Trade.Information

Topic Name: Researchers find television viewing linked to childhood obesity and hypertension in children

Category: Biomedical

Research persons: Jeffrey B. Schwimmer, MD.

Location: University of California, San Diego, United States

Details

Researchers from the University of California, San Diego; the Rady Children’s Hospital – San Diego; the University of California, San Francisco; and the University of South Alabama determined that television viewing is not only linked to childhood obesity, but also to hypertension in children, according to a study published in the December 2007 issue of the American Journal of Preventive Medicine.

Childhood obesity is a major health concern in the United States. As of 2004, the National Health and Nutrition Examination Survey (NHANES) estimated that 17% of children and adolescents were obese. Obesity is known to increase the possibility of cardiovascular risk factors, such as hypertension. Recent studies have shown that cardiovascular risk factors in childhood are significant predictors of preclinical atherosclerosis in adulthood.

Data was gathered regarding 546 subjects, aged 4 to 17 years, who were evaluated for obesity at pediatric subspecialty weight management clinics in San Diego CA, San Francisco CA, and Dayton, OH, from 2003 to 2005. Children and their parent(s) were given a written questionnaire, which was used to estimate the average daily time spent watching TV, and then a physician verbally reviewed and confirmed the time estimate. The height and weight of the children were measured to determine a Body Mass Index (BMI) and their blood pressures were recorded.

Investigators determined that TV time was positively correlated with the severity of obesity. After controlling for race, site, and BMI score, both the severity of obesity and daily TV time were significant independent predictors of the presence of hypertension. Children watching 2 to 4 hours of TV had 2.5 times the odds of hypertension compared with children watching 0 to <2 hours. The odds of hypertension for children watching 4 or more hours of TV were 3.3 times greater than for children watching 0 to <2 hours of TV.

Writing in the article, Jeffrey B. Schwimmer, MD (Associate Professor of Pediatrics at University of California, San Diego and Director of Weight and Wellness at Rady Children's Hospital – San Diego), states, “The current study illustrates the need for considerable physician and family involvement to decrease TV time among obese children. The American Academy of Pediatrics (AAP) recommends that children watch less than 2 hours of TV per day, but reports that only half (51%) of pediatricians make this recommendation to patients…TV viewing is an attractive target for intervention, particularly among obese children with hypertension. Several studies have demonstrated that changing TV time alone can lead to weight loss, without any changes in physical activity.”

In a commentary published in the same issue of the American Journal of Preventive Medicine, Stuart J.H. Biddle, from the School of Sport and Exercise Sciences, Loughborough University, UK, cautions that studies of TV viewing are part of a recent trend to study sedentary behaviors in general, and such studies are difficult to interpret.

He argues, “There is much debate concerning whether TV viewing is associated with obesity in young people…For example, an extensive meta-analysis of mainly cross-sectional studies showed that the relationship is very small…Moreover, the small relationship may be a reflection of other trends…If obesity is causally related to TV viewing, as some suggest, how do we account for the following paradoxes: (1) obesity levels are increasing but TV viewing figures are not, (2) obesity increases during adolescence at the same time that TV viewing decreases, and (3) boys watch more TV than girls but show less obesity and greater physical activity" Whatever the true findings, the association between sedentary behavior (TV viewing or other behaviors) and health outcomes, at least in youth, is likely to be complex and, as yet, unknown.”

Note for Hypertension

Hypertension, commonly referred to as "high blood pressure" or HTN, is a medical condition in which the blood pressure is chronically elevated. While it is formally called arterial hypertension, the word "hypertension" without a qualifier usually refers to arterial hypertension. Hypertension can be classified as either essential (primary) or secondary. Essential hypertension indicates that no specific medical cause can be found to explain a patient's condition. Secondary hypertension indicates that the high blood pressure is a result of (i.e. secondary to) another condition, such as kidney disease or certain tumors (especially of the adrenal gland). Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurysm, and is a leading cause of chronic renal failure. Even moderate elevation of arterial blood pressure leads to shortened life expectancy. At severely high pressures, mean arterial pressures 50% or more above average, a person can expect to live no more than a few years unless appropriately treated.

Hypertension is considered to be present when a person's systolic blood pressure is consistently 140 mmHg or greater, and/or their diastolic blood pressure is consistently 90 mmHg or greater. Recently, as of 2003, the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure has defined blood pressure 120/80 mmHg to 139/89 mmHg as "prehypertension." Prehypertension is not a disease category; rather, it is a designation chosen to identify individuals at high risk of developing hypertension. The Mayo Clinic website specifies blood pressure is "normal if it's below 120/80" but that "some data indicate that 115/75 mm Hg should be the gold standard." In patients with diabetes mellitus or kidney disease studies have shown that blood pressure over 130/80 mmHg should be considered high and warrants further treatment. Even higher numbers are considered diagnostic using home blood pressure monitoring devices.

Note for Childhood obesity

Childhood obesity is a medical condition that affects children. It is characterized by a weight well above the mean for their height and age and a body mass index well above the norm. Childhood obesity is considered by many to be an "epidemic" in Western countries, in particular, the United States, United Kingdom and Australia. Over 15% of American children are currently considered obese, and the number is growing  and about 20-25% of Australian children classified as overweight or obese.

As with many conditions, childhood obesity can be brought on by a range of factors, often in combination.

Acquired
Childhood obesity results from poor eating habits, as well as genetic and hormonal causes. Fast food restaurants and junk food are popular with children. In lieu of home cooking, it has become common for parents to take their children out to eat. Even when it is not a fast food restaurant, frequent eating out often results in weight gain.

Children who do not engage in frequent physical activity are much more likely to suffer from obesity. This is said to be due in part to the recent technological developments, including video games, computers, and mobile phones. Physically inactive children are unable to burn off the calories that they gain from eating. The body will store some or all of the unused energy as fat. 
Also, children in lower-income households are more likely to become overweight than those in higher-income households. Not eating breakfast is also associated with an increase in obesity.

Psychological factors
These factors influence a child's eating habits and many children eat in response to stress and or negative emotions such as boredom, anger, sadness, anxiety or depression.

Illness
Conditions such as hypothyroidism, Cushing's syndrome, depression and certain neurological problems can lead to obesity or a tendency to gain weight in a child. Also, drugs such as steroids and some antidepressants may lead to obesity or a tendency to gain weight in a child.

Note for Body mass index

Body mass index (BMI) or Quetelet Index is a statistical measure of the weight of a person scaled according to height. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing "social physics".
As a measure, BMI became popular during the early 1980s as obesity started to become a discernible issue in prosperous Western society. BMI provided a simple numeric measure of a person's "fatness" or "thinness", allowing health professionals to discuss over- and under-weight problems more objectively with their patients. However, BMI has become controversial because many people, including physicians, have come to rely on its apparent numerical authority for medical diagnosis, but that was never the BMI's purpose. It is meant to be used as a simple means of classifying sedentary (physically inactive) individuals with an average body composition. For these individuals, the current value settings are as follows: a BMI of 18.5 to 25 may indicate optimal weight; a BMI lower than 18.5 suggests the person is underweight while a number above 25 may indicate the person is overweight; a BMI below 17.5 may indicate the person has anorexia or a related disorder; a number above 30 suggests the person is obese (over 40, morbidly obese).

About Researchers:

Jeffrey B. Schwimmer, M.D.

Education:
University of California at Berkeley, Berkeley, California
B.A. in Biochemistry
English Minor Program in Creative Writing
New York University School of Medicine, New York
M.D.

Awards and Grants:
National Institute of Diabetes and Digestive and Kidney Diseases
Solvay Pharmaceuticals Fellow Award 
NIH Training Grant (Institutional NRSA DK07727) 
Ross Laboratories Educational Grant 
Allergic Colitis and The Role of Eosinophils

Publications:
Schwimmer JB, Behling C, Newbury R, Deutsch R, Nievergelt C, Schork NJ, Lavine JE. Histopathology of pediatric nonalcoholic fatty liver disease. Hepatology. 2005 Sep;42(3):641-9.
Xanthakos SA, Schwimmer JB, Melin-Aldana H, Rothenberg ME, Witte DP, Cohen MB. Prevalence and outcome of allergic colitis in healthy infants with rectal bleeding: a prospective cohort study. J Pediatr Gastroenterol Nutr. 2005 Jul;41(1):16-22.
Schwimmer JB, McGreal N, Deutsch R, Finegold MJ, Lavine JE. Influence of gender, race, and ethnicity on suspected fatty liver in obese adolescents. Pediatrics. 2005 May;115(5):e561-5.
Schwimmer JB, Middleton MS, Deutsch R, Lavine JE. A phase 2 clinical trial of metformin as a treatment for non-diabetic paediatric non-alcoholic steatohepatitis. Aliment Pharmacol Ther. 2005 Apr 1;21(7):871-9.