Lifestyle including dietary habits and changes in coronary artery calcium score: a retrospective cohort study

Study population

The participants consisted of individuals older than 18 years who underwent a baseline
comprehensive health examination at Kangbuk Samsung Hospital Health Screening Center
in Seoul and Suwon, South Korea, between 2010 and 2012 and had follow up at 2013.
A total of 2623 individuals were identified to have received non-enhanced coronary
computed tomography, completed the food frequency questionnaire (FFQ) in addition
to questionnaires for depressive symptoms and physical activity at baseline and follow
up. The following participants were excluded from analysis: 379 subjects with missing
data (on smoking, exercise, and alcohol intake), 44 subjects with a history of cancer,
and 52 subjects with a history of cardiovascular disease. As some individuals met
more than one criterion for exclusion, the total number of eligible subjects for the
study was 2175. Among these subjects we could obtain the answer for questionnaires;
1099 subjects for total energy intake, 917 subjects for composition of macronutrients,
907 subjects for sleep duration and 864 subjects for depression. In Korea, the Industrial
Safety and Health Law requires employees to participate in annual or biannual health
examinations. Approximately 60 % of the participants were employees of various companies
and local governmental organizations.

This study was approved by the Institutional Review Board (IRB) of Kangbuk Samsung
Hospital and informed consent requirement was waived as all personal identifiable
information was removed prior to accession.

Measurements

Anthropometric measurements and general characteristics

Body weight and height of subjects were measured to the nearest 0.1 kg and 0.1 cm,
respectively. Body mass index (BMI) was calculated as weight in kilograms divided
by the square of the height in meters. Obesity was defined as BMI???25 kg/m
²
. Data on past medical history, medication use, and health-related behaviors were
obtained by a self-administered questionnaire. Questionnaires were used to evaluate
education level, smoking status (current or non-current), alcohol consumption (frequency
per week, amount) and sleep duration (hours per day). Depression was evaluated by
CES-DK score 19] and food frequency data was calculated by CAN-pro 4.0 (Korean Nutrition Society 2010).

Alcohol intake was examined as unit per day of alcohol consumption. Smokers were divided
into two groups: current smoker and non-current smoker. Physical activity was evaluated
using the Korean version of the International Physical Activity Questionnaire (IPAQ)
short form 20], 21]. The number of days per week and time spent walking per day, as well as moderate
and vigorous activities were recorded. The collected data were converted to metabolic
equivalent scores (METS) for each type of activity. By multiplying the time engaged
in the activity in a week with consideration to the number of METs, metabolic equivalent
task minutes per week, MET-min/week, were calculated according to the IPAQ scoring
protocol 22]. Blood pressure was measured with electronic sphygmomanometer in the seated position
with more than 5 min of resting prior to the measuring.

Coronary Artery Calcification (CAC) measurement

Coronary artery calcification (CAC) was detected by a LightSpeed VCT XTe-64 slice
MDCT scanner (GE Healthcare, Tokyo, Japan) with the same standard scanning protocol
using 2.5-mm thickness, 400 ms rotation time, 120 kV tube voltage, and 124 mAs (310 mA
* 0.4 s) tube current under ECG-gated dose modulation. Coronary artery calcification
was defined as more than three contiguous pixels above a CT density of 130 Hounsfield
Units. The total CAC score was calculated by Agatston’s method 23]. Subjects were classified into two subgroups according to CAC score: CAC group (CAC
score 0) or non-CAC group (CAC score???0) by referring to previous studies.

Biochemical marker

Blood samples were taken from the antecubital vein, collected in serum-separating
tube (SST) after at least 10 h of fasting. Serum levels of total cholesterol and triglyceride
were determined using an enzymatic colorimetric assay; low-density lipoprotein cholesterol
(LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels were directly measured
using a homogeneous enzymatic colorimetric assay. Serum fasting glucose level was
measured using the hexokinase method. Fasting serum glucose, total cholesterol, LDL-C,
HDL-C, triglyceride (TG), alanine aminotransferase (ALT), gamma-glutamyl transferase
(GGT), were measured using Bayer Reagent Packs in an automated chemistry analyzer
(Advia 1650 Auto analyzer; Bayer Diagnostics, Leverkusen, Germany). High sensitivity
C-reactive protein (hsCRP) was analyzed by particle-enhanced immunonephelometry with
the BNII System (Dade Behring, Marburg, Germany). All hematologic measurements were
analyzed in one laboratory with the same machines by trained staff using the same
methodology throughout. The Korean Society of Laboratory Medicine (KSLM) biannually
certified the Laboratory Medicine Department at Kangbuk Samsung Hospital in Seoul,
Korea for the Korean Association of Quality Assurance for Clinical Laboratories (KAQACL)
and the CAP (Collage of American Pathologists) Proficiency Testing designations.

Nutrient intake measurements

Self-administered food frequency questionnaire (FFQ) was used to obtain nutrient intake
data which was designed and validated for use in Korea. Food frequency was estimated
by 9 scales (never, 1 time/month, 2 – 3 times/month, 1 – 2 times/week, 3 – 4 times/week,
5 – 6 times/week, 1 time/day, 2 times/day and 3 times/day) and portion size was estimated
by three scales (half dish, one dish, one and a half dish) for consumption of 103
food items over the past year. Nutrient intake data include total energy (kcal), carbohydrate
(g), protein (g) and fat (g). The Food Composition Table, a nutrient database produced
by the Korean Nutrition Society to convert food intake into nutrients, was used to
perform nutrient analysis 24]. The contribution of each macronutrient to energy was calculated as the ratio of
energy from each macronutrient to total energy: percentage of carbohydrate from total
energy intake (%), percentage of fat from total energy intake (%) and percentage of
protein from total energy intake (%). Food frequency data was calculated by CAN-pro
4.0 (Korean Nutrition Society 2010). Subjects were categorized into four groups according
to each macronutrient intake (Q1?~?Q4).

Statistical analyses

Normally distributed variables are presented as the mean?±?SD and skewed variables
are presented as the median (interquartile range). Continuous variables were compared
using independent t-test between CAC change???0 group and CAC change??0 group (CAC progression). Categorical
variables were expressed as number and percentages then compared between groups using
the ? 2 -test. Multiple logistic regression analysis were used to determine Hazard
Ratios (HRs) for CAC progression with 95 % confidence intervals (CIs) for quartile
groups of each total energy intake, macronutrient intake, physical activity and depression
using the lowest quartile group as the reference. To evaluate the significance, two
models were constructed. Model 1 was adjusted for age and sex and Model 2 was adjusted
for Model 1 and smoking, physical activity, alcohol intake, glucose, triglyceride,
HDL-cholesterol, LDL-cholesterol, and blood pressure. P values 0.05 were considered
statistically significant. The STATA 11.2 software package was used for statistical
analysis.