Relationship between modifiable lifestyle factors and chronic kidney disease: a bibliometric analysis of top-cited publications from 2011 to 2020

Chronic kidney disease (CKD), defined as abnormalities of kidney structure or function presenting for >3 months with health implications [1], affects 8–16% of the world’s population [2]. CKD is closely associated with an increased risk of adverse events, including end-stage renal disease (ESRD), cardiovascular events, hospitalizations, and mortality [3‐7]. The global all-age mortality rate from CKD increased by 41.5% from 1990 to 2017 [8]. It is currently ranking the 16th leading cause of years of life lost [2] and is projected to rise in the ranking, to the 5th, by 2040 [9].

CKD imposes great burdens in both developed and developing countries. For example, Medicare expenditures for ESRD in the United States (the US) increased by about 20.3% from 2009 to 2018 and accounted for 7.2% of overall Medicare fee-for-service spending in 2018 [10]. The burden of CKD is even more pronounced in low- and lower-middle-income countries [11]. In several regions, particularly Oceania, sub-Saharan Africa, and Latin America, the burden of CKD is much higher than expected for the level of development [8]. Thus, it is considered to be one of the top ten important drivers of increasing burden according to the latest analysis for the Global Burden of Disease Study [12].

CKD is affected by both genetic and environmental factors [13]. While modification of the genetic predisposition for CKD is quite challenging, evidence shows that the incidence and rapid progression of CKD can be protected via modifiable lifestyle factors, ie. diet, physical activity, alcohol consumption, tobacco smoking, sleep, and obesity [14‐18]. Recently, growing literature has addressed the underlying mechanism and the health impact of modifiable factors on CKD. However, to our knowledge, there have been no bibliometric analyses on this topic.

Bibliometric analysis is a valuable tool for navigation in a particular research area [19, 20]. It has been used to provide qualitative and quantitative analysis of publications, enabling researchers to identify core articles, study hotspots, and publishing patterns within a given subject area [21]. Thus, bibliometric analysis is an integral part of the evaluation methodology for assessment of the research evolution and current development stage of the discipline [19, 22]. In this study, based on bibliometric analysis of the top-cited articles, we aim to elucidate the current focus, growing trends, and future direction of the research about the impact of modifiable factors on CKD.

In this study, we used bibliometric analysis to identify and characterize the top 100-cited articles published between 2011 and 2020 in the field of lifestyle factors’ impact on CKD. Our study provides legible insights on the publishing trends and research themes on the topic. We found about two-thirds of the most cited papers addressing the association between modifiable factors and CKD were clinical research, while basic studies only accounted for a small fraction. Developed countries, especially the US, showed overwhelming influence in this field in terms of the number of top-cited publications. We also noticed the transition of research hotspots over the decade, with diet, nutrition, obesity, and physical activity being the factors constantly drawing attention, and alcohol consumption, gut-kidney axis, fish oil, chain fatty-acids, molecular-weight protein, and water-soluble vitamins being among the newly emerging keywords.

Our finding, that the modifiable factors gaining most popularity were diet or nutritional management, is consistent with the fact that diet contributes substantially to the incidence and progression of CKD, and stays focused in the academic community. Recommendations on protein and sodium intake have been incorporated into guidelines for clinical management of CKD, such as the Kidney Disease: Improving Global Outcomes guideline [1], National Institute for Health and Care Excellence guideline [45], and National Kidney Foundation Kidney Disease Outcomes Quality Initiative guideline [46]. However, as Suetonia C Palmer pointed out, current evidence for dietary interventions in the setting of CKD, with clinical uncertainty, is yet sufficient to guide comprehensive clinical practice [47]. For instance, there are very limited data available evaluating potential adverse effects and participants’ quality of life related to dietary protein restriction [48]. Thus, as indicated in our study, the impact of diet and nutrition on CKD remains an important research topic, and further studies to evaluate the effects of nutritional interventions in the general population for the prevention of incident CKD and in CKD participants for slowing the progression to ESRD are required [48].

Our study showed obesity and health-related behaviors, such as physical activity and smoking, were among the research hotspots of modifiable factors. This evidence supports the inclusion of advice on physical activity, healthy weight, and smoking cessation into CKD management guidelines [1]. This reflects the attention from the field of nephrology on the influence of emerging obesity issues and unhealthy behavioral factors on health outcomes. Both obesity and sedentary lifestyle have become major driving forces for global disease burdens [49‐51]. Their associations with CKD are investigated intensely by scholars. For example, in the top-cited articles included in the study, obesity is associated with increased CKD risk, and obese or overweight CKD patients are suggested to maintain a healthy weight and lifestyle [14]. A study evaluated the risk of ESRD associated with obesity at the time of donation among live kidney donors and found that obese live kidney donors have a significant 86% increased risk of ESRD compared to non-obese donors [52]. Regular physical activity instead of sedentariness can reduce the risk and mortality of CKD in type 2 diabetes [53]. A randomized clinical trial found that dietary calorie restriction and aerobic exercise can improve the metabolic milieu in patients with moderate to severe CKD [54]. Besides, a low-intensity exercise program may improve physical performance and quality of life in dialysis patients [55]. Studies suggest that cigarette smoking is an independent risk factor for incident CKD [56, 57], and nonsmoking is associated with a lower risk of adverse outcomes in CKD patients [58] and all-cause mortality [59].

It is interesting to investigate the evolution of research hotspots over time. For example, water intake and dietary sodium were factors receiving high citation years ago. A cross-sectional analysis of the National Health and Nutrition Examination Survey found that higher total water intake, particularly plain water, has a protective effect on CKD [60]. Julie Lin had analyzed longitudinal cohort data to fill the research vacancy of the influence of sodium intake on microalbuminuria and estimated glomerular filtration rate decline and found that less sodium intake can reduce the risk for estimated glomerular filtration rate decline [61]. Besides, dietary salt restriction is essential in patients with CKD and hypertension [62]. Nowadays, alcohol consumption, gut-kidney axis, fish oil, chain fatty-acids, and water-soluble vitamins have drawn more attention. Consuming a low or moderate amount of alcohol may lower the risk of developing CKD [63]. Gut microbiota dysbiosis induces gut-derived uremic toxins formation and is associated with CKD progression [64]. A recent study finds that omega-3 polyunsaturated fatty acids supplementation, such as fish oil can reduce cardiovascular mortality in patients on hemodialysis [65]. Short-chain fatty acids, being derived from fiber-rich diets [42], can delay CKD progression [66]. Vitamin K deficiency in patients on dialysis is associated with vascular calcification, bleeding risk, and cardiovascular disease [67]. Diet modification has been receiving persistent attention from scholars as most newly emerging keywords were related to diet. More research is needed to determine the optimal dietary patterns to prevent kidney disease and its progression [68]. Meanwhile, we noticed, certain research hotspot in other academic fields has not drawn as much attention in nephrology yet. For example, sleep, one of the important modifiable lifestyle factors, which was reported to be associated with a wide range of diseases [69], including CKD [18, 70, 71], was not found in the top 100-cited list. The low citation might be caused by the most recent publication time not allowing the papers to be fully cited, or might indicate not so many scholars were dedicated to the research of sleep and its relation to CKD. Lifestyle modification of sleep in CKD patients requires more attention.

The results showed the US was the most productive country on the current topic and with the most active international partnership. Journal of the American Society of Nephrology, American Journal of Kidney Diseases, Kidney International based in the US, and Nephrology Dialysis Transplantation based in Europe were the four journals with the most publications, indicating the US and European were pilots in the research field about the impact of modifiable factors on CKD; while developing countries were not active in producing highly influential research. The disparity of the quantity of academic publications between developing and developed world has long been recognized, which might be attributed to multifaced causes, to name a few, lacking of research capacity in developing countries [72], funding and principal investigator status owned by developed world [73], language and writing barriers, and editorial bias [74]. Considering the disease burden of CKD in developing countries are rising and might be more pronounced than that in developed countries, high-quality research about the impact of modifiable factors on CKD conducted in population from less developed regions, and more cooperations between developed countries and developing countries are required, such that the evidence can be disseminated to these population more precisely.

Our study has many strengths. To our knowledge, this is the first bibliometric analysis of the relationship between modifiable lifestyles and CKD. Our study finds the evolution of hot topics over the decade and provides clues for scholars to choose research themes. However, there are some limitations of our study. First, only English literature was included in the study, so we may fail to capture some landmark articles published in other languages. Second, all data were extracted from the SCIE of Web of Science, thus, we may fail to capture certain related publications provided in other sources. Third, despite we analyzed the top-cited articles in this field representing the research hotspots, we admit certain research topics with few publications due to publication bias [75], may be missed. In addition, ‘obliteration by incorporation’, which represents that the older publications are no longer cited because their findings are common-use and incorporated into the current discipline, is a notable concern in the bibliometric analysis [76]. Thus, we included publications within the last ten years and ranked articles based on an adjusted citation index rather than the number of citations received in the current year.

In summary, in the bibliometric analysis of the top 100-cited articles addressing the influence of modifiable factors on CKD, our study provides a comprehensive description of publishing trends and research focus over a decade. The association between modifiable factors and CKD has been among the research focus over the decade. While the study hotspots are evolving over time, diet, obesity, and physical activity were factors receiving the most attention in this topic.