Cholesterol levels tend to be higher right after the Christmas holiday period than at other times of the year, according to Danish researchers.
Their study, published recently in the journal Artherosclerosis, specifically found that the cholesterol levels — at least of Danes — tend to be 20 percent higher, on average, in January than in June.
It also found that people who had their cholesterol tested in January were six times more likely to be diagnosed with high cholesterol, a risk factor for heart disease and stroke, than those tested at other times of the year.
As the researchers somewhat amusingly point out, that finding that cholesterol levels shoot upward in January most likely reflects how Danes spend the days around Christmas — engaging with family and friends in “hygge” (very roughly translated as “cozy time together”) and feasting on rich food.
Being sedentary and eating fatty foods can, of course, make cholesterol levels climb — something people who have already been diagnosed with high cholesterol should be aware of during the holiday season.
But the study’s findings also suggest, say the Danish researchers, that people who are newly diagnosed with high cholesterol in late December or January may want to make sure their levels are retested a few months later. The first reading might have been a temporary spike.
For the study, the researchers randomly selected more than 25,000 people, aged 20 to 100 (average age: 59), from a group who were already participating in a larger, ongoing research project known as the Copenhagen General Population Study. None of the participants was taking cholesterol-lowering medications, such as statins.
The researchers analyzed data from blood lipid tests given to the participants between April 2014 and November 2017. For their primary findings, they looked specifically at the test results for total cholesterol and LDL (“bad”) cholesterol. They pooled and then averaged those results for different times of the year.
They found that the participants’ average total cholesterol, when measured across the entire year, was 205 mg/dL, while their average LDL cholesterol was 116 mg/dL. Both numbers are higher than recommended levels (which are similar in Denmark and the United States): less than 200 mg/dL for total cholesterol and less than 100 mg/dL for LDL.
When the researchers looked at the rolling averages of the test results, however, they saw that total and LDL cholesterol levels increased in late December and January and then decreased shortly after.
Remarkably, 89 percent of the study’s participants had high total cholesterol during the first week of January. That compared to 53 percent of the people tested in April, May and June combined.
Limitations and implications
The study comes with plenty of caveats. The participants were all volunteers. They could say yes or no to having their blood lipid levels tested. It may be that the people who said yes during January were more worried about their health — and thus, perhaps, more likely to have high cholesterol.
Also, the study’s primary results were based on a single blood test from each participant. Individual participants weren’t followed throughout the year to see if their cholesterol levels rose and fell with the seasons.
In addition, the study’s participants were white people living in Denmark. (The researchers say they selected only white Danes because they wanted to up the odds that the people in their study had indulged in traditional Danish Christmas foods.) The study’s results may not be applicable to populations in other parts of the world and/or to populations that are more ethnically and racially diverse.
Still, the findings support an earlier (but very small), British study that found slight increases of total and LDL cholesterol immediately after Christmas.
“Our study shows strong indications that cholesterol levels are influenced by the fatty food we consume when celebrating Christmas,” says Dr. Anne Langsted, the study’s lead author and a clinical biochemist at the University of Copenhagen, in a press release.
Individuals who receive a post-holiday high cholesterol reading may want to have another test taken later in the year to confirm the diagnosis, adds the study’s senior author, Dr. Signe Vedel-Krogh, in the same release.
“There is a greater risk of finding that you have elevated cholesterol if you go to the doctor and have your cholesterol tested straight after Christmas,” she says. “It is important to be aware of this, both for doctors who treat high cholesterol and those wishing to keep their cholesterol levels down.”