Rating Your Health: An Examination of Non-Health-Related Factors and Differential Item Functioning in the Self-Rating of Health

Cross-nationally comparative analyses are frequently used in order to identify social policy influences on health and health inequalities. A substantively meaningful comparison is based upon the assumption that subjects or data are comparable. In the case of self-rated health (SRH), this comparability is questionable due to manifold factors, such as differential expectations for ones' health, varying frames of reference, or cultural contexts. Also, it is highly likely that such ratings are influenced by non-health-related factors like personal, interviewer, or methodological characteristics. The present paper aims to identify such non-health-related influences on a person's SRH.

In a first step we predicted SRH using a wide range of objective health factors based on the information of 14,400 participants of the fifth wave of the Survey of Ageing, Retirement and Health in Europe (SHARE). In a second step, we used a model covering factors such as interviewer characteristics, satisfaction with life, and the country of origin in order to explain the residuals of this first regression, and thus the variance steming from non-health-related aspects. All analyses were also carried out separately by gender and age-groups in order to identify differential response behaviors for these groups.

The basic health model explained a high amount of the variance (R² = 0.46), with only minor differences by sex and some differences by age-groups. As for the non-health-related model, consistent influences of the interviewers' own SRH, the general life satisfaction of the participant and the country of residence (with Swedes and Belgians reporting more positively) were overall found to explain a modest amount of variance (R² = 0.09), with some differences by gender and age-group. These results illustrate the necessity for researchers to take factors such as age-specific response behavior and non-health-related influences into account to provide a valid base for evidence-based public policies.