From Medicine and Science in Sports and Exercise®
Association Between Physical Activity and Kidney Function
National Health and Nutrition Examination Survey
Posted: 08/10/2011; Medicine and Science in Sports and Exercise®. 2011;43(8):1457-1464. © 2011 American College of Sports Medicine
Abstract and Introduction
Abstract
Hawkins, M. S., M. A. Sevick, C. R. Richardson, L. F. Fried, V. C. Arena, and A. M. Kriska. Association between Physical Activity and Kidney Function: National Health and Nutrition Examination Survey.Med. Sci. Sports Exerc., Vol. 43, No. 8, pp. 1457–1464, 2011.Introduction: Chronic kidney disease is a condition characterized by the deterioration of the kidney's ability to remove waste products from the body. Although treatments to slow the progression of the disease are available, chronic kidney disease may eventually lead to a complete loss of kidney function. Previous studies have shown that physical activities of moderate intensity may have renal benefits. Few studies have examined the effects of total movement on kidney function. The purpose of this study was to determine the association between time spent at all levels of physical activity intensity and sedentary behavior and kidney function.
Methods: Data were obtained from the 2003–2004 and 2005–2006 National Health and Nutrition Examination Survey, a cross-sectional study of a complex, multistage probability sample of the US population. Physical activity was assessed using an accelerometer and questionnaire. Glomerular filtration rate (eGFR) was estimated using the Modification of Diet in Renal Disease study formula. To assess linear associations between levels of physical activity and sedentary behavior with log-transformed estimated GFR (eGFR), linear regression was used.
Results: In general, physical activity (light and total) was related to log eGFR in females and males. For females, the association between light and total physical activity with log eGFR was consistent regardless of diabetes status. For males, the association between light and total physical activity and log eGFR was only significant in males without diabetes.
Conclusions: When examining the association between physical activity, measured objectively with an accelerometer, and kidney function, total and light physical activities were found to be positively associated with kidney function.
Introduction
Chronic kidney disease (CKD) is the progressive deterioration of the kidney's ability to remove fluid and nitrogenous waste from the body as well as some other key functions. Diabetes and hypertension are the most common causes of CKD.[35] Although treatments to slow the progression of the disease are available, CKD may eventually lead to renal failure or end-stage renal disease (ESRD), which is the complete loss of kidney function. Once kidneys have failed, the only available treatment options are dialysis or kidney transplant.
CKD is of immense public health concern and is expected to become a bigger problem in the coming decades. A study of the US population using the National Health and Nutrition Examination Survey (NHANES) estimates that from 1999 to 2004, approximately 17% of adults older than 20 yr had CKD, which is an increase of approximately 16% compared with NHANES data from 1988 to 1994.[8,28] The prevalence of ESRD is growing as well, doubling since the early 1990s and is projected to reach 2 million by the year 2030.[32,34] The growing prevalence of CKD is alarming considering the economic and physical burdens it places on the individual as well as the health care system.[22]
Glomerular filtration rate (GFR), which is a measure of the kidney's ability to clear plasma of nitrogenous wastes over a specific amount of time, is regarded as the best way to assess kidney function. In clinical practice and epidemiologic studies, GFR is estimated (eGFR) using a formula based on serum creatinine, gender, race, and age. A reduction in GFR, along with other evidence of kidney damage, is in part used to classify severity/stages of kidney dysfunction. A recent analysis from the ATTICA study indicated that individuals with moderate to severe kidney dysfunction had more than three times the risk of developing a cardiovascular disease (CVD) during the 5-yr study follow-up compared with individuals with normal kidney function.[7] The Atherosclerosis Risk in Communities (ARIC) Study was a prospective population-based study that examined the relationship between change in eGFR with CHD and all-cause mortality in 13,029 white and black men and women between the ages of 45 and 64 yr. The study showed that individuals with annual declines in eGFR ≥5% had the highest risk for CHD and all-cause mortality compared with individuals with annual declines in eGFR of <5% during the 9-yr study follow-up after adjusting for age, gender, race, and baseline eGFR.[21] A meta-analysis by Tonelli et al.[33] showed that individuals with mildly decreased kidney function (80 mL·min−1·1.73 m−2) had an increased risk for all-cause mortality compared with individuals with a normal GFR (100 mL·min−1·1.73 m−2). The analysis also showed a progressive risk for mortality as kidney function deteriorated. To reduce this excess burden of the disease, it is important to identify modifiable factors associated with kidney function at earlier stages of the disease to better direct our intervention efforts in an attempt to slow down the progression.
Lifestyle modifications, including physical activity, have proven to be effective in the prevention of chronic conditions such as diabetes and hypertension.[2,26,36] The potential benefits of physical activity in preventing or delaying the development of diabetes and hypertension are significant considering the fact that these two conditions are the leading causes of CKD and ESRD.[27,34] There have been numerous investigations into the relationship between physical activity and other risk factors for CKD; however, few studies have examined the relationship between physical activity and CKD or kidney function.[4,10,18] Much of the existing literature focuses on patients on dialysis. Although exercise may be important for individuals on dialysis, CKD is associated with CVD, and those with CKD are more likely to die from CVD than they are to progress to ESRD.[30] CKD in early stages is typically asymptomatic, and individuals are often unaware they have the condition.[38] Analogous to hypertension, CKD can be a silent killer, which makes it important to understand the relationship between modifiable lifestyle factors, such as physical activity, and renal function in early stages of the disease.
The few studies that have examined the association between physical activity and kidney function at earlier stages of the disease used subjective measures such as questionnaires.[9,12,37] Although questionnaires perform relatively well at capturing activities of moderate to vigorous intensity, they have questionable accuracy in assessing lower-intensity activities, which is the largest component of total physical activity in most people.[14] To accurately assess total physical activity, which is composed of both light and moderate to vigorous physical activity, an objective measure is needed.[17] Recent studies using objective measures of physical activity have increased our knowledge regarding the contribution of lower intensity physical activity in reducing metabolic. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab) was a cross-sectional study of 11,247 men and women ≥25 yr. The study showed that time spent in activities of lower intensity and sedentary behavior are independently associated with 2-h fasting plasma glucose, waist circumference, and a clustered metabolic risk score (triglycerides, HDL cholesterol, systolic and diastolic blood pressure, fasting plasma glucose, and waist circumference).[15,16] This study highlights the importance of examining lower-intensity activity and its relationship to disease outcomes.
To date, no previous study has looked at the association between an objective measure of physical activity and kidney function in a nationally representative sample. The purpose of this study was to determine the association between time spent at various intensity levels of physical activity (light, moderate to vigorous, and total) and sedentary behavior with kidney function in individuals with mild to moderate kidney disease in a large national data set.
For further information: http://www.medscape.com/viewarticle/746893?src=mp&spon=8
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