High fitness levels offset the increased risk of chronic kidney disease due to low socioeconomic status: a prospective study.

Kunutsor SK; Jae SY; Kauhanen J; Laukkanen JA;

The American journal of medicine [Am J Med] 2022 Jul 09.
Date of Electronic Publication: 2022 Jul 09

Background: Socioeconomic status (SES) and cardiorespiratory fitness (CRF) are each independently associated with chronic kidney disease. The interplay between SES, CRF, and chronic kidney disease is not well understood. We aimed to evaluate the separate and joint associations of SES and CRF with chronic kidney disease risk in a cohort of Caucasian men.
Methods: In 2,099 men aged 42-61 years with normal kidney function at baseline, SES was self-reported and CRF was directly measured using a respiratory gas exchange analyzer during cardiopulmonary exercise testing. Hazard ratios (HRs) (95% CIs) were estimated for chronic kidney disease.
Results: A total of 197 chronic kidney disease events occurred during a median follow-up of 25.8 years. Comparing low vs high SES, the multivariable-adjusted HR (95% CI) for chronic kidney disease was 1.55 (1.06-2.25), which remained consistent on further adjustment for CRF 1.53 (1.06-2.22). Comparing high vs low CRF, the multivariable-adjusted HR for chronic kidney disease was 0.66 (0.45-0.96), which persisted on further adjustment for SES 0.67 (0.46-0.97). Compared with high SES-high CRF, low SES-low CRF was associated with an increased risk of chronic kidney disease 1.88 (1.23-2.87), with no evidence of an association for low SES-high CRF and chronic kidney disease risk 1.32 (0.85-2.05). Positive additive (RERI=0.31) and multiplicative (ratio of HRs=1.14) interactions were found between SES and CRF in relation to chronic kidney disease risk.
Conclusions: In middle-aged and older males, SES and CRF are each independently associated with risk of incident chronic kidney disease. There exists an interplay between SES, CRF and chronic kidney disease risk, with high CRF levels appearing to offset the increased chronic kidney disease risk related to low SES..