Warm Weather and Surgical Site Infections: A Meta-analysis

Abstract

Seasonal variability, in terms of warm weather, has been demonstrated to be a significant risk factor for surgical site infections (SSIs). However, this remains an underexposed risk factor for SSIs, and many clinicians are not aware of this. Therefore, a systematic review and meta-analysis has been conducted to investigate and quantify this matter.

Methods: Articles were searched in Embase, Medline Ovid, Web of Science, Cochrane Central, and Google Scholar, and data were extracted from relevant studies. Meta-analysis used random effects models to estimate and compare the pooled odds ratios (OR) and corresponding confidence intervals (CIs) of surgery performed during the warmest period of the year and the colder period of the year.

Results: The systematic review included 20 studies (58,599,475 patients), of which 14 studies (58,441,420 patients) were included for meta-analysis. Various types of surgical procedures across different geographic regions were included. The warmest period of the year was associated with a statistically significant increase in the risk of SSIs (OR 1.39, 95%CI: [1.34-1.45], P < 0.0001). Selection of specific types of surgical procedures (eg, orthopedic or spinal surgery) significantly altered this increased risk.

Conclusions: The current meta-analysis showed that warm weather seasons are associated with a statistically significant risk increasement of 39% in developing SSIs. This significant risk factor might aid clinicians in preoperative patient information, possible surgical planning adjustment for high risk patients, and potentially specific antibiotic treatments during the warmer weather seasons that could result in decrease of SSIs.

Fig. 1.

OR of SSIs among all patients. Forest plot of a random-effects model, without Hartung and Knapp correction, including all 14 studies describing OR and corresponding CI of SSIs among patients who underwent surgery during the warmest period of the year compared with those who underwent surgery during the colder period of the year. The lowest diamond represents the pooled OR and CI, demonstrating that SSIs are more common during the warmest period of the year, when compared with the colder period of the year (OR = 1.39, 95% CI: 1.34–1.45, P < 0.0001).

Fig. 2.

OR of SSIs among orthopedic surgery procedures versus nonorthopedic surgery procedures. Forest plot of a random-effects model, without Hartung and Knapp correction, comparing the OR and corresponding CI of SSIs among patients who underwent surgery during the warmest period of the year compared with those who underwent surgery during the colder period of the year. In this forest plot, five articles (six ORs) regarding orthopedic surgery procedures are compared with nine articles (nine ORs) regarding nonorthopedic surgery procedures. The diamonds following both orthopedic and nonorthopedic studies represent the pooled ORs and CIs of both all orthopedic studies and all nonorthopedic studies (OR = 1.26, 95% CI: 1.10–1.44 and OR = 1.48, 95% CI: 1.40–1.56, respectively). Both display a positive association between the risk of developing SSIs and the warmest period of the year. The lowest diamond represents the comparison between both pooled ORs and CIs, demonstrating that the positive association between the risk of developing SSIs and the warmest period of the year is less common after orthopedic surgery procedures when compared with nonorthopedic surgery procedures as a significant P value is found (OR = 1.39, 95% CI: 1.34–1.45, P = 0.029).

Fig. 3.

OR of SSIs among spinal surgery procedures versus nonspinal surgery procedures. Forest plot of a random-effects model, without Hartung and Knapp correction, comparing the OR and CI+ of SSIs among patients who underwent surgery during the warmest period of the year compared with the colder period of the year. In this forest plot, 10 articles (11 ORs) regarding nonspinal surgery procedures are compared with four articles (four ORs) regarding spinal surgery procedures. The diamonds following both nonspinal and spinal studies represent the pooled ORs and CIs of both all nonspinal studies and all spinal studies (OR = 1.31, 95% CI: 1.25–1.38 and OR = 1.65, 95% CI: 1.43–1.90, respectively). Both display a positive association between the risk of developing SSIs and the warmest period of the year. The lowest diamond represents the comparison between both pooled OR and CIs, demonstrating that the positive association between the risk of developing SSIs and the warmest period of the year is more common after spinal surgery procedures when compared to nonspinal surgery procedures as a significant P value is found (OR = 1.39, 95% CI: 1.34–1.45, P = 0.003).