Fit Middle-Aged Men May Maintain Youthful Lipid Levels Longer

Marlene Busko

May 16, 2015

COLUMBIA, SC — Levels of lipids other than HDL cholesterol increase from about age 20 to middle age and then decline, as a normal part of aging, but being very physically fit may delay middle-age dyslipidemia by 15 years, according to a new study published in the May 19, 2015 issue of the Journal of the American College of Cardiology (JACC)[1]

Dr Yoon-Moon Mark Park (University of South Carolina, Columbia) and colleagues created a model based on data from healthy 20- to 90-year-old men and found that total cholesterol, LDL cholesterol, triglycerides, and non–HDL cholesterol gradually increased until about age 45 to 55 and then subsequently declined. Moreover, men with low levels of cardiorespiratory fitness, as measured on a treadmill, reached above-normal levels of cholesterol (above 200 mg/dL) when they were in their 30s, but men with a high level of fitness had hypercholesterolemia only when they were about 45 years old.

Thus "a higher level of fitness is important to delay the age-associated increase in cholesterol," coauthor Dr Xuemei Sui (University of South Carolina) told heartwire from Medscape. These findings support other studies touting the benefits of exercise and reinforce the need for public-health policies that encourage people to keep active. "Clinicians should counsel their patients to maintain a higher fitness level for [multiple] health benefits, [including better lipid trajectory and], from 20 to 60 years, definitely give them an 'exercise prescription' or refer them to an exercise expert," she said.

Age-Related Lipid Trajectories

Park and colleagues aimed to determine whether cardiorespiratory fitness levels might alter age-related changes in lipids and lipoproteins, which has not been well explored until now.

They used data from 11,418 men who were seen at the Cooper Clinic in Dallas and were enrolled in the Aerobics Center Longitudinal Study, from 1970 to 2006. At enrollment, the men were 20 to 90 years old without known high cholesterol, high triglycerides, cardiovascular disease, or cancer.

The participants had two to 25 follow-up examinations (a mean of 3.5 examinations) where lipid values and cardiorespiratory fitness levels were determined.

The researchers found a U-shaped relationship between most lipids (total cholesterol, LDL cholesterol, triglycerides, and non–HDL cholesterol) and age, whereas HDL cholesterol rose in a linear fashion with age.

Independent of time, lifestyle, and metabolic characteristics, a higher level of cardiorespiratory fitness was associated with more favorable lipid and lipoprotein profiles, especially in young to middle-aged men. This is one more reason to encourage patients to engage in moderate exercising for at least 150 minutes a week, as recommended, Sui said.

Other Clinical Implications

According to JACC editor Dr Valentin Fuster (Mount Sinai Hospital, New York, NY), this paper is perhaps the most thorough evaluation of exercise and lipids to date. "I think what is most important about the paper is it [suggests] that perhaps people who exercise take better care of themselves—for example, they eat better, they avoid obesity—and as a consequence, their lipid profile is better." This may explain why the usual deterioration of the lipid profile that happens with age is somewhat delayed with an active vs a sedentary lifestyle, he suggested.

To heartwire , Dr Paul D Thompson (Hartford Hospital, Hartford, CT), who was not involved in the study, said that, interestingly, this study supports the concept that a high level of cardiorespiratory fitness may reduce a person's lifelong exposure to cholesterol. Clinicians should be thinking in terms of cardiovascular risk from years of exposure to high cholesterol, much like the concept of pack-years of cigarette smoking.

Although the less fit younger men had "old men's" cholesterol levels, "the actual differences were very small, and they really apply more to public-health messages than to individual patients," he cautioned. Moreover, this was a selected population of wealthy white men who were relatively fit to begin with. In addition, the treadmill test measures not only fitness but also reflects inherited physical ability, he noted

In an accompanying editorial[2], Drs Usman Baber and Paolo Boffetta (Icahn School of Medicine at Mount Sinai, New York, NY) also point out that the results of this study "should be interpreted in the context of the unique clinical, demographic, and risk characteristics of [healthy, fit] study participants." The prevalence of type 2 diabetes was only 2.8%; the mean body-mass index was 25.9; and more than 50% achieved maximal METs over 12, exceeding the conventional threshold of 10 METs that is associated with very low cardiac risk.

"These characteristics are not typical of the patients for whom an exercise prescription may be considered by physicians in daily clinical practice," they note. In a recent study, less than half of the patients referred for exercise stress testing could achieve 10 METs. However, this suggests that the favorable benefits of fitness on changes in lipoprotein levels might be even larger in typical higher-risk patients seen in clinical practice.

The study findings should not be generalized to women or to nonwhite men, they caution. Nevertheless it suggests that clinicians, healthcare policy makers, and other stakeholders should make a concerted effort so that these study findings can be translated into actions to encourage exercise to improve lipid levels.

"The current study by Park et al has provided novel, clinically relevant insights on the favorable impact of cardiorespiratory fitness on blood lipoprotein levels. Efforts should now be directed toward translating these findings to clinical and preventive practice," Baber and Bofetta conclude.

The study was supported by National Institutes of Health grants. Sui has no relevant financial relationships. Disclosures for the coauthors are listed in the article. The editorialists report they have no relevant financial relationships.

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