Diet and Other Modifiable Factors in Long-Term Decline of Kidney Function: Observational and Population-Based Cohort Study

Nutrients. 2023 Oct 11;15(20):4337. doi: 10.3390/nu15204337.

Abstract

Background: Lower physical activity, lower alcohol intake, higher protein intake, higher sodium intake, and lower potassium intake related to greater kidney function decline over time, according to previous studies. The present study aimed to analyze the cumulative effects of these factors.

Methods: This prospective, observational, population-based cohort study included 3039 adult examinees of the Gubbio study who participated in the baseline exam and 15-year follow-up exam. Kidney function was evaluated as estimated glomerular filtration rate (eGFR). Habitual physical activity in leisure time and habitual alcohol intake were assessed by questionnaires; dietary intakes of protein, sodium, and potassium were assessed by urinary markers. Based on previous reports, each one of the five modifiable factors was scored 0 for the tertile associated with smaller eGFR decline (low risk), 2 for the tertile associated with greater eGFR decline (high risk), and 1 for the intermediate tertile (intermediate risk). A cumulative score was calculated as the sum of the factor-specific scores and used as the main independent variable.

Results: The cumulative score ranged from 0 to 10, that is, from low risk for all factors to high risk for all factors (skewness = 0.032, mean ± SD = 5 ± 2). To avoid the bias of low-n analyses, score 0 was re-coded as 1 and score 10 was recoded as 9; after re-coding, the cumulative score ranged from 1 to 9 (skewness = 0.016, mean ± SD = 5 ± 2). The cumulative score related to annualized eGFR change in multi-variable linear regression (slope = -0.027, 95%CI = -0.039/-0.014, p < 0.001); findings were consistent in apparently healthy examinees and other subgroups. De novo incidence of eGFR < 60 mL/min × 1.73 m2 was higher along the cumulative score (p < 0.001). Compared to score 1 (n examinees = 35, adjusted incidence = 2.0%), incidence of low kidney function was 4.5 times higher in score 5 (n examinees = 624, adjusted incidence = 8.9%) and 6.5 times higher in score 9 (n examinees = 86, adjusted incidence = 12.9%). The cumulative score related to incidence of low kidney function in multi-variable logistic regression (odds ratio = 1.19, 95%CI = 1.08/1.32, p < 0.001).

Conclusions: The combination of five modifiable factors predicted large differences in long-term incidence of low kidney function.

Keywords: aging; alcohol intake; eGFR; physical activity; potassium; protein; sodium.

Publication types

  • Observational Study

MeSH terms

  • Adult
  • Cohort Studies
  • Diet*
  • Glomerular Filtration Rate
  • Humans
  • Kidney
  • Logistic Models
  • Potassium
  • Prospective Studies
  • Renal Insufficiency, Chronic* / epidemiology
  • Risk Factors

Substances

  • Potassium

Grants and funding

In the past, economic support to the Gubbio study was provided by Merck, Sharp and Dohme, Italy; the US National Heart, Lung and Blood Institute (grant R01HL-40397-02) and the Ministero Italiano di Università e Ricerca (grant 068034, PRIN 2004). None of the sponsors or funders had any role in the study design; in the collection, analysis and interpretation of data; in the writing of the report or in the decision to submit the article for publication.