Similar to the results obtained at the 2-year follow-up point [20
], greater improvements in both weight-specific and general HRQOL were observed at 6 years for the GB patients compared with the no GB group and Pop OB group. The improvements exhibited by the GB patients occurred with respect to all aspects of weight-specific and physical HRQOL and some aspects of mental/psychosocial HRQOL. The changes in weight-specific HRQOL were much larger (2.61 SD for the IWQOL-Lite total score) than the changes in the physical HRQOL (1.17 SD for PCS), consistent with other HRQOL research [31
]. The %EWL at 6 years, which was 56.4% for the GB group and negligible for the control groups, correlated significantly with changes in the IWQOL-Lite total score and PCS, but not the MCS. Because weight loss explained 59.0% of the variance in the IWQOL-Lite total score and 28.5% of the variance in the PCS, this suggests that factors other than weight loss might account for the HRQOL changes, such as increased attention to food intake/physical activity or improved self-efficacy (although these were not measured).
One of our research questions was whether early improvements in HRQOL obtained by the GB patients would persist over time. Although the HRQOL scores for the GB group decreased for most HRQOL subscales from 2 to 6 years, these decreases were generally small. Thus, the HRQOL was fairly stable during this period for the GB group, despite some weight regain (%EWL 69.1% at 2 yr and 56.4% at 6 yr) and some small decreases in HRQOL scores. That the HRQOL scores remained relatively high at 6 years for the GB group, especially in contrast to the control groups, is encouraging and perhaps can be used to motivate patients to continue healthy habits and weight maintenance. If these same patients considered their BMI only, they might become discouraged at the “failure” to maintain a nonobese BMI (mean adjusted BMI was 32.9 ± 7.4). Furthermore, it is worth noting that the 3 scales showing the greatest declines in the 2- to 6-year period were weight-related self-esteem, general health, and vitality, perhaps suggesting that health providers should pay particular attention to these areas of HRQOL in the long term.
Other studies examining whether the initial improvements in HRQOL are maintained at long-term follow-up have yielded conflicting results, perhaps because of the varying surgical procedures and HRQOL outcome measures used. Although the Swedish Obese Subjects study found that the pattern of change in HRQOL scores corresponded for the most part to phases of weight loss, regain, and weight stability [13
], several studies have reported stable HRQOL scores accompanying continuing long-term weight loss [14
] and another reported stable HRQOL scores accompanying weight regain [18
Our prospective study is unique in its use of 2 nonsurgically treated comparison groups and adds to the sparse data on HRQOL outcomes in prospective trials of bariatric surgery versus nonsurgically treated obese groups [1
]. Other strengths of the present study include the long-term follow-up of 6 years, the large sample size, and statistical adjustment for multiple tests. Because of the many areas of life that are considered when assessing HRQOL, most scientists and scholars agree that it is a multidimensional construct [32
], and assessment with multiple measures is generally recommended [33
]. Thus, another strength of the present study was the use of both general and weight-specific measures. Both the Swedish Obese Subjects study [1
] and the Helmiö study [16
] used both types of HRQOL measures, but others used only a single measure [14
Despite a very high response rate at 6 years, not all participants completed the 6-year HRQOL assessment, a limitation that possibly resulted in bias. However, no systematic differences were found between those who did and did not complete the HRQOL assessment at 6 years. Another limitation was the lack of diversity with respect to demographic characteristics and geographic location, which might limit the generalizability of our findings. In addition, 45 participants in the control groups ultimately underwent gastric bypass surgery, which decreased the sample size of the control groups and could have potentially diminished the differences between the GB and control groups.