Abstract
Various oral glucose-lowering agents are available in Japan. Although the objective characteristics of these drugs are well described, little is known about treatment satisfaction by patients using these agents. The aim of this study was to assess treatment satisfaction of diabetic patients visiting diabetes clinics using the Diabetes Treatment Satisfaction Questionnaire (DTSQ) and to determine the association of the DTSQ scores with various factors including oral glucose-lowering agents. The study subjects were 754 outpatients who had been treated with one or more oral glucose-lowering agents, but not insulin or glucagon-like peptide-1 receptor agonist. The collected data included the response to DTSQ as completed by the patients, various parameters pertaining diabetes treatment including adherence, motivation, life style, social support, complications and cost burden from the patients and attending physicians. The associations among satisfaction scores and various parameters were analyzed by multiple linear regression analysis. In all subjects, use of sodium-glucose cotransporter 2 inhibitor (SGLT2i) were positively, and irregular diet time were negatively associated with satisfaction scores significantly as well as some factors which had been previously reported to be associated. Subgroup analysis showed that adherence to diet and use of SGLT2i were positively in obese (body mass index ≥25 kg/m2), and HbA1c and irregular work time were negatively in non-obese (<25 kg/m2) patients associated with satisfaction scores. These results suggest that SGLT2i is really used with high satisfaction, especially by obese patients and that factors associated with treatment satisfaction might differ between obese and non-obese patients using oral glucose-lowering agents.
DIABETES MELLITUS is a chronic disease that compels patients to complete daily self-management tasks, such as diet control, exercise and medications. In most patients, such self-management is a burden and reduces their quality of life. Since the goal of treatment is to maintain quality of life as close as possible to that of healthy subjects, it is important to evaluate patient reported outcomes, in addition to the clinical outcome. Treatment satisfaction is one of the patient reported outcomes and has been often used as an indicator of quality of healthcare in diabetic patients [1].
Several studies investigated the factors associated with treatment satisfaction of patients with type 2 diabetes mellitus (T2DM). High levels of glycosylated hemoglobin (HbA1c) [1-3], body weight [2], and diabetes complications [4-6] were reported to be associated with less treatment satisfaction. Several other factors, such as visits to hospitals rather than primary health care centers [5], difficulties in attending follow-up clinic visits [4], and insulin treatment [3] also correlate with less treatment satisfaction. In the insulin-treated patients, self-monitoring of blood glucose and self-management of insulin doses are associated with higher treatment satisfaction [3]. However, treatment satisfaction of patients with T2DM on oral glucose-lowering agents (OGLAs) only has not been evaluated satisfactorily so far.
Various OGLAs, including sulfonylurea (SU), biguanide (BG), alfa-glucosidase inhibitor (αGI), thiazolidine (TZD), glinide (Gli), dipeptidyl peptidase 4 inhibitor (DPP4i) and sodium-glucose cotransporter 2 inhibitor (SGLT2i), are available in Japan. Although the objective characteristics, such as efficacy, hypoglycemic risk, adverse effects, weight gain and cost of these drugs, are well known, subjective treatment satisfaction of patients on these drugs has not been evaluated. To clarify the issue, we assessed treatment satisfaction of diabetic patients using the Diabetes Treatment Satisfaction Questionnaire (DTSQ) and analyzed the association of the scores with individual OGLAs used by the patients as well as various factors on diabetes treatment.
Methods
Subjects
We enrolled patients with T2DM who had been treated with one or more OGLAs during the past three months or longer without using insulin or glucagon-like peptide-1 receptor agonist, who attended the outpatient clinics of the following four diabetes clinics from April to September in 2016: Hayashi Clinic, Watanabe Clinic, Nakata Clinic, and Ryoya Komatsu Clinic located in the urban districts of the western area of Japan. In fact, these clinics had total 2,267 outpatients with T2DM treated with OGLAs during the period: 453 at Hayashi Clinic, 624 at Watanabe Clinic, 405 at Nakata Clinic, and 785 at Ryoya Komatsu Clinic. Among those patients, the patients satisfied with the above criteria were included and the following patients were excluded from the study, patients younger than 20 years, those who had difficulty completing questionnaires, and were judged to be inappropriate for the study by the attending physicians, and from whom consent for participation in this study could not be obtained. Thus, a total of 754 patients (142 at Hayashi Clinic, 296 at Watanabe Clinic, 205 at Nakata Clinic, and 111 at Ryoya Komatsu Clinic) participated in this study. The study protocol was approved by the Human Ethics Review Committee of our university and a signed consent form was obtained from each subject.
Questionnaires
We performed the DTSQ [7] (the Japanese version [8]) and a study-specific patient questionnaire designed to explore their treatment adherence, diabetes complications, cost burden, social support, and lifestyle (Supplement Table 1). We also collected detailed clinical data as well as prescriptions using a physician-completed form from the attending physicians (Supplement Table 2). The DTSQ covers eight items with regard to the treatment of diabetes. It measures 1) overall satisfaction, 2) perceived hyperglycemia, 3) perceived hypoglycemia, 4) convenience, 5) flexibility, 6) understanding of diabetes, 7) willingness to recommend current treatment to others, and 8) willingness to continue the current treatment. Each item is rated on a 7-point Likert scale with a score ranging from 0 (very dissatisfied or never) to 6 (very satisfied or most of the time). All scores, except items 2 and 3, are added up to produce the DTSQ total score (range 0–36), representing the treatment satisfaction level as reported by the patient. The study-specific questionnaire consisted of items related to treatment adherence, diabetes complications, motivation, cost burden, social support, and lifestyle. The physician-completed form consisted of clinical data on age, sex, anthropometric measurements, HbA1c, prescribed OGLAs, and interval between visits.
Study methods
The attending physician handed the patient the Japanese version of DTSQ and the study-specific questionnaire. At the outset, each patient was informed that the answers to the two questionnaires would not be viewed by the attending physician. The patient filled the forms, put them in the supplied envelop, and then handed it to the clinical staff in the clinic. At the same time, the physician completed the physician form on the same patient and handed it to the clinical staff in the clinic, who put the form in the same envelop, sealed it and sent it to the Department of Diabetes Care Medicine at Osaka University.
Statistical analysis
Sequential data were presented as mean ± SD, while categorical data were expressed as frequencies and percentages. The reported HbA1c (%) value represented the National Glycohemoglobin Standardization Program (NGSP). The DTSQ total scores were compared according to patient characteristics using student-t test and one-way ANOVA. The associations among DTSQ total score and various parameters were analyzed using multiple linear regression analysis with a backward variable selection similarly to the previous report [3]. Statistical analyses were performed using the statistical software ‘EZR (Easy R)’ (R × 64 3.2.2) [9]. Significance level was set at p-value <0.05.
Results
The characteristics of the study participants are listed in Tables 1 and 2. Age, sex, height, body weight, HbA1c, duration of diabetes, and visit interval were collected from the physician forms. Information on patient adherence to treatment, diabetes complications, cost burden, social support, and lifestyle were collected from the study-specific patient questionnaire. The mean age of the cohort was 65 and the mean HbA1c was 7.0%. With regard to diabetic complications, the prevalence of each complication as recognized by the patients was less than 10%. Almost all patients on OGLAs medications adhered to taking medicines (very good or good) whereas only about two-thirds and half of the patients adhered to diet therapy and exercise therapy (very good or good), respectively. The motivation for treatment was estimated as high or medium in most of the participants and low in only 1% of the participants. With regard to lifestyle, 14% and 25% of the patients reported irregularity of meal time and working time, respectively. Most of the patients visited the outpatient clinics once every 1 or 2 months. Family support was reported by 66% of the patients. Furthermore, more than half of the patients reported economic burdensome (high or medium) as a result of the diabetes.
Table 1
Characteristics of the study participants
| Age |
65 ± 11 |
| Sex (male/female) |
488/262 |
| Body mass index (kg/m2) |
24.8 ± 4.1 |
| Duration of diabetes (years) |
11.2 ± 7.6 |
| HbA1c (%) |
7.0 ± 0.6 |
Data are mean ± SD or number of patients.
Table 2
Number and percentage of patients with diabetes complications, treatment adherence, lifestyle, social support, and cost burden, obtained from the study-specific patient questionnaire
|
n (%) |
| Complications |
|
| Nephropathy (yes/no or
unknown) |
44/709 (6/94) |
| Retinopathy (yes/no or unknown) |
52/702 (7/93) |
| Neuropathy (yes/no or unknown) |
51/700 (7/93) |
| Cardiovascular diseases (yes/no or unknown) |
73/678 (10/90) |
| Diabetic foot (yes/no or unknown) |
22/729 (3/97) |
| Adherence |
|
| Adherence on diet therapy (very
good/good/not good/poor) |
42/451/228/33 (6/60/30/4) |
| Adherence on exercise therapy (very good/good/not
good/poor) |
88/325/271/68 (12/43/36/9) |
| Adherence on taking medications (very good/good/not
good/poor) |
568/180/6/0 (75/24/1/0) |
| Motivation for treatment (high/medium/low) |
656/91/5 (87/12/1) |
| Lifestyle |
|
| Regularity of diet time
(regular/almost regular/irregular) |
292/354/106 (39/47/14) |
| Regularity of working time (regular or no
work/irregular) |
567/185 (75/25) |
| Interval between visits to clinics (0.5/1/2/≥3 months) |
4/526/175/4 (1/74/24/1) |
| Social support |
|
| Family support (yes/no) |
496/256 (66/34) |
| Economics |
|
| Cost burden
(high/medium/low) |
82/361/308 (11/48/41) |
Table 3 summarizes the use of OGLAs and other prescriptions in detail, as reported in the physician form. DPP4i was used by about 70%, BG by about 60%, and SGLT2i by 12% of the patients. Once-weekly DPP4i was used only by 4 patients (data not shown). About half of the patients used anti-hypertensive and anti-hyperlipidemia medications. The dose of OGLAs and timing of taking such medications per day are listed in Table 3.
Table 3
Use of oral glucose-lowering agents (GLA), anti-hypertensive drugs, anti-hyperlipidemia drugs, and times of taking medications per day
|
n (%) |
| Sulfonylurea (yes/no) |
264/487 (35/65) |
| Biguanide (yes/no) |
450/303 (60/40) |
| Dipeptidyl peptidase 4 inhibitor (yes/no) |
527/227 (70/30) |
| Alpha-glucosidase inhibitor (yes/no) |
167/586 (22/78) |
| Thiazolidine (yes/no) |
36/715 (5/95) |
| Glinide (yes/no) |
153/600 (20/80) |
| Sodium-glucose cotransporter 2 inhibitor (yes/no) |
91/659 (12/88) |
| Anti-hypertensive drugs (yes/no) |
370/381 (49/51) |
| Anti-hyperlipidemia drugs (yes/no) |
347/405 (46/54) |
| Number of GLA tablets/day (≤3/4–6/7–9/≥10) |
392/250/95/16 (52/33/13/2) |
| Times of taking medications/day (1/2/3/≥4) |
125/277/179/173 (17/37/24/23) |
The results of DTSQ are shown in Table 4. The total score represented the sum of all scores excluding items 2 and 3. The mean DTSQ total score was 27.3. Table 5 shows the comparison of DTSQ total scores among groups divided by various clinical parameters. Among those parameters, DTSQ total scores were different significantly among groups divided by BMI, HbA1c, cardiovascular diseases, adherence to diet therapy, adherence to taking medications, motivation for treatment, diet time, work time, cost burden and number of times of taking medication per day. In addition, the scores were higher in patients with use of SGLT2i and lower in use of sulfonylurea. Furthermore, the scores of items 2 and 3 of DTSQ, which present perceived frequency of hyperglycemia and hypoglycemia, respectively, correlated significantly and negatively with DTSQ total scores similarly to the previous report [3]. Table 6 shows the results of the correlations analyzed by multiple linear regression analysis and also with a backward variable selection, among DTSQ total scores and various factors described as follows; those with significant difference in Table 5, items 2 and 3 of DTSQ, and all OGLAs. In total analysis, BMI, adherence to diet and taking medications, motivation for treatment, and use of SGLT2i were positively, and HbA1c, irregular diet time, cost burden and perceived hypoglycemia were negatively correlated with the scores significantly and independently. Furthermore, we also performed subgroup analysis after dividing the subjects into two groups; the obese group (n = 317, body mass index [BMI] ≥25 kg/m2) and non-obese group (n = 433, BMI <25 kg/m2). The use of SGLT2i also correlated significantly with DTSQ scores in the obese group, but not in the non-obese group (Table 6). In addition, adherence to diet therapy were correlated positively in the obese group, and HbA1c and irregular work time negatively in the non-obese group, respectively. Motivation for treatment were correlated positively in both of the groups.
Table 4
Individual item and total scores of the Diabetes Treatment Satisfaction Questionnaire (DTSQ)
|
mean ± SD |
| 1. overall satisfaction |
4.88 ± 1.02 |
| 2. perceived hyperglycemia |
2.36 ± 1.72 |
| 3. perceived hypoglycemia |
0.98 ± 1.44 |
| 4. convenience |
4.59 ± 1.27 |
| 5. flexibility |
4.44 ± 1.28 |
| 6. understanding of diabetes |
4.30 ± 1.15 |
| 7. willingness to recommend current treatment to others |
4.33 ± 1.51 |
| 8. willingness to continue current treatment |
4.78 ± 1.13 |
| DTSQ total score |
27.34 ± 5.47 |
Table 5
Comparison of DTSQ total scores among groups divided by various clinical parameters
|
DTSQ total score |
p value |
| Age |
|
|
| <65 years old |
27.6 ± 5.4 |
0.238 |
| ≥65 years old |
27.1 ± 5.5 |
| Sex |
|
|
| Male |
27.5 ± 5.4 |
0.305 |
| Female |
27.1 ± 5.5 |
| Body mass index |
|
|
| <25 kg/m2 |
27.0 ± 5.4 |
0.038 |
| ≥25 kg/m2 |
27.9 ± 5.5 |
| History and glycemic control |
|
|
| Duration of diabetes |
|
|
| <10 years |
27.4 ± 5.5 |
0.845 |
| ≥10 years |
27.4 ± 5.4 |
| HbA1c |
|
|
| <7 % |
28.0 ± 5.1 |
<0.001 |
| ≥7 % |
26.6 ± 5.7 |
| Complications |
|
|
| Nephropathy |
|
|
| yes |
27.7 ± 5.7 |
0.668 |
| no or unknown |
27.3 ± 5.5 |
| Retinopathy |
|
|
| yes |
26.3 ± 6.3 |
0.155 |
| no or unknown |
27.4 ± 5.4 |
| Neuropathy |
|
|
| yes |
27.3 ± 6.0 |
0.974 |
| no or unknown |
27.4 ± 5.4 |
| Cardiovascular diseases |
|
|
| yes |
26.1 ± 5.2 |
0.039 |
| no or unknown |
27.5 ± 5.5 |
| Diabetic foot |
|
|
| yes |
26.1 ± 7.5 |
0.280 |
| no or unknown |
27.4 ± 5.4 |
| Adherence |
|
|
| Adherence to diet therapy |
|
|
| very good |
28.6 ± 5.8 |
<0.001 |
| good |
27.9 ± 5.2 |
| not good |
26.4 ± 5.3 |
| poor |
25.0 ± 7.2 |
Table 5
continued
|
DTSQ total score |
p value |
| Adherence to exercise therapy |
|
|
| very good |
28.5 ± 5.2 |
0.117 |
| good |
27.4 ± 5.2 |
| not good |
26.9 ± 5.6 |
| poor |
27.0 ± 6.5 |
| Adherence to taking
medications |
|
|
| very good |
27.7 ± 5.4 |
<0.001 |
| good |
26.6 ± 5.3 |
| not good |
19.5 ± 11.7 |
| poor |
none |
|
| Motivation for treatment |
|
|
| high |
27.8 ± 5.3 |
<0.001 |
| medium |
24.4 ± 5.7 |
| low |
28.4 ± 6.7 |
| Lifestyle |
|
|
| Diet time |
|
|
| regular |
28.1 ± 5.3 |
0.002 |
| almost regular |
27.1 ± 5.3 |
| irregular |
26.1 ± 5.9 |
| Work time |
|
|
| regular or no work |
27.7 ± 5.4 |
0.013 |
| irregular |
26.5 ± 5.5 |
| Interval between visits to the
outpatient clinic |
|
|
| 0.5 month |
25.8 ± 6.4 |
0.731 |
| 1 month |
27.4 ± 5.5 |
| 2 months |
27.7 ± 5.4 |
| >3 months |
29.3 ± 4.9 |
| Social support |
|
|
| Family support |
|
|
| yes |
27.6 ± 5.2 |
0.068 |
| no |
26.9 ± 5.8 |
| Economics |
|
|
| Cost burden |
|
|
| high |
27.2 ± 6.6 |
0.012 |
| medium |
26.8 ± 5.2 |
| low |
28.1 ± 5.3 |
| Use of oral glucose lowering agents |
|
|
| Sulfonylurea |
|
|
| yes |
26.6 ± 5.8 |
0.009 |
| no |
27.7 ± 5.2 |
Table 5
continued
|
DTSQ total score |
p value |
| Biguanide |
|
|
| yes |
27.2 ± 5.5 |
0.462 |
| no |
27.5 ± 5.5 |
| DPP4i |
|
|
| yes |
27.3 ± 5.4 |
0.979 |
| no |
27.4 ± 5.6 |
| α-glucosidase inhibitor |
|
|
| yes |
27.1 ± 5.3 |
0.462 |
| no |
27.4 ± 5.5 |
| Thiazolidine |
|
|
| yes |
26.3 ± 6.1 |
0.208 |
| no |
27.4 ± 5.4 |
| Glinide |
|
|
| yes |
27.9 ± 5.1 |
0.181 |
| no |
27.2 ± 5.5 |
| SGLT2i |
|
|
| yes |
28.6 ± 4.7 |
0.017 |
| no |
27.2 ± 5.6 |
| Use of anti-hypertensive drugs |
|
|
| yes |
27.1 ± 5.5 |
0.215 |
| no |
27.6 ± 5.4 |
| Use of anti-hyperlipidemia drugs |
|
|
| yes |
27.1 ± 5.5 |
0.164 |
| no |
27.6 ± 5.4 |
| Number of oral glucose-lowering agents per day |
|
|
| ≤3 |
27.7 ± 5.4 |
0.095 |
| 4–6 |
27.0 ± 5.4 |
| 7–9 |
27.1 ± 5.6 |
| ≥10 |
24.8 ± 6.4 |
| Number of times of taking medications per day |
|
|
| 1 |
27.7 ± 5.3 |
0.019 |
| 2 |
26.9 ± 5.7 |
| 3 |
28.3 ± 4.9 |
| ≥4 |
26.8 ± 5.6 |
DPP4i, Dipeptidyl peptidase 4 inhibitor; SGLT2i, Sodium-glucose cotransporter 2 inhibitor
Table 6
Correlates of DTSQ total scores and various factors described below: results of multiple linear regression analysis
|
All subjects |
Obese subjects |
Non-obese subjects |
|
B |
p value |
B |
p value |
B |
p value |
| BMI (≥25 kg/m2) |
1.211 |
0.004 |
— |
— |
— |
— |
| HbA1c (≥7%) |
–0.975 |
0.023 |
–0.954 |
0.142 |
–0.980 |
0.087 |
| Cardiovascular disease |
–0.812 |
0.221 |
–0.673 |
0.533 |
–0.679 |
0.428 |
| Adherence to diet therapy |
0.800 |
0.013 |
1.633 |
0.001 |
0.102 |
0.817 |
| Adherence to taking medications |
1.022 |
0.022 |
1.188 |
0.072 |
0.772 |
0.214 |
| Motivation for treatment |
1.918 |
0.001 |
1.921 |
0.020 |
1.759 |
0.022 |
| Irregular diet time |
–0.638 |
0.053 |
–0.408 |
0.428 |
–0.802 |
0.072 |
| Irregular work time |
–0.396 |
0.424 |
0.356 |
0.631 |
–1.336 |
0.051 |
| Cost burden |
–0.589 |
0.049 |
–0.412 |
0.383 |
–0.621 |
0.117 |
| Sulfonylurea |
–0.658 |
0.145 |
–0.179 |
0.780 |
–0.629 |
0.302 |
| Biguanide |
0.152 |
0.737 |
0.179 |
0.817 |
0.149 |
0.794 |
| DPP4i |
0.549 |
0.207 |
1.097 |
0.102 |
0.274 |
0.648 |
| α-glucosidase inhibitor |
–0.345 |
0.567 |
–0.004 |
0.997 |
–0.506 |
0.500 |
| Thiazolidine |
–0.570 |
0.551 |
–0.742 |
0.505 |
–1.182 |
0.586 |
| Glinide |
0.275 |
0.659 |
–0.382 |
0.712 |
0.787 |
0.333 |
| SGLT2i |
1.544 |
0.013 |
2.287 |
0.004 |
0.240 |
0.823 |
| perceived hyperglycemia |
–0.142 |
0.255 |
–0.161 |
0.381 |
–0.139 |
0.422 |
| perceived hypoglycemia |
–0.214 |
0.130 |
–0.279 |
0.195 |
–0.120 |
0.530 |
| Stepwise backward selection procedure |
|
|
|
|
|
|
| BMI (≥25 kg/m2) |
1.219 |
0.003 |
|
|
|
|
| HbA1c (≥7%) |
–1.272 |
0.001 |
|
|
–1.568 |
0.002 |
| Adherence to diet therapy |
0.877 |
0.005 |
1.999 |
<0.001 |
|
|
| Adherence to taking medications |
0.929 |
0.034 |
|
|
|
|
| Motivation for treatment |
1.948 |
<0.001 |
2.421 |
0.002 |
2.391 |
0.001 |
| Irregular diet time |
–0.750 |
0.013 |
|
|
|
|
| Irregular work time |
|
|
|
|
–1.954 |
0.002 |
| Cost burden |
–0.576 |
0.049 |
|
|
|
|
| SGLT2i |
1.747 |
0.004 |
1.968 |
0.009 |
|
|
| perceived hypoglycemia |
–0.269 |
0.045 |
|
|
|
|
Discussion
Several studies have investigated the factors associated with diabetes treatment satisfaction, and insulin treatment proved to be inversely related with treatment satisfaction [2, 3]. On the other hand, there is controversy on whether treatment of T2DM with OGLAs correlates positively or negatively with treatment satisfaction [4, 5] compared with diet only therapy. The inconsistent results may be at least in part due to differences in OGLAs. Our study is unique since it was designed to clarify the association among various OGLAs (e.g., SU, BG, αGI, TZD, Gli, DPP4i and SGLT2i) and treatment satisfaction in diabetic patients. The main finding of the study was that the use of SGLT2i, but not other OGLAs, was associated with significant treatment satisfaction independent of HbA1c and perceived frequency of hyperglycemia and hypoglycemia. Furthermore, in subgroup analysis, the same association was found in obese subjects, but not in non-obese subjects. Although no causality can be determined because this is an observational study, we conclude that SGLT2i can be used with high satisfaction, especially in obese patients, in real world. While we do not have an explanation for the above association, it is important to note that it was independent of glycemic control. Gerlanc et al. [10] recently reported that patients treated with canagliflozin (SGLT2i) had better DTSQ scores in those who lost weight compared to those who did not. Although we have no data about weight change in this study, we speculate that the high satisfaction rate with the use of SGLT2i was probably based on weight loss. Then, why was the association found only in obese, not in non-obese, in our subgroup analysis? We previously reported that obese and non-obese patients with type 2 diabetes had different emotional distress in diabetes therapy and that obese patients had more “feelings of deprivation regarding food and meals” than non-obese patients [11], probably because their physicians usually advise them to lose weight more strongly. Thus, they are more eager to lose weight than non-obese patients. Although SGLT2i might have induced weight loss in all patients, obese patients may feel more released from distress about weight or diet and feel higher satisfaction when they lose weight.
In this study, we collected clinical data on treatment of T2DM, including glycemic control, complications, adherence, motivation, life style, social support, and cost burden, in addition to prescriptions, and analyzed the correlations of these parameters with the DTSQ total scores. Similar to the results of previous studies [2-4], HbA1c, adherence to diet therapy and taking medications, cost burden, and perceived frequency of hypoglycemia were correlated with satisfaction in multiple linear regression analysis with a backward variable selection. In addition, we also found that irregularity of meal time was correlated negatively with satisfaction. Furthermore, in subgroup analysis, we found the correlation of irregularity of work time with satisfaction negatively in non-obese subjects. To our knowledge, this is the first study that reports the correlation of irregularity of meal time or work time with treatment satisfaction. These results suggest that patients should be advised to modify their lifestyles with regard to diet therapy in obese and work time in non-obese subjects.
The treatment satisfaction scores were lower in patients with use of SU than in those without it. However, the negative association between them was not observed in multiple regression analysis. HbA1c levels were significantly higher in patients using SU than those not using them (data not shown). In addition, no such association was observed even after adjustment for HbA1c only (data not shown). Thus, the negative association between SU and treatment satisfaction is probably mainly due to the differences in HbA1c among patients treated with and without SU.
Our study has certain limitations. First, it is a cross-sectional observation study, thus no causality can be determined. Ishii et al. [12] have reported recently a randomized controlled study to identify the best OGLA associated with treatment satisfaction and concluded that DPP-4i was the most preferable option for initial treatment among SU, BG, αGI, and DPP4i. However, the use of SGLT2i was not evaluated in their study. Further randomized controlled studies that include SGLT2i are needed to confirm our findings of the important role of SGLT2i in treatment satisfaction, in comparison with other OGLAs. Second, we enrolled outpatients who had been treated with OGLAs for the past 3 months or longer, but we did not collect information about the exact period of use of each OGLA. Since the effects of OGLAs usually change during long-term use, treatment satisfaction might also be affected by the duration of their use. Further longitudinal observation study is needed to clarify this issue. Third, the participants enrolled in this study visited urban diabetes clinics and diabetes consulting specialists, and thus they are expected to be well educated about diabetes treatment. It is possible that treatment satisfaction reported by this population is affected by the level of education and the clinical experience of the attending physician. The glycemic control of these patients was relatively well and the frequency of complications was relatively low. In addition, the mean age of the participants was 65, relatively old. It is, therefore, possible that the results of the study may not be applicable to younger patients, those patients with less education, poor glycemic control or those with severe complications. However, we think the association between use of SGLT2i and satisfaction would be found even in younger patients and those with poorer glycemic control because the effects of SGLT2i were also found in those patients [13]. Anyway, another study of a heterogeneous group of patients with regard to background parameters and clinical complications is needed to clarify this issue.
In conclusion, SGLT2i was correlated with a significantly high satisfaction score independently from various parameters, especially in obese patients. Subgroup analysis showed that adherence to diet therapy were positively in obese and irregular work time were negatively in non-obese (<25 kg/m2) patients associated with satisfaction scores. These results suggest that SGLT2i is really used with high satisfaction, especially by obese patients and that factors associated with treatment satisfaction might differ between obese and non-obese patients using oral glucose-lowering agents.
Acknowledgments
The authors thank Prof. Shintani and Prof. Ishihara for the helpful advice on statistical analysis. We also thank Prof. Ishii for allowing us to use the Japanese version of DTSQ. We also thank Word-Medex Pty Ltd and Ms. Isabel Moore for help in the English language editing of this manuscript. This work was supported in part by JSPS KAKENHI (grant #JP16K09237).
Disclosure
N.W. performed clinical tests requested by Astellas Pharma, Inc. and Novo Nordisk Pharma Ltd. R.K. performed clinical tests requested by Novo Nordisk Pharma Ltd. and Sanofi. M.T. is a staff member of the endowed chair (Department of Diabetes Care Medicine) established by funds from Novo Nordisk Pharma Ltd.; Mitsubishi Tanabe Pharma Co.; AstraZeneca; Nippon Boehringer Ingelheim Co.; Taisho Toyama Pharmaceutical Co.; Ono Pharmaceutical Co.; MSD Co. A.I. has received lecture fees from Eli Lilly Japan and has received research funds from Novo Nordisk Pharma Ltd.; Eli Lilly Japan; Takeda Pharmaceutical Co. H.I. is a staff member of the endowed chair (Department of Diabetes Care Medicine) established by funds from Novo Nordisk Pharma Ltd.; Mitsubishi Tanabe Pharma Co.; AstraZeneca; Nippon Boehringer Ingelheim Co.; Taisho Toyama Pharmaceutical Co.; Ono Pharmaceutical Co.; MSD Co. I.S. has received lecture fees from Astellas Pharma, Inc.; AstraZeneca; Merck Sharp and Dohme K.K.; Ono Pharmaceutical Co.; Kyowa Hakko Kirin Co. Ltd.; Kowa Pharmaceutical Co. Ltd.; Sanofi; Sanwa Kagaku Kenkyusho Co.; Daiichi Sankyo Co.; Takeda Pharmaceutical Co.; Mitsubishi Tanabe Pharma Co.; Teijin Pharma Ltd.; Eli Lilly Japan; Nippon Boehringer Ingelheim Co.; Novartis Pharmaceuticals Corp.; Novo Nordisk Pharma Ltd.; Bayer Yakuhin Ltd.; Pfizer Japan, Inc.; Bristol-Myers Squibb; Mochida Pharmaceutical Co.; Shionogi & Co. Ltd.; Taisho Toyama Pharmaceutical Co.; and Shionogi & Co. Ltd. and has received research funds from Astellas Pharma, Inc.; AstraZeneca; Eisai Co.; Merck Sharp and Dohme K.K.; Otsuka Pharmaceutical Co.; Ono Pharmaceutical Co.; Kaken Pharmaceutical Co.; Kissei Pharmaceutical Co.; Kyowa Hakko Kirin Co. Ltd.; Sanofi; Shionogi & Co. Ltd.; Daiichi Sankyo Co.; Sumitomo Dainippon Pharma Co.; Takeda Pharmaceutical Co.; Mitsubishi Tanabe Pharma Co.; Teijin Pharma Ltd.; Nippon Boehringer Ingelheim Co.; Novartis Pharmaceuticals Corp.; Novo Nordisk Pharma Ltd.; Pfizer Japan, Inc.; Bristol-Myers Squibb; Mochida Pharmaceutical Co.; Eli Lilly Japan; Kowa Pharmaceutical Co. Ltd.; and Taisho Toyama Pharmaceutical Co.
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