It has recently been reported that cholesterol has improved among youths in the U.S over the past twenty years, following that study, the same trend is seen among U.S. adults.
According to background facts in this new study, published in JAMA:
"Epidemiologic studies have demonstrated that high concentrations of low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) and low levels of high-density lipoprotein cholesterol (HDL-C) are major risk factors for coronary heart disease (CHD)."
Serum total cholesterol and LDL-C can cause hardening of the arteries. TC and LDL-C declined in adults between the periods of 1988-1994 and 1999-2002. During these periods, adults were seen to be taking more lipid-lowering medications.
Margaret D. Carroll, M.S.P.H., of the Centers for Disease Control and Prevention, Hyattsville, Md., and colleagues, performed an analysis to assess trends in serum lipids in adults between 1988 and 2010, using three U.S. cross-sectional National Health and Nutrition Examination Surveys.
Calculations of average levels of TC, LDL-C, HDL-C, non-HDL-C, and geometric triglyceride were also included in the study, as well as incidence of lipid-lowering medication use.
The investigators found that average TC fell from 206 mg/dL in 1988-1994 to 203 mg/dL in 1999-2002 and to 196 mg/dL in 2007-2010. Equivalent patterns were seen over this 22-year period in age-adjusted average TC levels for all adults.
From 1988 to 2010, there was a declining linear trend in age-adjusted average LDL-C levels for both men and women, from 129 mg/dL in 1988-1994 to 123 mg/dL in 1999-2002 and 116 mg/dL during 2007-2010. However, men had a larger age-adjusted average LDL-C level than women during 1988-1994 and 1999-2002; as time went on, there was no longer a difference during 2007-2010.
From 1988-1994 to 2007-2010, a rising linear trend in age-adjusted average HDL-C levels was seen for men and women. Between 1988 and 2010, a linear decrease in age-adjusted average non HDL-C level was seen for all adults. The age-adjusted geometric average triglyceride level for all people rose from 118 mg/dL in 1988-1994 to 123 mg/dL in 1999-2002 and then decreased in 2007-2010 to 110 mg/dL.
Another important result discovered was that from 1988 to 2010, there was a rising trend in the age-adjusted percentage of adults taking lipid-lowering medications.
Between men and women age 50 years or older, rises in use of lipid-lowering medications of 35 percent were seen. Among men and women not taking lipid-lowering medications, pattens in lipids were almost identical to those documented for adults overall. Average TC, non HDL-C, LDL-C, and geometric mean triglycerides in obese adults decreased between 1988 and 2010.
The researchers explain:
"The favorable trends in TC, non-HDL-C, and LDL-C may be due in part to a decrease in consumption of trans-fatty acids or other healthy lifestyle changes, in addition to an increase in the percentage of adults taking lipid-lowering medications. They are unlikely to be the result of changes in physical activity, obesity, or intake of saturated fat."
They point out the consumption of saturated fat as a percentage of calories did not decline between 1999 and 2008. Almost no progress was made from 1998 to 2008 in increasing free-time physical activity levels of adults, and the incidence of obesity in adults remains high (more than one-third of the public).
The authors conclude that despite the fact that adults taking lipid-lowering medications kept on increasing between 1999-2002, and 2007-2010, decreasing patterns in TC, non-HDL-C, and LDL-C, still took place for adults not receiving lipid-lowering medications.
Additional studies will be needed to measure the simultaneous effects of trans-fatty acids, lipid-lowering medications, and healthy lifestyle factors on TC, non-HDL-C, HDL-C, and triglycerides.