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Central obesity is common in renal transplant recipients and is associated with increased prevalence of cardiovascular risk factors.

Article Excerpt
Abstract

Aim: Obesity following renal transplantation is common and may be associated with cardiovascular disease. We sought to investigate the prevalence of central obesity in renal transplant recipients (RTR) and its association with cardiovascular risk factors.

Methods: Weight, height, body mass index (BMI), waist and hip circumference, and biochemical cardiovascular risk factors were prospectively measured in 199 RTR, and were compared against published data from the Australian general population.

Results: When obesity was defined by BMI, there was no difference between RTR and the Australian population irrespective of age. Significantly more female RTR had central obesity (defined as waist circumference [greater than or equal to]90 cm for men and [greater than or equal to]80 cm for women) when compared with the general population, and this was apparent at a younger age. In younger women (<45 years), 76% of RTR had central obesity compared with 17% of women from the general population (P < 0.0001). This trend was also seen in older female RTR. Younger male RTR (<45 years) had a greater prevalence of central obesity than aged-matched men in the general population (66% vs 44%, respectively, P < 0.001). This trend was not seen in older male RTR. Centrally obese RTR gained significantly more weight post transplant than those who were lean (9.5 kg vs 2.4 kg, respectively, P < 0.0001), and were more likely to have a history of childhood obesity (P = 0.04). On multivariate analysis, central obesity was independently associated with weight gain post transplant (P < 0.001), a history of hyperlipidaemia (P = 0.01) and a history of hypertension (P = 0.02).

Conclusion: Central obesity is a common problem for all RTR, particularly women and men aged below 45 years. Measures of central obesity should be used for RTR in clinical practice. BMI is not a suitable measure to determine central obesity. Central obesity is associated with cardiovascular risk factors, and further studies targeting multi-disciplinary lifestyle interventions are recommended.

Key words: central obesity, glucose tolerance, insulin resistance, renal transplant recipient.

INTRODUCTION

Obesity following renal transplantation is common, and is associated with a sedentary lifestyle, metabolic effects of steroids and obesity prior to transplant. (1) Other factors associated with weight gain post transplant are female gender, African American race, young age and low income. (2,3) Obesity in renal transplant recipients (RTR) has been linked to cardiovascular disease (CVD) and other adverse health outcomes, including hypertension, dyslipidaemia, insulin resistance, post-transplant diabetes mellitus (PTDM), chronic allograft nephropathy, and graft loss and death. (1) CVD is the leading cause of mortality in RTR, accounting for more than 50% of deaths. (4) Central obesity is common in RTR and is associated with cardiovascular morbidity and mortality. (3,5) Central (or visceral) fat is considered more detrimental than subcutaneous fat as it is associated with a number of metabolic and cardiovascular disturbances, namely the increased production of free fatty acids, which may impair the action of insulin, leading to insulin resistance. (6) Waist circumference (WC) has been demonstrated as a good predictor of visceral fat and is easily measured in clinical practice. (6,7)

Although weight gain is a well-known consequence of renal transplantation, monitoring weight changes and cardiovascular risk factors such as WC, insulin resistance and dyslipidaemia are not necessarily routine practice in renal transplant centres. We sought to: (i) investigate the prevalence of central obesity in RTR at our centre and compare with the general Australian population; and (ii) determine the association between central obesity and cardiovascular risk factors (blood pressure, fasting lipids and oral glucose tolerance test (OGTT)).

PATIENTS AND METHODS

Subjects

The study protocol was approved by the Princess Alexandra Hospital Human Research Ethics Committee, which conforms to the provisions of the Declaration of Helsinki. All patients at the Princess Alexandra Hospital Renal Unit (PAHRU) were screened according to the following criteria: [greater than or equal to]6 months post transplant and with a functioning renal transplant; not known to be diabetic (self-reported or on oral hypoglycaemic agents); and regularly followed up at the PAHRU on a two- to three-monthly basis. Two hundred and eighty eligible patients were approached to undertake an OGTT for inclusion in the study, and observational data were collected on this cohort between January 2004 and January 2005. One hundred and ninety-nine patients (71%) underwent screening and were included in the present study. Written informed consent was obtained from all study participants. Some of the eligible patients did not attend for an OGTT for the following reasons: not interested in the study (n = 11, 13.6%); failed to attend OGTT appointment (n = 18, 22.2%);...

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