Physical inactivity in patients with hypertension: is coexisting CKD a common aggravating factor?

We read with interest the study by Han et al., offering important insights into the associations between different levels of physical and muscle-strengthening activities and chronic kidney disease (CKD) prevalence in hypertensive patients in Korea. However, when reading the paper, we noticed some issues that warrant discussion. First and most important one, the definition used for CKD is incomplete as the authors define CKD solely based on a single measurement of eGFR < 60 mL/min/1.73 m, neglecting other essential components of the CKD definition and therefore, misdiagnose CKD in several circumstances. This has likely led to misclassification of cases and underestimation of the true prevalence of CKD. Additionally, characteristics of residential environment as an independent variable, which have been reported by recent studies to be the only factors strongly associated with CKD patients' physical activity, were not considered in the analysis. Finally, the assessment of physical and muscle-strengthening activity relied only on self-reported questionnaires, which may have introduced recall biases and misclassification of activity levels. Overall, although novel, the observed findings need to be confirmed by future, larger and optimally designed studies.