The Core Reason: Age-Related Physiological Changes
One of the most significant factors contributing to the increased risk of adverse drug events (ADEs) and polypharmacy in older people is the profound physiological changes that occur with age. As the body ages, vital organ systems, particularly the kidneys and liver, become less efficient. The kidneys are responsible for clearing drugs from the bloodstream, while the liver metabolizes drugs into forms the body can excrete. A decline in the function of these organs means medications are not processed as quickly, leading to higher concentrations in the body and a greater risk of toxicity.
The Impact on Pharmacokinetics
Pharmacokinetics describes how a drug moves through the body—from absorption to distribution, metabolism, and elimination. With aging, each of these stages can be altered:
- Absorption: The rate of absorption can slow down due to changes in the gastrointestinal tract, though the total amount absorbed often remains consistent.
- Distribution: Older adults have a higher percentage of body fat and less lean body mass and total body water. This can cause fat-soluble drugs to accumulate in fatty tissues, prolonging their effects, while water-soluble drugs become more concentrated in the blood.
- Metabolism: The liver's size and blood flow decrease with age, reducing the efficiency of drug metabolism. This slows down the processing of many medications.
- Elimination: Renal blood flow and glomerular filtration rate (GFR) decrease with age, impairing the kidneys' ability to clear drugs and their metabolites. This is often considered the most significant age-related pharmacokinetic change.
The Consequences of Multimorbidity
It is well-documented that multimorbidity—the presence of multiple chronic diseases—is a major contributor to polypharmacy. As seniors acquire more health conditions over time, they are prescribed more medications. This can lead to a vicious cycle where a drug prescribed for one condition interacts with another, causing new symptoms that are then treated with yet another drug. This “prescribing cascade” is a key driver of polypharmacy and greatly increases the risk of ADEs.
Multiple Healthcare Providers and Information Gaps
Many older adults receive care from multiple healthcare providers, including a primary care physician and various specialists. Without a single, coordinated view of a patient's medication list, there is a heightened risk of prescribing drug-drug interactions or duplicating therapies. The use of multiple pharmacies can also exacerbate this issue by creating information gaps about a patient's complete medication history.
Over-the-Counter Medications and Supplements
Many seniors also use over-the-counter (OTC) medications and dietary supplements to manage various symptoms, often without informing their physicians. The potential for herb-drug or drug-OTC interactions is high and poses a serious, yet often unmonitored, risk for ADEs. Some of the most common offenders are OTC pain relievers, laxatives, and vitamins.
The Role of Pharmacodynamics
Beyond pharmacokinetics, pharmacodynamics—the effects of drugs on the body—also changes with age. For many medications, older adults have an altered response, which can increase sensitivity and the likelihood of adverse effects. For instance, sensitivity to central nervous system (CNS) depressants like benzodiazepines may increase, leading to heightened sedation and an increased risk of falls. Conversely, some medications may have a diminished effect, leading to a need for higher, potentially toxic doses. Careful dose adjustments and monitoring are therefore critical.
Comparing Drug Processing in Younger vs. Older Adults
| Factor | Younger Adults | Older Adults |
|---|---|---|
| Kidney Function | Typically high and efficient, rapidly clearing drugs. | Often reduced, leading to slower drug clearance and potential accumulation. |
| Liver Function | Strong and robust, effectively metabolizing medications. | Decreased mass and blood flow, reducing metabolic efficiency. |
| Body Composition | Higher lean body mass and total body water. | Higher body fat percentage and lower lean body mass. |
| Drug Distribution | Predictable distribution patterns for both fat- and water-soluble drugs. | Altered distribution, with fat-soluble drugs accumulating and water-soluble drugs becoming more concentrated. |
| Medication Usage | Fewer chronic conditions and fewer prescribed medications. | Higher prevalence of multimorbidity and subsequent polypharmacy. |
| Risk of ADEs | Generally lower, with more predictable drug responses. | Significantly higher due to cumulative effects of physiological changes and drug interactions. |
A Path Forward: Strategies for Safer Medication Management
Addressing the risks associated with polypharmacy requires a proactive, patient-centered approach. Healthcare providers and seniors must work together to regularly review all medications, including prescriptions, OTC drugs, and supplements. This process, sometimes called "deprescribing," aims to reduce unnecessary medications and simplify treatment regimens. Improved care coordination and thorough medication reconciliation can also help close the information gaps created by seeing multiple providers.
For more information on the dangers of polypharmacy and the role of deprescribing, the National Institute on Aging offers helpful guidance on their website, highlighting the need for vigilant medication management in older adults. For a better understanding of potential drug interactions and resources, visit the National Institute on Aging website.
Conclusion
While a single reason for the increased risk of adverse drug events and polypharmacy in older people cannot fully capture the complexity, age-related physiological changes, especially the decline in kidney and liver function, are a central contributing factor. Combined with other issues like multimorbidity, fragmented care, and OTC use, these changes create a heightened risk environment. Through careful management, regular medication reviews, and improved communication, these risks can be mitigated, leading to safer, more effective medication use for the aging population.
