In recognition of World Kidney Day 2014 on March 13, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and the National Institute on Aging (NIA) at the National Institutes of Health remind older Americans about the importance of protecting their kidneys and urge them to better understand the decline of kidney function as people age.

The kidneys' main job is to filter wastes and extra water from the blood to make urine. Chronic kidney disease (CKD) is defined by decreased kidney function and/or evidence of kidney damage, usually marked by protein in the urine. The U.S. Centers for Disease Control and Prevention estimates that more than 10 percent of adults in the United States - more than 20 million people - may have CKD. Diabetes and high blood pressure are the leading causes of kidney disease; and kidney failure. Together, diabetes and high blood pressure accounted for 72 percent of new kidney failure cases in 2011.

Age is also a major risk factor for kidney disease. With advancing years, kidney function generally declines, resulting in increased vulnerability of the older kidney to acute injury and CKD. As the kidney ages, filtering capacity decreases, the overall amount of kidney tissue may decrease, and the blood vessels that supply the kidney may narrow, further reducing the capacity of the kidneys to filter blood. This decline in kidney function with age is nearly universal, but occurs at different rates in different people. Conditions such as high blood pressure, smoking and diabetes can accelerate these changes.

Because healthy people have significant reserve kidney function, most age-related decline in kidney function does not make an older person feel or function any differently. However, it is important for older adults and their care providers to know whether kidney function is reduced. Moreover, if kidney function appears to be declining at a rate faster than expected, reversible or treatable causes might be identified to slow the process and preserve kidney function.

Regardless of whether the cause is aging, disease, or both, complications from certain medications increase as kidney function declines. The level of some medicines in the blood may increase because impaired kidneys are less able to eliminate them. The kidneys may also become more sensitive to certain medications. For example, non-steroidal anti-inflammatory drugs such as ibuprofen, some antibiotics, and x-ray contrast agents may be more likely to cause acute kidney injury.

There is a significant need to educate the aging population and their health care providers about ways to prevent kidney injury. Encouraging older Americans to know their level of kidney function and be mindful of the medicines they take is an important step toward reducing the growing rates of kidney injury in the United States.

As the U.S. population ages and rates of diabetes rise, the number of older Americans at risk for kidney disease will increase. Research has helped us to better understand the impact of aging on kidney function and how aging-related changes increase older adults vulnerability to acute and chronic kidney disease. NIDDK and NIA currently support several research initiatives to advance knowledge about age-related kidney function decline and approaches to prevent and treat CKD in older people.

We are learning a great deal about kidney disease in older adults, but more research needs to be done. The NIDDK and the NIA look forward to conducting and promoting research to reduce the burden of kidney disease in older people.

The National Institute of Diabetes and Digestive and Kidney Diseases, part of the NIH, conducts and supports basic and clinical research and research training on some of the most common, severe, and disabling conditions affecting Americans. NIDDK's research interests include diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition, and obesity; and kidney, urologic and hematologic diseases. For more information on CKD, visit the NIDDK's National Kidney Disease Education Program website at http://www.nkdep.nih.gov.

The National Institute on Aging, part of the NIH, leads the federal government in conducting and supporting research on aging and the health and well-being of older people. The Institute seeks to understand the nature of aging and the aging process, and diseases and conditions associated with growing older, in order to extend the healthy, active years of life. For more information on aging and kidney disease, visit http://www.nia.nih.gov/health/publication/kidney-disease.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.