Published research suggests that cholesterol levels commonly rise as people age and then decrease later in life. “Abnormal lipids are important risk factors that play a critical role in the development of cardiovascular disease (CVD),” says Xuemei Sui, MD, MPH, PhD. “Therefore, identifying modifiable risk factors that can affect lipid profiles might help reduce the burden of CVD.”
Some previous analyses have explored the effect of cardiorespiratory fitness (CRF) on changes in blood glucose and blood pressure and have shown beneficial changes with higher CRF levels. However, few studies have looked at the effect of CRF on age-related longitudinal changes of lipids and lipoproteins. “With the high percentage of sedentary people living in the United States, it is particularly important to understand the specific benefits of exercise and fitness and the roles they play in health,” says Dr. Sui.
In a study published in the Journal of the American College of Cardiology, Dr. Sui and colleagues used data from health exams performed during the Aerobics Center Longitudinal Study. The long-term study ran from 1970 to 2006 and included more than 11,400 men between the ages of 20 and 90. Patients did not have known high cholesterol, high triglycerides, CVD, and cancer at baseline. Each participant took a treadmill exercise test to determine their baseline CRF level and had their total cholesterol, LDL cholesterol, triglycerides, HDL cholesterol, and non-HDL cholesterol levels recorded.
Men with lower CRF levels had a greater risk of developing high cholesterol in their early 30s, according to the results. Men with higher levels of CRF did not develop high cholesterol until their middle 40s (Table). “Our findings demonstrate that lipid profile impairment is an inevitable, natural process with aging in men,” says Dr. Sui. “Higher CRF levels may help delay age-associated increases in total cholesterol, LDL cholesterol, and triglycerides.”
Dr. Sui says the results were not surprising since physicians are encouraged to use lifestyle modifications to help patients with abnormal lipid levels. “However,” she says, “the significant effects of CRF on blood lipids are novel findings. Physicians should realize the great benefits of higher levels of fitness related to delaying the onset of dyslipidemia.”
One key finding Dr. Sui notes is that men with low CRF reached abnormal total cholesterol values approximately 15 years earlier than those with higher CRF levels. “Medications always have the potential for side effects,” he says, “but lifestyle approaches aimed at becoming more physically active can bring many positive health changes.”
Importantly, the men in the higher CRF group in this study would not be classified as elite or professional athletes. Rather, they were considered relatively active people with an activity level of 150 minutes per week of moderate activity or 75 minutes per week of vigorous activity.
“Patients can accumulate 150 minutes per week of moderate-intensity physical activity by walking, jogging, running, swimming, bicycling, or other activities,” says Dr. Sui. “By achieving this goal, they can increase their CRF levels and appear likely to see benefits with regard to their lipid levels.” For those not currently exercising, guidelines recommend starting slowly and progressively working up to the physical activity guideline recommended levels.
In light of the results, Dr. Sui suggests that physicians actively counsel their patients to maintain a higher fitness level for various health benefits and to achieve better lipid profiles. “Depending on patient’s fitness level and their age, especially between ages 20 and 60, an exercise prescription is needed,” Dr. Sui says. “Another option to consider would be to refer patients to exercise experts who can help with developing and tailoring exercise regimens.” When considered collectively with previous research on the effect of CRF levels on glucose and blood pressure, findings of the study by Dr. Sui and colleagues further demonstrate the importance of improving CRF to delay the onset of high cholesterol, diabetes, or high blood pressure.
To further validate the findings, Dr. Sui says the effects of CRF on dyslipidemia should be explored in populations besides just men. “It will benefit us to study this connection in a more representative U.S. population,” she says. “We should also conduct research in women, though it is unlikely that results would be much different for these individuals. In addition, we should study patients who are using lipid-lowering medications and the effects of CRF levels on these people. In the meantime, clinicians should make every effort to have their patients maintain a higher level of CRF, exercise regularly, and be physically active in order to achieve good lipid goals.”