Contents lists available at ScienceDirect
Atherosclerosis
journal homepage: www.elsevier.com/locate/atherosclerosis
The Christmas holidays are immediately followed by a period of
hypercholesterolemia
Signe Vedel-Krogha,b
, Camilla J. Kobyleckia,b
, Børge G. Nordestgaarda,b,c
, Anne Langsteda,b,∗
a
Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Denmark
b
The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Denmark
c
Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
H I G H L I G H T S
• Celebrating Christmas is associated with higher levels of total and LDL cholesterol.
• Celebrating Christmas is associated with a higher risk of hypercholesterolemia.
• A diagnosis of hypercholesterolemia should not be made around Christmas.
A R T I C L E I N F O
Keywords:
Epidemiology
Cohort study
Total cholesterol
LDL cholesterol
A B S T R A C T
Background and aims: We aimed to test the hypothesis that levels of total and low-density lipoprotein cholesterol
are increased after Christmas and that the risk of hypercholesterolemia is increased after the Christmas holidays.
Methods: We conducted an observational study of 25,764 individuals from the Copenhagen General Population
Study, Denmark, aged 20–100 years. Main outcome measures were mean total and LDL cholesterol levels.
Hypercholesterolemia was defined as total cholesterol > 5 mmol/L (> 193 mg/dL) or LDL-cholesterol > 3
mmol/L (> 116 mg/dL).
Results: Mean levels of total and LDL cholesterol increased in individuals examined in summer through
December and January. Compared with individuals examined in May–June, those examined in
December–January had 15% higher total cholesterol levels (p < 0.001). The corresponding value for LDL
cholesterol was 20% (p < 0.001). Of the individuals attending the study during the first week of January,
immediately after the Christmas holidays, 77% had LDL cholesterol above 3 mmol/L (116 mg/dL) and 89% had
total cholesterol above 5 mmol/L (193 mg/dL). In individuals attending the Copenhagen General Population
Study in the first week of January, the multivariable adjusted odds ratio of hypercholesterolemia was 6.0 (95%
confidence interval 4.2–8.5) compared with individuals attending the study during the rest of the year.
Conclusions: Celebrating Christmas is associated with higher levels of total and LDL cholesterol and a higher risk
of hypercholesterolemia in individuals in the general population. Thus, a diagnosis of hypercholesterolemia
should not be made around Christmas, and our results stress the need for re-testing such patients later and
certainly prior to initiation of cholesterol-lowering treatment.
1. Introduction
During December, Danes have numerous gatherings with family,
friends, and colleagues to celebrate the upcoming Christmas holidays.
Likewise, Christmas Eve and the following days are spent with family
and friends to “hygge”, a special Danish term, which may be described
as “spending cozy time together” [1]. At most of these gatherings, large
amounts of food are consumed. Moreover, most individuals are seated
for several hours, while eating and drinking, and generally spend sedentary
time indoor during the cold and wet holiday season. Traditional
Danish Christmas food contains large amounts of fat and sugar. Dishes
such as roasted pork, rich sauces, sugar glazed potatoes, and desserts
with whipped cream represent a main part of the food ingested.
A long-term high-fat diet has been associated with higher total and
low-density lipoprotein (LDL) cholesterol compared with a low-fat diet,
at least in overweight and obese individuals [2]. Thus, a month of
https://doi.org/10.1016/j.atherosclerosis.2018.12.011
Received 4 October 2018; Received in revised form 15 November 2018; Accepted 13 December 2018
∗
Corresponding author. Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev Ringvej 75, DK-2730, Herlev,
Denmark.
E-mail address: anne.langsted.01@regionh.dk (A. Langsted).
Atherosclerosis 281 (2019) 121–127
Available online 19 December 2018
0021-9150/ © 2018 Elsevier B.V. All rights reserved.
T
“hygge” accompanied by a Danish Christmas diet could potentially
influence patients’ chance of a hypercholesterolemia diagnosis if cholesterol
levels are determined immediately following the Christmas
holidays. Indeed, in a study of 35 individuals 30 years ago, the UK
Christmas feast was associated with both gain in weight and slight increases
in levels of triglycerides and total and LDL cholesterol immediately
following Christmas [3], therefore any hypercholesterolemia
diagnosed around Christmas may not reflect the cholesterol levels
during the rest of the year.
High cholesterol is a major causal risk factor for cardiovascular
disease [4, 5] and targets for cholesterol-lowering therapy are to
achieve total cholesterol ≤5 mmol/L (≤193 mg/dL) generally, and
≤4 mmol/L (≤155 mg/dL) in high risk individuals [5]. Likewise, LDL
cholesterol should be ≤ 3 mmol/L (≤116 mg/dL) in low risk individuals,
≤2.5 mmol/L (≤97 mg/dL) in high risk individuals, and
≤1.8 mmol/L (≤70 mg/dL) in very high-risk individuals. As cholesterol-lowering
therapy is often lifelong, the need to accurately identify
individuals in true need of this treatment is pertinent. Thus, attention
on possible seasonal variation in cholesterol levels is important.
We hypothesized that in individuals in the general population, levels
of total and LDL cholesterol increase after Christmas and that the
risk of hypercholesterolemia is increased after the Christmas holidays.
2. Materials and methods
2.1. Study population
We included individuals from the Copenhagen General Population
Study (CGPS), a cohort study of the Danish general population of individuals
living in Greater Copenhagen.[6, 7] At birth, all individuals in
Denmark are assigned a unique identification number in the national
Danish Civil Registration System. Using this number, individuals
20–100 years of age were randomly selected to reflect the adult Danish
population. Importantly, people are invited randomly by age and sex,
year around, securing that the characteristics of individuals examined
at any time of year are similar. Also, only white individuals of Danish
Fig. 1. Moving averages for total and LDL cholesterol from April 2014 to November 2017 in individuals not on cholesterol-lowering therapy in the Copenhagen
General Population Study.
Moving averages of total and LDL cholesterol from April 2014 to November 2017. Each blue dot represents an individual measurement. Red dots represent moving
average values as the average for 150 individuals before and 150 individuals following each individual person. (For interpretation of the references to colour in this
figure legend, the reader is referred to the Web version of this article.)
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
122
descent mainly with a Christian upbringing are examined; naturally not
all people of Danish descent are active Christians, but essentially all
celebrate the Christmas holidays. The CGPS was initiated in 2003 with
ongoing follow-up examinations started in 2014. Individuals were invited
to participate from Monday through Thursday throughout the
year, except for national holidays including the Christmas holidays. All
participants completed a comprehensive questionnaire, underwent a
physical health examination, and had blood drawn for biochemical
tests. The study was conducted according to the Declaration of Helsinki,
approved by the Ethics Committee of the Capital Region of Denmark
(H-KF-01-144/01), and all individuals gave written informed consent.
For this study, we included 25,764 individuals from the second examination
of the CGPS not on cholesterol-lowering therapy and with
total and LDL cholesterol measurements from April 2014 through November
2017, simply to focus on the individuals examined most re-
cently.
2.2. Total and LDL cholesterol
For all subjects participating throughout the year, cholesterol levels
were analyzed within 24 h on fresh samples using standard hospital
assays. Nonfasting total and LDL cholesterol were measured using colorimetric
assays; from 2014 to 2016 levels were determined using a
Konelab autoanalyzer and from 2016 and onwards using a Roche Cobas
6000. Hypercholesterolemia was defined as total cholesterol > 5
mmol/L (> 193 mg/dL) or LDL cholesterol > 3 mmol/L (> 116 mg/
dL). In 11,055 individuals, we had repeated measurements of total and
LDL cholesterol approximately 10 years apart. Of these, 244 individuals
participated in the first week of January in 2014–2016 and at another
time of the year in 2004–2006 and 227 individuals participated in the
first week of January in 2004–2006 and at another time of the year in
2014–2016. Additionally, as a negative control we included repeated
measurements from 206 individuals who attended the CGPS in
2014–2016 in the first week of September but had also attended the
study at another time of the year in 2004–2006.
2.3. Myocardial infarction
We included the number of first time myocardial infarctions according
to time of the year in all 25,764 individuals. Information on
myocardial infarction (World Health Organization International
Classification of Diseases: ICD8: 410; ICD10: I21eI22) were obtained by
linking the CGPS to the national Danish Patient Registry which record
all discharge diagnoses from Danish hospitals. In total, we included 333
first time events of myocardial infarction.
2.4. Covariates
Measured weight (kg) and height (m) were used to calculate body
mass index (kg/m2
). Diabetes mellitus was defined as self-reported
disease, use of anti-diabetic medication, or a non-fasting plasma glucose
above 11 mmol/L. Alcohol consumption was self-reported. Smoking
was self-reported, and participants were grouped as never, former, or
current smokers according to the questions “Do you smoke?” and “Have
you previously smoked?“. Cholesterol-lowering therapy was self-re-
ported.
2.5. Statistical methods
Analyses were done in Stata/SE version 13 for Windows.
Moving average was calculated for every individual (termed the
“central individual”) by taking the mean of total and LDL cholesterol for
the 150 individuals before and the 150 individuals after this central
individual. P values for trends were estimated using Kruskal Wallis nonFig.
2. Seasonal variation in mean total and LDL cholesterol in individuals not on cholesterol-lowering therapy in the Copenhagen General Population Study.
Time is grouped from the 15th in the specific month to the 14th in the following month, to better capture the period surrounding the Christmas holidays.
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
123
parametric trend test or χ2 test. Comparison of total and LDL cholesterol
levels by months were done using Wilcoxon rank-sum test. A logistic
regression model with 95% confidence intervals was used to
compare risk of hypercholesterolemia according to time in a model
adjusted for possible confounders which were sex, age, body mass
index, diabetes mellitus, alcohol consumption, and smoking status. All
reported p-values are two sided.
3. Results
25,764 individuals not on cholesterol-lowering therapy with a
median age of 59 years (interquartile range 50–69) were included in the
study. Median total cholesterol in CGPS was 5.3 mmol/L (205 mg/dL)
(interquartile range 4.6–6.0 mmol/L (178–232 mg/dL)). Mean LDL
cholesterol was 3.0 mmol/L (116 mg/dL) (interquartile range
2.4–3.6 mmol/L (93–139 mg/dL)). Individuals attending the study in
the first week of January had a mean total and LDL cholesterol of
6.2 mmol/L (240 mg/dL) (interquartile range 5.5–7.0 mmol/L
(213–271 mg/dL)) and 3.7 mmol/L (143 mg/dL) (interquartile range
3.0–4.3 mmol/L (116–166 mg/dL)). In comparison, in June the mean
total and LDL cholesterol were 5.1 mmol/L (197 mg/dL) (interquartile
range 4.4–5.7 mmol/L (170–220 mg/dL)) and 2.8 mmol/L (108 mg/dL)
(interquartile range 2.2–3.4 mmol/L (85–131 mg/dL)).
3.1. Possible confounders
Characteristics of individuals attending the CGPS in the first week of
January following the Christmas holidays (N = 441) were similar to
those of individuals attending during the rest of the year
(Supplementary Table 1). We included possible confounders such as
sex, age, body mass index, alcohol consumption, smoking status, and
diabetes mellitus. We found no significant differences between individuals
attending the CGPS in the first week of January and individuals
attending in April, May, and June besides a slightly younger
age of the individuals attending the CGPS just after the Christmas
holiday.
3.2. Seasonal variation
The moving average of total cholesterol per 300 individuals from
April 2014 through November 2017 was relatively stable just above
5 mmol/L (193 mg/dL) but showed a tendency toward increases during
December and January and then returned to 5 mmol/L (193 mg/dL)
shortly after January (Fig. 1). Likewise, moving average LDL cholesterol
levels showed a tendency toward increases in the Christmas period and
decreases shortly after.
There was a yearly trend towards higher and higher total cholesterol
going from summer through to December and January (Fig. 2). The
percentage change in total cholesterol from reference values in May–June
was +15% in December–January (p < 0.001) (Fig. 3). For LDL
cholesterol, the corresponding change was +20% (p < 0.001). In
contrast to cholesterol levels, a seasonal pattern was not observed for
myocardial infarctions (Supplementary Fig. 1).
3.3. Hypercholesterolemia by season
Overall, 89% of individuals had total cholesterol levels above
5 mmol/L (193 mg/dL) in the first week of January, immediately following
the Christmas holidays, compared with only 53% in April, May,
and June combined (p < 0.001) (Fig. 4). The proportion of individuals
with LDL cholesterol levels above 3 mmol/L (116 mg/dL) was 77% in
the first week of January compared to 45% in April, May, and June,
combined (p < 0.001).
For individuals attending the Copenhagen General Population Study
in the first week of January, the multivariable adjusted odds ratio of
hypercholesterolemia, defined by total cholesterol above 5 mmol/L
(193 mg/dL) or LDL cholesterol above 3 mmol/L (116 mg/dL), was 6.0
(95% confidence interval 4.2–8.5).
3.4. Repeated measurements of total and LDL cholesterol
For 244 individuals, we had repeated measurements of total and
LDL cholesterol measured with a median of 10 years apart. Waterfall
plots of the change in total and LDL cholesterol from the first week of
January in 2014–2016 to other times of the year, 10 years earlier in
2004–2006, supported our overall findings of higher total and LDL
cholesterol immediately following the Christmas holiday with a median
change of −0.7 mmol/L (−27 mg/dL) (interquartile range −1.2;-
0.5 mmol/L (-46;-19 mg/dL)) and −0.5 mmol/L (−19 mg/dL) (interquartile
range −0.9; −0.1 mmol/L (−35;-4 mg/dL)), respectively
(Fig. 5). As higher age might be a confounder in the assessment of
longitudinal data, we also constructed waterfall plots for the change in
total and LDL cholesterol in the other time direction, that is, from individuals
attending the CGPS in 2004–2006 during the first week of
January and again 10 years later at another time of the year. These data
also showed a tendency towards higher total and LDL-cholesterol immediately
following Christmas with a median change of 0.6 mmol/L
(23 mg/dL) (interquartile range −0.1.; 1.3 mmol/L (−4; 50 mg/dL))
and 0.3 mmol/L (12 mg/dL) (interquartile range −0.2; 0.9 mmol/L
(−8; 35 mg/dL)) (Supplementary Fig. 2). Additionally, waterfall plots
of the difference in cholesterol levels from 2014 to 2016 to 2004–2006
in all 11,055 individuals with repeated measurements showed evenly
Fig. 3. Percent change in total and LDL cholesterol according to months of the
year in individuals not on cholesterol-lowering therapy in the Copenhagen
General Population Study.
Values are averaged from April 2014 through to November 2017. Time is
grouped from the 15th in the specific month to the 14th in the following month,
to better capture the period surrounding the Christmas holidays.
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
124
distributed differences indicating a minor role of higher age in the
observed change in cholesterol levels following the Christmas holiday
(Supplementary Fig. 3). Also, as a negative control of our findings we
did not observe similar differences over a decade when comparing a
non-holiday season (Supplementary Fig. 4).
4. Discussion
In this study of 25,764 individuals from the general population, we
found that levels of total and LDL cholesterol were higher during and
immediately following Christmas. Additionally, the fraction of individuals
with hypercholesterolemia was higher during Christmas and
immediately after the holidays compared to the rest of the year with a
6.0 times higher risk of hypercholesterolemia in individuals attending
the study in the first week of January compared to individuals attending
the study during the rest of the year. These are novel findings.
Mechanistically, the observed variations in total and LDL cholesterol
could be explained by intake of the high-fat diet traditionally
consumed during Danish Christmas season spanning all of December
until and including New Year's Eve. Furthermore, the corresponding
lower levels observed in late winter could partly be due to the tendency
to make New Year's resolutions and briefly engage in eating healthier
following the Christmas holidays. If this is the case, such resolutions
only last for a short period of time [8], as clearly supported by our
study.
In support of our findings, in a UK study of 35 individuals with and
without type 2 diabetes, the Christmas feast was associated with gain in
weight and a slight increase in cholesterol levels immediately following
Christmas [3]. The concept of seasonal variation in lipid levels has been
documented in previous studies which have reported seasonal variation
in cholesterol levels throughout the year [9–16]. In the SEASONS study
of 476 healthy volunteers, women had higher total cholesterol, LDL
cholesterol, and HDL cholesterol levels in winter compared to summer,
whereas in men, this was only the case for HDL cholesterol [15]. Another
study of 1446 hypercholesterolemic men with repeated cholesterol
measurements found total cholesterol to be 0.19 mmol/L (7.3 mg/
dL) higher in December–January than in June–July corresponding to
3% higher total cholesterol levels [10]. Also, in a study of 302 patients
with type 2 diabetes mellitus 30% of the patients were within LDL
cholesterol target of < 2.6 mmol/L (101 mg/dL) in summer and spring,
whereas this was only the case for 22% during fall and winter [9].
Studies from the general population including over 200,000 measurements
from routine health screening examinations in the UK and Japan
likewise found evidence of a seasonal variation in plasma total cholesterol
in both countries, with overall 3% higher cholesterol levels in
winter than in summer [16] and seasonal variations in the general
population have been confirmed by yet others.[13, 14] In the present
study, we found that total cholesterol was 15% higher and LDL cholesterol
20% higher in the months of December–January compared with
May–June, which are much higher levels than found in previous studies.
In contrast, a study of 2245 healthy blood donors in Denmark
found no distinct fluctuations in plasma cholesterol during the calendar
year [12], similar to what a study including 304,156 serum cholesterol
measurements from 14 Polish laboratories reported [11].
Apart from influencing the Christmas spirit, our results may also
have clinical implications. It has been proposed that the seasonal variation
in cholesterol levels could lead to failure to meet treatment goals
if treatment is initiated in summer with repeated measurements carried
out in winter [17]. Yet, the clinical importance of this depends on
whether it is the actual plasma total and LDL cholesterol concentration
at any given time that determines the rate of cholesterol deposition in
the arteries, in which case the high post-Christmas feasting cholesterol
levels are likely harmful, or if it is rather the long-term concentrations,
making these temporary increases in cholesterol levels less important.
In the present study, we observed no seasonal variation in first-time
events of myocardial infarction which support the latter. The question
Fig. 4. Total and LDL cholesterol and hypercholesterolemia according to time of year in individuals not on cholesterol-lowering therapy in the Copenhagen General
Population Study.
Green colour represent the fraction of individuals below the cut-off for hypercholesteolemia while red colour represent the fraction of individuals above the cut-off
for hypercholesteolemia. p-values for comparison of the fraction of individuals with total and LDL cholesterol above the cut-off in the first week of January versus in
April, May, and June (reference). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
125
of therapeutic interest is whether these changes in cholesterol levels can
be used as a rationale for being less aggressive with cholesterol-lowering
therapy in winter; however, given the undertreatment with cholesterol-lowering
therapy previously reported from our study [18] the
opposite could be argued, that is, too few people are treated because of
under-diagnosis in summer. Nevertheless, physicians should take these
results into consideration when diagnosing hypercholesterolemia
during December and January and, if the test has been done immediately
following Christmas, consider the possibility of re-testing the
patient some months later. Our study shows that lifestyle is an important
basis of treating individuals with hypercholesterolemia. However,
with an observed 15% change in total cholesterol going from
summer to winter, the study also depicts the quantitatively small effects
of extreme changes of diet and physical activity that cannot substitute
for statins in high risk individuals.
Our study has several strengths such as the use of a large general
population cohort of white individuals of Danish descent, essentially all
of whom celebrate Christmas with a large amount of “hygge” [1] during
all of December until and including New Year's Eve. Also, individuals in
the Copenhagen General Population Study are invited randomly by age
and sex throughout the year, securing that characteristics of those examined
is similar from month to month.
Some limitations should also be considered. First, although repeated
measurements from a relatively small subset of 244 individuals
supported our main findings, only one measurement of cholesterol from
each individual is included in the main analyses. While a design featuring
repeated measurements is generally preferable to one with only a
single measurement per subject, this may be compensated for by the
large cohort size from a homogenous population. Second, we cannot
exclude that individuals exhausted from celebrating Christmas and
eating large amounts of food would choose not to participate in the
CGPS, thereby introducing selection bias in the present study and a
tendency to bias our results towards the null hypotheses. If this was the
case, even larger increases in cholesterol levels may have occurred
following Christmas. On the other hand, it is also possible that individuals
who have been especially sedentary and eaten large amounts
of food during Christmas are more prone to participate in a health
examination following Christmas due to health concerns, in which case
our results cannot be extrapolated to the whole population. However,
we did not find major differences in characteristics between the individuals
participating immediately following Christmas and those
participating during the remaining part of the year, which does not
suggest major biases. Third, as all individuals were of white Danish
descent, our results may not necessarily apply to other ethnicities
especially those unfamiliar to the Danish concept of “hygge” [1].
Holiday traditions have a strong cultural foundation and thus it is uncertain
to what extent our findings might be generally applicable beyond
a Scandinavian or Northern European population.
In conclusion, celebrating Christmas is associated with increased
levels of total and LDL cholesterol in individuals in the general population
and a higher risk of hypercholesterolemia. Thus, a diagnosis of
hypercholesterolemia should not be made around Christmas and our
results stress the need for re-testing such patients later and certainly
prior to initiation of cholesterol-lowering treatment. Future research
may elucidate whether writing and reading these current results will be
associated with decreased Christmas spirit due to self-inflicted dietary
restrictions when celebrating future Christmas holidays.
Conflicts of interest
The authors declared they do not have anything to disclose regarding
conflict of interest with respect to this manuscript.
Financial support
This study was supported by Herlev and Gentofte Hospital,
Copenhagen University Hospital, Denmark financed through the Danish
tax system. The funder of this study had no role in the study design; in
the collection, analysis, and interpretation of data; in the writing of the
report; or in the decision to submit the article for publication.
All authors had full access to all of the data (including statistical
reports and tables) in the study and can take responsibility for the integrity
of the data and the accuracy of the data analysis.
Author contributions
Signe Vedel-Krogh, Camilla Kobylecki, Børge G. Nordestgaard, and
Anne Langsted designed the study together. Signe Vedel-Krogh, Camilla
Kobylecki, and Anne Langsted analyzed the data. Børge G.
Nordestgaard oversaw all analyses and contributed to the interpretation
of data. Signe Vedel-Krogh, Camilla Kobylecki, and Anne Langsted
wrote the first draft of the paper and Børge G. Nordestgaard edited the
paper. All authors approved this paper in its final form.
Acknowledgements
We are indebted to the staff and participants of the Copenhagen
General Population Study for their important contributions.
Fig. 5. Repeated measurements of total and LDL cholesterol according to time
of year in individuals not on cholesterol-lowering therapy in the Copenhagen
General Population Study.
Change from the first week of January in 2014–2016 to random day of the year
in 2004–2006. Based on 244 individuals not on cholesterol-lowering medication
with a measurement of total and LDL cholesterol in first week of January
and a measurement approximately 10 years later at another time of year.
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
126
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.atherosclerosis.2018.12.011.
References
[1] W. Meik, The Little Book of Hygge, William Morrow, 2017.
[2] L. Schwingshackl, G. Hoffmann, Comparison of effects of long-term low-fat vs highfat
diets on blood lipid levels in overweight or obese patients: a systematic review
and meta-analysis, J. Acad. Nutr. Diet. 113 (2013) 1640–1661, https://doi.org/10.
1016/j.jand.2013.07.010.
[3] S.G. Rees, R.R. Holman, R.C. Turner, The Christmas feast, Br. Med. J. 291 (1985)
1764–1765.
[4] NICE Guidance, Cardiovascular Disease: Risk Assessment and Reduction, Including
Lipid Modification, (2014) https://www.nice.org.uk/guidance/cg181/chapter/1-
Recommendations#lipid-modification-therapy-for-the-primary-and-secondaryprevention-of-cvd-2
, Accessed date: 26 June 2018.
[5] A.L. Catapano, Z. Reiner, G. De Backer, et al., ESC/EAS guidelines for the management
of dyslipidaemias the task force for the management of dyslipidaemias of
the European society of cardiology (ESC) and the European atherosclerosis society
(EAS), Atherosclerosis 217 (2011) 3–46.
[6] S. Afzal, A. Tybjaerg-Hansen, G.B. Jensen, et al., Change in body mass index associated
with lowest mortality in Denmark, 1976-2013, J. Am. Med. Assoc. 315
(2016) 1989–1996.
[7] A. Langsted, P.R. Kamstrup, M. Benn, et al., High lipoprotein(a) as a possible cause
of clinical familial hypercholesterolaemia: a prospective cohort study, Lancet Diab.
Endocrinol. 4 (2016) 577–587.
[8] K. Woolley, A. Fishbach, Immediate rewards predict adherence to long-term goals,
Pers. Soc. Psychol. Bull. 43 (2017) 151–162.
[9] G. Bardini, I. Dicembrini, C.M. Rotella, et al., Lipids seasonal variability in type 2
diabetes, Metabolism 61 (2012) 1674–1677.
[10] D.J. Gordon, D.C. Trost, J. Hyde, et al., Seasonal cholesterol cycles: the lipid research
clinics coronary primary prevention trial placebo group, Circulation 76
(1987) 1224–1231.
[11] J.M. Janecki, Cholesterol level in human serum: seasonal variations and differences
in 14 distant regions, Ann. Clin. Lab. Sci. 43 (2013) 407–413.
[12] E. Lund, T. Geill, P.H. Andresen, Serum-cholesterol in normal subjects in Denmark,
Lancet 2 (1961) 1383–1385.
[13] H. Marti-Soler, C. Gubelmann, S. Aeschbacher, et al., Seasonality of cardiovascular
risk factors: an analysis including over 230 000 participants in 15 countries, Heart
100 (2014) 1517–1523, https://doi.org/10.1136/heartjnl-2014-305623.
[14] F.A. Moura, M.S. Dutra-Rodrigues, A.S. Cassol, et al., Impact of seasonality on the
prevalence of dyslipidemia: a large population study, Chronobiol. Int. 30 (2013)
1011–1015, https://doi.org/10.3109/07420528.2013.793698.
[15] I.S. Ockene, D.E. Chiriboga, E.J. Stanek 3rdet al., Seasonal variation in serum
cholesterol levels: treatment implications and possible mechanisms, Arch. Intern.
Med. 164 (2004) 863–870.
[16] D. Robinson, E.A. Bevan, S. Hinohara, et al., Seasonal variation in serum cholesterol
levels–evidence from the UK and Japan, Atherosclerosis 95 (1992) 15–24.
[17] P. Tung, S.D. Wiviott, C.P. Cannon, et al., Seasonal variation in lipids in patients
following acute coronary syndrome on fixed doses of pravastatin (40 mg) or atorvastatin
(80 mg) (from the pravastatin or atorvastatin evaluation and infection
therapy-thrombolysis in myocardial infarction 22 [PROVE IT-TIMI 22] study), Am.
J. Cardiol. 103 (2009) 1056–1060.
[18] A. Langsted, J.J. Freiberg, B.G. Nordestgaard, Extent of undertreatment and overtreatment
with cholesterol-lowering therapy according to European guidelines in
92,348 Danes without ischemic cardiovascular disease and diabetes in 2004-2014,
Atherosclerosis 257 (2017) 9–15.
S. Vedel-Krogh et al. Atherosclerosis 281 (2019) 121–127
127