Pretransplant obesity and kidney transplant outcomes
Despite improvements in graft and recipient survival, some kidney transplants fail. Various causes and risk factors can result in graft loss, including acute or chronic rejection, vascular complications, delayed graft function or recipient age.
Obesity is known to impact kidney transplant outcomes through increased adiposity and related inflammation, and by elevating other risk factors, such as cardiovascular disease. Evidence on the strength of these relationships has, however, been conflicting.
The prospective study by Cho and colleagues analysed the relationship between pretransplant obesity (defined by the Asia–Pacific criterion of BMI ≥25 kg/m2) and kidney transplant outcomes. It used nationwide data from the Korean Organ Transplantation Registry (KOTRY) of all adult kidney transplant recipients (KTRs) from 2014 to 2021. KTRs were categorised into four groups based on pretransplant BMI: underweight (<18.5), normal weight (18.5–22.9), overweight (23–24.9) and obese (≥25).
A total of 9130 KTRs were followed-up for a mean duration of 2.5 years. Mean age was 49.9±11.6 years and 60.2% were male. The mean prevalence of obesity was 28.6%, rising from 24.8% in 2014 to 32.5% in 2021. Obese KTRs were characterised by a higher prevalence of males, more smokers and shorter dialysis vintage, and with diabetes being the primary aetiology of their kidney disease.
The Kaplan–Meier curve showed a significant difference in death-censored allograft loss between the BMI groups (log-rank P=0.007), with the lowest allograft survival in the obese KTRs. The incidence of acute rejection was also significantly higher in this group (20.3%, P=0.031). No differences were seen in the cumulative rates of cardiovascular events or all-cause mortality across BMI groups.
Multivariate analysis confirmed obesity as an independent risk factor for death-censored allograft loss (adjusted HR, 1.511 [95% CI, 1.063 to 2.148; P=0.021]). The underweight and overweight groups did not show significant changes in the incidence of death-censored allograft loss. However, obesity was not linked to the risk of cardiovascular events or all-cause mortality.
The association between pretransplant obesity and adverse graft outcomes suggests that optimising body weight prior to kidney transplantation may be beneficial. The authors caution that the follow-up period was short and that low event rates and small subgroup sizes meant that the study was underpowered. Also, the use of Asia–Pacific guidelines to define the weight categories limits the generalisability of the findings to other populations.
The full article can be read here.
