During the review, the following inclusion criteria were considered. Considering that this is a subject that has not been investigated in a large number of studies, and that the scientific evidence is limited, this study considered people of all ages and of both sexes, who did not have a known diagnosis of CKD as a base pathology or with a GFR of >60 mL/min per 1.73 m²; however, most studies focus on sedentary lifestyle and worsening CKD that lead to a rapid progression towards other stages, overall, in patients who are undergoing hemodialysis or peritoneal dialysis.

We considered studies that included people who had sedentary lifestyles and evaluated physical activity by different methods, among which, one was a standardized questionnaire administered by the interviewer, derived from the Leisure Time Physical Activity Questionnaire [31], complemented by lower intensity activities that were usually carried out by older adults [32]. Participants had reported the amount of time they spent doing domestic and care activities (housework, grocery shopping, and laundry), exercise (aerobic dance and weight training), and walking (walking for exercise, walking and climbing stairs) per week.

The comparators were people who regularly engaged in physical activity, which can be measured according to different questionnaires, such as the Rapid Assessment of Physical Activity [33]. The duration and intensity of weekly physical activity can be converted into hourly/weekly metabolic equivalents, based on the Ainsworth’s compendium of physical activities [34], which can help classify the intensity of physical activity; however, there are other methods to define a physical activity, as stated by each study separately, since not all studies use it.

The outcome sought was the development of CKD as a consequence of physical inactivity or sedentary lifestyle and not as another associated cause, considering that alterations in kidney function were determined according to the GFR of <60 mL/min for 1.73 m².

The eight studies included in this study were conducted in the United States (Hawkins et al. [39] in 2015, Pharr et al. [40] in 2018, Lee et al. [41] in 2020); Taiwan (Su et al. [42] in 2015), Japan (Lee et al. [43] in 2016), United Kingdom (Parsons et al. [44] in 2017, Bharakhada et al. [45] in 2012), and the Netherlands (Martens et al. [46] in 2018). The characteristics of the included studies are summarized in Table 1.

Of the eight articles selected for this systematic review, six were cross-sectional, one cohort study, and one case-control study. The methodological quality of the studies within this systematic review is acceptable, generally with low risk of selection bias, confusion, and information, in the studies by Su et al. [42], Parsons et al. [44], Lee et al. [43], and Martens et al. [46]. However, it should be noted that in a study of Pharr et al. [40], there was inadequate control for information bias and confounding, making its results unreliable and non-reproducible. In the study by Hawkins et al. [39], the methods for sample selection or the sequence of randomization of groups has not been described; thus, the risk of selection bias is unclear. In addition, the results, in general, were not comparable with each other due to the definitions of physical activity and sedentary lifestyle that each one used, since in some studies an accelerometer was used to measure the level of physical activity, while in others it was defined only by the report of the time of physical activity performed.

Likewise, the definition used for sedentary lifestyle was different in the studies, that of Martens et al. [46] quantified sedentary lifestyle in prolonged periods of rest, total sedentary time in hours per day, an average of minutes in prolonged periods of active rest, among others, making it difficult to identify the outcomes and the association measures for this study. In the studies by Lee et al. [41] and Bharakhada et al. [45], the data collection technique did not allow better control of possible information biases because self-filling surveys were used to capture mild, moderate, and intense physical activity, in addition to the sedentary or inactivity time, without carrying out objective measurements for these variables with the use of accelerometers as applied in other studies. Similarly, in a work of Lee et al. [41], the selection bias presented a considerable risk when taking inappropriate cut-off points in the level of physical activity of the participants to classify them into the different groups. The following Table 2 summarizes the risks of bias for each study.

Most of the studies included in this systematic review agree that there was an association between a sedentary lifestyle and CKD; however, not all used the same definition of this disease, understood from the criteria established by the “Kidney Disease: Improving Global Outcomes” 47) and in the same way, the definitions of physical activity and sedentary lifestyle were different between these studies. On the other hand, the method of collecting information was based on two main modalities: the survey was self-completed by the participants and the measurement of the variables under study. In the study by Hawkins et al., 39) the association measure obtained was a hazard ratio as it was a cohort type, and an OR was calculated for the other studies. Of the reviewed studies, the association between a sedentary lifestyle and CKD was found; 39,41-46) however, the study by Pharr et al. 40) did not show an association between a sedentary lifestyle and CKD (OR, 0.86; 95% CI, 0.7–1.06), and the other studies showed that there was a non-causal association between a sedentary lifestyle and chronic kidney failure, despite multivariate models, which were adjusted for comorbidities known as proven risk factors for its onset, including arterial hypertension, diabetes mellitus, and CVD among others. In some studies, the exposure consisted of physical activity with OR indicating a possible protective factor, while in others, it was a sedentary lifestyle with OR indicating a risk factor in relation to chronic kidney failure. Given the disparities between the studies, comparison and statistical analysis to pool the effect into a summary measure were not possible. The results of each study are summarized in Table 3.

In the study by Martens et al. [46], the comparison was physical activity, quantified as total hours per day, intense physical activity (>110 steps/min every 10 min/d), and light physical activity (<110 steps/min for every 10 min/d) versus sedentary lifestyle, quantified as resting time in h/d, sedentary breaks at 10 min/d, and the number of prolonged periods of sedentary lifestyle per day. The outcome considered was microalbuminuria, categorized into three groups: <15 mg/24 h, 15–<30 mg/24 h and >30 mg/24 h. In a study of Lee et al. [43], the comparison was sitting: <4 h/d, 4–<6 h/d, and >6 h/d, while the outcome was chronic renal failure defined as a GFR of <60 mL/min/1.73 m².

In the study by Parsons et al. [44], the level of physical activity was quantified as <100 counts/min (sedentary behavior), 100–1,040 counts/min (light activity), >1,040 counts/min (moderate to vigorous activity), and the outcome was GFR divided into <45 mL/min/1.73 m² and 45 mL/min/1.73 m² or higher.

In the study by Pharr, et al. [40] physical activity was measured as high activity (300 minutes of aerobic activity or 150 min/wk of vigorous aerobic exercise), moderate activity (150–300 min/wk of aerobic activity), insufficient activity (11–149 min/wk of aerobic activity), and inactivity, while the outcome was CKD, which was not clearly defined by the study.

In addition, the studies by Hawkins et al. [39] and Su et al. [42] measured physical activity based on calorie consumption, dividing it into three categories: 0–48 kcal/kg/wk, 48–93 kcal/kg/wk, and >93 kcal/kg/wk [39]; the absence or presence of physical activity: physical activity, 3 times/ wk (yes), activity <3 times/wk (no) [42]; and sedentary lifestyle as time watching television (TV), <2 h/d, 2–3 h/d, and >3 h/d [39]. The outcome for both was CKD as a GFR of <60 mL/min/1.73 m².

In the studies by Bharakhada et al. [45] and Lee et al. [41], low sitting or sedentary time and moderate to intense physical activity showed a possible relationship as protective factors against chronic kidney failure, while sitting for a long time and less physical activity were possible risk factors for this outcome. We found that the reviewed studies adjusted for potentially confusing variables, such as hypertension or diabetes mellitus, as well as for age, body mass index, and neoplasms, among others, the association between sedentary lifestyle/physical activity and chronic kidney failure was lost in the multivariate study analysis, as occurred in the work of Parsons et al. [44], and Pharr et al. [40], (OR, 1.05; 95% CI, 0.93–1.05; OR, 0.94; 95% CI, 0.73–1.21).

It was not possible to calculate the summary measure using meta-analysis because the measure of association of the studies was not comparable, due to the lack of uniformity in the definition of the interventions, the comparisons, and outcome of interest, in addition to studying different populations whose characteristics do not allow the extrapolation and generalization of the results found in each publication reviewed here. For this reason, the execution of studies that have a higher level of evidence and a better-structured protocol is pending to make it possible to compare them and obtain a summary measure using the meta-analysis technique.

The use of subjective self-reported questionnaires for the assessment of sedentary behavior might be subject to bias; therefore, more studies with measurements derived from precision devices, such as accelerometers, are required.

Despite the vast amount of scientific content on the relationship that may exist between sedentary lifestyle, whether in healthy people or not, and the development of CKD, there is evidence that there is a need to further distinguish between sedentary time by visualization of television and occupational sedentary lifestyle, to define exactly the health risks conferred by sedentary behavior, such as television viewing time that appears to be more detrimental with respect to health outcomes. These studies on the different types of sedentary time and the risk of renal dysfunction have not been reported in the study [55,56].

At the population level, it is necessary to understand and identify the environmental, social, and personal determinants of sedentary behavior and to investigate whether a sedentary lifestyle is equally relevant in healthy and physically active people, as in physically inactive participants with or without disease.

By working on modifiable risk factors in different population groups and, above all, in childhood and adolescence, the level of sedentary lifestyle can be improved, which could lead to a reduction in the risk of developing chronic diseases such as kidney disease. Since no definitive studies were found, it is suggested that more specific research should be conducted regarding factors associated with CKD.

There is little quality scientific evidence and homogenization; thus, more observational and interventional studies are needed, in which the same measurements are used for a sedentary lifestyle and physical inactivity, if possible, they are applied in different age and population groups, in order to measure the magnitude and association of these risk factors to trigger CKD.