Effects of body mass index (BMI) on surgical outcomes: a nationwide survey using a Japanese web-based database.
OBJECTIVE
To define the effects of body mass index (BMI) on operative outcomes for both gastroenterological and cardiovascular surgery, using the National Clinical Database (NCD) of the Japanese nationwide web-based database.


METHODS
The subjects of this study were 288,418 patients who underwent typical surgical procedures between January 2011 and December 2012. There were eight gastroenterological procedures, including esophagectomy, distal gastrectomy, total gastrectomy, right hemicolectomy, low anterior resection, hepatectomy of >1 segment excluding the lateral segment, pancreaticoduodenectomy, and surgery for acute diffuse peritonitis (n = 232,199); and five cardiovascular procedures, including aortic valve replacement, total arch replacement (TAR), descending thoracic aorta replacement (descending TAR), and on- or off-pump coronary artery bypass grafting (n = 56,219). The relationships of BMI with operation time and operative mortality for each procedure were investigated, using the NCD.


RESULTS
Operation times were longer for patients with a higher BMI. When a BMI cut-off of 30 was used, the operation time for obese patients was significantly longer than that for non-obese patients, for all procedures except esophagectomy (P < 0.01). The mortality rate based on BMI revealed a U-shaped distribution, with both underweight and obese patients having high mortality rates for almost all procedures.


CONCLUSIONS
This Japanese nationwide study provides solid evidence to reinforce that both obesity and excessively low weight are factors that impact operative outcomes significantly.
Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Motonari
M
Ri
National Clinical Database (NCD), Tokyo, Japan.
Hiroaki
H
Miyata
Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Susumu
S
Aikou
Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. seto-tky@umin.ac.jp.
Yasuyuki
Y
Seto
Department of Medical Informatics, Niigata University Medical and Dental Hospital, Niigata, Japan.
Kohei
K
Akazawa
Department of Clinical Medicine, School of Pharmacy, Kitasato University, Kanagawa, Japan.
Masahiro
M
Takeuchi
Department of Cardiovascular and Thoracic Surgery, Hokkaido University Graduate School of Medicine, Hokkaido, Japan.
Yoshiro
Y
Matsui
The Japanese Society of Gastroenterological Surgery, Tokyo, Japan.
Hiroyuki
H
Konno
The Japanese Society of Gastroenterological Surgery, Tokyo, Japan.
Mitsukazu
M
Gotoh
The Japanese Society of Gastroenterological Surgery, Tokyo, Japan.
Masaki
M
Mori
Japan Cardiovascular Surgery Database Organization, Tokyo, Japan.
Noboru
N
Motomura
Japan Cardiovascular Surgery Database Organization, Tokyo, Japan.
Shinichi
S
Takamoto
Department of Cardiovascular Surgery, Osaka University of Medicine, Osaka, Japan.
Yoshiki
Y
Sawa
Department of General Surgical Science, Graduate School of Medicine, Gunma University, Gunma, Japan.
Hiroyuki
H
Kuwano
Hepato-Biliary-Pancreatic Surgery Division, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Norihiro
N
Kokudo
D015992:Body Mass Index; D013504:Cardiovascular Surgical Procedures / Q000401:mortality; D016208:Databases, Factual; D013505:Digestive System Surgical Procedures / Q000401:mortality; D005260:Female; D006801:Humans; D020407:Internet; D007564:Japan; D008297:Male; D009765:Obesity; D061646:Operative Time; D012307:Risk Factors; D015996:Survival Rate; D013851:Thinness; D016896:Treatment Outcome
Body mass index; National clinical database; Nationwide web-based database; Operation time; Operative mortality