Verification of the serum lipid tracking phenomenon by a follow-up survey using mail-in medical examinations for participants who underwent lifestyle-related disease prevention examinations as children

Highlights

● Mail-in medical examinations can be carried out as a follow-up survey of lifestyle-related disease prevention examinations as children.

● When it comes to mail-in medical examinations, the participation rate is still not high.

● Among Japanese youth from the fourth grade of elementary school to age 20, the tracking phenomenon was suggested in serum cholesterol values, body mass index, and waist circumference.

Introduction

Lifestyle-related diseases such as obesity, dyslipidemia, and high blood pressure are believed to be associated with the tracking phenomenon from childhood to adulthood. The tracking phenomenon is a phenomenon in which people who suffer from obesity, high cholesterol, and high blood pressure in childhood are more likely to suffer from obesity, high cholesterol, and high blood pressure in adulthood as well (1).

One of the purposes of lifestyle-related disease prevention examinations in children targeting elementary and junior high school students is to screen children with lifestyle-related diseases such as obesity, dyslipidemia, and high blood pressure, so that they will be provided with lifestyle guidance in order to prevent these lifestyle-related diseases in adulthood. That is to say, this tracking phenomenon is one of the reasons to conduct lifestyle-related disease prevention examinations in children. However, there are few reports on Japanese people regarding verification of the tracking phenomenon (2).

Furthermore, a follow-up survey will be required on the condition of lifestyle-related diseases in adults among those who underwent examinations as a child, in order to review the effect of lifestyle-related disease prevention examinations in children. That said, these follow-up surveys are not easily conducted. The first reason for this is that these examinations are often carried out by municipalities, thus making it difficult to carry out follow-up surveys after high school age. The second reason is that it is difficult for adult subjects to visit a venue for examinations.

Clinical examinations using mail-in services have been making progress in recent years. This method involves pricking a finger and collecting blood, which is then placed in a special container and mailed to a testing facility (3, 4). This allows the subjects to conduct the clinical examination at home, even in adulthood. For this reason, mail-in medical examinations are expected to be useful as a follow-up survey method for those who underwent lifestyle-related disease prevention examinations as children (5). Mail-in medical examinations have several limitations. These include insufficient blood sample volume, hemolysis of the specimen, shipping delays, and uncertainty regarding fasting compliance. Therefore, researchers using mail-in medical examinations must consider these limitations.

The purpose of this study is to verify that mail-in medical examinations are useful as a follow-up survey method for those who underwent lifestyle-related disease prevention examinations as children. It is also to clarify whether the tracking phenomenon of lifestyle-related diseases can also be observed in Japanese children.

Participants and Methods

In Mitsuke City, Niigata Prefecture, lifestyle-related disease prevention examinations in children have been conducted since 1998, targeting students in the fourth grade of elementary school and the first grade of junior high school. The fourth grade elementary school students are 9 or 10 yr old, and the first grade junior high school students are 12 or 13 yr old. Mail-in medical examinations were performed as a follow-up survey to this examination. The subjects of the study consisted of adults who had undergone lifestyle-related disease prevention examinations by Mitsuke City as children, when they were fourth grade elementary school students in 2008 and when they turned 20 yr old in 2019. A follow-up survey “20-yr-old health check” was conducted at the time of their coming-of-age ceremony. To conduct this survey, an agreement was signed between Mitsuke City, Saitama Medical University, and Niigata University to conduct a joint epidemiological study. Furthermore, this study was approved by the University Ethics Committee of Saitama Medical University (Application No. 899).

A public health nurse from Mitsuke Municipal Office distributed the follow-up survey guide and consent form to 296 of those surveyed at the venue of the coming-of-age ceremony. Those interested in participating in the study signed the consent form and delivered it to Mitsuke City Hall. The subjects of the study included 42 participants (17 males and 25 females) who agreed to participate in the study.

The mail-in medical examination company (SUNPRE Co., Ltd.) delivered the mail-in medical examination kit “Prevention is the Best Health Checker” (DEMECAL, Leisure, Inc.) to the study participants. This kit is a medical device approved by the Ministry of Health, Labour and Welfare of Japan (controlled medical device approval number 21600BZ00007000). In addition, the inspection accuracy was approved by the cholesterol reference method laboratory network organized by the US CDC. Study participants provide a blood sample using the mail-in medical examination kit at fasting state in the early morning. First, approximately 65 μL of blood is collected by piercing a fingertip and placing blood in a dedicated container. Then, after stirring, a filtered cylinder is pressed to separate the plasma and create a blood sample. The study participants send the blood sample to the medical examination company. The medical examination company then sent the results to Mitsuke City Hall. And Mitsuke City Hall connected these results with the data of the lifestyle-related disease prevention examinations in children. Personal information was anonymized and sent to Saitama Medical University, Department of Pediatrics. And the data was analyzed at Saitama Medical University, Department of Pediatrics.

Total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) (direct method) were measured using the mail-in medical examination kit. And participants measured their waist circumference (WC) at the level of the navel using the tape measure included in the examination kit, either by themselves or with the help of a family member. They measured their weight using a scale they owned and reported their height as they remembered it. Height, weight, WC, and blood pressure were measured in the lifestyle-related disease prevention examinations in children, while TC, HDL-C, and LDL-C (direct method) were measured by blood sampling as needed. The TC, LDL-C, HDL-C, body mass index (BMI), and WC of the two examination results were analyzed by Pearson’s Simple Regression Analysis, quartile agreement. Standard-least-squares-models were also used to analyze the results using multiple regression analysis corrected on the basis of gender. The statistical analysis software program used was JMP14.2.0 (SAS Japan).

Results

Of the 296 subjects surveyed, 42 participants (14.2%) consented to participate in the study. Of the 17 male participants, four were obese and three had an increased WC in the fourth grade of elementary school. There was no participant with dyslipidemia in childhood. At age 20, four were obese, of these four, 3 had also been obese in the fourth grade of elementary school. Six had increased WC, 1 had high LDL-C, and none were smokers. Of the 25 female participants, two had childhood obesity and two had an increased WC in the fourth grade of elementary school. One participant had both high TC and high LDL-C, respectively. At age 20, two were obese, all of them had also been obese in the fourth grade of elementary school. Two had an increased WC, one had high LDL-C, and one was a smoker. Table 1 shows the mean, standard deviation, and number of cases with findings for each data among 129 non-participating boys. Differences in means between participants and non-participants were analyzed using t-tests, and differences in rates of findings were analyzed using chi-square tests. No significant differences were found in either case. Table 2 provides the same information for 126 non-participating girls. The results for girls were similar to those for boys. The male-to-female ratio among participants and non-participants was analyzed using the chi-square test and showed no significant difference. Among the 254 non-participants, baseline data for two individuals was unavailable and was therefore excluded from Tables 1 and 2.

Table 1. The characteristics at the fourth grade of elementary school and age 20 of male subjects.

Table 2. The characteristics at the fourth grade of elementary school and age 20 of female subjects.

TC, LDL-C, BMI, and WC showed a significant positive correlation as a result of the simple regression analysis of TC, LDL-C, HDL-C, BMI, and WC between the fourth grade of elementary school and age 20 (Fig. 1). As a result of the multiple regression analysis corrected on the basis of gender, there was a significant positive correlation found between TC, LDL-C, HDL-C, BMI, and WC between the fourth grade of elementary school and age 20 (Table 3). The quartile concordance rates between data from fourth grade and data from age 20 were calculated as the κ coefficient. The results are shown in Table 3. For total cholesterol, no significant concordance rate was observed, whereas significant concordance rates were found for LDL cholesterol, BMI, and waist circumference.

Fig. 1.

The correlation of serum cholesterol between 4^th grade of elementary school and age 20 using simple regression analysis. A: Total cholesterol (TC), (N = 42, r² = 0.34, p < 0.0001). B: low density lipoprotein cholesterol (LDL-C), (N = 42, r² = 0.53, p < 0.0001).

Table 3. Correlation between lipids and body size in the fourth grade of elementary school and lipids and body size at age 20.

Discussion

This study revealed that mail-in medical examinations can be conducted through public health agencies as a follow-up survey for lifestyle-related disease prevention examinations in children. It is possible to undergo clinical examinations even without visiting an examination site. Unfortunately, the participation rate in this study was low at 14.2%. However, no significant differences were found between participants and non-participants regarding the measured variables. Therefore, it was inferred that there was no major selective bias. In order to increase the rate of consultations, it is necessary to improve the health literacy of youth who have little interest in health issues. In sum, health education in elementary and junior high schools is considered important.

TC, LDL-C, HDL-C, BMI, and WC were all positively correlated between the fourth grade of elementary school and age 20. In particular, LDL-C, BMI, and WC had a relatively strong correlation with a correlation coefficient of 0.7 or higher. The analysis of the quartile agreement also revealed a significant association. These results were achieved despite height, weight, and WC being self-measured and self-reported by the participants. Based on the above results, TC, LDL-C, HDL-C, BMI, and WC were found to be associated with the tracking phenomenon from childhood to adolescence among Japanese. It is considered useful to screen children with lifestyle-related diseases and provide them with lifestyle guidance.

Conclusion

Mail-in medical examinations are a feasible method as a follow-up survey of the lifestyle-related disease prevention examinations in children. However, these examinations still had difficulty in terms of increasing the participation rate. Among Japanese youth from the fourth grade of elementary school to age 20, the tracking phenomenon was suggested in serum cholesterol values, BMI and WC.

Conflict of interests

The authors have nothing to declare.