Sleep positions and nocturnal body movements based on free-living accelerometer recordings: association with demographics, lifestyle, and insomnia symptoms.
Level 4 - case-series / case-control
Cross-sectional observational study.
PubMed 29138608 · doi:10.2147/NSS.S145777
What was done
This cross-sectional study evaluated 664 participants from a Danish working population (363 men and 301 women; DPHACTO cohort). Body positions and nocturnal movements during free-living sleep were measured objectively using actigraph accelerometers attached to the thigh, upper back, and upper arm. Linear regression was used to determine adjusted mean differences in movements across demographic and lifestyle factors, including sex, age, BMI, smoking, alcohol use, and insomnia symptoms.
What was found
Participants spent an average of 54.1% (SD 18.1%) of time in bed in the side position, 37.5% (SD 18.2%) in the back position, and 7.3% (SD 12.3%) in the front position. Increasing age and BMI were associated with more time in the side position and less in the back position. Participants averaged 1.6 (SD 0.7) position shifts per hour. Compared with men, women had fewer position shifts (-0.37, 95% CI -0.48 to -0.24) and fewer arm, thigh, and upper-back movements. Participants aged 20–34 years had more limb and upper-back movements than those ≥35 years. Obese participants had fewer position shifts (-0.15, 95% CI -0.27 to 0) but more arm, thigh, and upper-back movements than normal-weight participants. Smokers had fewer position shifts than nonsmokers (-0.27, 95% CI -0.4 to -0.13). Numerical associations for alcohol consumption and insomnia symptoms were not reported in the abstract.
Why it matters
This study provides normative, objective baseline data on spontaneous nocturnal sleep posture and movement patterns in a free-living adult cohort.
Limits
The study is cross-sectional and cannot establish longitudinal trajectories or causality. The sample is restricted to working-age Danish adults, limiting generalizability to children, older retired populations, or patients with clinical sleep disorders. Accelerometer recordings capture time in bed and gross movement but do not directly measure sleep architecture or polysomnography-confirmed sleep stages.
Cited by
- partial Roughly 75% of sleepers are side sleepers, 20% are back sleepers, and 5% are stomach sleepers.