Cardiorespiratory Fitness, the Triglyceride: HDL Ratio and Coronary Heart Disease Mortality Risk in Men

A while back, we talked about the importance of the blood Triglyceride:HDL ratio. To refresh your memory, we calculate the ratio simply by dividing the fasting blood triglyceride level by the blood level of HDL cholesterol. Here’s an example: Mark has a fasting blood triglyceride level of 100 mg/dL and an HDL-cholesterol level of 50 mg/dL. His Triglyceride:HDL ratio is 100 / 50 = 2. Low ratio values such as this one indicate good insulin sensitivity; which means that insulin is doing a great job helping to move glucose and amino acids from the blood into your cells. It also means that you have a relatively low risk of developing prediabetes, type 2 diabetes, and metabolic syndrome. Additionally, low ratios indicate that you have the relatively innocuous ‘large and fluffy’ LDL cholesterol type, which makes you less prone to coronary heart disease (CHD). On the other hand, let’s say that your blood triglycerides were 240 mg/dL and your HDL was 30 mg/dL. Some quick math tells us that the ratio this time is 8. This is a high ratio, suggesting that you are insulin resistant. Simply put, even though you are producing insulin, too much glucose is remaining in the blood. As a result, you have a relatively high risk of developing prediabetes, type 2 diabetes, and metabolic syndrome. A high ratio also tends to indicate that you have the more sinister ‘small and dense’ LDL cholesterol type, which makes you more prone to coronary heart disease (CHD) and stroke.                                                  

We’ve known for a few decades that having a moderate to high level of cardiorespiratory fitness (CRF) significantly decreases the risk of death from CHD as compared to having a low level of CRF. So with all this in mind, my colleagues and I decided to take a look at all possible combinations of CRF and Triglyceride:HDL ratio values to see how they impacted the risk of dying from CHD. We studied 40,269 apparently healthy men who underwent a comprehensive physical exam at the Cooper Clinic between 1978 and 2010. All of the men had a maximal treadmill stress test and blood work at the time of their exam.

Based on their treadmill test time and age, we divided them into 3 categories of CRF:

• ‍Low fit: men who scored in the bottom 20% (1st quintile) compared to other men in their age group.‍
• Moderate fit: men who scored in the next 40% (2nd and 3rd quintile) compared to other men in their age group.‍
• High fit: men who scored in the top 40% (4^th and 5^th quintile) compared to other men in their age group.

We also divided the men into four groups according to their Triglyceride:HDL ratio. Remember that the lower the ratio, the lower the risk of CHD:

• ‍Group 1: Triglyceride:HDL Ratio <1.51‍
• Group 2: Triglyceride:HDL Ratio 1.51-2.39‍
• Group 3: Triglyceride:HDL Ratio 2.40-3.90‍
• Group 4: Triglyceride:HDL Ratio >3.90

The group was then tracked for an average of 16.6 years. During that time, 556 men died from CHD. Not surprisingly, we found that both CRF and Triglyceride:HDL ratio were each very strong and independent predictors of CHD death. We took it a step further and looked at the risk of death in all 12 possible CRF and Triglyceride:HDL ratio combinations; this is shown in the Figure below. We took age, length of follow-up, family history of CHD, and smoking into consideration before doing the analyses. The different bars that you see in the Figure show the risk of CHD death within each CRF-Triglyceride:HDL ratio category; the higher the bar, the higher the risk of death. As you can see from the Figure, the lowest risk of CHD death was seen in Group 1 men with high levels of CRF, while the highest risk of death was seen in Group 4 men with low levels of CRF. The novel finding was that within all 4 Triglyceride:HDL ratio groups, we saw the greatest risk of death in low fit men, while the risk was decreased in moderate fit men, and tended to be the lowest in high fit men. Interestingly, among all Group 1 men, those who were low fit were more than twice as likely to die from CHD as high fit men! So, even though all the men in Group 1 had low risk Triglyceride:HDL ratios, their fitness level had a big impact on their risk of dying from CHD during the follow-up.

The take-home message is that regardless of the Triglyceride:HDL Ratio, men need to achieve at least a moderate level of CRF in order to achieve the lowest risk possible. Most men should be able to achieve this level of CRF by meeting the current public health guidelines for physical activity: Adults should accumulate at least 150 minutes per week of moderate aerobic activity or at least 75 minutes per week of vigorous aerobic activity. If achieving significant weight loss or a high level of CRF is the goal, then as much as 300 minutes per week of moderate, or 150 minutes per week of vigorous aerobic activity may be necessary. Be sure to start slowly and gradually work up to these suggested levels of activity.

So, the next time you have blood work done, calculate your Triglyceride:HDL Ratio if you do not see this value on your report. Remember that the higher the ratio, the higher the risk of developing prediabetes, diabetes, metabolic syndrome, and dying from CHD. It also pays to remember that unlike prescription medications, lifestyle changes (i.e. regular physical activity, healthy diet, quitting smoking, and modest weight loss if needed) cost nothing and have no side effects!

References

1. Lamarche, B., Lemieux, I., Despres, J.P. (1999). The small dense LDL phenotype and the risk of coronary heart disease: epidemiology, pathophysiology, and therapeutic aspects. Diabetes Metab. 25:199-211.

2. Farrell, S.W., Finley, C.E., Barlow, C.E., Willis, B.L., DeFina, L.F., Haskell, W.L., Vega, G.L. (2017). Moderate to high levels of cardiorespiratory fitness attenuate the effects of triglyceride to high-density lipoprotein cholesterol ratio on coronary heart disease mortality in men. Mayo Clin Proc, 92(12):1763-1771. http://dx.doi.org/10.1016/j.mayocp.2017.08.015