MO561: Salt and Chronic Kidney Disease: How Much Does the Patient Know? A Pilot Study
Authors: Colucci Marco , Gobbi Roberta , Adamo Gabriella , Pasquinucci Ettore , Sileno Giuseppe , Arazzi Marta , Esposito Vittoria , Esposito Ciro 
Published: May 2022

BACKGROUND AND AIMS

Despite World Health Organisation recommends a salt intake of &lt;5 g per day, many studies reported a much higher consumption in the general population. High salt intake is a known risk factor for hypertension and worsening of chronic kidney disease; however, studies assessing the effective sodium intake and patient's perspective towards salt in this population are lacking.

METHOD

We conducted a single centre, cross-sectional, observational study enrolling patients older than 18, with a diagnosis of chronic kidney disease stage 3 to 5, who underwent a regular visit at the outpatient clinic of our Unit, from 12 March 2021 to 10 October 2021. Clinical data, including medical history, treatments and sociodemographic information were collected from patients’ records. Anthropometric measurements were performed during the visit. Every patient was asked to provide a random urine sample, to perform a 24-h urine collection and filled a questionnaire on Knowledge, Attitude and Practice toward salt that we adapted from other studies[1,2]; a section was focused on Mediterranean Diet adherence. Salt intake was assessed by means of 24-h sodium excretion and using three equations (namely Tanaka, Nerbass and Kawasaki) to estimate it from spot urine. Adequacy of 24-h urine collection was defined upon values of creatininuria. We evaluated whether there was a correlation between sodium intake with demographic and clinical data and with the scores from various sections of the questionnaire.

RESULTS

We enrolled 90 patients, 55 males and 35 females, aged 73.7 ± 8.7 years; mean BMI was 29.1 ± 5.5. Of 90 patients, 78 provided the 24-h urine collection; however, 30 out of 78 were not included due to inadequacy. Twenty-four hours sodium excretion of remaining 48 was compared with the estimates obtained from spot urine. Bland Altman test revealed best performance for Tanaka equation (bias 0.99 ± 62.5 mEq/d, 95% LoA from -121.6 to 123.6); thus, this was used for subsequent analysis. Mean sodium intake in our population was 156.2 ± 50.5 mEq/d. We found no difference in sodium intake according to gender, age, stage of CKD, blood pressure, education, smoking habits or residency; however, we found higher intake in overweight (148.5 ± 38.9 mEq/d) and obese (179.5 ± 62.4 mEq/d) people when compared with normal weight subjects (142.2 ± 43.1 mEq/d; P = 0.0301). Patients on diuretic treatment were found to have higher sodium intake (173.6 ± 58.6 versus 137.9 ± 30.7 mEq/d, P = 0.0018), but there was no association of sodium intake with number of antihypertensive medications. Although 63.3% of patients thought of consuming a diet with the right amount of salt, less than 10% of them knew exactly the recommended daily salt intake. We found no correlation between the questionnaire scores and clinical and sociodemographic data, even if female patients showed a trend toward better performance in Knowledge (P = 0.0756) and Mediterranean Diet adherence (P = 0.0632). A positive correlation between Knowledge and Practice scores was found (r = 0.3506, P = 0.0007).

CONCLUSION

Our study shows that the mean salt intake in chronic kidney disease patient is much higher than recommended, despite the importance of a low salt diet. Obese patients showed the highest sodium intake, possibly due to the elevate intake of processed food. The questionnaire showed a lack of knowledge that encompasses every sociodemographic category. Also, the high number of inadequate 24-h urine collections points out the critical role of the assessment method, which may need to be reconsidered.