randomization or study completion . Our findings are not consistent with prior research suggesting that NHD may improve sexual activity and sexually related concerns.
Normal sexual function involves a complex interplay between the hormonal, vascular, neurological and psychological systems. These can all be impacted by ESRD. Patients with ESRD have abnormalities in the hypothalamic-pituitary axis, in particular, hypogonadism and hyperprolactinemia which are thought to be secondary to the accumulation of uremic toxins . The diseases that cause ESRD and the condition itself can cause vascular insufficiency as well as sensory and autonomic neuropathy . Finally, the complex social and psychological factors that are embroiled with ESRD impact normal sexual function . Given this, the mechanism by which NHD might improve sexual function in ESRD patients is not clear. Since NHD improves clearance of uremic toxins it might improve hormonal dysfunction, but it may not address other inhibitors of normal sexual function. NHD does not alleviate the comorbid conditions that cause ESRD which are well known to cause sexual dysfunction. Specifically, NHD is unlikely to reverse pre-existing vascular and neurological damage causing impairment. In addition, it may have variable effects on the social and psychological dynamics caused by ESRD. In particular, sexual activity might be either positively or negatively affected by undergoing dialysis in the home. Transplantation provides a good example of the potential multi-factorial nature of sexual dysfunction in that despite normalization of kidney function, many patients still experience sexual dysfunction .
While we did not note any improvement with NHD on sexual activity or self-reported arousal, enjoyment or burden of kidney disease on sex life overall, a subgroup analysis suggested that patients less than 60 years of age and women were less burdened by the effect of their kidney disease on their sex life after 6 months of NHD. It is plausible that younger patients might be more likely to experience benefit with NHD since it is conceivable that they might have fewer and less severe comorbid diseases, which themselves may impair sexual function. It is uncertain why women might benefit from NHD with respect to the burden of kidney disease of sex life. While both sexes suffer from decreased libido, there are differences in sexual dysfunction between men and women with ESRD with men generally suffering from impotence  and women suffering from anorgasmia, decreased lubrication and dyspareunia . NHD may have no impact on impotence in men, while it is possible that women perceive NHD to be less intrusive on normal sexual function than CvHD. While this study did not specifically measure these outcomes, it is possible that changes in these domains could have impacted the burden of kidney disease on sex-life in these sub-groups. Alternatively, while the burden kidney disease on sex life diminished in these patients, there are other burdens aside from kidney disease that may be impacting proper sexual activity and function which may explain why we did not observe a concomitant increase in sexual activity.
Our study is the first randomized controlled trial documenting the association between NHD and sexual activity and self-reported sexual function. However, it has several limitations which should be considered. The original RCT was not specifically designed to examine the impact of NHD on sexual function. While the KDQOL-SF does include domains designed to measure sexual function and activity, it would have been preferable to use dedicated sexual function scales such as the International Index of Erectile Function  or the Female Sexual Function Index . Despite this, we feel that our study provides much needed insight into a poorly studied area that is pervasive in dialysis patients. Other limitations include that the RCT was not powered to detect differences in quality of life, and that all analyses documented herein are posthoc and exploratory in nature. Given the limited number of patients and that few patients answered the sexual function questions, our subgroup findings should be interpreted with particular caution. However, our findings can be tested within secondary analyses of other recently reported randomized trials of frequent hemodialysis [24, 25]. It should also be noted that given the nature of the intervention it is highly unlikely that a randomized controlled trial focussed on this particular outcome will ever be undertaken.
In conclusion, our study is the first randomized controlled trial examining the effect of NHD on sexual activity or self-reported sexual arousal, enjoyment or burden of kidney disease on sex life. While NHD does not appear to improve sexual activity overall, women and patients younger than 60 years old might experience improvement - the validity of the subgroup findings should be assessed in future RCTs.
This research was supported by a grant from the Kidney Foundation of Canada. Dr. Manns is supported by an Alberta Innovates – Health Solutions Health Scholar Award. Dr. Ahmed is supported by an Alberta Heritage Foundation for Medical Research Clinical Investigator Award and a Canadian Institutes of Health Research New Investigator Award. Dr. Klarenbach is supported by an AHFMR Population Health Investigator award, and Dr Hemmelgarn is supported by a Population Health Investigator Award. The results of this paper have not been published previously except in abstract format.
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- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2369/13/67/prepub
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