Leung GM , Ho LM, Lam TH, Lau YL University of Hong Kong

1. Effects of breastfeeding on outpatient visits and hospitalizations during the first 18 months of life in Hong Kong Chinese infants Leung GM, Ho LM, Lam TH, Lau YL University of Hong Kong

2. Breast is Best ?

3. 1 hypothesis and 2 questions • To distinguish between real or biologic protective effects offered by breastfeeding and artifactual observations of benefit that arise due to associated influences affecting both health and the likelihood of breastfeeding • Do fewer illnesses mean lower health services use ? • Do Western findings translate well in Chinese or Asian populations ?

4. 1997 Hong Kong Birth Cohort Study A new study on health services use (outpatient consultations and hospitalization episodes) began in 1997 to examine the effects of breastfeeding on health services use in Chinese infants

5. Study Design • All 47 Maternal and Child Health Centres of the Department of Health • 88% capture of all births in April and May • 8,327 infants recruited • Prospective study - baseline (soon after birth), 3-, 9-, 18-month follow-up

6. Data and Methods • Detailed infant feeding practices included the initiation (ever vs. never), duration (months), and exclusivity of breastfeeding as per the WHO definition • Prospective follow-up of consultations (GP and specialist care; Western and Chinese medicine) and hospitalizations • Main outcome of interest • “High” vs “low” service utilisation by diagnosis groups (GI, respiratory/febrile, others) • defined by the median number of consultations or hospital episodes

7. Statistical analysis • Restricted to term singletons, non-smoking mothers and with no missing values (N=6608) • Multivariable logistic regression • Variable selection based on change in estimate criterion using backward deletion, or were selected based on known confounders documented previously • Variables found to confound the association between breastfeeding and any one of the outcome measures were adjusted for in all models to make meaningful comparisons possible

8. Breastfeeding Patterns • 39.4% were ever breastfed • Median duration of 8 weeks

9. Breastfeeding duration for those who were ever nursed

10. Protective of overall outpatient use but jaundice-specific increase

11. Excess risks of high inpatient use driven by jaundice-specific diagnosis

12. Summary of Findings Breastfeeding protects against doctor consultations overall in the first 18 months of life but increases outpatient and inpatient health services use due to jaundice mostly during the first three months

13. Our findings are likely real… • Prospective follow-up design • Clear distinction between formula feeding, mixed and exclusive breastfeeding and associated duration • Proper adjustment for a wide range of potential confounders in multivariable analyses • High rate of uptake and follow-up minimizing the possibilities of selection biases • Generalizability to the underlying population

14. Internal consistency • if findings were artifactual => more uniform associations with utilization patterns across different illness categories • increased hospitalization observed was selectively associated with jaundice-related conditions only • External consistency • Asian babies (vs Caucasians) at increased risk (OR = 3.5, 95% CI = 1.7, 7.4) for extreme neonatal hyperbilirubinemia in an HMO sample (Newman et al, APAM 2000) • mainland Chinese schoolchildren more likely to be hospitalized (OR = 1.28) if breastfed as infants (Zhang et al, EHP 2002)

15. How might these results be explained ? • More prolonged unconjugated hyperbilirubinemia likely accounts for late-onset jaundice associated with breastfeeding as a result of increased enterohepatic circulation of bile acids as well as bilirubin caused by a factor in human milk that promotes intestinal absorption, although the relation of bile acids to the etiology of the jaundice remains obscure

16. Prevalence of jaundice in HK very high – 5.1% to 9.3% of our ever breastfed sample were admitted for inpatient care within the first 18 months of life • G6PD (4.4% boys and 0.4% girls) and ABO incompatibility (12.5% in a hospital-based series) are the 2 commonest causes of pathologic jaundice in Hong Kong Chinese infants (Fok et al, Aust Paediatr J 1985 and 1986)

17. What are the clinical implications of our findings ? • Physiologic or pathologic ? • Observed relationship likely causal and a result of the synergistic interaction between breastfeeding and increased biological susceptibility of the babies due to their East Asian origins • Results should be confirmed in other East Asian settings • In the meantime, reconsideration of early hospital discharge <72 hours after birth • ? total serum bilirubin screening pre-discharge to be tested in RCT