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Juvenile Obesity
December  2016

A family is applying for life insurance for their 13-year-old daughter. The applied for amount, while high, appears consistent with siblings'. The child's APS has a few routine childhood illnesses noted, such as viral syndromes and Strep throat. There was no blood pressure recorded in the medical records reviewed nor were there any lab values. The most recently recorded height and weight calculated to a BMI (Body Mass Index) of 30.3. Looking back at previous well child visits, the heights and weights have all been in the higher percentiles for age.

Questions
1. Do BMIs in children correlate to BMIs in adults?
2. How does one determine risk stratification for BMIs in children?
3. How prevalent of a problem is juvenile obesity?
4. What are the morbidity and mortality concerns for elevated BMIs in juveniles?

Answers
A BMI chart is not recommended for use in babies aged newborn to 24 months. However, BMI charts for juveniles from ages 2-20 years have been developed and used by several different agencies, including the CDC and the World Health Organization (WHO), to track healthy weight ranges and determine when additional screening or intervention should
be obtained. More accurate measures of adiposity would include skinfold thickness and densitometry measurements among others, but these methods are inconvenient and impractical. BMI is considered an alternative to more direct methods as it is inexpensive and easy to perform.

In juveniles, the adult BMI ranges (Table 2) do not apply because of periods of rapid growth in children. Standard norms have been calculated from CDC growth charts based on United States national survey data collected between 1963-65 and 1988-94. As most are aware, there has been an increase in overweight and obesity in the past 40 years throughout the United States and the world, and data containing only recent measurements may be skewed toward overweight and obesity.

Table 2 - Definition of Juvenile Obesity by Percentile of BMI

Classification​Percentile BMI
​Underweight​< 5th
​Normal​5th - < 85th
​Overweight​85th - < 95th
​Obese​95th - < 99th
​Morbidly Obese​> 99th


BMI levels among juveniles are expressed relative to other children of the same age and sex. The expression of healthy BMIs in juveniles is a J-shaped curve with a nadir between 3-5 years of age (Figure 3).

Figure 3 - Percentiles of BMI Expected by Age for Boys Age 2-20 in the US

 

The categories of BMI for children are based on percentile compared to age and sex matched population (Table 2). Hence, a BMI of 18 would be considered underweight for an 18-year-old boy, about 50th percentile for a 12-year-old boy, and obese for a 4-year-old boy.

Differential diagnosis of childhood obesity
Although rare, the evaluation of a child with obesity must include the possibility of endocrine diseases, congenital and acquired hypothalamic defects, genetic syndromes or the use of medications affecting weight and/or appetite. If signs or symptoms are noted, e.g. decreased growth velocity despite continued weight gain, appropriate investigations should be taken, such as TSH and free T4 measurement or referral to an endocrinologist.

The vast majority of children, however, will fall into the category of energy intake/expenditure mismatch. Regardless of the cause of the obesity, modifiable lifestyle risk factors should be addressed and screening for comorbidities and complications of obesity should performed.

American Academy of Pediatrics recommendations
The American Academy of Pediatrics recommended in their 2007 Child and Adolescent Overweight and Obesity Summary Report that all children with BMIs greater than the 85th percentile should have a blood pressure taken (with the correct cuff size) and should have an initial fasting lipid profile (if over the age of 10 years), biannual fasting glucose and AST and ALT. Screening by history and physical for many of the morbidities of childhood obesity should be performed. It is also suggested that comprehensive multidisciplinary intervention should be offered.

Lifetime implications of childhood obesity
The prevalence of overweight and obesity in children and adults has risen substantially in the last several decades, initially in developed nations and now in developing countries. The rates of severe obesity >99th percentile in children in the United States in 2007 has risen 300% since the National Health and Nutrition Examination Survey (NHANES) in 1976 and has increased more than 70% since NHANES in 1994.

Obesity in the developed world may have leveled off, while it is still rising in developing countries. In developed countries obesity is of increasing concern in those of lower socioeconomic means, as nutrient poor, caloric-dense foods are readily available and low in cost. While in developing countries obesity is prominent in higher socioeconomic strata, pockets of undernutrition still exist throughout
the world. Obesity is a growing problem.

There are many morbidity and mortality implications to childhood obesity. Quite frequently an obese child becomes an obese adult, although about one half of currently obese adults were not obese as children. Approximately two-thirds of children in the highest BMI quartile become adults in the highest BMI quartile.

Comorbidities associated with childhood obesity include: asthma, Type 2 Diabetes Mellitus (T2DM), metabolic syndrome, nonalcoholic fatty liver disease (NAFLD), polycystic ovary syndrome (PCOS), obstructive sleep apnea (OSA), hypertension, premature puberty, slipped capital femoral epiphysis (SCFE) and acanthosis nigricans among others. Adolescents with a higher BMI experience higher mortality rates as young and
middle aged adults, although the mortality is mostly associated with the higher adult BMI. This suggests that an obese adolescent can decrease his risk by moving into a more healthy weight range.

However, being an obese adolescent is still associated with a higher risk of multiple comorbidities in adulthood even if the obesity did not persist. In 1992, the New England Journal of Medicine published “Long-Term Morbidity and Mortality of Overweight Adolescents: A follow-up of the Harvard Growth Study of 1922 to 1935,” which followed a group of elementary school children for 55 years. The study found that adolescent overweight (between 13-18 years old) was a more powerful indicator than adult overweight (at the age of 53 years) for all-cause mortality, coronary artery disease, angina and atherosclerosis for both men and women.

The risk of death from colorectal cancer was increased in men, and the risk of morbidity but not mortality from osteoarthritis was increased in women. An increased risk of diabetes was present only for those with adult overweight.

It has been well documented that adult obesity portends increased mortality risk from hypertension, coronary artery disease, NAFLD, T2DM, cerebrovascular disease, chronic kidney disease, respiratory disease and cancer. Several studies suggest that adolescents with higher percentile BMIs in the teen years continue on to be in the higher percentile BMIs in their adult years. That correlation has not been as strong with younger children; however, the likelihood of obesity in adulthood of younger children has been more correlated to the parents' obesity status.

Nonalcoholic Fatty Liver Disease
NAFLD in children has been increasing and has now become the most common liver abnormality in children aged 2-19 years. NAFLD is defined as hepatic fat infiltration in >5% hepatocytes in the absence of excessive alcohol intake, viral, autoimmune or drug induced liver disease (Figure 4). Childhood NAFLD, as in the adult variety, is associated with metabolic impairments such as insulin resistance, T2DM, hypertension, metabolic syndrome, abdominal obesity, dyslipidemia and cardiovascular disease.

Both genetic and environmental factors appear to be involved in developing NAFLD. Some populations have a higher incidence of NAFLD, such as Hispanics and Asians, while African Americans have the lowest incidence.

Figure 4 - Liver tissue showing large, clear vacuoles which contain fat in vivo, cell nuclei are pushed aside

 

The prevalence of NAFLD is difficult to determine as definitive diagnosis requires a liver biopsy. The liver function tests AST and ALT are often slightly elevated in children with NAFLD; therefore, their measurements are a valuable and noninvasive screen for the disease. Ultrasonography has also been used as a screening tool, although fibrosis is undetectable with either of these methods.

An autopsy study in San Diego County from 1993-2003 published in Pediatrics examined 742 children who died from unnatural causes. The prevalence of fatty liver, adjusted for age, gender, race and ethnicity was 9.6%.

A study in Taiwan in 2009 evaluated 748 school children aged 6-12 years by ultrasound. Some 219 children were found to have fatty liver. The rates of NAFLD were 3% in normal weight, 25% in overweight and 76% in obese children.

A 20-year study of 66 adolescents with NAFLD (but not T2DM) reported that 6% died or required a liver transplant. Those not requiring transplantation had a standardized mortality ratio of 13.6. Treatment to prevent the progression of NAFLD to cirrhosis and liver transplant includes lifestyle modifications of diet and exercise and often medical therapies (metformin, statins).

Type 2 Diabetes Mellitus
T2DM has increased in prevalence over the years. From 1982-1994, T2DM diagnosis in adolescents rose 10 fold in Cincinnati, Ohio, with an average BMI at the time of diagnosis of 37.7. T2DM has continued to increase in frequency and now accounts for 20-50% of new onset diabetics in youth aged 10-19, depending on the population examined. The overall prevalence of T2DM in youth has increased by 30.5% from 2001-2009 in five geographic areas in the US. Currently, T2DM is extremely rare under the age of 10 years. Obesity appears to be the driver of this increase in T2DM, and acanthosis nigricans and PCOS are frequently associated.

Children with T2DM have a higher risk of long term complications compared to adults with the same disease. They also have a higher risk of developing early diabetes-related complications such as cardiovascular disease, peripheral vascular disease and neuropathy than youth with T1DM with the same duration of illness.

Children with T2DM do not respond in the same fashion or to the same degree that adults do with the familiar medications. Depending on the severity of the hyperglycemia, the American Academy of Pediatrics recommends lifestyle changes along with insulin or metformin, the only medications currently approved for pediatric use.

Hypertension
Hypertension in children is defined as >95th percentile of blood pressure according the age, sex and height. Secondary hypertension is quite common in pediatrics, especially under the age of 10 years, with renal disease, coarctation of the aorta and adrenal disorders being three of the most common causes.

Post pubertal, a primary cause (idiopathic) hypertension is most likely. Primary hypertension is growing in prevalence and is highly associated with heredity and obesity. Hypertensive children, like adults, often are asymptomatic.

Twenty percent of obese children have primary hypertension. Obese children have a threefold higher risk for hypertension than non-obese children. Lifestyle changes and antihypertensive medications are the mainstays of treatment for primary hypertension, with the goal of limiting the long term results of left ventricular hypertrophy and myocardial infarction.

Mortality implications
A 2011 analysis in the International Journal of Obesity systematically reviews several recent studies and comes to the conclusion that adolescent obesity increases the risk of all-cause mortality, with increasing mortality ratios being associated with increasing BMI levels, especially > 99th percentile.

In the Annals of Internal Medicine in 2006, vanDam published the conclusion of the Nurses’ Health Study II, which compared BMI at age 18 of over 100,000 female nurses who were cancer free at baseline. They were enrolled at age 24-44 years, and were followed for 12 years. The overweight women had a standardized mortality ratio (SMR) of 1.52, and the obese women had an SMR of 1.99 in that short period of time.

Twig published in the New England Journal of Medicine in 2016 a study of 2.3 million Israeli 17 year olds (more males than females) who were examined in 1967-2010, one year before entering military service. They were followed for 1-44 years.

Those with a BMI of 85th-94th percentile were found to have a SMR of 1.3, while those with a BMI of 95th percentile or higher had an SMR of 1.68.

Must published a follow-up of the Harvard Growth Study of 1922-1935 in the New England Journal of Medicine in 1992. Some 508 elementary school children were followed for 55 years. BMIs between 13-18 years were used as baseline. They found that the all-cause mortality for overweight compared to lean had a relative risk of 1.8 for men but was 1.0 for women.

Evaluating the above mentioned studies along with other research in the literature leads to the conclusion that increasing BMI in adolescents predicts increased mortality risk as adults. A BMI in the 85th-94th percentile has an SMR of about 1.5, a BMI above the 95th percentile has an SMR of about 2, and at BMIs greater than the 99th percentile, the SMR is even higher starting at 2.5 and rising with increasing BMI.

Returning to the case
Our proposed insured has a BMI greater than the 99th percentile compared to her gender- and age-matched peers. There has been no screening for hypertension nor any screening lab values. Her risk of developing, if she has not already, the comorbidities of obesity are quite high. It would be prudent to check some baseline measurements, such as blood pressure, fasting glucose and ALT/AST. If all are normal, she would be assessed at a moderately increased mortality risk.

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