Impact of body mass index on short-term outcomes after differentiated thyroid cancer surgery: a nationwide inpatient database study in Japan

Abstract

Introduction Recent studies have shown worse post-operative outcomes following several surgeries in underweight or obese patients. However, the association between body mass index (BMI) and short-term outcomes following thyroid cancer surgery remains unclear because of the small number of patients, deficits in background data known as risk factors (e.g. cancer stage, operative procedure, intraoperative device use and hospital volume) and categorisation of BMI. Methods We identified patients who underwent thyroidectomy for differentiated thyroid cancer from July 2010 to March 2017 using a Japanese nationwide inpatient database. We used restricted cubic spline (RCS) analyses to investigate potential non-linear associations between BMI (without categorisation) and outcomes: post-operative complications (local and general), duration of anaesthesia, post-operative length of hospital stay and hospitalisation costs. The analyses were adjusted for demographic and clinical backgrounds including the above-stated factors. We also performed multivariable regression analyses for the outcomes with categorisation of BMI. Results Among 59,671 eligible patients, the median BMI was 22.9 kg/m2 (interquartile range (IQR), 20.7–25.6 kg/m2). In total, 3860 patients (6.5%) had local complications and 787 patients (1.3%) had general complications. Although there were no significant associations with local complications, such as bleeding, recurrent laryngeal nerve paralysis and surgical site infection, the occurrence of general complications was significantly associated with higher BMI. BMI showed a linear association with the duration of anaesthesia and U-shaped associations with post-operative length of stay and hospitalisation costs. The lowest points of the U-shaped curves occurred at a BMI of approximately 24 kg/m2. The multivariate regression analyses showed consistent results with the RCS analyses. Discussion/conclusion Whereas RCS analyses revealed no significant associations between BMI and post-operative local complications, obesity was significantly associated with the occurrence of general complications. The linear association between BMI and duration of anaesthesia corresponds to previous studies. Although post-operative length of stay and total hospitalisation costs demonstrated U-shaped associations, the slight differences would not be clinically important. Even if surgeons must pay attention to general complications in obese patients undergoing thyroid cancer surgery as well as other surgeries, underweight and overweight patients can undergo thyroidectomy as safely as patients with normal BMI.

Association of Operative Day of the Week with the Length of Stay and Total Hospitalization Costs in Patients with Partial Mastectomy: A Nationwide Database Study in Japan

“…Such a long LOS in Japan is partly explained by the smaller number of care facilities (e.g., nursing homes) compared with other countries (13) ; that is, acute care hospitals often cover postacute care for several days. Regarding postoperative situations, both clinicians and patients would consequently tend to closely monitor surgical wounds and laboratory findings in a hospital setting (31) . A previous study revealed that patients may wish to extend their discharge data even based on superstition (relating to the 6 day lunar calendar that is common in Japan) (32) .…”

“…Figure 1 shows that patients were unlikely to be discharged on Sunday, although their families could pick them up having to miss work on weekdays. Both doctors and patients may prefer to check the wound on the next weekday (i.e., Monday) rather than discharge on Sunday without a checkup (31) . Because patients who underwent surgery on Monday were discharged during weekdays, their postoperative LOS would not have been affected by the postoperative Sunday effect.…”

Association between body mass index and incidence of breast cancer in premenopausal women: A Japanese nationwide database study

“…As the RCS function enables a continuous variable to be analyzed without categorization, information and statistical power are not lost in RCS analysis, unlike general regression analysis, which requires categorization of continuous variables such as BMI [13][14][15][16][17]. In this study, we used 4 points (18.5, 22.0, 25.0, and 30.0 kg/m 2 ) as the knots in the cubic splines to allow for nonlinear dose-response effects of continuous BMI measurement, similar to that in previous studies [29,30]. The splines were restricted to be linear below the rst knot and above the last knot.…”

Perioperative outcomes of thyroid cancer surgery in children and adults: a nationwide inpatient database study in Japan

“…We defined general complications as respiratory complications, urinary tract infection, sepsis, heart failure, stroke, acute renal failure, and pulmonary embolism. The definitions of these terms are defined on the basis of the approach used in previous studies [ 7 , 29 ] and are listed in Supplemental Table E1 . The secondary outcomes were the duration of anesthesia, postoperative LOS, total hospitalization cost, and 30-day readmission at the same hospital.…”