Secondhand smoke could impair childhood kidney function

Whilst many teenagers may believe that smoking cigarettes will improve their popularity amongst friends and gain them misguided admiration in the playground, they should also be aware of the damage that cigarettes do to their adolescent bodies after a study has linked secondhand smoke exposure to effects on kidney function beginning in childhood.

The study, led by Esther Garcia-Esquinas, MD, of the Department of Environmental Health Sciences at John Hopkins University Bloomberg School of Public Health and published April 8 in the journal Pediatrics, was conducted to see if secondhand smoke exposure could be attributed to chronic kidney disease in children.

A cross-sectional study was therefore carried out, comprising of an analysis of 7,516 adolescents aged between 12 and 17; all of whom were involved in the 1999-2010 National Health and Nutrition Examination Survey.

The teens all had blood tests to determine any creatinine and cotinine levels. Creatinine is a waste break-down product from muscle tissue in the body that is filtered through the kidneys. Doctors look at a person’s blood creatinine level as a test to determine kidney function and the kidneys’ ability to handle creatinine is known as the ‘creatinine clearance rate’.

‘Cotinine’, an anagram of nicotine, is an alkaloid chemical contained in tobacco and is also a product that is created by metabolising nicotine. By measuring the levels of cotinine in an individual’s bloodstream, it is possible to extract information on their recent use of tobacco in addition to assessing how much secondhand smoking the person has been exposed to.

The teens within the study who admitted that they smoked or those with serum cotinine levels found to be over 10 ng/mL, were regarded as ‘active smokers’. Those who lived with at least one person who smoked or had cotinine levels measuring at least 0.05 ng/mL, were classified as being exposed to secondhand smoke. In addition, any study participants with serum cotinine levels under 0.05 ng/mL, not living with a smoker and had not smoked in the previous month, were viewed as being unexposed to tobacco.

Researchers analysed the glomerular filtration rate, or eGFR, level by looking at the creatinine levels. This helps to understand how much blood a person’s kidneys are filtering to get a better picture of kidney function.

It was discovered that the teens’ eGFR declined at the same rate that their cotinine concentration in the blood increased. This pattern was evident even after the participants’ weight was taken into account as well as and socioeconomic and demographic factors.

Jeffrey Fadrowski, MD, MHS, co-author of the study and an assistant professor in Pediatric Nephrology at the Johns Hopkins School of Medicine, commented: “Small changes in the distribution of estimated glomerular filtration rate levels in the population could have a substantial impact in kidney-related illness, as it is well known for changes in blood pressure levels and hypertension-related disease. Evaluating potential secondhand smoke exposure and providing recommendations to minimize exposure should continue to be incorporated as part of children’s routine medical care.”

Other researchers in the study added: “Evidence from studies in adult populations suggest that smoking, particularly heavy smoking and cumulative smoking exposure, is an independent risk factor for chronic kidney disease in both genders, as shown in large, prospective observational studies.”