Biomarkers of Physiological Reserve Under Polypharmacy: Clinical Insights and Emerging Evidence

Abstract

Polypharmacy, the concurrent use of multiple medications, has become increasingly prevalent in aging populations and individuals with complex comorbidities. This poses significant challenges in assessing physiological reserve—the capacity to withstand physiological stressors. Emerging research highlights the utility of specific biomarkers in evaluating physiological reserve among patients exposed to polypharmacy, enabling risk stratification and personalized care. This review synthesizes current evidence, elucidates mechanisms linking polypharmacy to diminished reserve, and discusses clinical applications, recent advances, and guideline recommendations for integrating biomarker assessment into routine practice.

Introduction

The global rise in chronic disease prevalence and aging has led to a dramatic increase in polypharmacy, especially in geriatric and multimorbid populations. Polypharmacy is defined as the use of five or more medications, though thresholds may vary. Assessing physiological reserve—the underlying ability to compensate for pharmacological and environmental stressors—has become paramount in this context. Traditional methods, such as comprehensive geriatric assessment, are time-consuming and may be insensitive to subclinical changes. The recent identification and validation of biomarkers offer a promising adjunct for clinicians managing patients under polypharmacy. This article provides a comprehensive review of the current landscape, focusing on the clinical significance, mechanisms, and practical use of physiological reserve biomarkers in polypharmacy.

Epidemiology / Disease Burden

Polypharmacy affects nearly 40% of adults over 65 years in developed countries, with higher rates in those with multimorbidity and institutionalized settings. This practice is associated with increased risks of adverse drug reactions, hospitalizations, frailty, and mortality. The burden of polypharmacy is particularly pronounced in populations with diminished physiological reserve, underscoring the need for objective measures to identify at-risk individuals. Studies from large-scale cohorts, such as the UK Biobank and NHANES, have consistently linked polypharmacy to poor outcomes, mediated in part by a reduced capacity to respond to stressors such as infection, surgery, or acute illness.

Pathophysiology

Physiological reserve encompasses multiple organ systems and reflects the ability to maintain homeostasis under stress. In polypharmacy, overlapping pharmacodynamic and pharmacokinetic interactions can blunt adaptive responses, leading to increased vulnerability. Mechanistically, medications may impair mitochondrial function, disrupt neuroendocrine signaling, and promote chronic low-grade inflammation, collectively eroding reserve. Biomarkers such as interleukin-6 (IL-6), C-reactive protein (CRP), brain natriuretic peptide (BNP), and sarcopenia-related indices (e.g., creatinine height index, myostatin) provide mechanistic insights into these processes by indicating subclinical organ dysfunction or systemic stress.

Risk Factors

Key risk factors for diminished physiological reserve under polypharmacy include advanced age, multimorbidity (especially cardiovascular, renal, and neurodegenerative diseases), frailty, cognitive impairment, and poor nutritional status. Social determinants, such as limited access to healthcare, and genetic predispositions, such as polymorphisms affecting drug metabolism (e.g., CYP450 variants), further modulate risk. Polypharmacy itself can exacerbate these risks through drug-drug and drug-disease interactions, making biomarker-based assessment particularly relevant in these populations.

Clinical Features

Clinically, reduced physiological reserve manifests as increased susceptibility to adverse drug events, prolonged recovery from acute illness, functional decline, and higher rates of hospitalization. Signs may be subtle and include fatigue, decreased mobility, cognitive changes, and reduced resilience to stressors such as surgery or infection. Traditional clinical assessments may underestimate subclinical impairment, highlighting the need for objective biomarkers that can signal early decompensation.

Diagnosis

Diagnosis of diminished physiological reserve in the context of polypharmacy increasingly incorporates biomarker evaluation alongside clinical assessment. Key biomarkers include inflammatory markers (IL-6, CRP), markers of sarcopenia (creatinine clearance, myostatin), cardiac biomarkers (BNP, troponin), and indices of oxidative stress. Novel approaches utilize composite biomarker panels and integrate them with frailty indices or functional tests (e.g., gait speed, grip strength) for more accurate risk stratification. The role of omics—genomics, proteomics, metabolomics—is also expanding, offering the potential for personalized medicine.

Treatment & Management

Management strategies focus on minimizing unnecessary polypharmacy through regular medication reviews, deprescribing where appropriate, and optimizing drug regimens according to physiological reserve. Biomarker-guided approaches can inform clinical decision-making by identifying patients at greatest risk of decompensation and tailoring interventions accordingly. Multidisciplinary collaboration is essential, involving geriatricians, pharmacists, and primary care providers. Non-pharmacologic interventions, including nutrition, physical rehabilitation, and cognitive training, may also improve reserve and mitigate drug-related risks.

Recent Advances / Emerging Therapies

Recent advances include the development of integrated biomarker panels combining inflammatory, metabolic, and functional indices to provide a holistic assessment of physiological reserve. Machine learning algorithms are being applied to electronic health records to predict adverse outcomes under polypharmacy, incorporating biomarker data for enhanced precision. Emerging therapies focus on targeting underlying mechanisms, such as anti-inflammatory agents, senolytics, and mitochondrial protectants, with early-phase trials showing promise in improving physiological resilience.

Guideline Recommendations

Current guidelines from bodies such as the American Geriatrics Society and European Society of Cardiology endorse regular medication reviews and individualized risk assessment in patients exposed to polypharmacy. While the routine use of biomarkers is not yet universally recommended, expert consensus highlights their potential utility in high-risk populations, especially for guiding deprescribing and predicting adverse outcomes. Ongoing research aims to clarify which biomarkers offer the greatest predictive value and how best to integrate them into clinical workflows.

Conclusion

Assessing physiological reserve using biomarkers in patients exposed to polypharmacy represents a pivotal shift toward personalized, risk-adapted care. Although challenges remain regarding standardization and clinical implementation, accumulating evidence supports the integration of biomarker assessment into routine practice, particularly for vulnerable populations. Continued research and guideline development will further refine these approaches, ultimately improving outcomes for individuals navigating the complexities of polypharmacy.