We previously reported on the high rates of chronic health conditions among ELBW children compared with NBW controls at the age of 8 years and sought to examine possible changes during the critical period of adolescence. Our results reveal that the overall rates of chronic conditions among both ELBW children and NBW controls were relatively stable. During adolescence, ELBW children continue to have significantly higher rates of functional limitations, compensatory dependencies and increased use of or need for services than NBW controls. Rates of asthma among ELBW children also remained stable whereas they increased among NBW controls such that when defined as current asthma, the differences between ELBW children and NBW controls were no longer significant at the age of 14 years.
Of major concern is the significant increase between the ages of 8 and 14 years in mean BMI z scores and rates of obesity among ELBW children when compared with the relatively stable rates among NBW controls. Our results thus indicate both positive and negative changes in the health trajectories of ELBW children during adolescence.
Reports of adolescent health outcomes of ELBW children born in the 1990s pertain to the early adolescence of children born prior to 26 weeks gestation in Sweden and the United Kingdom.3,4
Similar to our finding, Farooqi et al 3
reported significantly higher rates of chronic conditions as measured with the QUICCC at 11 to 12 years. Fawke et al 4
reported significantly higher rates of impaired respiratory morbidity in the British Epicure study population at the age of 11 years and a current rate of asthma of 25%, which is similar to our rate of 23%. Longitudinal changes in these outcomes have not been reported.
The studies of children born prior to 1990 similarly reported significantly higher rates of chronic illnesses among ELBW children during adolescence. These pertained mainly to neurocognitive disorders13,14
with functional problems and rehospitalizations resulting from a combination of these respiratory and neurologic conditions.16,17
Similar to our findings, Saigal et alt16
reported stability in the rates of chronic conditions among ELBW children born from 1977 through 1982 but reported an increase in medication use between the ages of 8 and 14 years.
Our results among the NBW controls are similar to those reported nationally. Rates of chronic conditions or special health care needs during childhood range from 12% to 37%, depending on the definition,18–20
, Between the ages of 12 and 17 years, the rate of ever diagnosed asthma is 16.6% and the rate of current asthma is 10.2%.21
Twenty percent of children are obese between the ages of 6 and 11 years and 18% are obese between the ages of 12 and 19 years.22
Chronic conditions and special healthcare needs are also reported to increase during adolescence.6
The high rate of chronic conditions in our NBW controls might be due to the low socioeconomic status of our cohort (60% of whom are minorities) and to current parent perceptions of children’s health.20
Our findings of an increase in the rates of asthma in the NBW population during adolescence reflects epidemiologic studies23
and national trends.24
The lack of an increase in our ELBW population during adolescence supports suggestions of a different asthma phenotype among preterm children.25,,26
The major etiologic determinant of asthma in normative populations is genetic susceptibility to atopic disease, which interacts with environmental factors, whereas the pathophysiology of asthma in preterm children is mainly associated with abnormal lung development, bronchopulmonary dysplasia and obstructive airway disease.6,26–29
Improvement in pulmonary function28,29
and stabilization in the rates of asthma during adolescence have been reported among ELBW children16,29
however, the way in which the trajectory differs from that of NBW children has not been reported.
Our rates of adolescent obesity among the ELBW children and NBW controls reflect the current obesity epidemic.22
The increase in BMI among ELBW children during adolescence compared with NBW children has been reported previously in addition to the long- term implications of catch-up growth for metabolic and cardiovascular disease. 7.8,30,31
However the considerable catch-up in obesity among ELBW children to the current very high prevalence of NBW children may further intensify the known threat to adult health.
Our findings of a significant association of neurosensory impairments and lower socioeconomic status with functional limitations and need for services indicates both biologic and sociodemographic influences on children’s health in both NBW and preterm children. The significant association of male sex with functional limitations, need for services in childhood asthma has been reported.20,24,27,32
Strengths of this study include our longitudinal design and use of both noncategorical and specific diagnostic categories of chronic illness, each of which has important epidemiologic and clinical implications. Our use of a generic or noncategorical approach, independent of diagnoses, provides an assessment of the multiple chronic sequelae of preterm birth and also incorporates a functional classification as suggested by the World Health Organization 33
Children’s special health care needs are used for the identification and planning of federal aid and services and also provide an indirect measure of the enormous cost of providing health care and education for these children of whom preterm survivors constitute an important subgroup.34–36
We chose to examine longitudinal changes in the rates of asthma and obesity because asthma is a common consequence of preterm birth and obesity may have long term metabolic and cardiovascular implications 30
We did not consider cerebral palsy or cognitive impairment, which are chronic conditions that are also prevalent among preterm children, because their rates are fairly stable after middle childhood37
; however, the QUICCC-R does include parent report of developmental problems and need for special education.
Possible limitations of our study include the fact that our population is based on birth weight rather than gestational age based and that our sample of ELBW children represents an urban perinatal center and is not representative of theentire United States. The follow-up rate of the NBW controls is lower than that of the ELBW children, which is probably due to their lesser commitment to the study. However, there were no sociodemographic differences between the 2 groups.
We excluded children with neurosensory abnormalities from the examination of obesity as they tend to grow poorly, which might have influenced outcomes. Fewer of the ELBW children followed up had bronchopulmonary dysplasia compared with those children who were not followed up, which might have influenced their rates of asthma.
Our results are based mainly on parent report, which may be biased and inconsistent between periods. However the QUICCC has been validated as a parent measure of child health.10
Some outcomes has small numbers of events which was reflected in the wide 95% CIs. There is always the possibility of detection bias among ELBW children; however, the detection of an increased rate of asthma in NBW controls argues against this. Finally, because the QUICCC-R provides a noncategorical measure of chronic health conditions, specific diagnoses aside from asthma and obesity were not examined.
Because mortality of ELBW infants has reached a plateau with the majority of infants currently surviving, the residual rates of neonatal morbidity and resultant chronic illness become critical. 38
. Rates of neonatal morbidity have decreased since 2000 but there is, as yet, no evidence of improved health outcomes.
Our results may thus have relevance to current survivors. The ELBW status may be considered a marker for the risk of multiple chronic conditions which warrant closer than average health surveillance during adolescence. In addition to therapy for neurodevelopmental disorders, ELBW children with asthma or obesity should receive interventions such as smoking prevention and exercise encouragement to reduce the consequences of these conditions and to possibly enhance their long-term adult outcomes.39,40