Safety and effectiveness of metabolic surgery in older Japanese patients

Abstract

Aim

According to the current guidelines in Japan, the upper age limit for bariatric and metabolic surgery is 65 y. This study aimed to examine the appropriateness of this upper age limit.

Methods

Using the database maintained by the Japanese Society for Treatment of Obesity, we conducted an analysis of patients in two age groups: those aged <65 y and those aged ≥65 y. Our analysis focused on postoperative weight loss, improvement in comorbidities, and frequency of perioperative complications.

Results

A total of 2885 patients aged <65 y (mean, 43.9 ± 9.5 y) with a preoperative body mass index of 42.4 ± 8.1 kg/m², while 56 aged ≥65 y (mean, 67.3 ± 3.2 y; maximum, 78 y) with a preoperative body mass index of 40.5 ± 6.6 kg/m². Patients aged ≥65 y had a higher rate of dyslipidemia and hypertension. The rates of reoperation, surgical complications, and postoperative complications did not differ between the age groups. Both groups achieved significant weight loss postoperatively, and no differences in the improvement of comorbidities were noted. After adjusting the covariate balance via propensity score matching, no age‐related differences in perioperative and postoperative complications were observed.

Conclusion

Metabolic surgery is safe and effective for older patients with clinically severe obesity. Weight loss was less in patients aged ≥65 y, but the percentage of total weight loss did not differ between the groups.

1. INTRODUCTION

Patients with a body mass index (BMI) ≥30 kg/m² account for 3.9% of 60–69‐y‐old individuals (male, 3.1%; female, 4.6%) and 2.7% of ≥70‐y‐old individuals (male, 2.3%; female, 3.6%) in Japan. ¹ Obesity leads to several health problems, including diabetes, hypertension, and dyslipidemia, and significantly reduces an individual's activities of daily living and quality of life. The quality of life of these patients is further affected by osteoarthritis and chronic lower back pain. While weight loss and obesity treatment may benefit older patients, their susceptibility to sarcopenia and frailty is concerning.

The initial treatment of obesity involves diet and exercise therapy. Cognitive‐behavioral therapy and recommended diet therapies aim to prevent skeletal muscle mass loss while balancing the reduction of calories. Liraglutide and semaglutide, drugs used to treat diabetes, have been reported to have cardioprotective and weight‐loss effects in large‐scale clinical trials of older patients with diabetes. ² , ³ In general, metabolic surgery is considered for patients with clinically severe obesity and obesity with associated comorbidities who fail to lose weight despite intensive medical treatment for at least 6 mo. Currently, the guidelines prepared by the Japanese Society for Treatment of Obesity (2013 edition) indicate surgical treatment for primary obesity in patients aged 18–65 y. ⁴ In contrast, the Guidelines for Obesity Treatment for the Elderly 2018 prepared by the Japan Geriatrics Society state that the decline in activities of daily living (ADL), diabetes, blood pressure, and dyslipidemia can be improved by correcting the body weight and BMI via bariatric surgery in patients up to 70 y of age. ⁵ These guidelines have identified an upper age limit primarily based on the results of clinical trials conducted in countries other than Japan, and they are not necessarily consistent with the large, healthy, aging population in Japan. Evidence specific to the Japanese population is needed to evaluate the age limit for metabolic surgery for older Japanese patients. Therefore, this study aimed to examine the significance of age for metabolic surgery outcomes based on the clinical data of Japanese patients.

2. PATIENTS AND METHODS

2.1. Patients

Patients who were registered in the database of the Japanese Society for Treatment of Obesity as of November 2021 were divided into two groups based on their age (<65 y or ≥65 y). The perioperative safety, improvement rate of comorbidities, postoperative complications, and weight loss of these two groups were compared. The improvements of comorbidities, including diabetes, hypertension, and dyslipidemia, were evaluated postoperatively by each facility using their own criteria. Patients with missing or unclear data were excluded from the study.

2.2. Database

The database maintained by the Japanese Society for the Treatment of Obesity (JSTO) aims to guarantee the safety and efficacy to promote the increased use of bariatric surgery. The database committee and board of directors determined the input and analysis items when it was launched, and its results have since been shared with the Board of Directors, Board of Trustees, and Surgery Subcommittee through an annual report released at each conference.

The following are the characteristic features of this database:

1. The database emphasizes easy input of search terms, in contrast to registries in Europe and the United States, with complicated input methods and a wide variety of input items that could not be used as models for the JSTO database.

2. An ID and password are issued to member facilities when they join the JSTO and they register. All facilities that were already members at the time when the database was launched were retroactively registered. Subsequently, new registrations were listed intermittently or at the end of the fiscal year.

3. In most cases of registered facilities, the postoperative follow‐up period was 1 year, at maximum.

4. Therapeutic effect was determined according to weight loss and improvement in comorbidities at the time of registration, and the specific criteria were left up to each facility to simplify the process.

5. Surgeon and facility criteria were implemented as ethical guidelines according to the conditions set for health insurance medical service fees or clinical research (treatment not covered by the health insurance system).

The JSTO database includes sex, date of birth, height, body weight, BMI, comorbidities (including diabetes, hypertension, dyslipidemia, venous thrombosis, sleep apnea syndrome, and other complications), medical treatment efficacy rate, abdominal fat area (%), the presence or absence of Heliobacter pylori, date of surgery, surgical technique, laparoscopy, conversion to open surgery, reoperation, surgical complications, surgical complications (other entries), postoperative complications, postoperative complications (by site), postoperative complications (other entries), duration of postoperative hospital stay, follow‐up time after operation, weight loss (kg), diabetes improvement, hypertension improvement, and dyslipidemia improvement for each registered patient.

2.3. The propensity score matching

We performed propensity score matching to justify the imbalance of covariates between groups. The propensity score of each subject was calculated by a multivariate logistic regression model using a history of diabetes and preoperative BMI as covariates. We performed one‐to‐one nearest neighbor matching with a caliper of 0.2 using the propensity score.

After matching, a standardized difference of the covariates between groups was calculated to check the balance, and t‐tests were conducted to compare hypertension, dyslipidemia, venous thrombosis, open conversion, repeat surgery, intraoperative complications, and postoperative complications between groups.

2.4. Statistical analyses

The duration of postoperative hospital stays, follow‐up time after operation, weight loss, postoperative weight, postoperative BMI, % excess body mass index loss (EBMIL), % total weight loss (TWL), and % excess weight loss (EWL) expressed using summary statistics (mean and standard deviation, median and range, or number of patients).

The postoperative improvements in comorbidities, including diabetes and hypertension, and the rates of venous thrombosis, conversion to open surgery, reoperation, surgical complications, and postoperative complications are presented as ratios and 95% confidence intervals (CIs).

Adjusted odds ratios (aORs) of the incidences of postoperative improvements in hypertension and dyslipidemia, venous thrombosis, conversion to open surgery, reoperation, surgical complications, and postoperative complications between the age groups were calculated using multivariate logistic regression. The multivariate logistic regression included two covariates. The first covariate was the presence or absence of diabetes, and the second was preoperative BMI, which was included as a continuous covariate.

To calculate the aOR of the incidences of postoperative improvements in diabetes, we included the preoperative BMI as a continuous covariate.

Statistical analysis was performed using SAS v. 9.4 (SAS Institute, Cary, NC, USA), and statistical significance was set at P < 0.05.

3. RESULTS

Of the 3643 patients registered in the database of the JSTO, 2941 were included in this study (Figure 1) from 19 facilities. In total, 2885 and 56 patients were aged <65 (mean, 43.9 ± 9.5) y and ≥65 (mean, 67.3 ± 3.2; maximum, 78) y, respectively. Most of the patients aged ≥65 y were women (73.2%, P = 0.0138), and the preoperative BMI was similar between the groups (age <65 y, 42.4 ± 8.1 kg/m²; age ≥65 y, 40.5 ± 6.6 kg/m²; P = 0.0933). Figure S1 shows the distribution of patients in each age group.

FIGURE 1.

Analysis of the database of the Japanese Society for Treatment of Obesity

The rates of hypertension (62.5% vs 80.4%. P = 0.0041) and dyslipidemia (65.7% vs 82.1%, P = 0.0067) were higher in the group aged ≥65 y, although the rate of diabetes did not differ between the groups (56.4% vs 67.9%, P = 0.0829, Table 1). Sleeve gastrectomy was used in 85% and 93% of patients aged <65 and ≥65 y, respectively. The two age groups had similar follow‐up times (age <65 y, 288 ± 262.7 d; age ≥65 y, 338.6 ± 318.0 d; P = 0.61), rates of reoperation (age <65 y, 1.6%; age ≥65 y, 0%; P = 0.18), surgical complications (age <65 y, 0.9%; age ≥65 y, 0%; P = 0.31), and postoperative complications (age <65 y, 6.6%; age ≥65 y, 5.4%, P = 0.70, Table 2). Older individuals had a longer postoperative hospital stay when comparing the mean value of postoperative hospital stay. However, when comparing the median value, there was no difference based on age. This result may have been influenced by the data of patients who had extremely long hospital stays, although the reason for their extended stays is unknown. Moreover, data regarding admission to intensive care units were not available.

TABLE 1.

Preoperative patient characteristics

	<65 y (n = 2885)	≥65 y (n = 56)	P‐value
Sex, male	1252 (43.4)	15 (26.8)	0.0138
Height (cm)	164.7 ± 9.1	156.8 ± 7.6	<0.01
Body weight (kg)	115.4 ± 25.9	98.8 ± 17.1	<0.01
BMI (kg/m2)	42.4 ± 8.1	40.5 ± 6.6	0.093
Diabetes	1628 (56.4)	38 (67.9)	0.083
Hypertension	1804 (62.5)	45 (80.4)	0.004
Dyslipidemia	1896 (65.7)	46 (82.1)	0.007
Venous thrombosis	51 (1.8)	0	0.16
Sleep apnea syndrome	1928 (66.8)	40 (71.4)	0.60
Medical treatment efficacy rate	440 (15.3)	6 (10.7)	0.95

Note: Data are provided as number (percentage) or mean ± standard deviation.

Abbreviation: BMI, body mass index.

TABLE 2.

Postoperative patient characteristics

	<65 y (n = 2885)	≥65 y (n = 56)	P‐value
Follow‐up time after operation (d)	288.0 ± 262.7	338.6 ± 318.0	0.61
Duration of postoperative hospital stay (d)	7.2 ± 27.1	11.1 ± 32.0	0.047
Postoperative weight loss (kg)	27.0 ± 15.7	20.3 ± 8.0	0.001
Postoperative BMI (kg/m2)	32.5 ± 7.0	31.9 ± 5.8	0.713
%EBMIL	61.8 ± 36.5	61.7 ± 29.1.	0.89
%TWL	22.9 ± 10.9	20.6 ± 7.4	0.12
%EWL	61.8 ± 36.6	61.3 ± 28.9	0.80
Postoperative improvement in diabetes	1439 / 1628 (88.4)	30 / 38 (78.9)	0.10
Postoperative improvement in hypertension	1374 / 1804 (76.2)	33/45 (73.3)	0.66
Postoperative improvement in dyslipidemia	1420 / 1896 (74.9)	35 / 46 (76.1)	0.92
Conversion to open surgery	33 (1.1)	0	0.26
Reoperation	46 (1.6)	0	0.18
Surgical complications	27 (0.94)	0	0.31
Postoperative complications	191 (6.6)	3 (5.4)	0.70

Note: Data are presented as number (percentage) or mean ± standard deviation.

Abbreviations: BMI, body mass index; %EBMIL, excess BMI loss [(preoperation BMI − postoperation BMI) / (preoperation BMI − 25) × 100]; %TWL, total body weight loss (prebody weight – postoperation body weight) / (prebody weight × 100); %EWL, excess weight loss [(prebody weight – postoperation body weight) / (postoperation body weight‐ideal body weight) × 100].

The %EBMIL, %TWL, and %EWL did not differ significantly between the groups (Table 2). We also performed the analysis for patients who underwent sleeve gastrectomy only and found similar results, as shown in Tables S1 and S2.

It should be noted that there was no rule regarding the timing of postoperative body weight evaluation in the database. However, 73.5% of patients underwent postoperative body weight assessment during follow‐up. This timing was 288.0 ± 262.7 d in young participants and 338.6 ± 318.0 d in older individuals. There were no differences between these patients, as shown in Table 2.

Based on the multivariate logistic regression analysis, the postoperative improvements in diabetes, hypertension and dyslipidemia, venous thrombosis, conversion to open surgery, surgical complications, and postoperative complications did not differ significantly between the groups (Table S3).

After propensity score matching, no differences in postoperative complications (Table 3) and in weight loss, postoperative weight, postoperative BMI, %EBMIL, %TWL, or %EWL were detected (Table S4). As no patients aged ≥65 y experienced venous thrombosis, conversion to open surgery, reoperation, or surgical complications, these clinical variables were not analyzed.

TABLE 3.

Propensity score matching analysis

Postoperative complications
	N	Mean	SD	SE	Minimum	Maximum
<65 y old	56	0.0714	0.2599	0.0347	0	1
65 y or older	56	0.0536	0.2272	0.0304	0	1
Difference (1, 2)		0.0179	0.2441	0.0461

	Mean	95% CL Mean		SD	95% CL SD
<65 y old	0.0714	0.0018	0.141	0.2599	0.2191	0.3194
65 y or older	0.0536	−0.0073	0.1144	0.2272	0.1916	0.2793
Difference (1, 2)	0.0179	−0.0736	0.1093	0.2441	0.2157	0.2812

Method	DF	t value	Pr > |t|
Pooled	110	0.39	0.6994

Abbreviations: CL, confidence limits; SD, standard deviation; SE, standard error.

4. DISCUSSION

Based on our results, metabolic surgery is safe for older patients when performed by experienced surgeons certified by the Japanese Society for Treatment of Obesity. Moreover, the same criteria used for younger patients should be used to determine the eligibility of older patients for bariatric surgery, especially if the patient is likely to experience health benefits in their remaining life expectancy.

The evidence supporting the safety of metabolic surgery for older patients is contradictory, and the safety may be associated with various factors. In 2005, Flum et al ⁶ retrospectively analyzed the data of 16 155 patients (including 1517 patients aged >65 y) who had undergone metabolic surgery and reported that the 30‐d, 90‐d, and 1‐year postoperative mortality rates were significantly higher among older patients. Flum et al ⁶ also reported that male sex and the number of annual operations were associated with higher postoperative mortality. This study was used to establish the age limit of 65 y currently stipulated in the Guidelines for Safe and Outstanding Surgical Treatment for Morbid Obesity in Japan published in 2013. ⁴ This age limit seems valid when performing surgery for benign diseases, such as clinically severe obesity and obesity with comorbidities, while considering safety.

However, a 2011 study by Dorman et al ⁷ analyzed the data of 48 378 patients (including 1994 patients aged >65 y) and reported no differences in the prevalence of complications and mortality of younger and older patients who underwent metabolic surgery. In 2019, Nevo et al ⁸ compared the outcomes of patients aged <65 y (n = 65) and those aged >65 y (n = 66) who underwent laparoscopic sleeve gastrectomy at their facility and found that older patients had a lower %EBMIL, improved postoperative obesity‐related health disorders, and similar complication rates to younger patients. Pechman et al ⁹ compared the postoperative mortality and complication rates in 1498 patients aged >70 y registered in the American College of Surgeons‐National Surgical Quality Improvement Project database who underwent metabolic surgery from 2005 to 2016 (LSG, 50.1%; laparoscopic Roux‐en‐Y gastric bypass [LRYGB], 49.9%) with those of 161 897 patients aged <70 y who underwent metabolic surgery (LSG, 57.7%; LRYGB, 42.3%). They found that older patients had higher postoperative mortality and complication rates than younger patients. Pechman et al ⁹ also found that postoperative complications differed based on the surgical technique, with patients who underwent LSG having similar prevalence of acute renal failure, myocardial infarction, and deep‐vein thrombosis irrespective of age. A study of 26 557 patients (including 5.6% aged >65 y) registered in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database found that older patients had higher postoperative mortality and complication rates. ¹⁰ , ¹¹ The increase in adverse events may be attributed to the high prevalence of comorbidities among older patients. In MBSAQIP database study, patients who were aged >65 y had much lower mortality rate than that reported by Flum et al ⁶ in 2005. Our findings are also in agreement with the findings of the Ontario Bariatric Registry study published in 2022 that found no difference in the perioperative complication rate between patients aged <65 y (n = 22 981) and >65 y (n = 532). ¹² Together, these results suggest that the safety of metabolic surgery has improved worldwide. O′Keefe ¹³ further reported that the quality of life improved in both younger and older patient groups after weight loss surgery, which is an important benefit of bariatric surgery.

Recent guidelines from the American Society for Metabolic and Bariatric Surgery and the International Federation for the Surgery of Obesity and Metabolic Disorders have described that factors other than age, such as frailty, cognitive capacity, smoking status, and end‐organ function, play an important role in determining the success of metabolic surgery. Therefore, there is no substantial evidence to place an age limit on patients seeking metabolic surgery; however, it is recommended that eligible elderly patients should be carefully selected by assessing their frailty. ¹⁴

Previously published overseas studies, such as that reported by Flum et al ⁶ have warned about the risks of performing bariatric and metabolic surgery on older patients. Therefore, the guidelines released by the JSTO in 2013, which set the maximum age for bariatric and metabolic surgery at 65 y, are considered valid. However, since the Flum et al study was conducted, bariatric and metabolic surgery techniques used in Japan have improved markedly, and the present study found that surgical outcomes for older patients in Japan are comparable to those for younger patients. This can be attributed to the improved skills of surgeons and the co‐medical staff supporting them.

Regarding body weight loss after surgery, the actual weight loss was greater in the younger group than in the older patients. These results might indicate that metabolic surgery is more effective in younger patients than in elderly patients. However, there were no differences between the two groups with respect to other indicators, such as postoperative BMI, %EBMIL, %TWL, and %EWL. This suggests that the statistical analysis may have been underpowered to determine a difference. Hence, a prospective study with adjustments for background factors, except for age, should be performed in the future to confirm these findings.

This study had some limitations. First, this study was conducted in facilities employing experienced surgeons who are certified by the JSTO, which may have affected the results. Second, the safety of metabolic surgery is affected by several factors, including surgical technique, proficiency of the surgeon, availability of a multidisciplinary support system, and patient sex, age, and number of comorbidities. Third, the selection of older patients for surgeries may have been biased after a careful examination of their risks and benefits at each institution. Fourth, in older patients the development of postoperative frailty and sarcopenia must be considered. This study is a relatively short‐term study. Long‐term studies with more patients are needed to further evaluate the safety of metabolic surgery in older patients. Fifth, the improvements in comorbidities, including diabetes, hypertension, and dyslipidemia, were evaluated postoperatively by each facility using their own criteria. Thus, the lack of a uniform criterion for evaluating improvement in comorbidities may have resulted in a bias that we were unable to avoid.

Given that Japan is a super‐aging society, guidelines for treating clinically severe obesity in older Japanese patients are necessary. The results of this study suggest that metabolic surgery is safe and may lead to significant improvement in comorbidities and weight loss among older patients in Japan. Our findings suggest the current upper age limit for metabolic surgery in Japan should be reconsidered.

AUTHOR CONTRIBUTIONS

M.T. conceived the ideas, designed the research, and wrote the article. A.H. and Y.I. performed the statistical analysis. T.T., T‐H.C., H.H., K.K., A.S., A.Sa., S.O., H.M., and I.T. conceived the ideas and designed the research.

FUNDING INFORMATION

None.

CONFLICT OF INTEREST

The authors declare no conflicts of interest for this article. Prof. Hisahiro Matsubara, an editorial member, also has no conflicts of interest and has registered this response in the system's query regarding conflict of interest.

ETHICS STATEMENTS

Approval of the research protocol: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent: Informed consent was obtained from all participants included in the study.

Registry and the registration No. of the study/trial: N/A.

Animal studies: N/A.

Supporting information

Figure S1.

Table S1.

Table S2.

Table S3.

Table S4.

Takemoto M, Hayashi A, Inaba Y, Tanaka T, Chun T‐H, Hayashi H, et al. Safety and effectiveness of metabolic surgery in older Japanese patients. Ann Gastroenterol Surg. 2023;7:750–756. 10.1002/ags3.12680