Psychometric properties of Antonovsky's 29-item Sense of Coherence scale in research on older home-dwelling Norwegians.

Aim: The aim of this study was to test the homogeneity and construct validity of the Sense of Coherence 29-item scale (SOC-29) among older home-dwelling Norwegians.

Methods: A postal questionnaire, consisting of background variables, five health-related questions, the SOC-29, and three other instruments measuring mental health, self-care ability, and risk for undernutrition, was sent to 6033 home-dwelling older people (65+ years) in southern Norway. A total of 2069 participants were included. Homogeneity was assessed with Cronbach's alpha coefficient and item-to-total correlations. The construct validity was assessed with "the known-groups technique," a linear stepwise regression analysis with SOC score serving as the dependent variable and with confirmatory factor analysis.

Results: With a Cronbach's alpha coefficient of 0.91 and statistically significant item-to-total correlations, the SOC-29 was found to be homogeneous. Construct validity was supported because the SOC-29 could separate known groups with expected high and low scores. The factors that could predict SOC were mental health, self-care ability, feeling lonely, being active, and chronic disease or handicap. Evidence of construct validity was displayed in a confirmatory factor analysis that confirmed SOC-29 as one theoretical construct with the three dimensions, comprehensibility, manageability, and meaningfulness.

Conclusions: The Norwegian version of the SOC-29 is a reliable and valid instrument for use in research among older people. The results confirm that SOC has a particularly strong relationship with mental health and self-care ability.