q Childhood Hearing is Associated with Growth Rates in Infancy and Adolescence

It is known that shorter stature is associated with sensorineural hearing loss; and that cochlear development is associated with activity of IGF1 (IGF-1), as are many important aspects of neurodevelopment.

Researchers at Dunedin School of Medicine, University of Otago, Dunedin, New Zealand hypothesized that this relation might be extrapolated to a normally hearing group, and that the strongest relation between hearing level and growth rate would be in late puberty, when serum IGF-1 levels are highest.

They examined the statistical relation between childhood hearing threshold and rate of growth in height at different times during the life course up to age 32. They found mixed support for the hypothesis. The strongest relations were observed in late puberty, at the ages which previous research shows are associated with the highest serum concentrations of IGF-1 in males and females, but also in infancy and early childhood. The association between hearing and height is present in a normally hearing, general population sample, and is associated with growth in late adolescence. (Pediatr Res. 2007 Jul 24;Epub ahead of print)

Comment: These findings support the idea that childhood hearing threshold may be predictive of IGF-1 mediated developmental characteristics. Further studies are required to come out with clear guidelines.

q The Association of Differing Measures of Overweight and Obesity with Prevalent Atherosclerosis

Although obesity is associated with cardiovascular mortality, it is unclear whether this relationship is mediated by increased atherosclerotic burden. To evaluate the associations between different measures of obesity and prevalent atherosclerosis in a large population-based cohort, this study was undertaken at Cardiovascular Clinical Research Center, the University of Texas Southwestern Medical Center, Dallas, Texas.

Using data from the Dallas Heart Study, researchers assessed the association between gender-specific obesity measures (i.e., body mass index [BMI]; waist circumference [WC]; waist-to-hip ratio [WHR]) and prevalent atherosclerosis defined as coronary artery calcium (CAC) score >10 Agatston units measured by electron-beam computed tomography and detectable aortic plaque measured by magnetic resonance imaging.

CAC prevalence was significantly greater only in the fifth versus first quintile of BMI, whereas it increased stepwise across quintiles of WC and WHR (P trend <0.001 for each). After multivariable adjustment for standard risk factors, prevalent CAC was more frequent in the fifth versus first quintile of WHR (odds ratio 1.91, 95% confidence interval 1.30 to 2.80), whereas no independent positive association was observed for BMI or WC. Similar results were observed for aortic plaque in both univariable and multivariable-adjusted analyses. The c-statistic for discrimination of prevalent CAC was greater for WHR compared with BMI and WC in women and men (P <0.001 vs. BMI; P <0.01 vs. WC). (J Am Coll Cardiol, 2007; 50: 752-759)

Comment: WHR was independently associated with prevalent atherosclerosis and provided better discrimination than either BMI or WC. The associations between obesity measurements and atherosclerosis mirror those observed between obesity and cardiovascular mortality, suggesting that obesity contributes to cardiovascular mortality via increased atherosclerotic burden. So, we should know that the waist-to-hip ratio has proven to be the most accurate measure of obesity for predicting the risk of atherosclerosis and we must emphasize that heart disease is a multifactorial process and that obesity is one of multiple factors that can be controlled. The best time to fight obesity is right from childhood.

q Hepatitis B Vaccine Protection may not be Long-Lasting?

According to findings published in the August issue of Pediatrics, whether to give booster dose of Hepatitis B or not is discussed.

It is always debatable whether to give Booster dose of Hepatitis B vaccine or not. Right now we do not recommend the booster dose of Hepatitis B vaccine.

In this study, only 60% of 14-year-olds had an anamnestic response to hepatitis B vaccine booster dose compared with 97% of five-year-olds.

"If immunity engendered by hepatitis B vaccine wanes in older adolescents and young adults who began their vaccine series as neonates, then HBV infections could occur in older adolescence and adulthood", wrote Taraz Samandar, MD, PhD, of the CDC, and colleagues from the Alaska Native Tribal Health Consortium in Anchorage.

Most studies of HBV vaccine in children have been conducted in children who had maternal HBV exposure or household exposure. By contrast this study was conducted in participants whose mothers were HBV negative and who had no environmental exposure.

The study was done with various parameters like use of recombinant versus plasma derived vaccine etc. but important fact to know about is "Among vaccinated persons who have lost the capacity to mount a detectable anamnestic response, protection from chronic infection or symptomatic infection might persist even if protection from acute, asymptomatic infection is no longer present". (Pediatrics 2007; 120: e373-e381.)

Comment: One might tempt to arrive at recommending booster dose of Hepatitis B vaccine but we must understand that this study suggests that the immunity conferred by Hepatitis B vaccine may wane over time. There are no recommendations for booster doses at present and more studies are needed before booster dose(s) of Hepatitis B vaccine intended to maintain long-term immunity can be recommended.

q Prepregnancy Obesity as a Risk Factor for Structural Birth Defects

This is an ongoing, multisite, case-control study to describe the relation between maternal obesity, overweight and underweight status, and 16 categories of structural birth defects, which is undertaken in USA in eight states with clinical geneticists reviewing all cases, excluding those that had or were strongly suspected to have a single-gene disorder or chromosomal abnormality. Mothers with preexisting diabetes were also excluded. Body mass index was based on maternal report of height and weight prior to pregnancy.

Mothers of offspring with spina bifida, heart defects, anorectal atresia, hypospadias, limb reduction defects, diaphragmatic hernia, and omphalocele were significantly more likely to be obese than mothers of controls, with odds ratios ranging between 1.33 and 2.10. Mothers of offspring with gastroschisis were significantly less likely to be obese than mothers of controls. (Arch Pediatr Adolesc Med 2007; 161: 745-750)

Comment: Probably this is the first population-based study of its scale to examine prepregnancy obesity and a range of structural birth defects. These results suggest a weak to moderate positive association of maternal obesity with 7 of 16 categories of birth defects and a strong inverse association with gastroschisis. The mechanisms underlying these associations are not yet understood but may be related to undiagnosed diabetes. Similar studies are needed for our country also where obesity is now no more uncommon.

Amit P. Shah
Consultant Pediatrician
Ahmedabad-380015,
India.
Email: [email protected]