Chair design affects how older adults rise from a chair.

OBJECTIVE To determine how modifications of key chair design aspects, such as seat height, posterior seat tilt, backrest recline, seat compressibility, and armrest placement, affect how older adults rise from a chair and the seating comfort they experience. DESIGN Cross-sectional comparison. SETTING Congregate housing facility and university laboratory. SUBJECTS Two groups of volunteers, Old (n = 29, mean age 84) and Young (n = 21, mean age 23). MEASUREMENTS Analysis of time to rise, body motion (determined by use of digitized videotaping), and self-reported difficulty when subjects rose from a variety of controlled chair settings thought to represent important chair design specifications encountered by older adults. Subjects also reported their comfort while being seated in these settings. RESULTS Lowered seat height, increased posterior seat tilt and backrest recline, and perhaps increased seat compressiblity cause increased time to rise, increased body motion, and increased self-reported ratings of rise difficulty in both Young and Old groups. Under the most challenging conditions, the effect appears to be stronger in the Old than in the Young: a few Old were unable to rise, and the Old took disproportionately longer to rise and used disproportionately greater neck motion (P generally < 0.001) compared with the Young. Arm rest placement did not alter rise performance or ratings significantly. The conditions in which rise difficulty increases or decreases do not correspond exactly to conditions in which comfort increases or decreases. Some aspects that increase rise difficulty, such as tilt/recline and seat compressiblity, may also increase comfort. CONCLUSIONS Aspects of chair design such as lowered seat height, increased posterior seat tilt, increased back recline, and increased compressibility interfere with chair egress in older adults. While decreasing ease of egress, however, these same factors may increase seating comfort. Furniture designers and manufacturers must find a balance between degree of sitting comfort, ease of egress and the degree to which the seating device facilitates functional independence, particularly to meet the needs of disable older adults.