Researchers followed patients with both chronic lung disease (COPD) and heart disease for five years to see how high blood sugar levels affected their health. They found that patients with high blood sugar had more serious lung flare-ups and higher death rates compared to those with normal blood sugar. The study combined data from a Chinese hospital and a large U.S. health survey, involving thousands of patients. High blood sugar appeared to be a major risk factor for worse outcomes, suggesting that controlling blood sugar levels could be an important part of treatment for people dealing with both of these serious conditions.

The Quick Take

  • What they studied: Whether high blood sugar levels make it harder for people who have both lung disease and heart disease to stay healthy
  • Who participated: Patients admitted to a Chinese hospital with both COPD and heart disease, plus data from thousands of Americans in a national health survey. Researchers tracked them for 5+ years.
  • Key finding: Patients with high blood sugar (above 7 mmol/L) were 3.6 times more likely to die and had significantly more serious lung flare-ups than those with normal blood sugar levels
  • What it means for you: If you have both lung disease and heart disease, keeping your blood sugar under control may be just as important as managing your lungs and heart. Talk to your doctor about blood sugar monitoring and control strategies.

The Research Details

This was a real-world study that followed actual patients over time rather than a controlled lab experiment. Researchers recruited patients from a hospital in China starting in December 2016 and tracked them until March 2023—a period of about 6 years. They also used data from a large U.S. national health survey that had been collecting information since 1999. All patients in the study had both COPD (chronic obstructive pulmonary disease, a serious lung condition) and CHD (coronary heart disease, a heart condition). The researchers divided patients into two groups based on their fasting blood sugar levels: those with normal levels and those with high levels (hyperglycemia). They then tracked what happened to these patients over time, recording how often they had serious lung flare-ups and whether they survived.

This type of study is valuable because it looks at real patients in real-world situations rather than controlled experiments. By following patients over 5+ years, researchers could see long-term effects that might not show up in shorter studies. Using data from both a Chinese hospital and a U.S. national survey helps confirm that the findings apply to different populations, not just one group of people.

The study’s strengths include its long follow-up period, large sample size combining multiple data sources, and use of established statistical methods to identify risk factors. However, the study relied partly on self-reported information from questionnaires, which can be less accurate than direct medical measurements. The study was observational, meaning researchers watched what happened naturally rather than randomly assigning people to different treatments, so we can’t be completely certain that high blood sugar directly causes worse outcomes versus being associated with other health problems.

What the Results Show

The main finding was clear: patients with high blood sugar had much worse outcomes than those with normal blood sugar. Over the 5+ year follow-up period, patients with high blood sugar were 3.6 times more likely to die from any cause. They also experienced significantly more frequent and severe lung flare-ups that required medical attention. When researchers looked at survival curves (graphs showing how many patients survived over time), the difference between the two groups became increasingly obvious as time went on. By the end of the study period, far fewer patients in the high blood sugar group were still alive compared to the normal blood sugar group.

The researchers also discovered that patients with high blood sugar had different blood test results compared to those with normal blood sugar. They had higher levels of inflammation markers (C-reactive protein and brain natriuretic peptide), lower levels of protective proteins (albumin), and were more likely to have fungal infections. Interestingly, the high blood sugar group had lower smoking rates, suggesting that high blood sugar itself—not just smoking—was driving the worse outcomes. Age and previous tuberculosis infection were also identified as independent risk factors for death, along with several blood test abnormalities.

This study fills an important gap in medical knowledge. While previous research has shown that high blood sugar is bad for people with either lung disease or heart disease separately, very little research had examined what happens when someone has both conditions simultaneously. This study suggests that the combination of COPD, heart disease, and high blood sugar creates a particularly dangerous situation. The findings align with general medical knowledge that blood sugar control is important for overall health, but this research specifically demonstrates its critical importance in this vulnerable population.

The study has several important limitations to consider. First, the sample size wasn’t clearly specified in all analyses, making it harder to judge statistical reliability. Second, the study relied partly on patient self-reporting and medical records rather than all measurements being taken directly by researchers. Third, because this was an observational study rather than a randomized controlled trial, we can’t be certain that high blood sugar directly causes worse outcomes—it’s possible that high blood sugar is a marker of other underlying health problems. Fourth, most of the hospital data came from China, which may have different healthcare practices than other countries. Finally, the study couldn’t account for all possible factors that might affect outcomes, such as medication adherence or specific treatments patients received.

The Bottom Line

If you have both COPD and heart disease, work closely with your doctor to monitor and control your blood sugar levels. This might include regular blood sugar testing, dietary changes, increased physical activity (as tolerated), and possibly medications. The evidence suggests this could significantly reduce your risk of serious complications and death. However, these recommendations should be personalized with your healthcare team based on your specific situation.

This research is most relevant to people who have been diagnosed with both COPD and coronary heart disease. It’s also important for their doctors and caregivers. People with only one of these conditions should still manage their blood sugar, but this study specifically highlights the extra importance for those with both. If you have risk factors for these conditions (like smoking, obesity, or family history), this research suggests that blood sugar control should be part of your prevention strategy.

Improvements in blood sugar control may reduce your risk of serious lung flare-ups within weeks to months, as inflammation markers can improve relatively quickly. However, the major benefits in terms of reducing mortality risk and long-term complications typically take months to years to become apparent. This is why consistent, long-term blood sugar management is so important.

Want to Apply This Research?

  • Log your fasting blood sugar readings daily (ideally first thing in the morning before eating). Set a target range with your doctor (typically 80-130 mg/dL for people with diabetes) and track how often you stay within that range. Aim for at least 80% of readings in your target range.
  • Use the app to set reminders for blood sugar testing at the same time each morning. Log meals and physical activity to see how they affect your blood sugar. Set a goal to increase physical activity by 10 minutes per day and track it in the app. Create alerts if readings go above your target range so you can take action quickly.
  • Review your weekly blood sugar trends in the app to identify patterns. Share monthly reports with your doctor to adjust medications or lifestyle changes as needed. Track correlations between blood sugar levels and lung symptoms or energy levels. Monitor for signs of lung flare-ups and note any relationship to blood sugar control.

This research describes associations between high blood sugar and worse outcomes in people with both COPD and heart disease, but it does not prove that high blood sugar directly causes these problems. This information is for educational purposes and should not replace professional medical advice. If you have COPD, heart disease, or high blood sugar, consult with your healthcare provider before making any changes to your treatment plan. Do not stop or change any medications without medical supervision. This study was observational in nature, meaning it tracked what happened naturally rather than testing a specific treatment, so individual results may vary.