Background: The purpose of the present study was to compare the participation of women and men in the protocols of the Modification of Diet in Renal Disease (MDRD) study, a multicenter prospective randomized clinical trial, and to assess gender differences in their renal outcomes.
Methods: Of the 840 participants in the MDRD study, 332 (39.5%) were women who were assigned randomly to the dietary protein and blood pressure groups and followed for a median of 2.2 years. A subgroup analysis of the MDRD study database was carried out to compare women and men participants in recruitment, baseline characteristics, adherence to protocol requirements, safety and outcomes, and progression of renal disease and its response to dietary and blood pressure interventions.
Results: Adherence by women to the requirements of the protocol including diet, record keeping, office visits, glomerular filtration rate (GFR) measurements and urine collections was equivalent to that of men. Women had different renal diagnoses, less proteinuria and lower serum creatinine levels for given GFRs than men. When participants were grouped above and below age 52, the younger women had lower mean arterial pressure than did the men. Older women compared with younger had higher mean arterial pressure, body weight and body mass index, and total low density lipoprotein cholesterol. These differences were not seen between males of the same two age groups. During follow-up, the rate of GFR fall was slower in women, especially in the younger group. However, the association between gender and the rate of fall in GFR was attenuated and became non-significant after adjusting for differences in blood pressure, proteinuria and high density lipoprotein cholesterol. In analyses of the full cohort, there were no significant differences between women and men in the effects of the low protein or low blood pressure intervention in patients with either moderate (study A) or advanced (study B) renal disease. However, in subgroup analyses of patients in study A, there was some evidence of a lesser effect in women than in men.
Conclusions: This exploratory analysis of the MDRD study indicates a slower mean GFR decline in women as compared with men. The slower mean GFR decline and suggestive evidence of a lesser beneficial effect of the low protein diet and low blood pressure interventions in women suggest that gender differences should be considered in trials of the effects of these interventions on the progression of renal disease. Also, the participation of women in the MDRD study was excellent and equivalent to that of men.