D3.1.20 Hormone replacement therapy and the risk of coronary heart disease (HL) Notes

Hormone Replacement Therapy and the Risk of Coronary Heart Disease

1. Consider a woman in her 50s experiencing menopausal symptoms like hot flashes and mood swings.
2. Her doctor suggests hormone replacement therapy (HRT) to ease these symptoms.
3. But then she hears that HRT might increase her risk of coronary heart disease (CHD).
4. Confused, she wonders: Is HRT safe?

What is Hormone Replacement Therapy (HRT)?

1. It helps alleviate symptoms such as:
   1. Hot flashes and night sweats
   2. Mood swings
   3. Vaginal dryness
   4. Reduced sex drive
   5. Bone weakening (osteoporosis)

Early Studies Suggested A Promising Correlation

1. In the 1980s and 1990s, epidemiological studies suggested that women using HRT had a lower incidence of CHD.
2. This led to the belief that HRT might protect the heart and became a widely accepted idea in the medical community.

Randomized Controlled Trials Indicated Slight Increases in CHD Risk

1. Later, randomized controlled trials (RCTs) the gold standard in research revealed a different story.
2. These studies showed that HRT was actually associated with a slight increase in CHD risk.

Correlation is Not Causation: Lessons from Early HRT Studies

1. The discrepancy between early studies and RCTs highlighted a key concept: correlation does not equal causation.
2. Early studies did not account for confounding factors that influenced the results.

The Role of Socioeconomic Status

1. One major confounding factor was the socioeconomic status of HRT users.
2. Women undergoing HRT in early studies were more likely to belong to higher socioeconomic groups.
3. These groups tend to have:
   1. Better access to healthcare.
   2. Healthier lifestyles (e.g., balanced diets, regular exercise).
   3. Lower stress levels.
4. These factors independently lower the risk of CHD and created the illusion that HRT itself was protective.

How HRT Affects the Heart

1. The relationship between HRT and CHD is complex and depends on multiple factors:
   1. Oestrogen’s Protective Role: Oestrogen can improve blood vessel function and reduce bad cholesterol (LDL), potentially lowering CHD risk.
   2. Timing Matters: Starting HRT soon after menopause may have different effects compared to starting it later.
      1. Early initiation might provide cardiovascular benefits, while later use could increase CHD risk.
   3. Individual Differences: Age, health status, and the type of HRT (oestrogen alone vs. combined with progesterone) influence outcomes.

Why RCTs Are Essential

1. The HRT-CHD debate highlights the importance of evidence-based medicine.
2. Randomized controlled trials (RCTs) are crucial because they:
   1. Eliminate confounding variables by randomly assigning participants to treatment or control groups.
   2. Provide more reliable data than observational studies.
3. Long-term studies are especially important for understanding treatments like HRT, where effects may vary over time.

Reflection

1. The story of HRT and CHD is a powerful reminder of the complexity of scientific inquiry.
2. It underscores the importance of rigorous research, critical thinking, and personalized healthcare decisions.