Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Diagnostic laparoscopy to exclude malrotation following inconclusive upper gastrointestinal contrast study in infants

PURPOSE

We report the use of diagnostic laparoscopy as an alternative to laparotomy in the investigation of infants with clinical features concerning for malrotation and inconclusive upper gastrointestinal contrast study.

METHOD

Case note review of all infants in whom laparoscopy was performed during 2016-2020 to investigate for possible malrotation.

RESULTS

Eight infants were identified. All presented with acute clinical features of malrotation (bilious vomit) without evidence of an alternate explanatory diagnosis. All underwent upper gastrointestinal contrast study, with three also undergoing abdominal ultrasound. The radiological examinations could not exclude malrotation and all proceeded to laparoscopy. At laparoscopy, the small intestine was run to exclude the presence of midgut volvulus. In six cases, normal rotation was confirmed and no abnormal pathology was found. Two proceeded to laparotomy and underwent correction of malrotation. All infants recovered without complication.

CONCLUSION

Laparoscopy is an excellent modality for further investigation of infants presenting acutely in whom intestinal malrotation cannot be formally excluded radiologically. The positive identification of the DJ flexure and cecum in correct anatomical sites, both fixed to the posterior abdominal wall, provides adequate reassurance of low risk of volvulus and avoids a full laparotomy. We recommend diagnostic laparoscopy in cases of inconclusive upper gastrointestinal contrast study.

P1621m6A RNA-methylation in the progression of heart failure

Introduction

N6-Methyladenosine (m6A) is the most abundant modification of RNA and was found to be a dynamic and reversible process. It is found in many classes of RNA, such as mRNA, noncodingRNA (ncRNA) and microRNA (miR). mRNA methylation can affect splicing, transport and storage or decay, ncRNA methylation might influence signal transduction directly as well as it might affect miR interference. Deregulation of such epigenetic processes and aberrant gene expressions are important mechanisms in heart failure. Here we studied the potential relevance of m6A RNA-methylation in cardiac hypertrophy and heart failure development.

Methods and results

m6A RNA-methylation was analysed via methylated RNA immunoprecipitation (meRIP) and subsequent next generation sequencing (NGS). Our data shows that approximately one quarter of the transcripts in the healthy mouse (24.09%) and human heart (14.6%) exhibit m6A RNA-methylation. A mild positive correlation of m6A RNA-methylation at the 5'UTR and coding region with transcript level was observed while m6A RNA-methylation at the 3'UTR showed a mild negative correlation.

We analysed heart failure in mice and humans and observed that changes in m6A RNA-methylation exceed changes in gene-expression (in human data 1219 differentially methylated and 198 diff. expressed, with 30 showing changes in both methylation and expression; in mouse data 1135 diff. methylated and 127 diff. expressed, with 47 showing changes in both methylation and expression). In mouse and human heart failure, transcripts with altered m6A RNA-methylation were mainly linked to metabolic and regulatory pathways while changes in transcript level mainly represented changes in structural plasticity. In the diseased state m6A RNA-methylation showed no correlation to transcript level. To gain further insight into m6A mediated effects on the translational level, polysome-sequencing was applied. These data provide evidence that in the diseased heart changes in m6A RNA-methylation affect RNA translation, represented by a positive correlation (r=0.37, p=2.2e-16) of log2fc changes in translation and m6A methylation.

Conclusions

Our study describes m6A RNA-methylation at the genome-wide level in the human heart. The mouse model provides evidence that changes in m6A RNA-methylation plays an important role in heart failure development by affecting regulatory pathways distinct from those genes with altered expression levels. Our data suggest that modulation of epitranscriptomic processes such as m6A-methylation might be an interesting target for therapeutic interventions.

Acknowledgement/Funding

CRC 1002

Straight-to-test for the two-week-wait colorectal cancer pathway under the updated NICE guidelines reduces time to cancer diagnosis and treatment

INTRODUCTION

The 2015 National Institute for Health and Care Excellence guidelines widened the referral criteria for the two-week-wait pathway for suspected lower gastrointestinal cancer. We implemented a straight-to-test protocol to accommodate the anticipated increase in referrals. We evaluated the impact of these changes for relevant pathway metrics and clinical outcomes using a retrospective cohort study with historic controls.

MATERIALS AND METHODS

We analysed data from all patients referred to a teaching hospital via the two-week-wait pathway for suspected lower gastrointestinal cancer under the previous guidelines between 1 March and 31 August 2015 compared with the same period in 2016, when the updated guidelines and straight-to-test protocol had been implemented.

RESULTS

In the 2015 cohort, there were 64 cancer diagnoses from 664 referrals (9.6% pick-up) compared with 58 cancer diagnoses from 954 referrals in the 2016 cohort (6.1% pick-up). Our straight-to-test protocol reduced the median time to cancer diagnosis by 12.5 days (P < 0.001) and reduced the median time to cancer treatment by 7.5 days (P < 0.05) An increased proportion of non-colorectal cancers were diagnosed in 2016 compared with 2015, (37.9% vs 17.2%, P < 0.05) and more adenomas were removed in 2016 compared with 2015 (377 vs 193).

DISCUSSION AND CONCLUSION

Our straight-to-test protocol has resulted in a reduction in times to cancer diagnosis and cancer treatment, despite an increase in the number of referrals. The new referral criteria have considerable resource implications, but their implementation did not result in an increase in the total number of cancers diagnosed.

The effect of the native kinematics of the knee on the outcome following total knee arthroplasty

AIMS

The aim of this study was to investigate differences in pain, range of movement function and satisfaction at three months and one year after total knee arthroplasty (TKA) in patients with an oblique pattern of kinematic graph of the knee and those with a varus pattern.

PATIENTS AND METHODS

A total of 91 patients who underwent TKA were included in this retrospective study. Patients (59 women and 32 men with mean age of 68.7 years; 38.6 to 88.4) were grouped according to kinematic graphs which were generated during navigated TKA and the outcomes between the groups were compared.

RESULTS

The graphs were varus in 50 patients (55%), oblique in 19 (21%), neutral in 17 (18.5%) and valgus in five (5.5%). After adjustment for pre-operative scores and gender, compared with patients with varus knee kinematics, patients with an oblique kinematic graph had a poorer outcome with lower Knee Society scores at three months (9.2 points, p = 0.038).

CONCLUSION

We found four distinct kinematic graphs in knees and that patients with an oblique graph have a poorer outcome in the short-term after TKA. Cite this article: Bone Joint J 2016;98-B:1471-8.

Corrosion at the neck-stem junction as a cause of metal ion release and pseudotumour formation

We present a series of 35 patients (19 men and 16 women) with a mean age of 64 years (36.7 to 75.9), who underwent total hip replacement using the ESKA dual-modular short stem with metal on-polyethylene bearing surfaces. This implant has a modular neck section in addition to the modular head. Of these patients, three presented with increasing post-operative pain due to pseudotumour formation that resulted from corrosion at the modular neck-stem junction. These patients underwent further surgery and aseptic lymphocytic vaculitis associated lesions were demonstrated on histological analysis. Retrieval analysis of two modular necks showed corrosion at the neck-stem taper. Blood cobalt and chromium levels were measured at a mean of nine months (3 to 28) following surgery. These were compared with the levels in seven control patients (three men and four women) with a mean age of 53.4 years (32.1 to 64.1), who had an identical prosthesis and articulation but with a prosthesis that had no modularity at neck-stem junction. The mean blood levels of cobalt in the study group were raised at 50.75 nmol/l (5 to 145) compared with 5.6 nmol/l (2 to 13) in control patients. Corrosion at neck-stem tapers has been identified as an important source of metal ion release and pseudotumour formation requiring revision surgery. Finite element modelling of the dual modular stem demonstrated high stresses at the modular stem-neck junction. Dual modular cobalt-chrome hip prostheses should be used with caution due to these concerns.

Computer navigated total knee arthroplasty: aspects of a single unit's experience of 777 cases

The use of computer navigation and conventional techniques in total knee arthroplasty remains controversial. Advocates of computer navigated techniques cite better alignment of components and reduced morbidity associated with avoidance of intramedullary instrumentation as a rationale for their use. In contrast, proponents of conventional techniques argue that better alignment does not correlate with a better functional outcome and that the conventional approach avoids the perceived risk of fracture associated with bicortical insertion of navigation tracker pins. All total knee arthoplasties performed at our institution are prospectively monitored for life in a dedicated Joint Replacement Assessment Clinic (JRAC). Patients are reviewed by physiotherapists, independent of the surgeons who performed surgery, both preoperatively and at six weeks, three and six months, and one, two and five years postoperatively (and every five years thereafter). Patients are assessed using validated outcome measures (Knee Society Score, Western Ontario and McMaster Universities (WOMAC) osteoarthritis index, Short Form SF-36 Health Survey (version 2) and a patient satisfaction score). In addition, at 6 months post surgery, a CT scan of each implanted prosthesis is performed using the Perth CT knee protocol. The findings of a single unit's experience of 777 navigated primary total knee replacements are discussed and critically compared to the body of literature that currently relates to this controversial topic.

Computer navigation versus conventional total knee replacement

We previously compared the component alignment in total knee replacement using a computer-navigated technique with a conventional jig-based method. We randomly allocated 71 patients to undergo either computer-navigated or conventional replacement. An improved alignment was seen in the computer-navigated group.

The patients were then followed up post-operatively for two years, using the Knee Society score, the Short Form-36 health survey, the Western Ontario and McMaster Universities osteoarthritis index, the Bartlett Patellar pain questionnaire and the Oxford knee score, to assess functional outcome.

At two years post-operatively 60 patients were available for assessment, 30 in each group and 62 patients completed a postal survey. No patient in either group had undergone revision. All variables were analysed for differences between the groups either by Student’s t-test or the Mann-Whitney U test. Differences between the two groups did not reach significance for any of the outcome measures at any time point. At two years postoperatively, the frequency of mild to severe anterior pain was not significantly different (p = 0.818), varying between 44% (14) for the computer-navigated group, and 47% (14) for the conventionally-replaced group. The Bartlett Patellar score and the Oxford knee score were also not significantly different (t-test p = 0.161 and p = 0.607, respectively).

The clinical outcome of the patients with a computer-navigated knee replacement appears to be no different to that of a more conventional jig-based technique at two years post-operatively, despite the better alignment achieved with computer-navigated surgery.

Carbon dioxide laser-treatment of resistant verrucae vulgaris: retrospective analysis

BACKGROUND

Verrucae are a very common dermatological problem that can be both painful and bothersome to the individual as well as costly to the health care system. In some cases verrucae can be notoriously resistant to therapy.

OBJECTIVE

To determine the cure rate, side effect profile, and overall satisfaction with CO2 laser treatment of recalcitrant verrucae vulgaris.

METHODS

A retrospective survey was sent to over 200 patients who had resistant verrucae vulgaris treated with the carbon dioxide laser at The Toronto Hospital (Western Division) from 1989 to 1994.

RESULTS

Ninety-two complete responses were received. The overall cure rate was 64.1% at 12 months. There was no significant difference in cure rates between single compared to multiple warts (p = .824 Fisher's exact test). The duration of the wart being present showed no difference in cure rate (p = .801 Fisher's exact test). The location of the wart also had no influence on the cure rate (p = .433 Fisher's exact test). Overall, 71.7% of the patients were happy with the laser treatment and 85.7% would have it done again.

CONCLUSION

The carbon dioxide laser is an effective treatment of resistant verrucae vulgaris.

Assessment of the hygienic performances of hamburger patty production processes

The hygienic conditions of the hamburger patties collected from three patty manufacturing plants and six retail outlets were examined. At each manufacturing plant a sample from newly formed, chilled patties and one from frozen patties were collected from each of 25 batches of patties selected at random. At three, two or one retail outlet, respectively, 25 samples from frozen, chilled or both frozen and chilled patties were collected at random. Each sample consisted of 30 g of meat obtained from five or six patties. Total aerobic, coliform and Escherichia coli counts per gram were enumerated for each sample. The mean log (x) and standard deviation (s) were calculated for the log10 values for each set of 25 counts, on the assumption that the distribution of counts approximated the log normal. A value for the log10 of the arithmetic mean (log A) was calculated for each set from the values of x and s. A chi2 statistic was calculated for each set as a test of the assumption of the log normal distribution. The chi2 statistic was calculable for 32 of the 39 sets. Four of the sets gave chi2 values indicative of gross deviation from log normality. On inspection of those sets, distributions obviously differing from the log normal were apparent in two. Log A values for total, coliform and E. coli counts for chilled patties from manufacturing plants ranged from 4.4 to 5.1, 1.7 to 2.3 and 0.9 to 1.5, respectively. Log A values for frozen patties from manufacturing plants were between < 0.1 and 0.5 log10 units less than the equivalent values for chilled patties. Log A values for total, coliform and E. coli counts for frozen patties on retail sale ranged from 3.8 to 8.5, < 0.5 to 3.6 and < 0 to 1.9, respectively. The equivalent ranges for chilled patties on retail sale were 4.8 to 8.5, 1.8 to 3.7 and 1.4 to 2.7, respectively. The findings indicate that the general hygienic condition of hamburgers patties could be improved by their being manufactured from only manufacturing beef of superior hygienic quality, and by the better management of chilled patties at retail outlets.

Efficacy of buspirone in smoking cessation: a placebo-controlled trial

Buspirone, a non-sedating anxiolytic, has yielded contradictory results in smoking cessation pilot studies and trials. We tested buspirone (n = 51) versus placebo (n = 49) in a placebo-controlled, double-blind trial of smoking cessation. Survival analyses were performed with use of strict abstinence criteria for efficacy (carbon monoxide levels < or = 8 ppm; no self-reported slips to smoking). No treatment differences were observed between active and placebo groups. There were also no differences among "anxiety" level groups formed post hoc from high versus low, pre-quit anxiety test scores. A number of withdrawal symptoms increased significantly after subjects quit smoking for both the active drug and placebo groups, but these symptoms were not relieved by treatment. There appears to be little evidence that buspirone is effective in smoking cessation or in the relief of withdrawal associated with cessation in a general sample. Selecting for generalized anxiety or anxiety related to cessation is suggested for future testing.

Analgesic and immunomodulatory effects of codeine and codeine 6-glucuronide

PURPOSE

The antinociceptive and immunosuppressive effects of codeine and codeine 6-glucuronide were determined in rats after intracerebroventricular administration.

METHODS

Codeine 6-glucuronide was synthesized using a modification of the Koenigs-Knorr reaction. A lipophilic intermediate formed during synthesis, methyl [codein-6-yl-2,3,4-tri-O-acetyl-beta-D-glucopyranosid] uronate, was also tested. Morphine was used as a positive control to compare antinociceptive potencies of these compounds.

RESULTS

All compounds tested produced significant analgesic responses, as assessed by the tail flick model. Additionally, codeine 6-glucuronide showed significantly less immunosuppressive effects than codeine in vitro.

CONCLUSIONS

We conclude that codeine 6-glucuronide and related compounds may have clinical benefit in the treatment of pain in immune compromised patients.

Antialiased ray tracing by adaptive progressive refinement

We describe an antialiasing system for ray tracing based on adaptive progressive refinement. The goals of the system are to produce high quality antialiased images at a modest average sample rate, and to refine the image progressively so that the image is available in a usable form early and is refined gradually toward the final result.The method proceeds by adaptive stochastic sampling of the image plane, evaluation of the samples by ray tracing, and image reconstruction from the samples. Adaptive control of the sample generation process is driven by three basic goals: coverage of the image, location of features, and confidence in the values at a distinguished "pixel level" of resolution.A three-stage process of interpolation, filtering, and resampling is used to reconstruct a regular grid of display pixels. This reconstruction can be either batch or incremental.

Sonographic characterization of carotid plaque: detection of hemorrhage

By careful evaluation of the sonographic characteristics of carotid plaques, two patterns can be identified: a homogeneous pattern containing uniform echoes corresponding to dense fibrous tissue and a heterogeneous pattern containing mixed echoes and anechoic areas that represent intraplaque hemorrhage pathologically. A prospective study was conducted of 50 patients to determine the accuracy of identifying these different forms of plaque. The patients' carotid arteries were examined by a high-resolution duplex scanner before carotid endarterectomy. The plaques were evaluated carefully by vascular surgeons and pathologists for the presence of intraplaque hemorrhage. In this study, the accuracy of identifying the presence or absence of intraplaque hemorrhage with sonography was 90% (48 of 54); sensitivity, 94% (17 of 18); and specificity, 88% (27 of 31). High-resolution sonography appears to be an accurate means of identifying intraplaque hemorrhage and may ultimately be useful in identifying patients at risk for embolic disease.

Amiodarone for refractory atrial fibrillation

Atrial fibrillation (AF) is a difficult arrhythmia to manage with antiarrhythmic agents. Amiodarone is highly effective in restoring and maintaining normal sinus rhythm in patients with AF. However, the mechanism and predictors of efficacy for amiodarone in treating AF have not been adequately addressed. Various measures of success or failure of amiodarone therapy were examined in 68 patients who had paroxysmal or chronic, established AF refractory to conventional antiarrhythmic agents. The patients were 25 to 75 years old (mean 59) and mean follow-up was 21 months (range 3 to 56). Maintenance amiodarone dosages were 200 to 400 mg/day. Overall, amiodarone therapy was effective long term in 54 of the 68 patients (79%). Left atrial diameter, age, gender and origin of AF were not helpful in predicting success or failure of amiodarone therapy. The presence of chronic AF for longer than 1 year was an adverse factor in maintaining normal sinus rhythm (p = 0.007), although the success rate even in this group was relatively high (57%). Thirty-five percent of the patients had adverse effects, which precluded long-term therapy with amiodarone in 10%.

Use of continuous monitoring of mixed venous saturation in the coronary care unit

Recent advances in catheter technology that enable continuous measurement of mixed venous oxygen saturation (SvO2) have improved diagnostic and therapeutic capabilities in the critical care setting. The utilization of the Opticath has provided valuable information in the diagnosis and treatment of many critically ill patients in our coronary care unit. In many instances, a change in SvO2 supplied the first indication of a hemodynamic change in the patient. Specific clinical situations in which the Opticath was used are reviewed.

REM sleep reduction effects on depression syndromes

Thirty-four endogenous and 18 reactive, depressed patients (hospitalized and nonschizophrenic) were treated in a double-blind, crossover study of the hypothesis that rapid eye movement (REM) sleep reduction (by awakenings) relieves depression. In the endogenous group-but not in the reactive group-subjects deprived of REM sleep for three weeks improved significantly more than control subjects awakened from non-REM sleep. Therapeutic efficacy of REM sleep reduction appeared similar to reported efficacy of imipramine hydrochloride treatment of depression. Eight of nine endogenous patients, unimproved by REM sleep deprivation, did not improve with imipramine. Results suggested (1) that substantial REM sleep reduction has antidepressant activity, and (2) since imipramine and other drug antidepressants reduce REM sleep much more so than nonantidepressant drugs, that an antidepressant "mechanism" of drugs resides in their capacity to substantially reduce REM sleep.