Renal Health in Chile

Abstract

The prevalence of 20 diseases was studied in a representative sample of 3619 individuals in Chile. Twelve percent of the participants were younger than 25, 63% were 25–64 years old, and 25% were at least 65 years old. Thirty-four percent had high blood pressure, 60% were aware of their condition, 36% received treatment, and 12% reached their goal blood pressure. Renal function was assessed by serum creatinine and glomerular filtration rate, as estimated by the Cockroft-Gault formula. In all, 6.7% had elevated creatinine, 14% showed proteinuria, and 0.2% showed advanced renal damage. The results of this study will contribute to the prevention of renal diseases in Chile.

Keywords:

• renal diseases
• Chile
• prevalence
• renal failure
• hypertension

INTRODUCTION

Chile, located along the west coast of South America, has a population of 15 million distributed in 13 regions. Eighty-seven percent live in urban areas, and 40% live in Santiago, the capital city. Aboriginal people, mainly from mapuche ethnia, represent 4% of the total population. Per capita income is US $4,620 with large differences between rich and poor; 18.8% of the population lives below the poverty line.[1]

Chile has a long-standing national public health system that provides health care to approximately 70% of the population. This system works within a well-structured network that is based on a primary health level with universal coverage, in coordination with secondary and tertiary levels that give more complex and specialized care. Chile also has a very well-developed private health system, which provides services to the younger, healthier, and wealthier groups of the population.[2]

End-stage renal disease has had public financial support for many years. New regulations that are part of the health reform process in Chile give explicit guarantees that assure timely access, basic standards of care, and financial protection for all those who require hemodialysis, both in the public and private systems. In the year 2004, there were 10,693 patients in chronic hemodialysis in the country, a rate of 685 per million inhabitants.

As has occurred in other developing countries, the causes of chronic renal failure in Chile have changed throughout time. Diabetes is currently the main cause of end-stage renal disease, accounting for 33% of patients in hemodialysis, followed by nephrosclerosis and glomerulopathies (13% and 9%, respectively).[3] A high proportion of patients (23%) requiring renal replacement therapy begin dialysis without a previous identification of the original disease.

The purpose of this study is to analyze the prevalence of chronic kidney disease and its major risk factors based on the data obtained from the First National Health Survey, Chile 2003 (NHS 2003).[4]

METHODS

The NHS 2003 was performed in a representative national sample of Chilean population composed of 3619 individuals 17 years of age and above; 45% were males, and 18% were from rural areas. Pregnant women and complex psychiatric patients were excluded. Twelve percent of the sample was 24 years old and younger, 63% was between 25 and 64 years old, and 25% was 65 years old and older.

Arterial blood pressure was measured twice on the same day using automated equipment (OMRON HEM 713C). Hypertension was defined as systolic blood pressure >140 mmHg and/or a diastolic blood pressure >90 mmHg. Persons with normal blood pressure who reported to be on pharmacologic treatment for hypertension were also considered as hypertensive.

An elevated level of blood glucose >126 mg/dL on two determinations was diagnosed as diabetes, as well as persons on pharmacologic therapy for the disease.

Proteinuria was measured in an isolated urine sample with a dipstick test for albuminuria (Nephur7); persons were considered to be proteinuric if the dipstick was positive in any range (approximately >30 mg/dL).

Serum creatinine was measured using the Jaffé method (Hitachi) and was considered to be elevated if values were >1.2 and 1.0 mg/dL in men and women (respectively) under the age of 50 and >1.3 and 1.0 mg/dL in men and women (respectively) at least 50 years old. Glomerular filtration rate (GFR) was estimated using the Cockroft-Gault equation, adjusted by body surface:

The presence of chronic kidney disease (CKD) was established based on the presence of proteinuria as a marker of renal damage and the level of kidney function on the estimated glomerular filtration rate (GFR) using the National Kidney Foundation classification. Estimated GFR values >90 mL/min/mt² were considered normal or increased and <30 mL/min/1.73 mt² as severely decreased. For more details on the methodology and results of the survey, refer to the publication of the Chilean Ministry of Health.[3]

RESULTS

The prevalence of diabetes, hypertension, and other risk factors for renal and cardiovascular diseases are presented in Table 1.

Table 1 Prevalence of major cardiovascular risk factors. NHS 2003, Chile

Condition	Prevalence (%)
Diabetes (>126 mg/dL in 2 samples)	4.2
Total cholesterol (>200 mg/dL)	35.4
Reduced HDL cholesterol (<40 mg/dL)	39.3
Hypertension (>140/90 mmHg in 2 measurements)	33.7
Overweight (BMI 25–29)	37.8
Obesity (BMI >30)	23.2
Physical inactivity (<3 times/week)	90.8
Smoking (>1 cigarette/day)	42.0

Thirty-four percent of the subjects had high blood pressure, with higher rates in males at all ages, except in those at least 65 years old, where the prevalence was higher in women. Sixty-six percent of those with high blood pressure were aware of their condition; 36% were under treatment, but only 12% reached normal levels of blood pressure (<140/90 mm Hg). Isolated systolic hypertension was found in 8.8% of cases, though more frequently in women at all ages. Isolated diastolic hypertension had a prevalence of 5.3%, more frequently in males.

The prevalence of diabetes was 4.2%. Under the age of 44, the prevalence was 0.1%, 9.4% in the group 45–64 years old, and 15.2% in those older than 64. Eighty-five percent of diabetic persons were aware of their condition; 77.3% were under therapy, and 25% of those on treatment had normal glycemic levels. The prevalence of diabetes increased as the social and economic levels decreased.

The general prevalence of proteinuria was 14.2%, 15.2% in those 17–24 years old, and 22.7% in those at least 65 years old.

Elevated creatinine levels were found in 6.7% of the sample, with significantly higher prevalence (20%) in male or females over 64 years.

The prevalence of chronic kidney disease, according to the NKF K/DOQI stages, is presented in Table 2, with a prevalence of 28.5%, 5.7% and 0.2% of mildly, moderately, and severely decreased GFR, respectively. There were no cases of severely reduced renal function in the age group of 17–24, 0.04% in those between 25–44 years of age, and 0.14% in the 45–64 group. In those at least 65 years old, the prevalence was 1.12%, with a higher prevalence in women.

Table 2 Prevalence of chronic kidney disease by NKF stages. NHS 2003, Chile

Stages of chronic kidney Disease	GFR (ml/min × 1.73 mt^2)	Prevalence (%)
1. Normal or increased GFR	>89	65.6
2. Mildly decreased GFR	60–89	28.5
3. Moderately decreased GFR	30–59	5.7
4. Severely decreased GFR	15–29	0.2

An unexpected high prevalence, 34.2%, of non-severe (mildly and moderately reduced renal function, GFR 30–90 mL/min/mt²) was found in this sample. Persons with hypertension or diabetes had a significant higher prevalence of reduced GFR.

DISCUSSION

The NHS 2003 represents the first study to explore the prevalence of diseases in the adult population at a national level in Chile. The study contains information about many of the most important described risk factors for CKD.

A high prevalence of high blood pressure (33.7%), with higher rates in males at all ages except after the age of 64, was found in this study. Although comparisons of prevalence rates with previous studies would be not appropriate due to differences in the cut-off points, definitions of hypertension, conditions and number of measurements, and the populations studied, a significant increase in the prevalence rates is seen throughout time: 8.8% in 1986, rising to 11% in 1999 and 25% in 2003 (see Figure 1).[6],[7]

Figure 1 Prevalence of hypertension in Chile.[4],[5]

The prevalence of diabetes in this study, 4.2%, is lower than the reported 5.4% in a 2002 study performed in the VII Region of the country.[8] In any case, the higher prevalence of diabetes found in people over 44 years old in a country with life expectance >70 years is a matter of concern because of the greater risk of renal disease in these individuals.

The high prevalence (14%) of proteinuria, a main marker and recognized participant of progressive chronic renal damage, deserves discussion. As this finding was based on a single-dipstick, semi-quantitative determination, no conclusion should be obtained before serial and quantitative determinations can be performed in future studies.

The high prevalence of mild and moderately severe renal dysfunction found in this study deserves special attention. It might be attributed to a methodological error; however, more research is required to confirm this unexpected and disturbing finding in order to develop the best approach to face the problem if it is a real phenomenon.

Important data are contained in the NHS 2003 that will contribute to design strategies for the prevention and control of the expanding epidemic of renal disease and other chronic conditions in Chile and other Latin American countries.