|Year : 2022 | Volume
| Issue : 2 | Page : 166-168
Association between socioeconomic status and homeostasis model assessment-insulin resistance index and mediating variables at the first trimester of pregnancy
Raziyeh Mohammadi1, Masoomeh Goodarzi-Khoigani2, Zahra Allameh3, Seyed Saeed Mazloomy Mahmoodabad4, Mohammad Hossein Baghiani Moghadam5, Azadeh Nadjarzadeh6, Farahnaz Mardanian3
1 Department of Mathematical Sciences, Isfahan University of Technology, Isfahan, Iran
2 Child Growth and Development Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran
3 Department of Obstetrics and Gynecology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
4 Department of Health Education And Promotion, Social Determinants Of Health Research Center, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
5 Department of Health, Azad University of Firoozabad Branch, Fars, Iran
6 Nutrition and Food Security Research Center, Shahid Sadoughi University of Medical Sciences, Yazd. Department of Nutrition, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
|Date of Submission||24-Feb-2021|
|Date of Decision||26-Mar-2021|
|Date of Acceptance||24-Nov-2021|
|Date of Web Publication||14-Mar-2022|
Dr. Masoomeh Goodarzi-Khoigani
Child Growth and Development Research Center, Research Institute for Primordial Prevention of Noncommunicable Disease, Isfahan University of Medical Sciences, Isfahan
Source of Support: None, Conflict of Interest: None
Background: Some studies have shown that Socioeconomic Status (SES) is positively related to insulin resistance among different population groups, except for pregnant women. Therefore, we examined the relationship between SES and Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) index as well as mediating variables. Materials and Methods: This study was performed on 138 primiparous healthy women at 6–10 weeks of pregnancy. The association between SES and HOMA-IR was analyzed by regression analysis, and mediating variables were determined by mediation analysis. Results: SES score was positively correlated with HOMA-IR index [β = 0.02, t101 = 2.20, p = 0.03, 95% CI: (0.00–0.05]. The higher percentage of mediation was related to maternal weigh (70.80%). Job activity had a protective effect on the association between SES and HOMA-IR (-62.50%). The total percentage of two mediators was 25%. Conclusions: The positive relationship between SES and (HOMA-IR) in early pregnancy may provide a way to control this condition.
Keywords: Insulin resistance, mediation analysis, occupations, social class
|How to cite this article:|
Mohammadi R, Goodarzi-Khoigani M, Allameh Z, Mazloomy Mahmoodabad SS, Baghiani Moghadam MH, Nadjarzadeh A, Mardanian F. Association between socioeconomic status and homeostasis model assessment-insulin resistance index and mediating variables at the first trimester of pregnancy. Iranian J Nursing Midwifery Res 2022;27:166-8
|How to cite this URL:|
Mohammadi R, Goodarzi-Khoigani M, Allameh Z, Mazloomy Mahmoodabad SS, Baghiani Moghadam MH, Nadjarzadeh A, Mardanian F. Association between socioeconomic status and homeostasis model assessment-insulin resistance index and mediating variables at the first trimester of pregnancy. Iranian J Nursing Midwifery Res [serial online] 2022 [cited 2023 Feb 4];27:166-8. Available from: https://www.ijnmrjournal.net/text.asp?2022/27/2/166/339422
| Introduction|| |
As the pregnancy progress to the third trimester, resistance to the normal action of insulin occurs, which leads to usage of fats by maternal tissues and maintenance of carbohydrate for growing fetus. This physiological state can lead to gestational diabetes, which has side effects for both mother and fetus. In Brazilian young adults with high Socioeconomic Status (SES), high recreational screen time and low fruit and vegetable consumption were significantly associated with metabolic syndrome. However, a review was conducted with 191 studies involving obese persons confirmed that the lower SES was associated with insulin resistance. Despite much efforts to find the early determinants of gestational insulin resistance, few studies have been performed to investigate the relationship between SES and IR index during pregnancy. In addition, determining the mechanism of this relationship requires finding intermediates that are correlated with both variables.
The association between nutritional status and HOMA-IR index has been previously studied, and the results showed that maternal occupational activity score, weight, systolic blood pressure, and intakes of α-linolenic acid and maltose were associated with both of SES and IR. Therefore, in this paper, which is part of a study on the association between nutritional status and HOMA-IR, we assessed the relationship between SES (predictor variable) and HOMA-IR index (outcome variable) as an insulin resistance score at the first trimester of gestation. Also, we determined the mediating role of correlated variables with both of SES and IR.
| Materials and Methods|| |
This cross-sectional study was performed on 138 primiparous healthy women aged 18–40 years at 6–10 weeks of pregnancy in Isfahan, Iran, between June 2017 and September 2019. Assuming α = 0.05 or a significant level of 0.95%, β = 0.20 or power of 0.80%, and p = 0.03 as the least acceptable correlation in terms of performance, minimum sample size with a 10% drop rate was estimated 134. Exclusion criteria included twin or higher-order multiple pregnancy, medical problems affecting body weight (untreated thyroid disease), drug-related hypertension, type 1 or 2 diabetes mellitus, addiction, nutritional problems, being on a special diet, chronic illness, kidney disease, anemia, and body mass index (BMI) ≥35 kg/m2. Stratified sampling was considered to take into account the effect of participants' socioeconomic conditions on study results.
Individual and family characteristics were collected using a researcher-administered questionnaire. The ultrashort version of SES tool (SES-Iran) was used to estimate SES. After obtaining written consent, participants' weight and prepregnancy BMI were measured by a digital scale. We measured blood pressure twice at 5 min intervals using an automatic BP monitor. The physical activity score as the confounding variable was determined by a pregnancy physical activity scale. The HOMA-IR index was calculated by fasting insulin (micro unit/mL) multiplied by fasting glucose (mg/deciliter) divided on 405.
Then, we investigated the relationship between SES and HOMA-IR index by regression analysis. Mackinnon's product-of-coefficients test was used to analyze whether this relationship were mediated by maternal occupational activity score, weight, systolic blood pressure, and intakes of α-linolenic acid and maltose. To use mediation analysis model, the predictor variable needs to be significantly associated with outcome variable. Also, mediators need to be significantly correlated with both predictor and outcome variables. The sum of the individual mediated effects [Σ(a × b)] was used to obtain the total mediated effect. The mediated percentages were computed as the mediation effect divided by the total effect (path c) [(a × b)/c] and [Σ(a × b)/c] [Table 1]. We calculated total effects through regression models without the possible mediators. Standard errors were considered to make the 95% confidence intervals for the direct and total effects. The SPSS version 20 (SPSS Inc., Chicago, IL USA) displayed bootstrap, which modified confidence intervals applied for indirect and mediated effects. The probable mediators with the mentioned criteria were entered in the final multiple mediator model to estimate mediation effects and mediated percentage
|Table 1: Results from the mediation analyses in the association between SES and HOMA-IR index (part 1), and from the multiple mediation analyses considering two significant mediators simultaneously (part 2)|
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Written consent obtained, and the study protocol was approved by Ethic Committee of School of Public Health of Shahid Sadoughi University (IR.SSU.SPH.REC.1395.13).
| Results|| |
The results indicated that SES was positively associated with HOMA-IR index [β = 0.02, t101 =2.20, p = 0.03, 95% CI: (0.00–0.04] [Figure 1]. Every 0.02 increase in SES score was related to one-unit enhancement in IR (path-c). As shown in the second column of [Table 1] (part 1), SES was associated with maternal weight and job-activity level at 6–10 weeks of gestation (path-a). The fourth column indicates the calculated mediation effects. Statistically significant indirect effects were positive for maternal weight and negative for job activity. The last column of [Table 1] provides mediated percentages, whereas the higher percentage is related to maternal weigh (70.80%). Job activity had a negative (protective) effect on the association between SES and HOMA-IR (-62.50%). The total percentage of the complete effect mediated by two mediators was 25%.
|Figure 1: Multiple mediator mode|
X*: Predictor variable; **: socio economic status; Y***: Outcome variable; M: Mediator variable ****: homeostasis model assessment-insulin resistance;a$: Association between (X) and potential mediator (M1, M2, M3, M4, and M5); b$$: Association between potential mediator and (Y); c$$$: Total association; c: Overall association between predictor variable (X) and outcome variable (Y); c'$$$$: Direct effect (unmediated) of predictor variable (X) on outcome variable (Y).
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| Discussion|| |
Higher SES increases HOMA-IR index by maternal weight in the first trimester of gestation, while the occupational activity has a protective effect. The total percentage of the overall effect mediated by two variables was 25%. We obtained no mediation effects for systolic blood pressure and intakes of α-linolenic acid and maltose. We previously showed that nutrients' intake and the components of physical activity were not correlated with SES and insulin resistance index, except for occupational activity and intakes of α-linolenic acid and maltose. Therefore, the association between high SES and insulin-resistance index during pregnancy is not entirely due to nutrients intake and physical activity, as some studies have suggested. Similarly, another study showed that SES was positively related to IR; and usual risk factors such as sleep duration, diet, and physical activity were poor predictors of IR. The first limitation is a cross-sectional design that limits cause–effect interpretations. The second is small sample size.
| Conclusion|| |
The positive relationship between SES and insulin resistance in early pregnancy may provide a way to control this condition. Also, this study could be a guide to clarifying the mechanism of this relationship, as it determined up to 25% is related to weight and job activity.
We thank Shahid Sadoughi University of medical sciences for providing financial support and Isfahan University of Medical Sciences for providing research environment(provided the budget 4326).
Financial support and sponsorship
Public Health College of Shahid Sadoughi University of Medical Sciences
Conflicts of interest
Nothing to declare.
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