Background: A growing number of studies have reported that occupational psychosocial factors increase the risk of CVD. CVD risk factors, such as hypertension and dyslipidemia, are prevalent among younger individuals who have dual roles at both work and home. This suggests that conflict between these two domains may cause stress that contributes to CVD. Work-family conflict has two directions: work-to-family conflict (WFC), where work roles interfere with family roles, and family-to-work conflict (FWC), where family roles interfere with work roles. Although many workers experience work-family conflict, research examining its effects is still lacking.
Allostatic load (AL) represents a phase of failing adaptation to stress, which is a main biological mechanism that explains the pathway from stress to disease. Lipid risk factors are well-established cardiovascular biomarkers, and the associations between allostatic load index (ALI) and CVD have also been documented. Both ALI and lipid risk factors can capture the wear and tear of the biological system prior to the disease manifestation. Research also indicates that increased perceived stress leads to CVD risk factors, such as unhealthy dietary choices, health risk behaviors, elevated waist-to-hip ratio, lower cardiovascular reactivity, and increased glycosylated hemoglobin levels. Therefore, this dissertation research used the Midlife in Japan longitudinal data set to investigate the impact of WFC and FWC on risk factors for cardiovascular disease that included increased blood lipid risk factors, ALI, and perceived stress, with three aims listed below:
Aim 1: To investigate the impact of baseline WFC and FWC on changes in lipid levels measured at baseline and at a four-year follow-up point.
Aim 2: To examine whether WFC and FWC at baseline would be associated with changes in ALI measured at baseline and at a four-year follow-up point.
Aim 3: To investigate whether exposure to work-family conflict would be associated with changes in perceived stress measured at baseline and at a four-year follow-up point.
Methods: This study used longitudinal data from the Midlife in Japan study with a four-year interval. Inclusion criteria were participants employed at baseline without missing variables of interest. Each study had a different number of participants. Aims 1 and 2 included 152 participants, and Aim 3 included 419 participants. Work-family conflict was measured using a validated scale with eight items (each WFC and FWC has four items), and higher scores indicated higher levels of WFC or FWC. WFC and FWC were used as continuous variables in this study.
Aim 1 assessed the associations of baseline WFC and FWC with changes in metabolic risk factors between baseline and follow-up using Generalized Estimating Equations (GEE) linear regression. Results were reported as beta coefficients (beta) and 95% confidence intervals (CIs).
Aim 2 examined the four-year longitudinal changes in the ALI using two methods: comparing ALI scores at baseline and follow-up, named “Two ALI approach,” and creating one ALI score considering changes at baseline and follow-up, named “One ALI approach.” GEE negative binomial regression was used for analyses. The results were reported by count ratios (CRs) and 95% CIs.
Aim 3 investigated the associations of baseline WFC and FWC with changes in perceived stress measured by the Perceived Stress Scale 10-item version (PSS-10). For this analysis, in addition to continuous WFC and FWC, they were dichotomized at the median to create binary (low and high) WFC and FWC. The higher perceived stress scores indicated higher levels of perceived stress. GEE linear regression was applied in this study. The results were reported as beta and 95% CIs.
Results:
Aim 1: After adjusting for baseline sociodemographic, work and family-related, and lifestyle factors, the fully adjusted model showed that WFC was significantly associated with increased low-density lipoprotein cholesterol (LDL-C), with beta = 1.73, 95% CIs (0.13, 3.33), as well as the increased total cholesterol (TC)/high-density lipoprotein cholesterol (HDL-C) ratio, with beta = 0.04 (0.00, 0.09). However, FWC was not significantly associated with changes in any lipid risk factors.
Aim 2: In the final model, our results demonstrated that WFC at baseline was significantly associated with increased ALI using “Two ALI approach” CR = 1.15, 95% CIs (1.03, 1.28) and “One ALI approach” CR = 1.15, 95% CIs (1.01, 1.32), whereas FWC did not show statistical significance in both methods.
Aim 3: In the fully adjusted model, dichotomized and continuous WFC were significantly associated with increased perceived stress, with beta = 2.33, 95% CIs (1.28, 3.37) and beta = 1.53, 95% CIs (0.93, 2.13), respectively. Both dichotomized and continuous FWC were also significantly associated with increased perceived stress across models. The final model showed dichotomized and continuous FWC with beta = 2.29, 95% CIs (1.35, 3.22) and beta = 1.30, 95% CIs (0.80, 1.80), respectively.
Conclusion: Our findings indicated a significant impact of WFC on LDL-C, TC/HDL-C ratio, and ALI, but no significant impact of FWC on lipid risk factors and ALI. In contrast, both WFC and FWC increased perceived stress compared at baseline and at a four-year follow-up time point. Since lipid risk factors, ALI, and perceived stress are associated with CVD, it is crucial to mitigate the effects of work-to-family conflict. Stress management that addresses work-family conflict can be beneficial when occupational health nurses develop interventions to enhance workers’ cardiovascular health. Intervention studies to mitigate work-family conflict will be warranted.