Bikbov B, Perico N, Remuzzi G: Disparities in Chronic Kidney Disease Prevalence among Males and Females in 195 Countries: Analysis of the Global Burden of Disease 2016 Study. Nephron 10.1159/000489897
The presence of CKD in adults (mostly older) is a common global problem, although the precise incidence and prevalence of CKD, the changes in frequency over-time and its variation between and within countries, ancestries and genders remain a matter of controversy. The Global Burden of Disease (GBD) Study has provided much useful information on the epidemiology of this important socio-medial issue.
Bikbov and colleagues have added to our knowledge of this issue by conducting a systematic review, including unpublished studies, in order to examine CKD prevalence rates in 195 countries, using 6 categories of CKD, largely based on the KDIGO schema of estimated glomerular filtration rate (eGFR) and albuminuria, including those subjects receiving renal replacement therapy (RRT; dialysis, or renal transplantation). In this study emphasis was placed on disparities between countries that are resource rich or poor and upon gender based differences in epidemiology of CKD, so defined. Impaired kidney function (IKF) is a term introduced by the GBD to encompass the 6 subgroups of CKD, defined by eGFR and/or albuminuria.
According to this study, the global prevalence of IKF (in adults) was 753 M in 2016, or about 1 in 9 adults (≈ 120,000 pmp). The male (M) / female (F) ratio was 0.80 (different from the general population M : F ratio = 1.01). Abnormal albuminuria with preserved GFR accounted for 467 M of 753 M (62 %) while a GFR of 45 – 59 ml/min/1,73m2 accounted for 243 M of 753 M (32 %). Patients with RRT accounted for only 3.7 M of 753 M (0.5 %). Interestingly, the M : F ratio was 1.31 among those with RRT. Thus, a great gender disparity exists for both pre end-stage renal disease (ESRD) and ESRD with RRT, but in completely opposite directions. The RRT prevalence also varied considerably between countries. In 38 of 195 countries the dialysis RRT prevalence rate was < 20 pmp and in 52 of 195 countries the renal transplantation RRT prevalence rate was 0 – 10 pmp. The M : F ratio for both CKD and RRT varied widely between counties and gross domestic product (GDP) but the M : F ratio for CKD showed no correlation with GDP. However, the dialysis / renal transplantation prevalence ratio was sensitive to GDP in both M and F, implying an important socio-economic impact on access to transplantation.
The interpretation of these findings is complex. Many of the studies identifying CKD used only one determination of eGFR or albuminuria, so an overestimation (of about 30 %) for the prevalence of pre-ESRD due to “false positives” is very likely. While part of the gender disparity of the pre-ESRD CKD prevalence can be attributed to the use of a single (non-gender or age stratified) GFR (< 60 ml/min/1.73m2) for defining CKD, the observation that CKD defined by albuminuria alone (again not gender stratified) is higher in women indicates that the arbitrary selection of GFR thresholds for defining CKD is not the whole explanation for the observed gender disparities in CKD prevalence. If abnormal proteinuria in women is linked to fetal dysmaturity and consequent nephron under-development, it is possible that this might play a role in inter-generational transfer of CKD risk and prevalence.
The higher prevalence of RRT in males is commonly observed but its explanation remains poorly understood. It could bed due to a greater propensity for CKD to progress to ESRD in males compared to females. Perhaps women are being excluded from RRT for other reasons in low-GDP countries, but similar M : F ratios (> 1.1) are observed for RRT in high-GDP countries. Gender inequalities of access to renal transplantation are implied by very high M : F ratios for functioning renal transplants in some countries.
The global gender disparity issues in CKD epidemiology are very complex and multi-factorial, but are deserving of careful study and rigorous analysis in order to identify causative factors.