Why do older people get more infections? Understanding the aging immune system

According to the CDC, older adults are at a significantly higher risk for serious complications from respiratory illnesses. This increased vulnerability is primarily due to a natural, age-related decline in immune function, a process called immunosenescence, which explains why do older people get more infections.

Quick Summary

An aging immune system, a process known as immunosenescence, becomes slower to respond and less effective at detecting new pathogens, driven by declines in vital T-cell and B-cell function and a state of chronic inflammation. This makes older adults more vulnerable and reduces vaccine efficacy.

Key Points

• Immunosenescence Explained: The immune system's function declines with age, a process called immunosenescence, making older adults more vulnerable to infection.

• Fewer Naïve Cells: Older adults have fewer new, or 'naïve,' T-cells and B-cells, impairing their ability to fight new or unfamiliar pathogens.

• The Problem with Inflammaging: A chronic, low-grade inflammatory state, or 'inflammaging,' wears down the immune system over time and contributes to many age-related diseases.

• Chronic Illness Impact: Existing chronic conditions like diabetes or heart disease place extra strain on the immune system, further increasing the risk of infection.

• Atypical Symptoms: Infections in seniors may present with subtle or confusing symptoms like confusion or fatigue, rather than a fever, delaying diagnosis and treatment.

• Vaccines Are Crucial: While vaccine effectiveness may decrease with age, getting recommended immunizations is still vital for reducing the severity of illness.

• Prevention is Possible: Maintaining good hygiene, a healthy lifestyle, and proactive medical care are the best defenses against increased infection risk in older adults.

The Science of an Aging Immune System: Immunosenescence

Immunosenescence is the natural, age-related decline in immune system function, affecting both innate and adaptive immunity. This complex process isn't an immune deficiency, but it results in a less effective and slower response to new pathogens, increasing susceptibility to infections. Changes occur from the bone marrow to circulating immune cells, impacting their quantity, variety, and performance.

Changes in T-Cells and B-Cells

The adaptive immune system, particularly T-cells and B-cells, shows the most significant effects of immunosenescence. These lymphocytes are crucial for recognizing and remembering specific pathogens.

• T-Cell Decline: The thymus, responsible for T-cell maturation, shrinks after puberty, reducing the production of new 'naïve' T-cells. Older adults are left with a smaller, less diverse pool of memory T-cells, which are less efficient against new infections. T-cell signaling also weakens.
• B-Cell Dysfunction: While B-cell numbers may stay consistent, their function changes with age. Older adults' B-cells produce antibodies that are less diverse and have lower affinity, hindering the body's antibody-mediated response. This reduces vaccine effectiveness and raises the risk of common infections.

The Role of 'Inflammaging'

Inflammaging is a chronic, low-grade inflammation that is a key aspect of immune aging. Unlike necessary acute inflammation, inflammaging is persistent and affects the whole body.

This continuous inflammation is caused by factors like the accumulation of senescent cells and low-level viral infections such as cytomegalovirus (CMV). Inflammaging is linked to age-related diseases like heart disease and diabetes. It further stresses the aging immune system, worsening its decline.

Increased Susceptibility Due to Chronic Conditions

Chronic health issues, common in older adults, further increase infection risk by impacting immune function.

• Diabetes: Impairs neutrophil function, reduces circulation, and damages skin barriers, increasing the risk of infections like UTIs and skin infections.
• Heart Disease: Involves systemic inflammation that exacerbates inflammaging and compromises the ability to fight infections.
• Neurological Diseases: Conditions like dementia can affect hygiene and alter behavior, potentially hiding infection symptoms and delaying treatment.

Common Infections in the Elderly

Certain infections are more common and can present with unusual symptoms in older adults.

• Urinary Tract Infections (UTIs): The most frequent bacterial infection, often causing confusion or behavioral changes instead of typical symptoms.
• Bacterial Pneumonia: A significant cause of hospitalization and death, often complicated by existing health issues.
• Influenza and Respiratory Viruses: Weaker immune response increases the likelihood of severe complications. Vaccination is important despite potentially lower efficacy.
• Skin Infections: Changes in skin and conditions like diabetes increase risk of infections such as cellulitis.
• Gastrointestinal Infections: Altered gut flora can make older adults more prone to infections like Clostridioides difficile, especially after antibiotic use.

Prevention and Mitigation Strategies

While immunosenescence is natural, several steps can help support immune function and lower infection risk.

1. Stay Vaccinated: Ensure all recommended vaccinations, like flu, pneumonia, and shingles, are current. High-dose vaccines may be more effective for older adults.
2. Practice Good Hygiene: Regular handwashing is essential. Maintain good oral hygiene and proper wound care.
3. Manage Chronic Conditions: Controlling conditions like diabetes and heart disease reduces inflammation and supports immune health.
4. Prioritize a Healthy Lifestyle: A balanced diet, sufficient sleep, and regular exercise boost overall health and immune function. Stay hydrated to help prevent UTIs.
5. Seek Early Medical Attention: Recognize atypical signs of infection in seniors and get prompt medical help.

For specific immunization schedules, consult the CDC website for vaccine recommendations for older adults.

Comparing Immune Responses: Younger vs. Older Adults

Aspect	Younger Adults	Older Adults
T-Cell Population	High numbers of diverse, 'naïve' T-cells, readily able to respond to new pathogens.	Fewer naïve T-cells and a smaller, less diverse T-cell repertoire, with more memory T-cells.
Antibody Production	Strong, high-affinity antibody response from B-cells.	Lower antibody avidity and less diverse antibodies, reducing effectiveness against new antigens.
Response Speed	Quick and robust immune response, resolving infections efficiently.	Slower immune response with a higher risk of prolonged or severe illness.
Inflammatory State	Primarily acute, temporary inflammation for healing.	Higher levels of chronic, low-grade systemic inflammation ('inflammaging').
Vaccine Efficacy	Strong immune response to vaccination, providing robust, long-lasting protection.	Reduced response to vaccines, potentially requiring higher doses or boosters.

Conclusion: Proactive Care for a Stronger Defense

Older people get more infections due to immunosenescence, inflammaging, and chronic diseases. While the immune system naturally weakens with age, this risk can be mitigated. Understanding these factors allows for proactive strategies like good hygiene, vaccination, managing health conditions, and early symptom detection. Focusing on a healthy lifestyle throughout life also helps lessen the effects of immunosenescence, promoting healthier aging.

Frequently Asked Questions

What is the primary reason why do older people get more infections?

The primary reason is immunosenescence, the gradual weakening of the immune system that occurs with age. This makes the body's response to pathogens slower and less effective.

Does a weakened immune system mean older adults are always sick?

No, a weakened immune system doesn't mean constant sickness. It means the body is less robust and has a harder time fighting off new infections, so what might be a minor cold for a young person could become a more serious illness for an older adult.

What common infections are more dangerous for older people?

Common infections that can be more dangerous for older people include bacterial pneumonia, influenza, urinary tract infections (UTIs), shingles, and Clostridioides difficile.

Why might a fever not be a reliable sign of infection in the elderly?

Infections in older adults can present with atypical symptoms due to a blunted inflammatory response. Instead of a fever, look for nonspecific symptoms like new confusion, increased fatigue, loss of appetite, or behavioral changes.

How can managing chronic diseases help an older person's immune system?

Managing chronic diseases helps by reducing the overall inflammatory burden on the body. Conditions like diabetes and heart disease create a state of chronic inflammation that can exhaust the immune system, so controlling them improves immune resilience.

Is it true that vaccines are less effective for older people?

Vaccines can be less effective in older adults because the aging immune system has a weaker response. However, they are still highly recommended as they significantly reduce the risk of severe illness, hospitalization, and death. High-dose or adjuvanted vaccines are sometimes recommended to boost the immune response.

What can older adults do to boost their immune system naturally?

Older adults can support their immune system through a healthy lifestyle that includes a balanced diet, adequate sleep, regular physical activity, and good hygiene practices. Managing stress and staying hydrated also play a role.