Rising triglyceride levels may be behind rising rates of obesity

Nov 10 2008

A new 30-year analysis of the National Health and Nutrition Examination Survey (NHANES) database conducted by the National Lipid Association (NLA) indicates that while Americans are doing a better job of managing LDL or "bad" cholesterol, the percentage of adults with high triglycerides, a blood fat linked to heart disease, has doubled, leaving many people at risk for potentially life-threatening events such as heart attack or stroke.

Results of the analysis were presented today at the American Heart Association's Annual Scientific Sessions in New Orleans.

Between 1976 and 2006 the number of Americans with unhealthy isolated LDL levels dropped from 43 percent to 40 percent, an improvement that researchers attribute to more aggressive educational initiatives and treatment. However, far less emphasis has been placed on controlling triglycerides. The rising rates of isolated high triglycerides seen over the last three decades underscore the need for physicians and patients to understand and treat all three key lipids, which include LDL, HDL or "good" cholesterol and triglycerides.

"Studies have shown that unhealthy levels of triglycerides and HDL can lead to heart attack and stroke," said study author Jerome D. Cohen, M.D., chairman of the National Lipid Association's consumer affairs committee and professor emeritus of internal medicine and cardiology at the St. Louis University School of Medicine. "As we continue our efforts to reduce the toll of heart disease in America, this study clearly shows the need for increased focus on controlling triglycerides, in addition to the other components of the lipid profile."

Along with LDL and HDL, triglycerides are the third component of the lipid profile and are an independent and compounding risk factor for heart disease, the leading cause of death in the U.S. Studies have shown that the risk of developing heart disease doubles when triglyceride levels are above 200 mg/dL. When triglycerides are above 200 mg/dL and HDL is below 40 mg/dL, a person is at four times the risk of developing heart disease. Other studies have shown that low HDL is predictive of cardiovascular events even when LDL is at goal.

While the percentage of the population with unhealthy HDL levels has remained relatively consistent over the past 30 years, the percentage of adults with a combination of high triglycerides and low levels of HDL doubled from two to four percent, further highlighting the need to simultaneously treat multiple lipids.

Obesity, Age and Triglycerides

The analysis cited dramatic increases in the number of obese Americans as one possible explanation for the spike in triglycerides over the last three decades. Data indicate a strong correlation between obesity (defined as a BMI greater than or equal to 30 kg/m2) and high triglycerides. Rates of obesity more than doubled from 15 percent in 1976 to 33.7 percent in 2006, while the percentage of Americans with isolated high triglycerides also doubled from 2.4 to 5.5 percent.

The study also revealed a strong increase in elevated triglyceride levels among people over the age of 60, with the likelihood of having unhealthy triglycerides increasing nearly five-fold from 1.8 percent in 1976 to 8.7 percent in 2006. This extensive analysis provides strong evidence of the connections between age, weight and lipid levels over the last 30 years.

"As Americans age and rates of obesity continue to grow exponentially, it is becoming more important to monitor and manage HDL and triglycerides, along with LDL," said Thomas Bersot, M.D., president of the National Lipid Association. "By elevating the need to address all three lipids, we hope to improve heart health in America."

Conclusions

Researchers involved with the study concluded that based on these findings, physicians and other healthcare professionals should closely monitor patients' triglyceride levels in an effort to improve preventive care. Patients, for their part, should be aware of all three lipids and work with their healthcare professionals to reach optimal lipid levels.

Study Methodology

Adults aged 20 to 74 years who took the blood lipid examination were selected from NHANES II (1976-1980), NHANES III (1988-1994), and NHANES 1999-2006. Adults missing values on total cholesterol, HDL cholesterol or triglycerides were excluded. Where LDL was missing, the Friedewald equation was used to calculate LDL for patients with TG < 400 and the Hattori equation was used to calculate LDL for patients with TG greater than or equal to 400.

Lipid levels were measured for the sample of adults with laboratory data who were examined in the morning and had fasted for 8.5 to 23 hours. High triglycerides and LDL and low HDL levels were characterized in the analysis as non-optimal, defined as greater than or equal to 150 mg/dL for triglycerides, < 40 mg/dL for HDL and greater than or equal to 100 mg/dL for LDL. Obesity was defined as BMI greater than or equal to 30 kg/m2.

This study was conducted by the National Lipid Association and analysis and research were performed by HealthCore, with the support of an independent grant from Abbott Laboratories.

About the National Lipid Association

The National Lipid Association (NLA) is a multidisciplinary non-profit membership association that serves the community of healthcare professionals who manage patients with lipid disorders and cardiovascular disease. The NLA's public health mission is to help reduce deaths related to dyslipidemias. To help consumers better understand and manage lipids the NLA launched the www.learnyourlipids.com Web site.