Individual and contextual characteristics as determinants of sagittal standing posture: a population-based study of adults.

BACKGROUND CONTEXT Sagittal standing posture is associated with musculoskeletal symptoms and quality of life. However, the frequency and determinants of suboptimal sagittal alignment outside the clinical context remain to be clarified. PURPOSE To estimate the association of sociodemographic, anthropometric, and behavioral characteristics with sagittal standing posture among adults from the general population. STUDY DESIGN Cross-sectional evaluation of a population-based sample. PATIENT SAMPLE As part of the EPIPorto study, 489 adults were assessed during 2005 to 2008. OUTCOME MEASURES Individual spinopelvic parameters were measured. Additionally, participants were classified into one of four types of sagittal postural patterns (Roussouly classification: Types 1, 2, and 4 corresponding to nonneutral postures and Type 3 to a neutral posture). METHODS Spinopelvic parameters were recorded from 36-inch sagittal radiographs obtained in free-standing posture. Age, sex, education, occupation, body mass index (BMI), waist circumference, total physical activity, leisure time physical activity, time spent in sitting position, smoking status, and tobacco cumulative exposure were collected. Individual parameters and patterns of sagittal posture were compared across categories of participants' characteristics. RESULTS Older age, lower educational level, blue collar occupation, and overall and central obesity were associated with increased sagittal vertical axis and pelvic tilt/pelvic incidence ratio. Taking the neutral postural pattern (Type 3) as reference for the outcome in a multinomial regression model, independently of age, sex, education, total physical activity, and smoking status, overweight adults had higher odds of Type 2 (odds ratio [OR]=1.92; 95% confidence interval [CI]: 1.13-3.27) and Type 4 (OR=2.13; 95% CI: 1.16-3.91) postural patterns in comparison with normal weight subjects. Overall and central obesity were positively related with Type 1 postural pattern (OR=6.10, 95% CI: 1.52-24.57 and OR=3.54, 95% CI: 1.13-11.11, respectively). There was also a weak direct association between female sex and Type 1 postural pattern. Regarding behavioral factors, subjects with total physical activity above the first third exhibited all nonneutral postural patterns less frequently, and current smokers were more likely to present a Type 4 postural pattern. CONCLUSIONS Higher BMI and central obesity were important potential determinants of nonneutral posture among adults from the general population. Future research should investigate the potential effectiveness of overweight prevention and management in avoiding sagittal misalignment conditions.