Higher levels of non-fasting triglycerides are linked to an increased risk of ischemic stroke in men and women, while higher cholesterol only appears to affect men, whose stroke risk rises only when cholesterol levels are above a very high threshold, according to a new study from Denmark.
You can read how lead author Dr Marianne Benn from Copenhagen University Hospital, and colleagues, arrived at these findings in the Annals of Neurology, where an early online report on their 33-year study appeared on 18 February.
Current guidelines on stroke prevention include recommended levels for cholesterol, but not on non-fasting triglycerides, Benn told the press.
“Our study was the first to examine how the risk of stroke for very high levels of non-fasting triglycerides compared with very high cholesterol levels in the general population,” she added.
A stroke is where the blood supply to a part of the brain is interrupted or cut off completely, resulting in damaged brain tissue. The vast majority of strokes are of the ischemic type, where an obstruction in an artery cuts off the blood supply, often as a result of fatty deposits building up on the inside of the artery wall (atherosclerosis).
Our blood contains lots of compounds essential for life: including a range of fats or lipids. These include cholesterol, essential for cell building and maintenace, and for making some hormones, and triglycerides, which supply essential energy. However, while they are vital for life, when levels of these fats or lipids get too high, they can also contribute to cardiovascular illness and death.
Particles of low density lipoprotein (LDL), or “bad” cholesterol, and similar remnants of other lipids, are thought to be the main culprits in the fatty deposits or plaque that builds up inside arteries (leading to atherosclerosis), and some evidence suggests that higher levels of non-fasting triglycerides are markers of elevated levels of the lipoprotein remnants.
Figures from the World Health Organization (WHO) for 2004 show that 5.7 million deaths worldwide were due to stroke, which together with other cardiovascular diseases accounted for a total estimated 17.1 million deaths in that year.
For their study, Benn and colleagues examined data on 7,579 white women and 6,372 white men of Danish descent who were taking part in the Copenhagen City Heart Study.
When they joined the study between 1976 and 1978, the participants underwent tests that measured their baseline non-fasting triglyceride and cholesterol levels.
After this they were followed for up to 33 years, during which time 837 of the women and 837 of the men developed ischemic stroke, which was diagnosed when focal neurological symptoms lasted more than 24 hours. All the participants completed the follow up.
When they analyzed this data, Benn and colleagues found that:
- For both men and women, there was a step by step increase in risk of ischemic stroke in line with increasing levels of non-fasting triglycerides.
- In women, triglycerides levels of 1-2 mmol/L (89-177 mg/dL) were tied to 1.2 higher relative risk of stroke, which rose to 3.9-fold when triglycerides levels were 5 mmol/L (443 mg/dL) or higher, compared with women whose levels were under 1 mmol/L (89 mg/dL).
- In men, the relative risk ranged from 1.2 to 2.3, for similar triglyceride levels.
- There was no such increase in relative risk of stroke with increase in cholesterol, except in men whose levels were at 9 mmol/L (348 mg/dL) or higher, and for them the relative risk shot up to 4.4.
Benn said these findings suggest that “levels of non-fasting triglycerides should be included in stroke prevention guidelines which currently focus on total cholesterol and LDL cholesterol levels”.
“Nonfasting triglycerides, cholesterol, and ischemic stroke in the general population.”
Anette Varbo, Børge G. Nordestgaard, Anne Tybjærg-Hansen, Peter Schnohr, Gorm B. Jensen and Marianne Benn.
DOI: 10.1002/ana.22384
Additional source: Wiley-Blackwell (press release, 21 Feb 2011).
Written by: Catharine Paddock, PhD