Background: Orthostatic hypertension was associated with worse cardiovascular outcomes, although the factors responsible for an orthostatic rise in blood pressure (BP) are uncertain. We investigated a possible relationship between a stooping posture and orthostatic BP change.
Methods: Study participants consisted of 1,992 older individuals. Orthostatic BP change was calculated by systolic BP measured at sitting position, and again 1 and 3 minutes after standing up. Spinal alignment and curvature was assessed by guiding the SpinalMouse device on the surface of the skin along the spine.
Results: Mean lumbar lordosis at standing position was 13.4° ± 12.4°. The degree of lumbar lordosis was significantly smaller in orthostatic hypertensive individuals (systolic BP change, ≥+20 mm Hg: 3.3° ± 15.6°, ≥+10 mm Hg: 10.4° ± 14.3°) than in individuals who were orthostatic normotensive (14.2° ± 11.9°). Multiple linear regression analysis identified lumbar lordosis (β = -0.171, P < 0.001) and thoracic kyphosis (β = 0.062, P = 0.007), but not sacral inclination (β = 0.033, P = 0.303), as independent determinants for orthostatic BP change. As waist circumference was another independent determinant, the frequency of orthostatic hypertensive individuals was linearly increased with the combination of abdominal obesity and small degree of lumbar lordosis (control: 9.9%, abdominal obesity: 17.4%, small degree of lordosis: 19.4%, both: 24.1%, P < 0.001). Participants who sustained orthostatic hypertension for 3 minutes after standing up had the smallest degree of lumbar lordosis (5.2° ± 16.4°).
Conclusion: Stooped posture was an overlooked determinant for orthostatic increases in BP.