Purpose <p>Spinopelvic sagittal alignment is a critical determinant of the quality of life and clinical outcomes in older adults. Although pelvic incidence (PI) is a well-established morphological parameter influencing spinopelvic alignment, its role in age-related alignment changes and compensatory mechanisms remains incompletely understood. This study aimed to investigate the influence of PI magnitude on 10-year changes in spinopelvic sagittal alignment and compensatory adaptations in a community-dwelling older population.</p> Methods <p>We analyzed 135 adults (mean age: 68.5 years in 2012) who underwent whole-spine lateral radiography between 2012 and 2022. Participants were classified into three groups based on their 2012 PI values: Low PI, Mid PI, and High PI. Radiographic parameters, including thoracic kyphosis (TK), upper and lower lumbar lordosis, sacral slope, pelvic tilt (PT), and sagittal vertical axis (SVA), were compared longitudinally. Changes in alignment were assessed, and compensatory mechanisms were evaluated in relation to PI magnitude.</p> Results <p>Regardless of PI magnitude, participants demonstrated pelvic retroversion and kyphotic changes in the upper lumbar spine over the 10-year period. However, compensatory strategies differed among the groups. Individuals with low PI exhibited increased TK and compensatory hyperlordosis in the lower lumbar region. Conversely, those with high PI showed decreased TK and progressive kyphotic changes in the lower lumbar spine. Notably, no significant group differences were observed in SVA or PT progression.</p> Conclusion <p>PI magnitude significantly influences compensatory mechanisms associated with age-related deterioration of spinopelvic alignment. These findings highlight the need for individualized evaluation and management strategies based on PI morphology in aging populations.</p>