High-density lipoproteins (HDL) are molecules that transport fat through the body and to the liver so that it can be processed.
This helps to prevent excess accumulation, which is why it is also referred to as "good cholesterol."
High levels of HDL cholesterol have always been considered to be protective for heart health.
For this reason, specialists will often advise women on how to raise their "good cholesterol" levels at middle age. However, in recent years, some studies have suggested that HDL cholesterol may not, in fact, be as good for heart health as previous believed.
Now, researchers at the University of Pittsburgh Graduate School of Public Health in Pennsylvania — in collaboration with colleagues from other institutions — are questioning whether the ways in which we look at HDL cholesterol levels to predict cardiovascular risk may not be helpful for women.
"The results of our study," says lead author Samar El Khoudary, "are particularly interesting to both the public and clinicians because total HDL cholesterol is still used to predict cardiovascular disease risk."
Questioning the usefulness of looking at "good cholesterol" as protective for the heart, the team's findings are published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology of the American Heart Association.
Current notions may be inaccurate
The scientists analyzed the medical data of 1,138 women, aged 45–84, recruited through the Multi-Ethnic Study of Atherosclerosis.
"We have been seeing an unexpected relationship between HDL cholesterol and postmenopausal women in previous studies, but have never deeply explored it," notes El Khoudary.
At menopause, women's bodies go through several changes, especially hormonal fluctuations that can influence various physiological processes and measurements. El Khoudary and team believe that changes in estrogen levels, as well as other metabolic alterations, might lead to chronic inflammation, which can affect the quality of HDL particles over time.
The research assessed the number and size of HDL particles, as well as the total cholesterol that these particles carried, to establish whether high HDL levels were, in fact, protective for cardiovascular health in postmenopausal women.
El Khoudary and team also considered the influence of women's age at menopause and the time it took for women to transition to the postmenopausal period on HDL's contribution to heart health.
'Total HDL could mask significant risk'
Following their analysis, the researchers concluded that traditional methods of assesing HDL levels and their impact on cardiovascular health are not reliable enough in the case of postmenopausal women.
The scientists found a link between high HDL cholesterol and increased risk of atherosclerosis, particularly among women who had a greater age at the time of menopause and those at least 10 years into the postmenopausal period.
However, the researchers also found that a higher concentration of total HDL particles indicated a lower risk of developing atherosclerosis among the study participants.
But the results get even more complicated: having a high number of small-sized HDL particles, El Koudary and team observed, seemed to have cardioprotective effects for all postmenopausal women, regardless of their age at menopause or how far into postmenopause they were.
Conversely, large-sized HDL particles indicated an increased risk of cardiovascular disease in the case of women who were close to menopause. This, the researchers explain, is likely due to the fact that at this time, the quality of HDL is affected.
But as women transition away from the menopause period, later in life, it may be that HDL quality increases once more, meaning that HDL cholesterol regains its protective effects.
"Identifying the proper method to measure active 'good' HDL is critical to understanding the true cardiovascular health of these women," notes senior study author Dr. Matthew Budoff.
El Khoudary explains, "This study confirms our previous work on a different group of women and suggests that clinicians need to take a closer look at the type of HDL in middle-aged and older women, because higher HDL cholesterol may not always be as protective in postmenopausal women as we once thought."
"High total HDL cholesterol in postmenopausal women could mask a significant heart disease risk that we still need to understand."
Samar El Khoudary