Physical Activity Levels and Energy Intake According to the Presence of Metabolic Syndrome Among Single-household Elderly in Korea: Korean National Health and Nutrition Examination Survey 2016‒2018

Abstract

Background: Exercise and dietary and nutritional intake affect the risk and prevalence of metabolic syndrome (MetS) in elderly people, effects that may differ according to sex in elderly single households (ESH). This study aimed to analyze the differences in physical activity (PA) levels and energy intake according to sex and prevalence of MetS among elderly people in Korea to investigate the relationships between these factors.

Methods: Data from 893 elderly individuals (aged >65 years) were obtained from the Korean National Health and Nutrition Examination Survey (2016‒2018). We analyzed PA levels (occupational and recreational PA and place movement) and energy intake (EI; total, carbohydrate, protein, and fat), and found that there were sex differences in both according to the presence or absence of MetS in ESH.

Results: Among both males and females, the MetS group had a significantly lower recreational moderate PA than the non-MetS group. However, total PA in males was significantly higher in the non-MetS than in the MetS group, but there was no significant difference in females. Furthermore, the EI of females did not differ in the presence or absence of MetS, except for fat intake, and in the nutritional intake of ESH in males, no difference was found in the presence or absence of MetS.

Conclusions: Therefore, although no major problem was found in the EI of ESH in the MetS group, an increase in PA level appeared to be a more important factor in preventing MetS. Male ESH require interventions that increase PA, while female ESH require nutrition interventions that increase and balance PA. Therefore, a new program is needed that promotes continuous interest and healthy lifestyles in consideration of the characteristics of ESH. 

1. Introduction

The proportion of the elderly population in Korea is increasing and will reach 20.3% by 2025, and it is expected that about half of all households will be elderly by 2047 [1]. In addition, due to the low fertility rate and aging population, a typical household consisting of a man, a woman, and one or two children is gradually shifting to a one-person household. According to the National Statistical Office, the proportion of single households among the elderly aged 60 years and over is expected to increase from 30% in 2015 to 54% in 2045 [2].

The most common cause of medical expenses among the elderly is metabolic syndrome (MetS), which causes chronic diseases, such as cardiovascular disease and diabetes [3]. According to the Korean National Health and Nutrition Survey (KNHANES), the incidence of MetS has increased by 0.6% every 10 years since 1998 [4]. MetS comprises a bundle of metabolic risk factors, including hyperglycemia, dyslipidemia, abdominal obesity, and hypertension [5]. Higher levels of physical activity (PA) may protect against the progression of cardiovascular disease [6], type 2 diabetes [7], and MetS [8–10], and people with MetS who participate in PA have a lower risk of mortality from MetS than those with normal weight; however, sedentary adults have been reported as evidence[11]. Moreover, the consumption of a Western diet, meat and fried foods favors the occurrence of MetS. [12]. Although the main aim of nutrition is the prevention and treatment of nutritional deficiencies, overnutrition can negatively affect health and cause many metabolic disorders such as diabetes, obesity, hypertension, and hyperlipidemia [13–17]. A previous study showed that all five components of MetS were improved through modifications in energy intake (EI) and exercise [18]. Therefore, EI, similar to exercise, is an important component of MetS prevention. A previous study in Korea found that adult single households were associated with insufficient PA and unbalanced EI habits compared to mixed households [19]. A decrease in moderate PA and walking was induced at low PA levels, and reduced PA contributed to the incidence of MetS in elderly single households (ESH) [20]. Among elderly people, living alone has been found to be associated with specific health concerns, such as poor EI and PA[21]. A previous study demonstrated that elderly people, who eat alone was associated with several health problems, including MetS [22], lower caloric intake, and a less-varied diet [23]. Elderly people who lived alone had a higher risk of MetS than those who did not.

The importance of sex has also been considered when distinguishing the influence of living alone on MetS [24]. Elderly men living alone are associated with poorer diets [25], whereas elderly women living alone are more likely to have physical limitations [26]. A previous study reported that elderly women living alone were not socially isolated nor were they at high risk of deterioration in their functional health status. Instead, they reported more contact with close friends outside the household [27]. A previous study reported that elderly women living alone did not have a high risk of deterioration in their functional health status and that they engaged in more activities with friends outside the household [28]. These sex differences in the characteristics of elderly people living alone could be relevant by sex, PA, and EI differences in the relationship between living alone and MetS. However, there is little research on housing and MetS among elderly people, particularly among ESH with sex differences.

Therefore, this study aimed to analyze the relationship between PA levels, and EI in the presence and absence of MetS, and the sex differences between PA levels, and EI in the presence and absence of MetS in an ESH Korean population, based on data from the 7th Korea National Health and Nutrition Examination Survey (2016‒2018), to investigate the relationships between these factors.

2. Materials And Methods

3. Results

Table 2 shows the differences in variables considered risk factors for MetS according to the presence or absence of MetS and sex. There were significant differences in waist circumference (p = 0.000), TG (p = 0.000), HDL-C (p = 0.000), SBP (p = 0.000), DBP (p < 0.002), and FG (p = 0.000) between MetS and non-MetS in the total group and females. In males, there was a significant difference in all MetS components (p = 0.000), except DBP (p = 0.126), between MetS and non-MetS groups.

Table 3 shows significant difference in recreational moderate PA between Mets and non-MetS in total (p = 0.001), males (p = 0.016), and females (p = 0.012). There was significant difference in total PA between Mets and non-MetS in total (p = 0.021) and males (p = 0.036). In females, there was not a significant difference in total PA (p = 0.150).

Values are expressed as mean ± standard error; MetS, metabolic syndrome. Main effect = SD (sex difference) and M (Metabolic syndrome), Interaction effect = SD × M (sex difference × Metabolic syndrome), p < 0.05: *, p < 0.001: **

Table 4 shows the differences in energy intake according to the presence or absence of MetS and sex. There was no significant difference in total energy intake, carbohydrate intake, or fat intake between the MetS and non-MetS groups in the total group and males. In females, fat intake (p = 0.011) was lower in those with MetS than in those without MetS. As shown by sex differences, females had significantly lower total energy intake (p = 0.000), carbohydrate intake (p = .000), fat intake (p = 0.011), and protein intake (p = .000) in the non-MetS group. In MetS, females had significantly lower total energy intake (p = 0.000), carbohydrate intake (p = 0.001), and protein intake (p = 0.003) but tended to have lower fat intake than males (p = 0.053).

The ORs for MetS and MetS components according to PA level and energy intake are presented in Table 7. Model 1 was an uncorrected crude model, and Model 2 was adjusted for sex, smoking, alcohol consumption, and body mass index.

We found that in Model 1, being "somewhat active" was associated with MetS occurrence (OR = 0.59, 95%CI = 0.38‒0.90) and lowering of high TG (OR = 0.54, 95%CI = 0.30‒0.98). "Very active" was associated with lower MetS occurrence (OR = 0.56, 95%CI = 0.36‒0.86) and TG (OR = 0.63, 95%CI = 0.40‒0.97) and low-level HDL-C (OR = 0.48, 95%CI = 0.32‒0.72). In addition, "moderate energy intake" was found to be associated with low HDL-C levels (OR = 0.53, 95%CI = 0.29‒0.96). We also found that in Model 2, "active" was associated with lowering high waist circumference (OR = 0.40, 95%CI = 0.21‒0.76), and "very active" was associated with lower MetS occurrence (OR = 0.51, 95%CI = 0.33‒0.81) and low HDL-C (OR = 0.55, 95%CI = 0.37‒0.83), as in Model 1.

4. Discussion

This study examined the differences in PA levels and EI according to the presence or absence of MetS and sex among ESH in Korea to understand the correlations between these factors. The total MetS group engaged in significantly less recreational moderate PA and total PA than the non-MetS group. In particular, the recreational moderate and total PA levels were significantly lower in males with MetS, whereas females with MetS had only significantly lower recreational moderate PA. "Active" was associated with lowering high waist circumference and "Very active" with lower MetS occurrence and low HDL-C as in Model 2 using adjustments for sex, smoking, alcohol consumption, and body mass index. Examination of differences in energy intake according to the presence or absence of MetS showed that there was a significant difference only in fat intake in females, which was lower in those with MetS; no significant difference was found in the total group or in males. According to the odds ratio of EI, "moderate energy intake" was found to be associated with only HDL-C in Model 2, and there was no association between components of EI and MetS. Taken together, our results suggest that single-household MetS prevention is more strongly associated with PA than EI.

In the present study, we found that higher recreational moderate PA was associated with low MetS morbidity in both males and females. A previous study of 477 people (aged 55–80 years) in Spain found that the MetS group had lower energy expenditure and less leisure-time PA (< 4 MET) than the non-MetS group [39]. Jung et al. [40] investigated 3,720 participants in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2016 to 2018, aged > 65 years irrespective of household type, and compared MetS risk with PA level. They reported that the extent of PA according to the presence or absence of MetS differed more in terms of recreational PA than occupational PA. Our study also showed that MetS was more inactive than non-MetS in the total group; therefore, it appears that recreational moderate PA is important to lower the risk factors for MetS in elderly people. In addition, in relation to PA level, Smith et al. (2017) [41] and Sarkar et al. (2016) [42] reported that having someone (e.g. family and friends) is positively correlated with PA level, whereas living alone may promote a decrease in total PA, which may be as a risk factor for increased occurrence of MetS. Comparing our study with ESH and with mixed households (single and mixed-household type) [40], PA at the total PA and recreational moderate levels of elderly people with MetS in the mixed-household type was higher than in our study; therefore, it can be observed that PA among ESH is low. Moreover, when the total PA level of mixed-households and ESH in our study was compared by sex, there was no significant difference in the presence or absence of MetS in males by mixed-household type, but there was a significant difference in females. Conversely, in our study, there was a significant difference in the presence or absence of MetS in males, but not in females. Previous studies have shown that older women living alone engage in more activities and contact with friends through social relationships than older men living alone [43]. There appeared to be no difference in PA levels between the MetS and non-MetS groups due to the social characteristics of women. Furthermore, in the study by Jung et al. [40], according to sex, the male total PA in the MetS group of mixed households was higher and female total PA and recreational moderate PA in the MetS group of mixed households was higher than in our study. This difference can be interpreted as a result according to the type of household, and it can be expected that single households are more exposed to risk factors of MetS because the PA level is lower than that of mixed households.

In our study, an analysis of dietary intake in relation to the presence or absence of MetS was also performed in elderly people. This showed that total EI and carbohydrate, fat, and protein intakes did not show significantly different between MetS and non-MetS in both sexes, with the exception of fat intake in females. According to the results for a mixed household [40], carbohydrate, fat, and protein intakes were also not significantly different between MetS and non-MetS groups in males. However, in females, the total energy intake (carbohydrate, fat, and protein) was significantly different between the MetS and non-MetS groups. This result is supported by a previous study, which reported that the dietary quality and food diversity of females was better than that of males [44]. Moreover, the overall low nutrient intake and low nutrient density of meals were the major nutritional problems in the group of ESH. As in the previous study mentioned above, ESH also consumed less than the recommended dietary intake. Therefore, malnutrition rather than a nutrient excess appears to be the problem in ESH, and consumption of a balanced diet may be more important than deficient intake of a single nutrient. These dietary intake patterns of the elderly have been described in more detail in previous studies. Giezenaar et al. reported that low EI is a strong predictor of poor outcomes, including the development of pathological undernutrition and sarcopenia, as well as reduced functioning and frailty; this low EI in the elderly affects the decline in PA [45]. Therefore, ESH appear to experience a greater reduction in PA compared with mixed households.

The results of this study should be interpreted with the following limitations in mind. First, we assessed ESH with MetS but did not consider the timing of MetS development or the duration of MetS. Second, PA levels were not determined using heart rate measurements or an accelerometer but were based on survey results, which are prone to errors. Third, this study found only simple differences without establishing causality of underlying the association between PA and nutrition. Finally, the data obtained using the 24-hour reminder may not reflect long-term dietary habits. The 24-hour recall is essentially a retrospective method of diet assessment, in which an individual is asked about their food and beverage consumption during the previous day or the 24 hours. However, a single 24 hour-recall may not be representative of the habitual diet at an individual level. The strength of this study is that it analyzed PA levels and energy intake of ESH as a function of the prevalence of MetS. Most studies examining the relationship between MetS, PA levels, and energy intake have not considered household types in the elderly. In particular, this study classified them according to sex and investigated the PA levels and energy intake of ESH. Therefore, the risk of MetS depends on lifestyle habits, such as PA level and energy intake, and the risk of MetS can be prevented by increased PA levels, and a balanced dietary and healthy energy intake. In this study, we identified sex-specific aspects of PA levels and energy intake with and without MetS in ESH. In addition, this information can be used to reduce the incidence of MetS in ESH according to sex.

5. Conclusions

In this study, we found that there was a sex difference in PA level and EI according to the presence or absence of MetS in ESH. Among both men and women, the MetS group engaged in significantly lower recreational moderate PA than the non-MetS group. However, total PA in males was significantly higher in non-MetS than in MetS, but there was no significant difference in females. Furthermore, the EI of females did not differ in the presence or absence of MetS, except for fat intake, and in the nutritional intake of ESH in males, no difference was found in the presence or absence of MetS. Therefore, although no major problem was found in the EI of ESH in the MetS group in this study, the increase in PA level appeared to be a more important factor in preventing MetS. These findings highlight the need for different approaches to implementing PA and nutrition strategies depending on sex to prevent MetS in ESH. Male ESH require a program that increases the amount of PA, while female ESH require a nutrition program that increases and balances PA. Therefore, a new program is needed that promotes continuous interest and healthy lifestyles in consideration of the characteristics of ESH.

Declarations

Acknowledgments: This study analyzed the data provided by the Korean National Health and Nutrition Examination Survey 2016-2018, conducted by the Korea Centers for Disease Control and Prevention. 

Author Contributions: Conception and study design, E.S and J.P.; Statistical Analysis, E.S and J.P.; Investigation, E.S and J.P., and Data Interpretation E.S and J.P.; Writing-Original Draft Preparation, E.S and J.P.;   Writing-Review & Editing, E.S and J.P.; Supervision, J.P. All authors have read and approved the final manuscript.

Funding: No specific funding was received for this study.

Availability of data and materials: The dataset can be downloaded from Korea National Health and Nutrition Examination Survey website (https://www.kdca.go.kr/index.es?sid=a3)

Ethics approval and consent to participate: The KNHANES was approved by the Institutional Review Board of the Korea Centers for Disease Control and Prevention (KCDC), and written consent was obtained from all participants. These are from the public database of the Korea Centers for Disease Control and Prevention (https://www.kdca.go.kr/index.es?sid=a3).

Consent for publication: Not applicable.

Competing interests: The authors declare no conflict of interest.

Author details: ¹ Exercise Nutrition and Biochemistry Laboratory, Department of Physical Education, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea.

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