How Do You Feel and Where Do You Feel it? A Cross-Sectional Study of Somatic Symptoms and Their Relationship to Age, Sex and Self-perceived Health.

Somatic symptoms arise from a complex interplay of factors and are a major reason for seeking medical health care. The Patient Health Questionnaire-15 (PHQ-15) is a widely used tool for assessing these symptoms and can be analysed using a bifactor model comprising a total score and four domain-specific factors: Pain, Cardiopulmonary, Fatigue, and Gastrointestinal. The main purpose of this quantitative study was to investigate to what extent age, sex and Self-Rated Health (SRH) together and independently explain the variance in different somatic symptoms as measured by the PHQ-15 and its domain-specific factors. Questionnaire data collected in 2010 from VEHS (Västerbotten Environmental Health Study), yielded a sample of N=3405 (age 18-79, women= 55.7%) with characteristics similar to the Swedish population was used. A multiple analysis of variance indicated that sex and SRH independently explained the variance on outcomes on PHQ-15 Total and most domain-specific factors, except sex was not linked to Cardiopulmonary symptoms. SRH has a larger effect on the variance compared to sex. Women experienced more somatic symptoms compared to men, and those with poor SRH experienced more somatic symptoms compared to those with good SRH. Age was not associated with PHQ-15 nor its domain-specific factors and no interaction between sex and SRH was found. Our study provides a novel and deeper understanding of the relationship between sex, SRH and PHQ-15 and its domain-specific factors. Future research may investigate the domain-specific factors of PHQ-15 and their relationship to other factors, e.g. socioeconomic and mental health status.