Influence of Lateral Motion Transfer on Sleep
Study by J. J. Wellman, M. Bohannon and G. W. Vogel (Sleep Disorders Center of Georgia, Atlanta)
Sleep Lab Study of 24 Adults · Perceptual and Motor Skills (Vol. 89, Issue 1, pp. 209-217) · DOI: 10.2466/pms.1999.89.1.209
Key Takeaway
Motion from the Other Side of the Bed Made Sleep Lighter
What was tested: A 240-lb roller rocked on one side of a king-size mattress while an adult slept on the other side. 24 adults were randomly assigned to one of 3 mattresses with different designs and motion transfer (Wellman et al., 1999).
What the numbers showed: On nights when the roller moved, sleepers spent more time in light Stage 1 sleep and less in deep Stage 3/4 sleep. The changes were larger on the mattresses that passed along more motion.
What this means for you: If a partner's movement bothers you, a mattress that passes along less motion may help. This study does not name the mattress designs, so it cannot tell you whether pocket coils beat other designs.
Key Numbers
How the Study Was Done
Researchers at the Sleep Disorders Center of Georgia used a 240-lb, eight-sided roller as a stand-in bed partner. The roller sat on one side of a king-size mattress, and a healthy adult slept on the other half. On test nights the roller rocked back and forth in short bursts, adding up to about 13% of total sleep time. On control nights it stayed still, and the order of the nights was random (Wellman et al., 1999).
24 people were randomly assigned to 3 mattresses with different designs and different amounts of motion transfer. After one night to get used to the lab, each person spent two more nights there. Sleep was measured with overnight lab recordings of brain waves and other signals (polysomnography) and with a questionnaire each morning.
What the Study Compared
Roller Still (Control Nights)
The baseline. Each sleeper's normal sleep on the same mattress with no motion from the other side.
Roller Rocking (Test Nights)
More light Stage 1 sleep and less deep Stage 3/4 sleep, with bigger changes on mattresses that passed along more motion.
What the Study Found
Motion passed sideways across the mattress was linked to a significant rise in Stage 1 sleep, the lightest stage, and a significant fall in deep Stage 3/4 sleep. Overall sleep efficiency, the number of awakenings and time awake after falling asleep did not change significantly. The shift toward lighter sleep was larger on the mattresses that passed along more motion (Wellman et al., 1999).
The authors suggest that lighter sleep makes it easier for other things, such as noise, to wake you. The abstract does not describe the 3 mattresses, and we could not find a peer-reviewed study that measured pocket coils against linked-coil innersprings. An earlier version of this page gave a percentage for pocket coils that we could not trace to any study, so it has been removed.
Real bed partners do move together at night. In a separate study, 46 couples wore wrist movement monitors for 8 nights. About a third of each person's movements happened in the same 30-second window as their partner's, and women reported being disturbed by their partner more often than men did. Most people still said they slept better when their partner was there (Pankhurst and Horne, 1994).
How to Apply This Study When Choosing a Mattress
What to look for: If a partner's movement wakes you, low motion transfer is worth checking.
Makers describe motion isolation in their own words, and there is no standard rating. Ask about the return window and use it to judge how much you feel your partner move.
Study Scope and Limitations
24 adults, a mechanical roller rather than a real partner, and 3 mattresses the abstract does not describe. The study is from 1999, so it did not test today's mattresses or any brand.
Primary Citation
Wellman, J. J., Bohannon, M., & Vogel, G. W. (1999). Influence of lateral motion transfer on sleep. Perceptual and Motor Skills, 89(1), 209-217. https://doi.org/10.2466/pms.1999.89.1.209