Today, in a study published online in the journal Pediatrics, researchers asked the question of whether sleeping patterns are related more to genes or the environment. In other words, are some babies and little kids just inherently programed to wake up more during the night and sleep a shorter time overall, or do parenting style, schedule, and all the other aspects of our daily life patterns make more of a difference?
The researchers studied 314 pairs of 18-month-old twins and looked at co-sleeping, total sleep duration, and night wakings to see how nature and nurture played in to each. Here’s what they found:
Not surprisingly, co-sleeping was explained almost entirely (98.3%) by environmental factors (the family’s preference and habits), and had nothing to do with genetics and temperament.
How long a toddler slept at night was also more related to the environment, but not as heavily, with the researchers calculating that roughly 64 percent of the variability in sleep duration had to go with environment, 31 percent related to genes. Night-wakings were also shown to be similarly environment-based (63%).
This seems about right to me. All of us, adults and children, have different set points and natural sleep cycles. Adults are known to vary between needing 6.5 – 9 hours of nighttime sleep (although the majority need 7-8), so it makes sense that we would see some natural variation in children’s biological patterns at night. Some babies are probably natural 10.5-hour-a-night sleepers, while others need 12.
But the patterns, expectations, and daily routines in the house have more to do with children’s sleep than genes. The one thing I would add is that “night wakings” are a little misleading, because all babies wake up at night (just like all adults), the real difference being measured here is whether or not a baby calls out to the parent, or whether they get comfy and go back to sleep on their own.
Does that sound right to you too? Do you think the routines and patterns in the family environment explain more of our kids sleep differences, or do genes win out?