The individualized optimal pillow height and neck support design for side sleepers.

An optimal pillow effectively increases sleep quality and prevents cervical symptoms. However, the influence of body dimension on optimal pillow design or selection strategy has not been clarified quantitatively. This study aims to investigate the individualized optimal pillow height and neck support for side sleepers. Nine healthy subjects were recruited and laid laterally on foam-latex pillow with four height levels (8 cm, 10 cm, 12 cm, 14 cm) and with/without neck support, respectively. Healthiness was evaluated using cervical spine morphology (measured by motion capturing system) and musculoskeletal internal force (simulated by a multi-body model). Comfortability was evaluated by a deviation standardized overall comfort rating. Individualized pillow height was identified by Hφ (calculated by the subject's shoulder width and absolute pillow height). Correlation analysis and linear mixed model were performed between C1-T1 slope and Hφ. A paired-t test was performed on the cervical curve and comfort score comparisons between neck support pillow and flat pillow. The C1-T1 slope of the cervical curve showed statistically significant correlation to Hφ and was well predicted by Hφ through linear relation (R = 0.80 for flat pillow, R = 0.82 for neck support pillow). The correlation between comfort score and Hφ was moderate or weak. Medium individualized height pillow (Hφ 9.74-11.76 cm) with neck support showed a cervical curve closest to natural standing and the lowest musculoskeletal internal force. Sub-low individualized height pillow (Hφ 11.76-13.78 cm) with neck support showed the highest average comfort score. For side sleepers, cervical curve morphology and optimal individualized pillow height are well predicted by Hφ. Comfortability perception is not sensitive to Hφ. Sub-low individualized height pillow showed the best comfortability and relatively good healthiness. Medium individualized height pillow with neck support showed the best healthiness.