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Dec. 3 (UPI) -- Men under 45 have as much as a 50-50 chance of developing heart disease or having a stroke by the time they turn 75, while nearly one in four women face the same risk, a new analysis suggests. These are just two of the findings from what is being billed as the "most comprehensive analysis of long-term risk for cardiovascular disease related to non-high-density lipoprotein, or non-HDL, cholesterol" -- the type of cholesterol most linked with heart health.
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The study, published Tuesday in The Lancet, is the first to document an elevated risk for heart disease and stroke among younger people with high levels of non-HDL cholesterol, researchers say.
The researchers say, however, the study suggests that earlier intervention can lower younger people's risk for heart disease.
"This increased risk in younger people could be due to the longer exposure to harmful lipids in the blood," study co-author Barbara Thorand, of the German Research Center for Environmental Health, said in a statement.
Levels of non-HDL cholesterol and low-density lipoproteins, or LDL, in the blood are accepted as "causal risk factors" for cardiovascular disease, the authors say. But both also play a significant part in predicting a person's risk of developing cardiovascular disease, they added.
To learn just how much, the researchers analyzed individual-level data from nearly 400,000 participants in 38 studies from 19 countries in Europe, Australia and North America. Study participants had no cardiovascular disease at the start of the analysis and were monitored for up to 43.5 years for the occurrence of a fatal or non-fatal coronary heart disease event or ischemic stroke.
Using this data, the authors assessed and confirmed the long-term association between cholesterol levels and cardiovascular event risk.
They did this by estimating the probability of a cardiovascular event by age 75 for people between 35 and 70 based on gender, non-HDL cholesterol levels, age and the presence of known risk factors for cardiovascular disease like smoking, diabetes, high body weight and high blood pressure, among others. They also estimated how much risk could be reduced if non-HDL cholesterol levels were lessened by 50 percent.
Looking at data for all age groups and both sexes, the authors found that the risk for a cardiovascular event decreased continuously with decreasing non-HDL levels. And the risk was lowest for those individuals with the lowest non-HDL levels, defined as below 2.6 mmol non-HDL cholesterol per liter in the study.
For example, women with non-HDL cholesterol levels between 3.7 and 4.8 mmol/liter, who were younger than 45, and had at least two additional cardiovascular risk factors, had a 16 percent probability of experiencing a cardiovascular disease event by the time they reached 75 years of age. Notably, though, for women aged 60 or over with the same characteristics, the estimated risk was 12 percent, the study found.
For men, these figures were 29 percent and 21 percent, respectively.
In all, they found that men and women under 45 years of age have, respectively, a 12 percent to 43 percent and 6 percent to 24 percent risk having fatal or non-fatal heart disease or stroke by the age of 75. In general, individual risk depends on cholesterol level and the presence of other cardiovascular risk factors, the authors emphasized.
"The risk may also appear larger compared to older ages because people aged 60 years and older in our study had not developed cardiovascular disease up to this age, so they may be healthier than others of their age who were excluded from the study because they had had cardiovascular disease," Thorand said.
Among the 400,000 people included in the analysis, there were 54,542 fatal or non-fatal cases of heart disease and stroke.
In addition to the number of study participants, the Lancet study is unique because most similar analyses to date have focused on risk among older adults, and followed them for a period of 10 years or less.
"Our estimates suggest that halving non-HDL cholesterol levels may be associated with reduced risk of cardiovascular events by the age of 75 years, and that this reduction in risk is larger the sooner cholesterol levels are reduced," co-author Stefan Blankenberg said. "The risk scores currently used in the clinic to decide whether a person should have lipid-lowering treatment only assess the risk of cardiovascular disease over 10 years, and so may underestimate lifetime risk, particularly in young people."
On the positive side, Blankenberg and his colleagues noted that incidence of these cardiovascular problems may be reduced intervening early and intensively to reduce non-HDL cholesterol levels.
They found that if non-HDL cholesterol levels were reduced by 50 percent, for example, women and men younger than 45 years of age with starting levels of non-HDL cholesterol between 3.7 to 4.8 mmol/liter and who had two additional cardiovascular risk factors could reduce their risk from around 16 percent to 4 percent, and from around 29 percent to 6 percent, respectively.
According to the authors, these percentages are based on the use of cholesterol-lowering treatments for a longer period -- 30 years -- than has been studied in clinical trials -- which is, to date, roughly seven years.
"In lieu of needed clinical trial results investigating the benefits of long-term lipid-lowering therapy in people younger than 45, this study may provide helpful insights on the benefits of lipid-lowering therapy as primary prevention from an earlier age," Blankenberg said. "However, future research is needed to understand whether intervention in young people with a high lifetime risk, but low 10-year risk, would have more benefits than later intervention."
