Parents are commonly concerned when their baby does not sleep through the night, especially if the largest stretch of sleep is not when they sleep. The results of this study give us a guide of appropriate developmental expectations for infant sleep, and help determine the optimal timing for prevention and intervention of sleep problems. From a developmental perspective it reflects an understanding of infant’s physiological capabilities in self-soothing and sustained sleep, showing the large variability of this from one baby to another.
This NZ based study enrolled 75 parents of healthy, developing infants and parents completed sleep diaries for 6 days each month for 12 months. Parents recorded the time and at what state the infant was placed into the cot and then the duration of time until the infant fell asleep. Parents also recorded the time and duration of each night-awakening and the time that their baby woke in the morning. Accuracy of parent reports were assessed by using videosomnography (diagnosis by behavioural observation).
The sleep of each infant was classified based on the three criteria below:
1) 2400hrs to 0500hrs
2) 8 hours of uninterrupted sleep
3) 2200hrs to 0600hrs
The findings of the study showed that self-regulated sleep (without behavioural intervention) became apparent most rapidly in the first four months, with 50 percent of infants meeting criterion 3) at 5 months. From 4-9mths age infant sleep length tended to plateau and began to lengthen again between 10 and 12months. However at 12 months age, 32 percent of infants still did not meet criterion 3) - many babies do not sleep through the night by one year of age but are still perfectly healthy and this is not necessarily problematic.
The authors of the study recommend that criterion 3) should be used to define ‘sleeping through the night’ for babies from the age of 4 months. The reason for this is because it is harmonious with family sleep patterns, and falls within typical sleep times of the parents. Additionally, it is recommended that prevention of sleep challenges should begin before 3 months, emphasising the importance of working with infant sleep biology to determine healthy sleep habits in the long-term.
Many families aim to put their baby to sleep at 7pm but why do we place this expectation on our baby? A later bedtime may be better suited for baby’s actual sleep patterns and may also be beneficial in synchronising their sleep with their parents. It is actually possible to aid in the prevention of sleep challenges by achieving a synchronised sustained period of sleep during the night after completing day to day activities and self-care tasks. For example moving bed time routines out to a later hour can not only help with preventing sleep challenges but perhaps even more importantly, reset parents’ expectations of their baby’s developmental capabilities.
One of the main limitations of this study was that there was no data provided on the method of infant feeding (i.e. breastfeeding or formula feeding) as this does seem to impact sleep duration and quality of sleep. Many parents believe that supplementing their babies with formula feeds will encourage earlier sleeping through the night. A separate study has found that although breastfed babies do wake more frequently in the night, they often get better quality sleep as they settle back to sleep more easily.
Additional research is now needed to establish the factors that precede and predict infant sleep problems.
For full aticle please see:
Sleeping Through the Night: The Consolidation of Self-regulated Sleep Across the First Year of Life
Amy and Elspeth