Risk pattern of common infectious diseases after bariatric surgery found to be divergent
The risks of four common infectious diseases after bariatric surgery show a varied pattern, such that the risks of skin and soft-tissue infection (SSTI) and respiratory infection are lower while those of intra-abdominal infection and urinary tract infection (UTI) are elevated, according to US-based researchers.
In a cohort of 56,277 obese adults who underwent bariatric surgery (median age 45 years; 79 percent female), a self-controlled case series analysis of data on 2-year presurgery and 2-year postsurgery revealed that the risk of emergency department (ED) visit or hospitalization in the 0 to 12 months postsurgery period vs the presurgery months 13 to 24 (reference) decreased significantly for SSTI (adjusted odds ratio [aOR ], 0.85; 95 percent CI, 0.76 to 0.95) and respiratory infection (aOR, 0.82; 0.75 to 0.90). [Clin Infect Dis 2017;doi:10.1093/cid/cix541]
On the other hand, the risk increased significantly for intra-abdominal infection (aOR, 2.09; 1.78 to 2.46) and UTI (aOR, 1.93; 1.74 to 2.15) in the postsurgery period of 0 to 12 months vs reference.
The risk pattern was sustained in the postsurgery months 13 to 24, remaining low for SSTI (aOR, 0.77; 0.68 to 0.86) and respiratory infection (aOR, 0.75; 0.68 to 0.82) and remaining high for intra-abdominal infection (aOR, 1.29; 1.09 to 1.54) and UTI (aOR, 1.31; 1.17 to 1.47).
Additionally, there was heterogeneity in the risk pattern of four common infectious diseases between men and women. The risk of SSTI and respiratory infections during the 2-year period after bariatric surgery was particularly greater in men, whereas the risk of intra-abdominal infection and UTI was especially increased in women.
Recent data collectively indicate that obesity is an important and potentially modifiable risk factor for infectious diseases, researchers said. In this context, the current findings support the hypothesis that bariatric surgery can lower the risk of infectious diseases, particularly SSTI and respiratory infection. [Epidemiology 2015;26:580-589; Am J Epidemiol 2016;183:1008-1017]
While unclear, the mechanisms underlying the association between bariatric surgery and reduced risk of infectious diseases may potentially be explained by anatomical changes and improvement of immune systems achieved by weight reduction, researchers pointed out.
“For example, improvement of blood perfusion to (and venous return from) the peripheral tissues and decreases of skin folds may reduce the risk of SSTI. Additionally, bariatric surgery and weight reduction may reverse the obesity-associated restrictive ventilatory pattern and the decreased residual volumes that might facilitate airway infections,” they said. [Int J Obes (Lond) 2013;37:333-340; Can Respir J 2006;13:203-210]
In contrast, the increased risk of intra-abdominal infection postsurgery is driven by an increase in the risk of both enteric infection and hepatobiliary infection. Moreover, the heightened risk of UTI, which was observed only in women, may be attributed to a higher frequency of sexual intercourse in lean women than in obese women and to a loss of adipose tissue that protects the female genital membranes during intercourse. [J Sex Marital Ther 2004;30:251-261; Lancet Infect Dis 2006;6:438-446]
Despite the presence of several limitations including the possible misclassification of healthcare utilization in the administrative data and lack of information on patient weight and body mass index, researchers said, “The validity of our findings is supported by the self-controlled case series study design in which each patient functions as a control for him/herself, thereby reducing the intraperson variations and unmeasured confounding that can occur with traditional cohort and case-control studies.”
“[Additionally], analysis of a large population-based dataset demonstrates an association of bariatric surgery and risk of infectious diseases in a real-world setting and hence augments the potential generalizability of the findings,” they added.
Further studies are warranted to elucidate the mechanisms linking obesity and weight reduction to the risk of infectious diseases, they said.