The Impact of Gender on Post-Operative Length of Stay after Lumbar Decompression Fusion Surgery Referable to Possible Comorbidity Factors

Proportionally more healthcare dollars are devoted to the care of females than their male counterparts (Lassman, Hartman, Washington, Andrews, & Catlin, 2014); rightfully so, as females have a greater life expectancy and a special reproductive burden (Owens, 2008; Vaidya, Gautam, & Karmakar, 2012). In neurosurgery, some controversy exists as to the influence of gender on prolonging hospital stay, particularly following operative intervention for spinal column difficulties (Table 1). To clarify such issues we conducted the following study.


Introduction
Proportionally more healthcare dollars are devoted to the care of females than their male counterparts (Lassman, Hartman, Washington, Andrews, & Catlin, 2014); rightfully so, as females have a greater life expectancy and a special reproductive burden (Owens, 2008;Vaidya, Gautam, & Karmakar, 2012).In neurosurgery, some controversy exists as to the influence of gender on prolonging hospital stay, particularly following operative intervention for spinal column difficulties (Table 1).To clarify such issues we conducted the following study.

Methods
A retrospective review of the clinical course of all patients that underwent elective lumbar spinal fusion procedures by five neurosurgeons between October 2010 and November 2013 at The Georgia Neurosurgical Institute was undertaken.Comorbidities, complications, and other relevant general variables were obtained.Comorbidities which included twenty four variables relating to preexisting diseases were collected from patients' past medical histories and their preoperative evaluation visit forms (Table 2).Complications were twelve secondary medical problems that developed during hospital stays that were not existent prior to the operation (Table 3).Other collected variables contained age, gender, race, Length of hospital Stay (LOS), Body Mass Index (BMI), and nine others (Table 4).LOS was measured from the day of procedure until the time of discharge (up to the first decimal of a day).As our patient's sample is relatively small in size, we chose to exclude those outliers who stayed more than 4 standard deviations above the mean length of stay (>25.3days).There were only 4 patients that fell into this category.in LOS.Then, the variables that showed more prevalence in one gender were identified using chi-squared analysis.Finally, each gender cohort was statistically studied separately in order to identify which variables lead to a prolonged LOS in each gender using multivariate linear regression analysis.SPSS-19 software was used to perform all statistics.

Discussion
Our study demonstrated that females have more comorbidities than males which might be referable to the different hormonal structures between genders.Our study also recognized that the variables that influence LOS in each gender cohort are different.However, age did not show an independent influence on LOS in either of the genders, despite females being significantly older than males in our study.Recognizing this age disparity, statistical adjustments were accordingly instituted.Following such statistical adjustment, age by itself did change gender's impact on LOS.
Another variable that should be discussed is rehabilitation status.Ireland, Kelly, and Cumming (2015) stated that "referral to hospital-based rehabilitation effectively doubles the total LOS," suggesting that anyone who is subject to rehabilitation after their acute hospital stay will have a longer LOS.This suggests that a patient's post-operative rehabilitation status should be taken into account when determining their LOS.It may be that patients pain states are more prevalent in patients with anxiety disorders (Dersh, Polatin, Gatchel, 2000;Lachlan, McWilliams, Cox, 2003;Demyttenaere, Bruffaerts, Lee, 2007) and depressive disorders (Banks, Kerns, 1996;Dersh, Polatin, Gatchel, 2000;Von Korff, et al., 2005;Currie and Wang, 2004).Furthermore, women tend to have more severe pain scores, and perform more poorly on tests of cognitive function postoperatively than men (Heyer, et al., 2000).Also, it was suggested by Korovessis, Pepantis, Papazisis, and Iliopoulos (2010) that males show significantly better improvement in their lower back pain scores than their female counterparts following spine surgery.The psychological, pain, and cognitive burdens that females must face after surgery suggest that females are innately inclined to poorer postoperative outcomes and, thus, an elongated LOS.
In our study cohort females were afflicted with more comorbidites than were males possibly referable to the differing hormonal profile of females that could provide further insight as to why female's have a longer LOS than men.Studies consistently mentioned that estrogen modulates pain sensation via its α and β receptors that spread throughout the central and peripheral nervous systems (Alstergren, Ernberg, Kvarnström, Kopp, 1998;Nomura, et al., 2005; McEwen and Alves, 1999), including the dorsal root ganglia (Papka, et al., 2001), as well as throughout inflammatory cells like monocytes (Phiel, Henderson, Adelman, Elloso, Lett, 2005).The study performed by Craft et al. implicated that estrogen was a stimulant of nociceptive afferents in the peripheral nervous system via different mechanisms (Craft, 2007).Female's inclination to have a higher sensitivity to pain, and their increased tendency to psychiatric distress both could contribute to their elongated LOS.

Conclusion
Understanding the differences in gender for different operative interventions and paying special attention to gender dissimilarities might be useful to decrease postoperative stay and, thus, diminish healthcare expenditure.
We suggest additional inquiry into the impact of comorbidities and complications with particular reference as to why certain comorbidities and complications contribute to prolonging female LOS and not male.otherwise able to depart a tertiary care facility are shunted into a rehabilitation facility because of inadequate domestic support apparatus.Secondly, in some circumstances, discharge arrangements may have been expedited, preoperatively, so that in some cases those patients going to rehabilitation facilities will leave the hospital sooner than a cohort returning to a home environment.

Implications for Practice and/or Policy
A past history of anxiety disorders and developing postoperative psychiatric symptoms occurred more frequently in females than in males; issues which have been suggested to cause a prolonged hospital LOS (Stundner, et al., 2013;Zatzick, et al., 2000).Moreover, studies consistently assert that chronic

Table 1 :
Review of articles published in Pub Med since January 2013 about the impact of gender on length of stay in Spine Procedures.
Keywords: Costs; Comorbidities; Complications; Gender; Health Care Expenditure; Length of Stay; Lumbar Decompression and Fusion

Table 2 :
The Collected Co morbidities.

Table 4 :
The Collected General Variables.