Measures

The questionnaire was divided into 3 main sections: demographic characteristics, symptoms, and severity of long COVID, and HRQoL. Demographic characteristics included age, sex, place of residence, educational level, annual household income, marital status, health insurance, smoking, drinking, physical exercise, and chronic diseases.

Following the National Institutes of Health report ¹⁶ and some relevant studies^17,18 on long COVID, the symptoms of long COVID that we listed in the questionnaire were fatigue, weakness, cough, memory loss, poor concentration, phlegm in the throat, shortness of breath/difficulty breathing, irregular menstruation, hair loss, drowsiness, chest pain/tightness, sleep disorders, headache, loss of taste or distorted sense of taste, loss of smell or distorted sense of smell, loss of appetite, runny/stuffy nose, myalgia, palpitations, diarrhea, tinnitus, nausea and vomiting, and night sweats. The severity of long COVID was measured as slight, mild, moderate, severe, or very severe.

The presence of chronic diseases and the severity of long-COVID symptoms were obtained by self-report. To ensure the credibility of the questionnaire, the investigators were trained postgraduates at medical colleges. At the time of the survey, the investigators conducted detailed counseling on chronic diseases, long-COVID symptoms and their severity to improve the accuracy of the respondents’ answers.

HRQoL was assessed using the EQ-5D-5L. ¹⁹ The EQ-5D-5L was developed by the EuroQol Group and is considered one of the best tools for measuring HRQoL. The EQ-5D-5L descriptive system comprises five dimensions—mobility, self-care, usual activities, pain/discomfort, and anxiety/depression—each of which has 5 levels (no problem, slight problem, moderate problem, severe problem, and unable to do). The Chinese version ²⁰ of the EQ-5D-5L has been validated with satisfactory reliability and validity. The EQ-5D-5L has a corresponding Chinese utility point system that converts EQ-5D-5L values to health utility values. ²¹