Cardiovascular disease (CVD), a condition affecting the heart and blood vessels, has been reported by the World Health Organization (WHO) as a major cause of death worldwide [1]. In addition, according to Korea's cause of death statistics, CVD will be the second leading cause of death in 2022, with mortality rates increasing with age [2]. According to the Statistics 2023 report, the CVD mortality rate per 100,000 people in 2022 varies by age group. The rate starts low at 6.8 in the 30s, but increases to 20.4 in the 40s, then more significantly to 46.5 in the 50s. It surpasses 100 in the 60s (104.2) and rises sharply to 2,283.5 in the 70s and older [2].

Factors that increase the risk of occurrence and death from CVDs include various health and clinical indicators such as age, sex, hypertension, diabetes, blood lipid level, family history of CVD, and smoking [3]. Particularly, the risk of asymptomatic arteriosclerosis increases as arterial stiffness increases [4, 5]. Arterial stiffness refers to a state in which the arterial wall loses its original elasticity and becomes hard due to structural and functional changes; it is used as an independent indicator to predict the risk of CVD [5, 6]. Factors closely related to associated arterial stiffness include aging, hypertension, diabetes, and dyslipidemia, as well as physical activity and dietary factors [5, 6, 7]. Among these, increased physical activity and improved diet are positive factors for preventing CVDs and improving arterial stiffness [7, 8].

Methods for measuring arterial stiffness include invasive methods such as coronary angiography and non-invasive methods such as ultrasound imaging and computed tomography. However, their clinical use is limited by high costs and surgical risks [9]. Bachial-ankle pulse wave velocity (baPWV), a non-invasive method of measuring pulse waves, was recently assessed using an oscillometric method incorporated into a blood pressure monitor cuff and paired with brachial-ankle blood pressure measurement. The ankle-brachial index (ABI) is used as an indicator of arterial stiffness [10]. baPWV refers to the speed of blood flow through the upper arm and ankle and is used to evaluate the stiffness of the arterial wall. It is known that the harder the artery, the faster the speed and the higher the risk of arteriosclerosis increases [10]. The ABI measures the blood pressure in the upper arm and ankle and is calculated by dividing the ankle systolic blood pressure by the brachial systolic blood pressure. In general, the normal level in healthy individuals is 1.0–1.4, and it has been reported that the risk of developing peripheral vascular disease increases as the level decreases to 0.9 or less [11]. On the other hand, if the ABI level is 1.4 or more, it indicates the uncompressed state due to calcification of the artery; however, this subject is excluded from the study [12].

baPWV and ABI are recognized for their high clinical utility due to several factors: simple and economical measurement methods, the ability to obtain repeatable measurements, and a growing body of research actively investigating their applications [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23]. Therefore, studies on the relevance of physical activity, a factor affecting arteriosclerosis, have used baPWV and ABI as indicators of arterial stiffness [10, 11, 12, 13, 14, 15, 16, 17, 18].

Methods for assessing physical activity include measuring body movements using tools such as accelerometers and self-recording methods using questionnaires [10]. Because the self-recording method places a relatively low cost and burden on the subject, the Korean National Health and Nutrition Examination Survey (KNHANES) also uses the Global Physical Activity Questionnaire (GPAQ) as a physical activity evaluation tool. The GPAQ is classified into four domains: work, recreational activities, moving from place to place, and sedentary behavior; therefore, it has the advantage of being able to interpret physical activity by domain [24].

Recent studies using baPWV and ABI include the relationship between physical activity and arterial stiffness assessed with an accelerometer, an objective measurement tool in healthy adults [10]; the relationship between physical activity level assessed with an accelerometer in adult females and baPWV [12]; and the relationship between physical activity level and arterial stiffness surveyed using the GPAQ in the elderly [13].

Based on the results of previous studies [10, 13], the longer the sedentary behavior continued, the higher the risk of arteriosclerosis and peripheral arterial disease [10], and the risk of arteriosclerosis was low in the elderly who followed the WHO physical activity guidelines (moderate-intensity physical activity for a total of 150 minutes or more per week) [13]. However, since arterial stiffness is influenced not only by physical activity but also by dietary factors, it has been suggested that future research on the relationship between arterial stiffness and diet is necessary [10].

Dietary intake survey methods that can determine an individual’s food and nutrient intake include the 24-hour recall method, food recording method, and food frequency questionnaire (FFQ). Among them, the FFQ is a method for investigating the frequency of consumption over a period for the presented food items, which has the advantage of being effective in identifying long-term daily consumption trends compared with other survey methods [25]. Accordingly, it is useful for analyzing the relationship between chronic diseases and dietary factors in epidemiological research. Therefore, the FFQ is appropriate for investigating diet-related factors that affect the development of arteriosclerosis over a long period of time [26].

Kim et al. [27] compared the calculated food and nutrient intake using the FFQ and 24-hour recall in postmenopausal females, while Ha et al. [28] compared the frequency of intake of specific foods obtained from the FFQ and daily intake in adults aged 40–64 with CVD risk. However, the risk of CVD applied in these studies was the Framingham General Cardiovascular Risk Score (FRS) presented by the American Heart Association in 2008 [29], which was calculated based on sex, age, blood pressure, total cholesterol and high-density lipoprotein cholesterol in the blood, smoking status, and presence of diabetes. Iso et al. [23] also used this FRS index to track fish and ω-3 fatty acid intake and the risk of coronary artery disease in a cohort study targeting Japanese people aged 40–59 years.

Meanwhile, since arterial stiffness progresses over a long period, studies on the relationship between arterial stiffness and dietary factors [26, 30] mainly used the FFQ as a dietary survey method. Maruyama et al. [26] investigated the relationship between intake of fish and ω-3 fatty acids and carotid intima-media thickness (C-IMT) measured with ultrasound imaging equipment in adults aged 30–84 years, and Moyama et al. [30] evaluated the relationship between dietary patterns and baPWV (measured with VP-1000 Plus; Omron) in middle-aged adults.

However, it is difficult to find domestic studies that evaluate the relationship between physical activity and food and nutrient intakes by directly measuring arterial stiffness based on baPWV and ABI.

Therefore, in this study, we sought to examine arterial stiffness index, physical activity, and food and nutrient intake in middle-aged adults over 40 years in which the incidence of CVD is gradually increasing. Arterial stiffness was assessed using baPWV and ABI; physical activity was assessed using the GPAQ; and food and nutrient intake was assessed using the FFQ.

In this study, we examined arterial stiffness index, physical activity, and food and nutrient intake in middle-aged adults over 40 years—a demographic group with a rising incidence of CVD. Arterial stiffness was assessed using PWV and ABI, physical activity was assessed using the GPAQ, and food and nutrient intake was assessed using the FFQ.

The average age of the subjects of this study was 53.3 and 55.2 years for males and females, respectively, and their average height and body weight were similar to the average height and body weight of adults in the Gangwon region reported in the 2021 Health Checkup Statistical Yearbook [32]. This study’s obesity rates, determined using a BMI cut-off of 25 kg/m², were 43.8% for males and 22.4% for females. These values are similar to the national obesity rates reported in the 2021 Statistical Yearbook of Health Examination (48.8% for males and 29.4% for females), which employed the same BMI criteria. The smoking rate of the subjects in this study (males, 22.9%; females, 1.7%) was lower than what was reported in the 2021 KNHANES (males, 31.3%; females, 7.1%) [33].

The blood pressure and arterial stiffness index of the subjects (Table 2) did not show any significant differences by sex or age group. The baPWV (male, 1,332.2 cm/sec; female, 1,325.8 cm/sec) obtained by this study was similar to the baPWV (male, 1,302.2 cm/sec; female, 1,259.7 cm/sec) of Korean adult males and females aged 20–64 years (average age 47.7 years), with no significant difference between sexes as reported by Lee et al. [10].

Meanwhile, our analysis of baPWV by age group revealed a significant difference. The group aged 60–64 years (1,412.0 cm/sec) had a higher baPWV compared to the group aged 40–49 years (1,265.6 cm/sec). This shows a significant difference between age and baPWV (r = 0.278, P < 0.01), showing that the baPWV also increased with age (the correlation between the basic characteristics of the study subjects, such as age, height, body weight, and BMI, and the arterial stiffness index is not shown in the table). Tomiyama et al. [19] also reported that baPWV significantly increased with age in Japanese people aged 25–87 years, and Ishida et al. [12] also reported that there was a significant positive correlation between baPWV and age in Japanese people aged 21–89 years. These findings suggest that arterial wall tissue changes and decreased elasticity as individuals age [6].

In this study, the ABI (1.16 for males, 1.11 for females) obtained were similar to those of American adults (1.13 for males, 1.09 for females; average age 57.0 years) reported by Kapoor et al. [20] and was significantly lower in females than in males. In a study by Ishida et al. [12], which evaluated the relationship between ABI, age, and sex, the ABI of females was found to be lower than that of males, similar to this study. These results may be related to the high proportion of postmenopausal females (79.3%) among the female subjects in this study. In other words, it has been reported that a decrease in the secretion of estrogen, a female hormone, after menopause affects the development of CVDs such as arteriosclerosis [34]. In addition, a study by Li et al. [35] also reported an increased risk of developing arteriosclerosis in postmenopausal females. Based on these previous studies [12, 20, 34, 35], ABI is associated with age, sex and menopause.

When ABI was compared by age group in this study, those aged 40–49 years had significantly lower ABI than those aged 50–59 and 60–64 years. About this, a study by Matt et al. [21] observed increasing ABI with age in Americans aged 27–95 years, showing that ABI also increased with age in subjects aged 70 years or younger. Since the stiffness of arteries due to aging increases more rapidly in central arteries than in peripheral blood vessels, it has been reported that the increase in systolic blood pressure in the upper arm is greater than in the systolic blood pressure in the ankle [36]. These results were also found to affect the ABI, which is the ratio of the ankle to brachial systolic blood pressure.

Using the GPAQ to examine physical activity levels (Table 3), we found that the time spent on moderate-intensity physical activity in the work domain, which includes household tasks such as cleaning, kitchen work, and childcare, was significantly higher for females, at about 8.5 hours per week (510.2 min/week), compared to about 5 hours per week (297.1 min/week) for males. A possible explanation for this observation is the gender disparity in housework and childcare participation, with females typically taking on a larger share of these responsibilities.

On the other hand, the time spent on vigorous recreational physical activities, including climbing, swimming, and badminton, was significantly higher for males at about 2 hours per week (115.0 min/week) compared to females at about 30 minutes per week (31.0 min/week). This is related to the fact that in the one-on-one interviews conducted with the GPAQ for this study, 24 (50.0%) of all male subjects engaged in vigorous physical activities such as biking and swimming for more than 1 hour.

Meanwhile, males spent about 9 hours and 22 minutes (562.5 min/day) per day in sedentary behavior, which was significantly higher than females who spent about 7 hours and 26 minutes (446.0 min/day). Looking at the time spent on sedentary behavior reported by Lim et al. [37], who analyzed data from the 2014–2015 KNHANES and evaluated the physical activities of Koreans (19–64 years old) using an accelerometer, males spent approximately 8 hours and 22 minutes (502.9 minutes/day for males), and females spent approximately 8 hours and 18 minutes (498.9 minutes/day for females). In this study, males spent approximately 1 more hour and females spent approximately 53 minutes less. This is believed to be related to differences in the subjects or measurement tools used in each study. In general, physical activity questionnaires such as the GPAQ are subjective measurement methods that rely on the memory of the respondents and may have lower accuracy than an accelerometer, which is an objective measurement tool [38].

The GPAQ used in this study to investigate physical activity does not assess the time allotment and intensity of all physical activities within 24 hours, which can be done with physical activity diaries; instead, the questionnaire assesses the time allotment by activity intensity (moderate and vigorous) according to the domain of physical activity (work, recreational activities, moving from place to place, and sedentary behavior) for a week. Therefore, to predict the subject’s overall physical activity level, the sum of the time spent on moderate to vigorous physical activity in all domains (MVPA) is presented.

Ishida et al. [12] found that out of 91,962 people who participated in the daily health examination program organized by the Okinawa General Health Maintenance Association from 2003 to 2010, only 13,211 people (51.4 years for males and 52.8 years for females) voluntarily participated in the ABI measurement and only 67 people had an ABI of less than 0.5%. Therefore, to better understand the relationship between the arterial stiffness index (ABI) and related factors, further research is needed. This could involve large-scale studies similar to those described earlier or utilizing existing data from national surveys like the National Health and Nutrition Examination Survey (NHANES) as in Kulinski et al. [17]. Additionally, studies should aim to include patients with low-grade peripheral vascular disease. However, since this study was conducted on mostly healthy adults (106 people) in addition to some patients with diabetes, hypertension, and dyslipidemia, all subjects showed ABI values in the normal range (1.0–1.4).

In the case of physical activity, the time spent on vigorous leisure-time activity in males was significantly higher in the upper ABI group at T3 (129.4 min/week) than in the lower ABI group at T1 (11.3 min/week). Wilson et al. [15] surveyed American adults aged 40 years or older and found that the prevalence of peripheral artery disease significantly decreased in the group that spent more time engaging in recreational activities. In addition, a study by Heikkilä et al. [16] in Finland investigated adults (average age 59.0 years) with borderline ABI levels (0.90–1.00) who had undergone CVD procedures. Interestingly, the group with high ABI was found to engage in a significant amount of leisure-time activities. These results suggest that physical activities, such as recreational activities, can reduce the risk of developing CVD.

Meanwhile, the time spent on sedentary behavior by females was significantly higher at T1 (472.1 min/week) than at T3 (294.5 min/week). In a study by Kulinski et al. [17], who investigated the time spent on sedentary behavior among American adults (average age 61.0 years) using accelerometers, the ABI (1.05) of the group spending approximately 10.2 hours per day on sedentary behavior was 1.05. This was significantly lower than the ABI (1.08) of the group that spent approximately 6 hours. Additionally, in a study by Lee et al. [10] targeting Korean adults aged 20–64 years, a negative correlation was found between the ABI and sedentary behavior. These results show that the longer the time spent in sedentary behavior, the higher the risk of developing peripheral artery disease.

In terms of daily intake frequency by food group, there was no significant difference between T1, T2, and T3 in males, whereas in females, the fish intake frequency of T3 (1.27 frequency/day) was significantly higher than that of T1 (0.64 frequency/day). In this regard, a study by Frank et al. [22] on female nurses (34–59 years old) in the United States showed that the risk of CVD decreased as the frequency of consumption of fish and ω-3 fatty acids increased. Additionally, a Japanese (40–59 years old) cohort study by Iso et al. [23] found that fish consumption more than once per week reduced the risk of heart disease.

There was no significant correlation between arterial stiffness index and physical activity (Table 6). In a study by Lee et al. [10], no significant correlation was found between physical activity-related indicators assessed using an accelerometer and arterial stiffness index in healthy adults. On the other hand, a study by Hawkins et al. [18], which evaluated the relationship between physical activity and ABI in Americans aged 40 years or older, found that the group of subjects with an ABI level of 0.9 or less spent less time on physical activity. These results are thought to be related to the fact that among the study subjects of Hawkins et al. [18], 98 (17.5%) had an ABI of less than 1.0, whereas this study had no comparable subjects.

Meanwhile, in this study, a significant positive correlation was found between the intake of PUFAs and ω-3 fatty acids adjusted for energy intake and ABI (Table 6). This is supported by the study of Zanetti et al. [39], which reported that ω-3 fatty acids can have a beneficial effect on reducing arterial wall stiffness and the occurrence of CVDs. In addition, a study by Maruyama et al. [26] on Japanese people (30–84 years old) also showed a significant negative correlation between ω-3 fatty acid intake and C-IMT.

This study has several limitations. First, because this study was conducted in a small number of people, most of whom were healthy, all subjects had ABI values within the normal range. Accordingly, a major limitation is that even for subjects within the normal ABI range, their ABI values could be divided into tertiles to examine how related factors differ depending on high and low ABI. Second, it is difficult to determine the relationship between exposure factors and disease, as this was a cross-sectional study that simultaneously investigated exposure and outcome factors. Third, considering that arteriosclerosis progresses over a long period, there may be limitations in evaluating the relationship with arterial stiffness using only the amount of physical activity during a week, that is, a short period of physical activity. In addition, the physical activity questionnaire (GPAQ) used in this study may have limitations in terms of accuracy and reliability, because it relies on the memory of respondents.

Nevertheless, this study is meaningful in that it directly measured baPWV, which represents central artery stiffness, and ABI, which represents peripheral vascular stiffness, in middle-aged adults over 40 years, considering that most studies that have evaluated cardiovascular risk in Korea used the Framingham General Cardiovascular Risk Center (FRS) suggested by the American Heart Association [29] in 2008. In addition, food and nutrient intakes were investigated using the FFQ, which can identify long-term daily intake patterns, as well as physical activity, using the GPAQ. This study observed that males in the high ABI group (T3), which had relatively low peripheral artery stiffness, spent more time on vigorous leisure activities such as biking, swimming, and badminton compared to the low ABI group (T1), while females in the high ABI group (T3) spent less time on sedentary behavior compared to the low ABI group (T1). Additionally, the intake of fish, PUFA, and ω-3 fatty acids showed a significant positive correlation with ABI.

In this study, we examined arterial stiffness index, physical activity, and food and nutrient intake in middle-aged adults over 40 years in which the incidence of CVD is gradually increasing. In Korea, surveys using accelerometers and arterial stiffness index have been conducted by the Rural Development Administration. Accordingly, in the future, research results on the factors affecting arterial stiffness should be reported through large-scale epidemiological studies at the national level, as in other countries. In addition, follow-up studies should be conducted to measure arterial stiffness in middle-aged and elderly people with a high mortality rate from CVD and analyze the relationship between food and nutrient intake, along with evaluating physical activity using objective physical activity measurement tools such as accelerometers. Based on these results, we hope to establish a detailed dietary and physical activity guideline to prevent arteriosclerosis in Koreans.