Guidelines Could Lead to Missed Urine Reflux in Kids

ORLANDO, Florida — The use of recommended diagnostic tests declined within months of the publication of revised guidelines for the management of first-episode febrile urinary tract infection (UTI) in children, a new study shows.

The use of renal–bladder ultrasonography to detect reflux of urine into the ureter and kidneys decreased by 17%, and the use of voiding cystourethrogram to identify the severity of reflux plummeted by 42% after the American Academy of Pediatrics (AAP) guidelines were issued in 2011, said Andrew Kirsch, MD, clinical professor of urology at the Emory University School of Medicine in Atlanta.

"The decreased ultrasound use is very concerning to pediatricians, to nephrologists, and to urologists, particularly because there is a strong association with hospitalization. But what we consider an even bigger factor is that we may be missing other diagnoses," he explained here at the American Urological Association 2014 Annual Scientific Meeting.

The Guidelines

About 1% of all office visits by children are related to UTIs, as are about 10% of all emergency department visits. Approximately 15% of children with UTIs will develop renal scarring, and the risk of scarring rises as the number of recurrent UTIs increases, Dr. Kirsch reported.

The most common cause of UTI in children is vesicoureteral reflux, which accounts for about 40% of cases, he said.

The UTI guidelines unequivocally state that "febrile infants with UTI should undergo renal and bladder ultrasonography" (Pediatrics. 2011;128:595-610).

They also state that voiding cystourethrogram "should not be performed routinely after the first febrile UTI," but is warranted if ultrasound shows hydronephrosis, renal scarring, or findings that indicate high-grade vesicoureteral reflux or an obstructive uropathy.

But the guidelines do not take into account results from trials conducted in Sweden and the United States that involved a combined total of 810 children with vesicoureteral reflux.

The Swedish reflux trial showed that antibiotic prophylaxis and endoscopic injection were more effective than observation in preventing febrile UTIs, and that there is a strong correlation between febrile UTIs and the risk of new renal scarring (J Urol. 2010;184:280-285).

More recently, the American RIVUR trial showed that antimicrobial prophylaxis in children with vesicoureteral reflux is associated with a 50% reduction in the risk for recurrent UTI (N Engl J Med. Published online May 4, 2014). In that study, the researchers conclude that the findings might warrant reconsideration of the AAP recommendation to omit voiding cystourethrogram after first-episode febrile UTI.

Before and After Review

To see what effects the guidelines had on imaging studies in young children with febrile UTI, Dr. Kirsch's team looked at emergency department visits for febrile UTI at Emory from January to June 2011, before the guidelines were published, and from January to June 2012, after publication.

They looked at patient demographics (age and sex), urine culture and lab results, radiographic studies, and admission/discharge status. Patients with a history of febrile UTI, known reflux, or other urologic problems were excluded from the analysis. Patients ranged in age from 2 months to 2 years.

All of these children should have been examined with renal–bladder ultrasound, Dr. Kirsch pointed out, but use decreased from 75.6% in the 2011 cohort to 58.4% in the 2012 cohort (P < .001).

Despite this decline, the proportion of abnormal findings was not significantly different in the 2011 and 2012 cohorts (28.5% vs 23.1%).

Similarly, the use of voiding cystourethrogram decreased from 2011 to 2012 (72.1% vs 38.2%; P < .001).

The risk for vesicoureteral reflux was not significantly different from 2011 to 2012 (36.3% vs 38.2%), nor was reflux severity (mean maximum grade, 2.9 vs 2.5).

These findings show that although physicians are following the recommendations for voiding cystourethrograms, selective use of cystourethrogram on the basis of ultrasound results did not identify higher grades of vesicoureteral reflux.

"We're just missing the same patients," said Dr. Kirsch.

Abnormal ultrasound findings did not accurately predict the presence of reflux. It identified only 36.4% of cases later proven to be reflux, and falsely identified reflux in 24.8% of cases without reflux.

In addition, the reduced use of cystourethrogram resulted in more cases of moderate to severe vesicoureteral reflux being missed in the 2012 cohort than in the 2011 cohort.

Abnormal ultrasounds, being male, and being younger were independently associated with risk for hospitalization. Reflux grade did not differ between patients who were admitted to the hospital and those discharged from the emergency department.

Foregoing the routine use of voiding cystourethrogram, as recommended in the guidelines, "sends a dangerous message to referring physicians that somehow reflux and other things we see on ultrasound are really not important. We believe there is going to be increased morbidity due to undiagnosed reflux," Dr. Kirsch said.

"Applying the UTI guidelines to young children, particularly in the emergency room setting, requires careful reconsideration," he concluded.

In the 1970s, vesicoureteral reflux was the most common cause of kidney failure in the pediatric population, said Anthony Atala, MD, chair of the Department of Urology at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, who was not involved in the study.

"Over the past few decades, there has been such an improvement in the management of reflux that people forget that undiagnosed and untreated reflux can be really bad for you," he told Medscape Medical News.

American Urological Association (AUA) 2014 Annual Scientific Meeting: Abstract MP44-03. Presented May 18, 2014.

Drinking Water: What's the Science?

Jeffrey S. Berns, MD, Stanley Goldfarb, MD

June 18, 2014

Jeffrey S. Berns, MD: Hello. This is Jeffrey Berns, Editor-in-Chief of Medscape Nephrology. With me today is Dr. Stan Goldfarb, who has a special interest in water. I have asked him to join me to talk about water, in particular how much water we should be drinking.

There is a theory in the lay press that we should be drinking at least 6 or 8 glasses of water a day, so let us begin with that. Where did that advice come from?

Stanley Goldfarb, MD: It is hard to say where it came from. People have tried to trace its origins. More than anything else, it may relate to the fact that people actually do consume about 6-8 glasses of water per day, including water in their food and all the liquids they consume. That is based on studies^[1] that have been carried out by the National Academy of Sciences.

The issue is that the lay press has promoted the "urban myth" that not only should you drink 6-8 glasses of water a day as a typical intake, but in addition you should drink another 6 or 8 glasses a day in order to have some sort of improvement in your health. For that, there is virtually no basis at all.

Dr. Berns: Is it harmful, do you think?

Dr. Goldfarb: It is not harmful unless, of course, you drink it more rapidly than your renal excretory capacity. The excretory capacity is something on the order of 15-20 L over 24 hours as long as it is consumed at that rate. But if a person consumes several liters during a brief period of time, some have developed acute hyponatremia on that basis. So there is that risk, but it is a minor risk. The bigger issue is that it is expensive to drink bottled water, and the bottles are additional items that fill up the dumps that blight the environment.

Dr. Berns: So there is an environmental question, too.

Dr. Goldfarb: Absolutely.

Dr. Berns: Is there any physiologic reason to think that drinking more water than our thirst dictates may be beneficial?

Dr. Goldfarb: One hypothesis, primarily based on animal studies, is that animals that consume large amounts of fluid, usually stimulated by adding some sugar to the drinking water, have better outcomes in terms of experimental disease. A few studies have suggested this.^[2] The explanation is that vasopressin is believed to be a culprit and somehow is producing alterations in the glomerular hemodynamics and perhaps also other effects. On the other hand, human studies have not shown similar findings.

A couple of human studies have suggested that individuals who drink very, very small amounts of fluid, significantly less than 800-900 mL/day, may be at higher risk for some cardiovascular diseases, perhaps bladder cancer, and strokes.^[3] On the other hand, there is no evidence that people who consume normal amounts of water and have urine outputs of over 1 L/day are healthier when their outputs are 2-3 L/day. The most recent epidemiologic studies^[4] that have been conducted have suggested that increased water intake is not associated with better cardiovascular outcomes or improved mortality.

Dr. Berns: Two patient populations come to mind that might benefit from a higher water intake: people who have a history of kidney stones and people who have polycystic kidney disease.

Dr. Goldfarb: Yes, absolutely. For people with kidney stones, certainly the evidence is incontrovertible. As a matter of fact, there was a literature review in Kidney International fairly recently, "The Medicinal Uses of Water in Renal Diseases,"^[5] about water therapy, and most of the article is devoted to discussing the multiple studies that show the benefits of increasing water intake above 2 L/day for people with recurrent stone disease. It is quite clear that it is beneficial in that group.

With polycystic kidney disease, there is the observation that using vasopressin antagonists may reduce the cyst growth. As you know, studies have suggested that there may be some side effects that make the medications less useful. The logic was, if we can block cyst growth with vasopressin antagonists, perhaps high water intake will suppress vasopressin physiologically, and it would be beneficial in that way.

Some studies have shown that, depending on the level of kidney function, anywhere from perhaps 3 to as high as 4 or 5 L of water intake a day can keep the vasopressin levels relatively low and get urine osmolality to the same level as plasma osmolality. It is pretty hard to get it below plasma osmolality. But there is no evidence yet that that kind of strategy will actually reduce the growth of cysts.

Dr. Berns: Is your advice to our patients and to ourselves to drink as thirst dictates?

Dr. Goldfarb: I think you should drink when you are thirsty. I should point out that the one retrospective study of high fluid intake in people with kidney disease that came out regarding nondiabetic renal disease showed fairly impressively that individuals who had the highest urine output actually had the most rapid deterioration of renal function.^[6] That study has been criticized because the study population may have had more kidney disease, and that is why they had less concentrating ability. However, the group of patients with the highest urine output also had the lowest serum sodium, suggesting that, in fact, they were driving the high urine output with a high fluid intake.

I believe the advice nephrologists should give patients with chronic kidney disease is that other than in certain circumstances -- foreign bodies in the urinary tract such as calculi and so on -- patients should not push a high fluid intake. There is no evidence that it is beneficial, and there may be some evidence that it's harmful.

Dr. Berns: And, finally, tap water vs bottled water.

Dr. Goldfarb: Tap water is a lot cheaper. Water is tested several times a day by most water departments. And I do not believe there is any rationale other than being a victim of really effective marketing techniques to drink bottled water.

Dr. Berns: Very good. Thanks. I have been speaking with Dr. Stanley Goldfarb, one of my colleagues from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. I am Jeff Berns, Editor-in-Chief of Medscape Nephrology.

References

1. Institute of Medicine Report. Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate. February 11,2004.http://www.iom.edu/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx Accessed June 10, 2014.
2. Torres VE, Bankir L, Grantham JJ. A case for water in the treatment of polycystic kidney disease. Clin J Am Soc Nephrol. 2009;4:1140-1150.
3. Sontrop JM, Dixon SN, Garg AX, et al. Association between water intake, chronic kidney disease, and cardiovascular disease: a cross-sectional analysis of NHANES data. Am J Nephrol. 2013;37:434-442.
4. Palmer SC, Wong G, Iff S, et al. Fluid intake and all-cause mortality, cardiovascular mortality, and kidney function: a population-based longitudinal cohort study. Nephrol Dial Transplant. 2014 Jan 6. [Epub ahead of print]
5. Wang CJ, Grantham JJ, Wetmore JB. The medicinal use of water in renal disease. Kidney Int. 2013;84:45-53.
6. Hebert LA, Greene T, Levey A, Falkenhain ME, Klahr S. High urine volume and low urine osmolality are risk factors for faster progression of renal disease. Am J Kidney Dis. 2003;41:962-971.

 

Medscape Nephrology © 2014  WebMD, LLC 

Cite this article: Drinking Water: What's the Science? Medscape. Jun 18, 2014.

Can a Teaspoon of Probiotic Keep the Diarrhea Away?

William T. Basco, Jr., MD, MS

June 20, 2014

Diarrhea and Preschool Children and Lactobacillus reuteri: A Randomized Controlled Trial

Gutierrez-Castrellon P, Lopez-Velazquez G, Diaz-Garcia L, et al

Pediatrics. 2014;133:e904-e909

Study Summary

A problem with studies supporting the prophylactic use of probiotics for diarrhea has been the use of different preparations. Gutierrez-Castrellon and colleagues studiedLactobacillus reuteri 17938, a preparation used in several previous studies, to improve the ability to extrapolate findings across studies.

This prospective trial was conducted from 2011 through 2012 at 4 Mexican child-care centers. Children were randomly assigned to treatment or placebo groups, and both parents and investigators were blinded to study assignment. The children were 6-36 months of age, at least 37 weeks gestational age at birth, and attended one of the 4 day care centers studied. Children with low birthweight or other chronic diseases that might alter findings were excluded.

The outcome of interest in this study was a comparison of the number of days with diarrhea. A day with diarrhea was defined as any 24-hour period during which the child had 3 or more stools that were "loose or watery." Days with both loose stools and emesis were excluded. They also evaluated secondary outcomes, including number of days with respiratory tract infection symptoms, missed time at day care owing to illness, antibiotic use, and healthcare utilization. The intervention ran for 12 weeks, and the children were followed for an additional 12 weeks thereafter.

Intervention group children received 5 drops of freeze-dried Lactobacillus suspended in oil. The placebo included only the oil preparation, but the appearance and taste of the formulations were the same. The preparation was administered by the parents at the child's first morning meal.

Outcomes were assessed by parental completion of a symptom diary. However, they were also instructed to call the investigation team when their child had diarrhea, and the investigators prescribed an oral rehydration solution as indicated when a child had a diarrheal illness. Parents also reported respiratory symptoms. The parents and children had monthly follow-up visits, at which time the diaries were reviewed and symptom recording was reinforced.

Study Findings

The 2 arms of the study each enrolled 168 children, and the groups were similar at the time of enrollment. For the primary outcome, the treatment group had markedly fewer days of diarrhea, with an average of 0.32 day compared with 0.96 day among the control group. The benefit appeared to extend into the follow-up period (weeks 13-24), when the children were not receiving any preparations, and children in the treatment group experienced only 0.5 day of diarrhea on average compared with a mean of 1.1 days of diarrhea among the placebo group. The average duration of diarrheal episodes was also shorter for treatment group children, at 1.4 days compared with 2.5 days among the placebo group.

Both the number of respiratory tract illnesses and mean duration of respiratory symptoms per child were lower among the treatment group. Febrile episodes were also lower among treatment group children, who had 0.4 episode of fever per child during the intervention period compared with 1.1 episodes in the placebo group. The benefit of fever reduction extended into weeks 13-24.

Most of the other secondary outcomes, including school and parental work absenteeism, medical visits, and emergency department visits, all favored the treatment group. Secondary outcomes that did not significantly differ between the 2 groups included the number of emergency department visits, average weight gain during the study period, and the frequency of stools.

The investigators concluded that among healthy children in day care centers, daily administration of Lactobacillus reduced gastrointestinal illnesses as well as respiratory illnesses.

Viewpoint

Along with a study of Lactobacillus to prevent infantile functional gastrointestinal disorders that was published recently in JAMA Pediatrics,^[1] the findings of Gutierrez-Castrellon and colleagues are interesting, although both studies need to be replicated in other populations. However, I am struck by the very similar findings between these 2 randomized, double-blind, clinical trials. Both showed substantial reductions in healthcare utilization, in addition to reductions in their primary physiologic outcomes.

Here's hoping that there is a building consensus on which product to use, leading to clinical trials that can use the same preparation, so that providers can compare and assimilate the findings from these multiple studies into some guidance on which patients might benefit from Lactobacillus administration.

Abstract

References

1. Indrio F, Di Mauro A, Riezzo G, et al. Prophylactic use of a probiotic in the prevention of colic, regurgitation, and functional constipation: a randomized clinical trial. JAMA Pediatr. 2014;168:228-233.
   
   

Lipid Screening in Kids -- Who's Doing It?

William T. Basco, Jr., MD, MS

June 11, 2014

Implementation of Lipid Screening Guidelines in Children by Primary Pediatric Providers

Dixon DN, Kornblum AP, Steffen LM, Zhou X, Steinberger J

J Pediatr. 2014;164;572-576

Study Summary

Before 2011, guidelines to screen children for lipid disorders or hyperlipidemia focused on identifying "high-risk" children on the basis of family history. However, those guidelines were revised in 2011 to promote universal lipid screening of children aged 9-11 years.^[1] Part of the reason for the recommendation was that screening on the basis of family history may miss as many as one half of all children with elevated lipid levels.

This study was a survey of medical providers in Minnesota, and it sought to assess clinician awareness of the 2011 pediatric lipid screening guidelines. Responses were obtained from 548 clinicians (a 39% response rate), who were surveyed from December 2012 through February 2013. Respondents included pediatricians (36.7%), family medicine physicians (37%), general practitioners (11%), nurse practitioners (5.5%), physician assistants (1.6%), and pediatric subspecialists (5.3%). Only 16% of the respondents worked in a university or academic setting.

Overall, 16% of respondents performed universal lipid screening, 50% screened on the basis of either family history or patient risk factors, and 34% performed no lipid screening in children. Approximately two thirds of the respondents were unfamiliar with normative values for pediatric lipid laboratory studies. Reimbursement concerns were not considered to be barriers to lipid screening; instead, respondents identified unfamiliarity with the guidelines (31%) and discomfort addressing lipid disorders (42%) as the most prevalent barriers to providing universal lipid screening.

The study investigators concluded that education of providers is needed to move toward universal pediatric lipid screening.

Viewpoint

In their discussion, Dixon and colleagues lament that the prevalence of universal screening in this study did not vary significantly from that found in studies from 1988 and 1995. On the positive side, they identify several leverage points that could improve practice.

First, the 2011 guidelines need to be reintroduced to pediatric practitioners; this could be a role taken by professional societies. They also identify specific problems that individual practices might address, such as moving to universal screening at age 9-11 years (regardless of family history) and obtaining nonfasting, non-high-density lipoprotein (HDL) cholesterol as the first screening test. This would involve obtaining a cholesterol panel and subtracting the HDL cholesterol level, with a goal non-HDL cholesterol level < 145 mg/dL. Screening is recommended for younger children with a positive family history of an early cardiovascular event or if the child is obese or hypertensive.

Helping providers become more comfortable with addressing any abnormal laboratory values is a more involved prospect, but it certainly seems that such counseling could be worked into other efforts that a practice is undertaking to address obesity. In fact, improving lipid screening in a given practice strikes me as a very good "maintenance of certification" effort -- so who's interested?

Infant Colic May Be Early Migraine

Pauline Anderson

July 03, 2014

LOS ANGELES — There is growing evidence that infant colic is a type of migraine headache.

The results of a new meta-analysis linking the 2 conditions suggest that "colic is an age-sensitive phenotype of migraine," according to lead researcher Amy Gelfand, MD, assistant professor, Clinical Neurology and Pediatrics, University of California, San Francisco, and child neurologist, University of California, San Francisco, Headache Center.

Dr. Gelfand believes it may be time to bring colic into the main body of the International Classification of Headache Disorders (ICHD) document from the appendix, where it's now an "episodic syndrome that may be associated with migraine."

Getting a better handle on the association between infant colic and migraine could help put to rest the oft-repeated theory that colic has something to do with feeding and gastrointestinal disorders, said Dr. Gelfand.

Dr. Amy Gelfand

She presented results of the new meta-analysis here at the American Headache Society (AHS) 56th Annual Scientific Meeting.

Fussing, Crying

According to the ICHD-III, colic refers to recurrent episodes of irritability, fussing, or crying. Episodes must last for 3 or more hours a day and occur on 3 or more days a week for 3 or more weeks. Colic peaks at 6 to 8 weeks of age and typically resolves by 4 months of age. The prevalence of colic is between 5% and 19%.

Researchers searched 2 electronic databases (PubMed and ScienceDirect), as well as recent AHS and International Headache Society conference proceedings, for relevant studies.

The primary analysis included studies that examined the association between infant colic and migraine. For a secondary analysis, researchers also included studies that collected data on infant colic and migraine but had a different primary research question.

The primary analysis included 3 studies with a total of 891 participants. One of these studies was conducted by Dr. Gelfand and colleagues. In it, the researchers analyzed 154 surveys and found that infants whose moms had migraine were 2.6 times more likely to have colic.

Another study found that children or adolescents with migraine were 6.6 times more likely to have had infantile colic than those without migraine; a third article included 58 participants and uncovered a similar link.

In a pooled random effects model (which Dr. Gelfand said is "more conservative" than the pooled fixed effects model), the odds ratio (OR) for the relationship was 5.6 (95% confidence interval [CI], 3.3 - 9.5; P = .004).

For the secondary analysis, researchers added 2 more studies, bringing the total number of participants to 1984. Here, the pooled random effects model had an OR of 3.2 (95% CI, 1.4 - 7.5; P = .007).

A sensitivity analysis that removed the largest study did not meaningfully change the results for the primary and secondary analysis or for both the fixed and random effects models, said Dr. Gelfand.

"It appears that the association between infant colic and migraine is quite robust," she noted.

"I think it's justified that infant colic is in the ICHD-III in the section on episodic syndromes that might be associated with migraine, but in the next iteration, it would make sense to pull it from the appendix section and [put it] into the main document," she added.

Infant colic can be extremely stressful for parents. According to research cited by Dr. Gelfand, 2.2% of parents with 1-month-old babies admitted shaking, slapping, or smothering their child to try to stop the crying. By age 6 months, 5.6% of parents have tried one of these "dangerous techniques."

"I don't think that 5.6% of parents are horrible people; it just says that parents are human and by the time their baby is 6 weeks old, they are really tired," and feel at the end of their rope, said Dr. Gelfand.

Cause Unknown

Nobody knows what causes colic, although people have looked at gastrointestinal pathology for clues. However, it is unlikely that colic is caused by intestinal gas.

Dr. Gelfand cited a randomized controlled trial of simethicone (an antifoaming agent sold over the counter to treat gas and bloating) versus placebo that showed no difference in effect.

Furthermore, colic is also not likely a result of feeding methods. Research shows that breast-milk vs formula makes no difference in colic rates. There is also no evidence of lactose intolerance in colicky babies, although an allergy to cow's milk protein may play a role in a subset of infants, said Dr. Gelfand.

She pointed to a recent randomized controlled trial that showed no benefit of probiotics for colicky babies. In fact, some formula-fed infants who were given the probiotic cried or fussed 78 minutes more per day than those who received the placebo (P = .005), she said.

Asked by Vincent Martin, MD, codirector, University of Cincinnati Headache and Facial Pain Program, Ohio, whether autonomic mechanisms could be at play, as these tend to kick in at night, when infants are most colicky, Dr. Gelfand clarified that colic typically occurs in the evening hours, from about 5 to 11 pm, rather than "the wee hours of the morning."

"The way I tend to think of it, is that after they have accumulated a lot of stimulation over the course of the day, babies just need to wind down and let it all go, but there could be some circadian variability."

Although the new meta-analysis included a relatively small number of studies, the overall number of subjects was large (almost 900 for the primary analysis and almost 2000 for secondary analysis).

This research is worthwhile, "given that the tummy way of looking at the problem has failed miserably, and given that shaken baby syndrome is an incredibly serious issue," commented Peter Goadsby, MD, PhD, director, Headache Center, University of California, San Francisco, who was involved in the study.

"It seems to me that shedding new light and getting people to think about this very serious problem in a totally different way is very important."

A prospective cohort study that uses some kind of mobile device to objectively measure crying time without relying on parental input could help objectively determine which babies develop colic and then, over time, which will develop migraine.

"It would be an expensive undertaking and would take lot of patience, but it would be a treasure trove of natural history data about what migraine looks like in the developing brain," said Dr. Gelfand.

Modern technology that can design an instrument that counts footsteps should be able to come up with such a device, perhaps an alarm attached to the baby's foot, said Dr. Gelfand.

In the meantime, parents should be advised to pursue safe and relatively inexpensive means of trying to quiet their baby, including giving acetaminophen, removing stimulation, and holding him or her.

"Holding the baby doesn't require [US Food and Drug Administration] approval, and acetaminophen is a regular sort of medicine," said Dr. Goadsby. "So you can start to look at simple, cheap, globally useful things that could be done everywhere tomorrow. If that reduces even by a small amount the number of kids who have a problem like this, I'm happy with that."

The investigators have disclosed no relevant financial relationships.

American Headache Society (AHS) 56th Annual Scientific Meeting. Presented June 27, 2014.

Send the Kids Outside to Play: Study

By Ronnie Cohen

July 22, 2014

NEW YORK (Reuters Health) - Kids who spent most of their after-school time outside were three times as likely to meet guidelines for daily physical activity and were in better shape than those who spent all of their after-school time indoors, in a recent study from Canada.

Lee Schaefer from the University of Regina in Saskatchewan, and his colleagues studied 306 urban youths between 9 and 17 years old.

Participants wore devices that measured their steps for a week and reported the amount of time they spent outdoors after school, in both organized activities and free play.

Kids who reported being outside during most or all of their after-school hours got almost 20 more minutes of moderate-to-vigorous exercise per day compared with those who spent most or all of their time indoors, the researchers found. That was after taking into account children's age, sex and weight and the time of year.

"It's important for students to be outside because when they're in outdoor spaces, they're more active," Schaefer said. "What's really important about the study is not just that kids are moving more, but they're moving more in a moderate-to-vigorous way."

The U.S. Centers for Disease Control and Prevention recommends that children get at least one hour of moderate-to-vigorous exercise every day. But few kids living in developed countries meet those guidelines, the authors write in The Journal of Pediatrics.

Prior studies attribute children's generally low levels of exercise to a variety of factors, the researchers say, including the pervasiveness of videogames and computers as well as changes in the built environment, which includes parks and other green spaces.

Earlier studies found that youths get most of their moderate and vigorous exercise during school and average only 10 minutes a day after school, they add.

But increasingly stringent academic demands have led to less outdoor play time at school, leaving children even more deficient in that area, Schaefer said.

Given how much time children spend in school, school wellness policies should include increasing outdoor activity, the authors write.

Several groups have called for more outdoor time as a strategy to boost kids' physical activity levels, but evidence to support those calls had been lacking, they note.

The new study stops short of recommending ways to get children who tend to stay inside out the door. The researchers also don't know what the children who went outside were doing during that time.

"That's definitely what we'll be looking at in the future," Schaefer said.

There were no weight differences between children who spent their time indoors and outdoors, the study found.

Schaefer said he was a bit surprised by that finding. But, he said, "Weight is not always the best way to measure whether somebody's healthy or not. When we weigh somebody, we don't really know how much of that weight is fat or muscle."

"There's a lot we don't know yet," Schaefer said. "I would love to see students outside more."

SOURCE: http://bit.ly/1oA8U0b

J Pediatrics 2014.