High blood pressure (hypertension) is an increase in blood pressure figures greater than 140 mmHg for systolic blood pressure and/or greater than 90 mmHg for diastolic blood pressure [1]. It represents a major public health problem because it affects more than a billion people worldwide, i.e., more than a quarter of the world’s population [2][3]. Its prevalence has doubled over the years, from 648 million adults affected in 1990 to 1278 million in 2019, with a predominance in industrialized countries among adult males [4]. In the United States, about 46% of adults are affected; in France, a study conducted in 2015 revealed 32.3% hypertension [5]. It affects 10 to 15% of adults in sub-Saharan Africa, with a high rate in urban areas [6]. In South Africa, the prevalence is estimated at 46%, while in Cameroon it is 24% [7].

Hypertension is the main modifiable risk factor for heart disease (coronary artery disease) and stroke, but also for kidney disease, which in turn are precursors to hypertension [8]. On the one hand, hypertension is a potential cause of chronic kidney disease (CKD) insofar as it is responsible for nearly 30% of cases of end-stage chronic kidney disease (ESRD). On the other hand, hypertension is a common consequence of CKD, regardless of its cause [9]. It is currently the main global burden of morbidity and mortality because reaches up to 90% of people with chronic kidney disease and also potentiates the risk of acute kidney injury in intraoperative patients [9][10]. In Europe, particularly in France, hypertension is the second cause of CKD with an incidence of 22%, and this incidence increases with age and sex, as men are at excess risk [9]. The prevalence in adult subjects is more than 30%; it is estimated that it concerns 12 to 13 million people. In African studies, hypertension is the leading cause of kidney disease, while in the world it is the second leading cause of kidney disease [11]. In Cameroon, hypertension is the leading cause of CKD with a prevalence of 32.3% [12].

In Africa, and particularly in Cameroon, kidney disease remains a concern in the face of risk factors and the heavy economic burden of care. Nearly 12.4% of newly diagnosed hypertensive patients have CKD [13]. This proportion was higher in the cohort of Hamadou et al. in the city of Garoua, where 32.3% of hypertensive patients had CKD [12]. The rate of blood pressure control is low in Africa, explaining the rapid progression of CKD [14]. In this context, we thought it would be interesting to evaluate not only the prevalence of CKD but also the profile of kidney disease markers on kidney health, as well as the determinants to optimize adequate management focused on prevention measures and early and systematic detection of kidney disease.

A total of 356 participants were included among the 372 eligible participants (16 lost to follow-up at 3 months). The study population was predominantly female (54.21%) with a mean age ± standard deviation of 55.57 ± 12.13 years, with extremes ranging from 19 to 89 years. The most represented age group was [41 - 60] years old. The most common comorbidity was diabetes mellitus (31.17%) and the use of nephrotoxics was common (43.53%). The general characteristics of the study population are summarized in Table 1.

At the end of this study, which included 356 known hypertensive participants over the age of 18 and followed at the Garoua Regional Hospital, it emerged that:

The overall prevalence of chronic kidney disease (CKD) in the study population is 28.3%, marked by renal failure (69.3%), proteinuria (52.47%), and hematuria (25.74%);Age > 59 years (OR 1.76), obesity (OR 2.16), diabetes (OR 2.93), and hyperuricemia (OR 3.61) are statistically associated with CKD.

A Recent meta-analysis estimates the prevalence of CKD at 29% among hypertensive people in sub-Saharan Africa [17]. It points out that West and Central Africa are the most affected areas because of genetic susceptibilities (mutation of apolipoprotein 1). The prevalence of CKD in our hypertensive population is comparable to that reported in the Senegalese (25%), Nigerian (29.8%), Cameroonian (32.3%) series, and also to the results of the systematic review of Yirga et al. (29.01%) [12][18]-[20]. This prevalence is much lower than that found in Bamako (58%) and Guinea (51.4%). Kaze et al. in Cameroon found a prevalence of CKD of 50% in a group of hypertensives; this difference in prevalence could be based on the higher frequency of risk factors for CKD (62% diabetics vs. 31% in our series). However, the reported prevalence of CKD in African hypertensive patients remains higher than in the Caucasian series. This could be explained contextually by weak literacy medical conditions that make treatment compliance difficult. But also, the lack of health insurance is a real obstacle to the early diagnosis of non-communicable diseases. On the other hand, the high frequency of comorbidities in our context is directly related to the westernization of our societies and explains the high prevalence of CKD in non-Caucasian subjects. Also, we found that despite the reported good therapeutic compliance, only 26.21% of the participants had optimal blood pressure control. This underlines the therapeutic inertia of healthcare providers as reported elsewhere [21][22].

Stage 3 of KDIGO was the most represented stage, as in the Congolese study [23]. This is in line with the community nature of our work because, due to the delay in care, stage 5 is common in our environment at the first hospital consultation. This is how an African study reported that 82.5% of hypertensive patients who arrived for a kidney complication were already at stage 5 [20]. CKD was prevalent in 59 ± 16.50 years in our series and, although not statistically significant, was more common in female subjects; women are more represented in our cohort. In African women, hypertension is very often associated with obesity and type 2 diabetes. This “triplet” multiplies the aggressions on the nephron.

More than one in two patients had proteinuria. Although not specific to high blood pressure, proteinuria is an early marker of renal dysfunction and a potent progression factor during CKD. Aka et al., during analysis of the profile of patients admitted to emergency rooms in Abidjan, showed that 95.9% of patients with malignant hypertension already had renal failure, 78% of whom were at the chronic stage at the first diagnosis [24]. Mi Yeon Yu etal. in Korea reported that microscopic hematuria in hypertensive patients without comorbidities would be rare but would be a predictive factor for mortality in hypertensive patients [25].

Age, obesity, diabetes, hyperuricemia, and the duration of hypertension are factors associated with CKD in our cohort. These factors are the same as those reported in the Cameroonian cohorts [12]. Long-standing hypertension predisposes to CKD. Indeed, even moderate hypertension, if it lasts, inevitably leads to a decline in kidney function in Black subjects [26]. Sumaili et al., in Congo-Kinshasa, showed that old hypertension was responsible for more than 60% of chronic kidney disease cases [23]. They pointed out that the risk of CKD increased exponentially with each additional year of uncontrolled hypertension.

This epidemiological study, which is important for understanding the factors associated with CKD in our context, has limitations:

Selection bias due to the hospital nature of recruitment.Imputability of CKD is difficult to establish in the absence of renal histology.

More than one in four patients with chronic kidney disease (CKD) in our series had classic chronic kidney disease risk factors coexisting. Proteinuria is prevalent and underlines the importance of its regular evaluation in all hypertensive patients in view of its ease and speed of implementation. More proactive therapeutic adjustments would be important to address for better prevention of CKD progression.

All authors contributed to the study conception. The study was designed by Hanadou Ba and Kaze F François. Material preparation, data collection, and analysis were performed by Maimouna Mahamat, Mebomie Essono, Ndobo Valerie, Moussa Oumarou, and Ali Abas. The first draft of the manuscript was written by Maimouna Mahamat and Teuwafeu Denis. All authors read and approved the final manuscript.

Not applicable.

The materials described in the manuscript, including all relevant raw data, will be freely available to any scientist wishing to use them for non-commercial purposes. The data that support the findings of this study are also available from the corresponding author.

The authors did not receive any funding for the study or the publication.