Seasonal Variation in Baseline Characteristics, Comorbidities, and in-Hospital Outcomes Among Elderly Cancer Patients: A Comparative Study of Summer and Non-Summer Admissions (2016-2020)
Authors: Rajarajan Srinishant , Chakilam Rumitha , Parvez Maahin , Kondaveety Soumya , Chauhan Sumit , Avaiya Niyati Shambhubhai , Igbenabor Christiana Aina , Kotla Nikhil Kumar , Thappar Karanbir Singh , Asfeen Ummul , Desai Rupak 
Published: December 2024

Background: Seasonal variations in hospitalizations and outcomes have been documented across various medical conditions. Additionally, climate change has been associated with an increased risk of cancer and disruptions in cancer care. Rising global temperatures and extreme weather events may negatively affect cancer patient outcomes due to environmental stressors and challenges in healthcare delivery. This study aims to determine whether hospitalizations for cancer during the summer months are linked to worse cardiovascular outcomes compared to other seasons among elderly patients (aged ≥65 years). The primary focus is on Major Adverse Cardiac and Cerebrovascular Events (MACCE) and Venous Thromboembolic Events (VTE), with a consideration of gender and race disparities.

Methods: The objective of this nationwide retrospective study is to determine if cancer hospitalizations in the summer months (June, July & August) predict worse cardiovascular outcomes compared to other seasons among elderly patients.. We utilized the National Inpatient Sample (NIS) datasets from 2016-2020 (ICD-10 CM codes). Elderly ( ≥65 years) hospitalized patients with cancer were identified, and the rates and odds of MACCE, VTE, healthcare resource utilization (including disposition, length of stay, and cost) were analyzed and compared between summer and non-summer months. Multivariable logistic regression analysis was performed to adjust for covariates and determine the independent association of summer month admissions with in-hospital outcomes.

Results: A total of 6,579,778 hospitalizations of elderly cancer patients were identified from 2016-2020, of which 75.2% in non-summer and 24.8% in summer were identified. The median age at admission for both groups was 75 years. The gender distribution showed a slight predominance of males (54.4%) over females (45.6%). Racial composition was predominantly White (78.9%), followed by Black (11.4%), Hispanic (6.5%), Asian or Pacific Islander (2.8%), and Native American (0.4%). Most patients were covered by Medicare (89.7%), with minor proportions on Medicaid (1.4%), Private insurance (8.3%), and Self-pay (0.5%). The income distribution across national quartiles was relatively even. Elective admissions were slightly higher during the summer months (14.5% vs. 14.2%). The majority of admissions occurred in urban teaching hospitals (72.1%), with a significant concentration in the South region (36.4%).

Comorbidity analysis revealed that uncomplicated hypertension was more prevalent during summer months (41.0% vs. 40.5%, p&lt;0.001), while chronic pulmonary disease was slightly lower (26.7% vs. 27.4%, p&lt;0.001). Chronic kidney disease (CKD) also showed a marginally lower prevalence in summer admissions (25.4% vs. 25.6%, p&lt;0.001). Other comorbidities, including autoimmune conditions, depression, diabetes, and obesity, showed similar prevalence rates across both groups.

In-hospital outcomes indicated that all-cause mortality was significantly lower for summer admissions (6.7% vs. 7.1%, OR: 0.94, 95% CI: 0.92-0.96, p&lt;0.001). Major adverse cardiovascular and cerebrovascular events (MACCE) were also less frequent in the summer (6.8% vs. 7.0%, OR: 0.97, 95% CI: 0.95-0.98, p&lt;0.001). Venous thromboembolism (VTE) rates were similar between the two periods (3.8% for both, OR: 0.98, 95% CI: 0.96-1.00, p=0.075). The median length of hospital stay was shorter during the summer months (4.2 days vs. 4.3 days, p&lt;0.001), and hospital costs were slightly lower (Median $47,317 vs. $47,844, p&lt;0.001).

Conclusion: These findings suggest that elderly cancer patients admitted during the summer months experience better in-hospital outcomes, including lower mortality and MACCE rates, despite similar comorbidity profiles. The study underscores the need for heightened vigilance and proactive management strategies for cancer patients hospitalized during summer months to mitigate cardiovascular risks. Additionally, it highlights the importance of emergency preparedness and climate resilience in healthcare facilities to ensure uninterrupted cancer care during extreme weather events. Addressing gender and race disparities in outcomes further aids in developing equitable healthcare interventions. Further investigation is warranted to identify the underlying reasons and enhance patient care across different seasons.