Chronic inflammation is associated with many of the world’s leading causes of death, including heart disease, stroke, respiratory illness, diabetes and kidney disease.
Chronic inflammation and disease are closely connected—but the relationship is more complicated than describing inflammation as the single cause of every major illness.
Inflammation is an essential part of the immune system. It helps the body respond to infection, injury and damaged tissue. Problems can develop when inflammatory activity continues for too long, fails to resolve properly or becomes dysregulated.
Persistent low-grade inflammation is associated with cardiovascular disease, type 2 diabetes, chronic respiratory illness, kidney disease, some cancers and several neurological conditions.
A major scientific review published in Nature Medicine described chronic inflammatory diseases as an important contributor to global mortality, estimating that more than half of deaths worldwide are associated with inflammation-related conditions. However, inflammation is not always the original cause of disease. Depending on the condition, it may be a risk factor, consequence, amplifier or marker of underlying damage.
This article examines how inflammation is connected with the World Health Organization’s leading global causes of death—and why molecular hydrogen has become an emerging, but still investigational, area of research.
What Is Inflammation?
Inflammation is the body’s coordinated response to infection, injury or other potentially harmful stimuli.
Acute inflammation
Acute inflammation normally develops quickly and resolves once the threat has been controlled.
Examples include:
- Redness surrounding a minor cut
- Swelling after an injury
- Fever during an infection
- Temporary muscle soreness after unfamiliar exercise
This type of inflammation is usually protective. It recruits immune cells, removes damaged material and helps initiate healing.
Chronic inflammation
Chronic inflammation can persist for months or years. It may occur when the original trigger remains present, the immune response becomes dysregulated or normal resolution mechanisms do not work effectively.
Potential contributors include:
- Smoking
- Air pollution
- Excess visceral body fat
- Persistent infections
- Autoimmune conditions
- Poorly controlled metabolic disease
- Long-term psychological stress
- Insufficient or disrupted sleep
- Physical inactivity
- Age-related immune changes
- Diets low in fibre and nutrient-dense foods
Chronic inflammation does not necessarily produce obvious symptoms. Blood tests such as C-reactive protein may sometimes help identify inflammatory activity, but no single test can explain its cause or diagnose every inflammation-related condition.
The WHO’s Leading Global Causes of Death
The World Health Organization’s latest published global ranking uses mortality data from 2021.
The ten leading causes were:
- Ischaemic heart disease
- COVID-19
- Stroke
- Chronic obstructive pulmonary disease
- Lower respiratory infections
- Tracheal, bronchial and lung cancers
- Alzheimer’s disease and other dementias
- Diabetes mellitus
- Kidney diseases
- Tuberculosis
Together, these conditions accounted for a substantial proportion of worldwide deaths. Importantly, inflammation is involved in each condition differently—it should not be presented as their only cause. WHO global causes of death.
1. Ischaemic Heart Disease
Ischaemic heart disease occurs when the heart muscle does not receive enough oxygen-rich blood, commonly because the coronary arteries have become narrowed.
Atherosclerosis was once viewed mainly as a problem of cholesterol accumulation. It is now understood as a complex process involving lipids, immune cells, endothelial dysfunction and inflammatory signalling.
Inflammatory activity can contribute to:
- Endothelial damage and dysfunction
- Recruitment of immune cells into artery walls
- Development and progression of atherosclerotic plaques
- Plaque instability
- Blood-clot formation
Inflammation is therefore an important part of cardiovascular disease, but blood pressure, cholesterol, smoking, diabetes, age, genetics and other factors remain equally important.
For a closer examination of H₂ and cardiovascular research, read our article about molecular hydrogen and heart health.
2. COVID-19
COVID-19 became the second leading global cause of death in 2021, reflecting the exceptional circumstances of the pandemic.
Severe COVID-19 can involve an excessive or dysregulated immune response, endothelial injury, abnormal blood clotting and widespread inflammatory activity.
Inflammation is part of the body’s attempt to control the virus. In severe disease, however, an uncontrolled response can damage the lungs and other organs.
This illustrates an important distinction: inflammation is not always chronic and is not always harmful. The timing, location and intensity of the response all matter.
3. Stroke
Most strokes occur when a blood clot interrupts blood flow to part of the brain. A smaller proportion result from bleeding within or around the brain.
Inflammation can contribute at several stages:
- Atherosclerosis can narrow arteries supplying the brain.
- Inflammatory activity may affect plaque stability.
- Brain tissue deprived of oxygen releases signals that activate immune cells.
- Reperfusion can produce additional oxidative and inflammatory stress.
Inflammation may therefore influence both stroke risk and the brain’s response after a stroke. This does not mean that lowering inflammation alone prevents or treats stroke.
Anyone experiencing facial weakness, arm weakness or speech difficulty requires emergency medical attention.
4. Chronic Obstructive Pulmonary Disease
Chronic obstructive pulmonary disease, or COPD, includes long-term lung conditions that obstruct airflow and make breathing increasingly difficult.
Smoking is the principal cause in many countries, although pollution, occupational exposure and genetic factors can also contribute.
Long-term exposure to irritating particles may produce:
- Persistent airway inflammation
- Excess mucus production
- Structural changes in the lungs
- Oxidative stress
- Destruction of lung tissue
Once COPD is established, infections and exacerbations can intensify the inflammatory response.
5. Lower Respiratory Infections
Lower respiratory infections include pneumonia and other infections affecting the lungs.
Inflammation is essential for fighting bacteria, viruses and other pathogens. Immune cells and inflammatory molecules help identify and remove the infection.
However, an excessive response can impair gas exchange and damage lung tissue. In severe cases, infection may progress to sepsis or acute respiratory distress.
This is another example of inflammation having two sides: insufficient immune activity may allow infection to spread, while excessive activity can harm healthy tissue.
6. Lung Cancer
The WHO groups cancers of the trachea, bronchus and lung among the ten leading causes of death.
Tobacco smoke is the dominant preventable risk factor. It exposes lung tissue to carcinogens while repeatedly provoking injury, oxidative stress and inflammatory activity.
Chronic inflammation may contribute to a tissue environment that supports:
- DNA damage
- Abnormal cell growth
- New blood-vessel formation
- Changes in immune surveillance
- Tumour progression
Cancer is nevertheless a group of complex genetic and biological diseases. It would be inaccurate to describe inflammation as its single root cause.
Molecular hydrogen has not been proven to prevent, treat or cure cancer and must never replace oncology care.
7. Alzheimer’s Disease and Other Dementias
The immune system of the brain includes specialised cells called microglia. These cells help remove cellular debris and respond to infection or damage.
In Alzheimer’s disease, sustained microglial activation and inflammatory signalling may contribute to neuronal stress and disease progression. Researchers are investigating how this response interacts with amyloid, tau, vascular health, metabolism and ageing.
It remains uncertain whether neuroinflammation initiates the disease, develops in response to existing pathology or does both at different stages.
Therefore, reducing general inflammation should not be promoted as a proven method of preventing dementia.
8. Diabetes Mellitus
Type 2 diabetes develops through a combination of insulin resistance and a progressive inability of pancreatic beta cells to meet the body’s insulin requirements.
Low-grade inflammation associated with visceral fat and metabolic dysfunction may interfere with insulin signalling. High blood sugar can then further increase oxidative and inflammatory stress, creating a self-reinforcing cycle.
Factors involved include:
- Excess visceral body fat
- Genetics and family history
- Physical inactivity
- Sleep disruption
- Diet
- Age
- Certain medicines or medical conditions
A randomised trial involving 60 people with metabolic syndrome reported changes in several metabolic and inflammatory biomarkers after 24 weeks of high-concentration hydrogen-rich water. However, this was a relatively small study and investigated water—not hydrogen inhalation. It does not establish H₂ as a treatment for diabetes. Metabolic syndrome hydrogen-water trial.
9. Kidney Disease
The kidneys filter the blood, regulate fluid and electrolytes and help control blood pressure.
Diabetes and hypertension are two major causes of chronic kidney disease. Inflammatory processes can contribute to kidney injury, fibrosis and progressive loss of functioning nephrons.
At the same time, declining kidney function may increase systemic inflammation because waste products accumulate and normal metabolic regulation becomes disrupted.
This relationship can therefore operate in both directions.
10. Tuberculosis
Tuberculosis is caused by infection with Mycobacterium tuberculosis.
The immune system attempts to contain the bacteria by forming organised structures called granulomas. This inflammatory response can help prevent the infection from spreading, but persistent immune activation may also damage lung tissue.
Tuberculosis illustrates why “reducing inflammation” is not always a safe or complete objective. Suppressing the immune response without treating the underlying infection could be harmful.
TB requires appropriate antibiotic treatment and specialist medical care.
Chronic Inflammation and Oxidative Stress
Oxidative stress occurs when reactive molecules and the body’s antioxidant systems become imbalanced.
Oxidative stress and inflammation can reinforce one another:
- Cellular damage activates immune and inflammatory pathways.
- Activated immune cells produce reactive molecules to help control threats.
- Excess reactive activity can damage surrounding tissue.
- Damaged tissue may generate further inflammatory signals.
This feedback loop has been studied in cardiovascular, metabolic, respiratory, neurological and other chronic diseases.
However, reactive oxygen species are not universally harmful. At controlled levels, they perform important roles in cellular signalling, immunity and adaptation to exercise.
The goal is therefore not to eliminate oxidation or inflammation completely, but to maintain appropriate biological regulation.
Where Does Molecular Hydrogen Fit In?
Molecular hydrogen, or H₂, is being studied because it can diffuse rapidly through biological tissues and may influence redox-sensitive and inflammatory signalling pathways.
Early research proposed that molecular hydrogen could interact selectively with highly reactive species. More recent work suggests its biological effects may also involve signalling networks such as:
- Nrf2-related antioxidant responses
- NF-κB inflammatory signalling
- Cellular stress responses
- Mitochondrial regulation
- Cytokine activity
These mechanisms are scientifically interesting, but they do not prove that molecular hydrogen treats inflammation-related disease.
A review of 81 clinical studies found encouraging signals across several medical fields, but also highlighted small samples, varied delivery methods, inconsistent protocols and the need for stronger trials. Review of molecular hydrogen clinical studies.
What Does the Human Evidence Show?
Human research has investigated hydrogen-rich water, hydrogen-containing gas, hydrogen-rich saline and other delivery methods.
Some studies have reported changes in markers associated with oxidative stress or inflammation. Others have produced neutral or inconsistent findings.
For example, a 2024 systematic review of exercise studies found that molecular hydrogen improved one measure of antioxidant capacity but did not significantly reduce exercise-induced oxidative stress. Only six studies with 76 total participants were included, demonstrating how limited the evidence remains. Systematic review and meta-analysis.
Critical limitations include:
- Small participant numbers
- Short study durations
- Different hydrogen concentrations
- Different administration methods
- Different patient populations
- Inconsistent outcome measures
- Limited independent replication
- A lack of long-term clinical outcomes
Evidence involving hydrogen-rich water should not automatically be applied to hydrogen inhalation, and changes in biomarkers should not automatically be interpreted as prevention of heart disease, cancer or another clinical condition.
For a balanced overview of the research, visit our guide to hydrogen therapy benefits and current scientific evidence.
Can Molecular Hydrogen Reduce Chronic Inflammation?
The most accurate answer is that molecular hydrogen may influence some inflammatory and redox pathways, but its clinical effects remain uncertain.
It has not been demonstrated to:
- Prevent the world’s leading causes of death
- Replace medication or medical treatment
- Cure chronic inflammatory disease
- Eliminate systemic inflammation
- Guarantee improved health or longevity
Molecular hydrogen should currently be presented as an investigational wellness approach rather than an established anti-inflammatory medical treatment.
Anyone with a diagnosed condition should speak to their healthcare professional before using hydrogen alongside existing care.
Evidence-Based Ways to Support Healthy Inflammatory Regulation
No single supplement, food or therapy can control every source of chronic inflammation.
The strongest foundations include:
- Not smoking
- Maintaining regular physical activity
- Eating a varied, fibre-rich diet
- Managing blood pressure, cholesterol and blood sugar
- Maintaining a suitable body weight
- Obtaining adequate sleep
- Limiting excessive alcohol intake
- Receiving appropriate vaccinations
- Treating chronic infections and medical conditions
- Attending recommended health checks and screenings
These steps do not guarantee disease prevention, but they are supported by much stronger evidence than any single emerging wellness intervention.
The Bottom Line
The relationship between chronic inflammation and disease is one of the most important areas of modern medical research.
Inflammatory activity contributes to many leading causes of death, including heart disease, stroke, COPD, diabetes and kidney disease. In infections, inflammation can be protective but may become damaging when the response is excessive or poorly controlled.
Molecular hydrogen is being investigated for possible effects on oxidative balance and inflammatory signalling. Preliminary human studies are interesting, but the evidence is not strong enough to describe hydrogen therapy as a proven treatment for chronic inflammation or any major disease.
The scientifically responsible conclusion is therefore:
Promising research does not yet equal proven clinical benefit.
Molecular hydrogen should complement—not replace—healthy habits, appropriate screening and evidence-based medical care.
