Maria Iacovou University of Cambridge UNICEF UK Baby Friendly Initiative Conference

1. Scheduled or on-demand feeding? Effects on children’s educational outcomes, psycho-social development and sleeping patterns Maria Iacovou University of Cambridge UNICEF UK Baby Friendly Initiative Conference Glasgow, 27th-28th November 2013

2. What we know already what you feed a baby when you feed a baby

3. What we know already what you feed a baby when you feed a baby

4. Questions • Do feeding schedules affect babies’ and children’s development? • Growth and health? • Cognitive development? • Psycho-social adjustment? • Later sleeping patterns? • And mothers’ wellbeing?

5. Data: ALSPAC • Avon Longitudinal Study of Parents and Children • About 10,500 babies born in 1990 and 1991 • Based in and around Bristol • Information from: • Both parents, 3x during pregnancy • Both parents, repeatedly over childhood • Weights, measures and various tests • Teacher assessments • Data from national tests

6. Variable of interest: feeding schedules Asked at 4 weeks: “Is your baby fed (either by breast or bottle) on a regular schedule (e.g. every 4 hours)?” “Yes, always” (7.2%) “Try to” (23.4%) “No, fed on demand” (69.4%).

7. 1. Maternal wellbeing • “Getting enough sleep?” • “Feeling: weepy or tearful? irritable? exhausted?” • Maternal confidence and enjoyment scales • “Motherhood is something a woman learns naturally” • “...Pretty sure I’m doing the right thing for my child”. • Depression measures: Edinburgh & Crown-Crisp scales. Continuous variables are standardised; discrete variables are collapsed into two categories.

8. 2. Cognitive attainment • SATs scores in Reception class (age 5), KS1 (age 7), KS2 (age 11) and KS3 (age 14) • Ages 5 and 7: Reading, writing, maths • Ages 11 and 14: English, maths, science • Separate IQ test at age 8 • All standardised (0,1)

9. 3. Psycho-social outcomes • Strengths & Difficulties questionnaire • Teacher assessments in Years 3 & 6 (ages 8 & 11) • Five domains • Hyperactivity • Emotional problems • Peer problems • Conduct problems • Prosocial score • Aggregate composed of the 4 “problem” scores

10. 4. Sleeping • 6 months, 18 months, 9 years: does child sleep regularly? • 9 years: Refusing to go to bed, difficulty falling asleep, night waking, early morning waking, nightmares. • 9 and 11 years: sleep durations

11. The ideal: a randomised controlled trial • Mothers and babies randomly assigned to scheduling or demand groups • Unfortunately, no such trial exists • Feeding mode is a choice mothers make, based on various factors.... • ... which may also affect their babies’ development • Use statistical techniques which account for this selection

12. Who feeds to a schedule? • Demand-feeding mothers in the sample are from more socially privileged groups. For example: • 6% of schedule-feeding mothers have a degree • 8% of “tried a schedule” mothers • 18% of demand-feeding mothers • “Tried-a-schedule” mothers are much more similar to schedule-feeding mothers than to demand-feeding mothers.

13. Analytical methods • Ordinary Least Squares and logistic regression • Control for factors including social class, education, marital situation, mother’s work, health behaviours, housing, breastfeeding, etc etc • Propensity Score Matching • Compare “like with like” • Compare schedule-feeding mother-baby pairs with demand-feeding pairs who look just like them

14. Results: maternal wellbeing • On almost all measures, schedule-feeding mothers report significantly higher levels of wellbeing than demand-feeding mothers. • These differences persist for at least 3 years • However, on the formal measures of depression, there is NO difference between the two groups • Mothers who tried to schedule have the same outcomes as demand-feeding mothers.

16. Results: cognitive development • After controlling for observable differences between the samples, demand-fed babies do significantly better than schedule-fed babies on all SATs tests and IQ tests. • The outcomes of “tried-a-schedule” babies are no different to those of demand-fed babies • Iacovou, M. and Sevilla-Sanz, A (2013). "Infant feeding: the effects of scheduled vs. on-demand feeding on mothers' wellbeing and children's cognitive development" European Journal of Public Health (2013) 23(1) pp 13-19

17. Questions: • How big is the effect? • About 17% of a standard deviation • Conservative estimate: about 3 “positions” in a class of 30 children • What might be the mechanisms? • Discuss this later

18. Cognitive attainment

19. Cognitive attainment Full

20. Cognitive attainment

21. A question on breastfeeding • Could the relationship between demand feeding and better cognitive outcomes arise because of longer breastfeeding durations for demand-feeding mothers? • Answer: yes, but only partially • (about 2 points of the 17-point difference comes via breastfeeding durations)

22. Perhaps the most important question of all • We’ve controlled for observable differences between mothers. But what if unobservable differences are driving the relationship between feeding mode and children’s outcomes? • Two reasons why this probably isn’t a major issue. • First, the outcomes of “tried-to-schedule” babies. • Second, look at this graph...

23. Is unobserved heterogeneity driving the effect?

24. Results: psycho-social adjustment

25. Year 6 SDQ scores, by sex

26. Year 6 SDQ scores, by sex

27. Results: psycho-social adjustment • Results differ by gender • For boys: no difference in outcomes between schedule- and demand-fed children. • For girls: significant differences in outcomes, with demand-fed babies having a lower incidence of later problems. • Effects are concentrated in the hyperactivity and emotional components of SDQ

28. Results: sleeping habits • Question: do schedule-fed babies have better/different sleep habits than demand-fed babies? • Answer: not really • Schedule-fed babies are more likely to sleep regularly at 6 months • But not at older ages • At age 9, schedule-fed babies more likely to refuse to go to bed and to wake at night • But differences are really very small

29. Results: sleep durations • Schedule-fed babies: 20 mins longer sleep durations • Fairly large difference: 0.5 SD

30. School-day sleep durations, age 9 by feeding mode schedule demand

31. Implications • Robust relationship • Possible issues with parental reporting • Next step: get hold of data on ALSPAC subsample who were “metered” • Assess whether 20 mins extra sleep is a good thing

32. What are the mechanisms? • Heterogeneity between mothers • Possible, but unlikely to be a major factor • Heterogeneity between babies • Possible: investigate with observational studies

33. Possible causal mechanisms • Breastfeeding duration • Biological – frequency of feeding affecting concentration of lipids in milk? • Demand-feeding encourages interactive “asking-and-getting”? • Maternal responsiveness

34. Next steps • Collaborate with psychologists to measure effects of feeding mode on (eg) stress hormones • Collect more detailed data on the nature of feeding schedules (and demand feeding) • More work on sleep!