Association of protein intake with discordance between cystatin C- and creatinine-based eGFR in community-dwelling Japanese adults

Objective: Recent studies have reported the prognostic implications of the discordance between creatinine-based and cystatin C-based estimated glomerular filtration rates (eGFR_cr and eGFR_cys, respectively); however, the associations of protein intake with the eGFR discordance have not been investigated. The present study investigated whether protein intake was associated with the discordance between eGFR_cr and eGFR_cys.

Design and methods: We cross-sectionally analyzed data from a Japanese community-based cohort including 6,143 participants (50.7% women; age range, 40-97 years). Protein intake was estimated by food groups derived from a validated food frequency questionnaire. As a measure of discordance, we modeled the ratio of eGFR_cys and eGFR_cr (eGFR_cys divided by eGFR_cr) continuously in multivariable linear regression models and categorically (<0.8, 0.8-1.1, and ≥1.2) in multinomial logistic regression models. We analyzed men and women separately given their distinct dietary patterns.

Results: The mean eGFR ratio was 1.15 in men and 1.19 in women. In multivariable linear regression analysis, total protein was positively associated with the eGFR ratio in men (regression coefficient, 0.005 [95% CI, 0.003, 0.007]). When animal and plant proteins were analyzed separately, a significant positive association was seen for animal protein only in men (0.005 [0.003, 0.007]). The results were similar when we modeled protein intake categorically by multinomial logistic regression.

Conclusion: This study suggests intake of dietary protein, especially animal protein in men, as a determinant of eGFR discordance. Future studies exploring eGFR discordance and health outcomes should consider simultaneously assessing dietary protein intake.