Objective: To examine with psychometric analysis techniques the potential for constructing valid composite variables of "The Göteborg Quality of Life Instruments".
Design: Prospective population study of women in 1974-75 and in 1980-81.
Setting: City of Göteborg, Sweden.
Participants: Representative samples of the general population of women in five age strata between 44 and 66 years of age in 1974-75, followed 1980-81 including new cohorts of women aged 26 and 38. 1302 women were examined in 1974-75 and 1408 in 1980-81.
Main outcome measure: "The Göteborg Quality of Life instrument", constructed in the early 1970s to measure symptoms and well-being in a population study of men.
Results: Four multi-item scales were identified with satisfactory reliability and validity, i.e., they met defined criteria of multi-item scales and benefit from higher reliability than single questions. The psychological symptom scale comprised all ten questions intended to reflect depression and tension, while the physical symptom scale included all six pain questions, the general symptoms dizziness, breathlessness, and nausea, and general fatigue that belonged to both symptom scales. The social well-being scale comprises all well-being questions believed to reflect the broad concept of life satisfaction. The physical-mental wellbeing scale reflected satisfaction with both general and mental health. Several symptom and well-being questions were clearly outside the main clusters and should be treated as single items.
Conclusions: Use of a few, distinct scales instead of a number of single questions should increase statistical power because the number of comparisons is greatly reduced and problems of chance findings are thus minimized.