Predictors of Sleep Outcomes
Given that previous research found that parental presence appears to moderate the
relationship between breastfeeding and sleep, hierarchical linear regressions were
BREASTFEEDING AND SLEEP 197
used to investigate the relative importance of breastfeeding and parental presence
at sleep onset for various sleep outcomes. For all regressions, parental presence at
sleep onset was entered at Step 1 followed by breastfeeding at Step 2, to assess
the independent contribution of breastfeeding beyond parental presence at sleep
onset. Regression results at each time point are presented in Table 3. At base-line, breastfeeding was relatively more important in explaining increased night
wakings (R
2
change=0.09, Total R
2 =.10), daytime naps (R
2
change=0.09,
Total R
2=.09) and decreased likelihood of waking in own bed (R
2
change=0.14,
Total R
2 =.16) than parental presence. In contrast, parental presence explained
more variance in longest continuous sleep period (R2
change =0.05, Total
R
2=.06) and sleep onset latency (R
2
change=0.06, Total R
2=.07). Regressions
for sleep onset latency and perception of sleep problems were not statistically
significant. Taken together, breastfeeding and parental presence accounted for
between 1% and 16% of the variance in sleep outcomes at baseline.