Longitudinal observational study conducted from December 2016 to October 2017 in a private bariatric surgery clinic in the central region of the state of Rio Grande do Sul, Brazil.
The convenience sample consisted of 104 obese individuals eligible to undergo gastric bypass bariatric surgery (through videolaparoscopy) after clinical evaluation. The loss to follow-up was 34 patients after 6 months of study.
Inclusion criteria were: age above 18 years of age, BMI of 35 kg/m² and presence of associated comorbidities, or BMI > 40 Kg/m² regardless of the presence of comorbidities. Exclusion criteria were: patients with some cognitive limitation, since the questionnaire is self-administered and may compromise responses.
Data collection was performed after consultations with a multidisciplinary team in the pre- and postoperative periods at 1, 2 and 6 months, and the research is in continuity.
The quality of life evaluation was performed through the completion of the SF-36 (The Medical Outcomes Study Short Form Health Survey), translated and validated in Brazil by Ciconelli et al., 1999 .
The anthropometric data of the patients (weight, height, BMI), were obtained by analyzing their medical records, as well as the characteristics of the sample (age, gender and physical activity self-reported, and comorbidities through exams and clinical evaluation).
BMI was assessed according to the World Health Organization International Classification of obesity, which divides adiposity into grades or classes . Overweight was calculated preoperatively, using the following formula: current weight - ideal weight (BMI 25 kg/m²) = overweight.
The percentage of excess weight loss (%EWL) was calculated using the formula: preoperative weight - current weight x 100 / preoperative weight - ideal weight.
The research was approved by the research ethics committee of the Universidad Franciscana, nº 1.830.670. All individuals invited to participate signed the Free and Informed Consent Term after receiving clarification on the research.
The SF-36 quality of life assessment instrument was created with the purpose of being a generic health assessment questionnaire, easy to administer and understand. It is a multidimensional questionnaire consisting of 36 items, distributed in 8 domains: functional capacity (10 items), physical aspects (4 items), pain (2 items), general health status (5 items), vitality (4 items), social aspects (2 items), emotional aspects (3 items), mental health (5 items) and a comparative evaluation question between the current health conditions and that of a year ago. It assesses both the negative aspects of health (illness or disease) and the positive aspects (well-being) .
The score is calculated and the final score is obtained through a raw scale (0-100), the closer to 100, the better the quality of life perception. The scores of the 8 domains are calculated individually and then combined to calculate 2 components: physical health component (PHC), composed of functional capacity, physical aspects, pain and general health; and mental health component (MHC) that includes vitality, social aspects, emotional aspects and mental health.
Data were analyzed using version 23 of the SPSS program. To verify the normality of data distribution, the Kolmogorov-Smirnov test was used. The correlation between the variables body mass index, domains and components of physical and mental health of the SF-36 instrument, in the pre (time 0) and postoperative periods at 1, 2 and 6 months (times 1, 2 and 6), was evaluated through Spearman's Rho (not normality) and Pearson's r (normality) and the values of the correlation coefficient were classified according to Hopkins (2000) , where: 0.0 to 0.1 very low; 0.1 to 0.3 low; 0.3 to 0.5 moderate; 0.5 to 0.7 high; 0.7 to 0.9 very high; and 0.9 to 1.0 near perfect. In the analysis between the sexes the Mann-Whitney test was used. The Friedman 2-way ANOVA test by ranks was used to compare the means of the 8 SF-36 domains among the times.