Is the Association Between Education and Sympathovagal Balance Mediated by Chronic Stressors?

BACKGROUND: This study investigated whether raised chronic stress in low education groups contributes to education differences in cardiovascular disease by altering sympathovagal balance. METHODS: This study included cross-sectional data of 10,202 participants from the multi-ethnic, population-based HELIUS-study. Sympathovagal balance was measured by baroreflex sensitivity (BRS), the standard deviation of the inter-beat interval (SDNN) and the root mean square of successive differences between normal heartbeats (RMSSD). The associations between chronic stressors (work, home, psychiatric, financial, negative life events, lack of job control and perceived discrimination) in a variety of domains and BRS, SDNN and RMSSD were assessed using linear regression, adjusted for age, ethnicity, waist-to-hip ratio and pack-years smoked. Mediation analysis was used to assess the contribution of chronic stress to the association between education and sympathovagal balance. RESULTS: Modest but significant associations were observed between financial stress and BRS and SDNN in women, but not in RMSSD nor for any outcome measure in men. Women with the highest category of financial stress had 0.55% lower BRS (ms/mmHg; ß = -0.055; CI = -0.098, -0.011) and 0.61% lower SDNN (ms; ß = -0.061; CI = -0.099, -0.024) than those in the lowest category. Financial stress in women contributed 7.1% to the association between education and BRS, and 13.8% to the association between education and SDNN. CONCLUSION: No evidence was found for the hypothesized pathway in which sympathovagal balance is altered by chronic stress, except for a small contribution of financial stress in women.

Socioeconomic Differences in Sympathovagal Balance: The Healthy Life in an Urban Setting Study.

OBJECTIVE: Alterations in sympathovagal balance are associated with cardiovascular disease. If sympathovagal balance differs across socioeconomic groups, it may reflect a mechanism through which disparities in cardiovascular disease occur. We therefore assessed the association between education and occupation with measures of sympathovagal balance in a large multiethnic sample. METHODS: We included cross-sectional data of 10,202 South Asian Surinamese, African Surinamese, Ghanaian, Turkish, Moroccan, and Dutch-origin participants from the Healthy Life in an Urban Setting study. Sympathovagal balance was measured by baroreflex sensitivity (BRS) and the standard deviation of the interbeat interval, calculated from changes in blood pressure and interbeat intervals, from 5-minute recordings. We calculated geometric means and estimated the relative index of inequality, using age- and ethnicity-adjusted linear regression, to quantify the association between education and occupation and sympathovagal balance. In addition, we assessed whether the association was consistent across ethnic groups. RESULTS: The geometric means of BRS ranged from 8.16 ms/mm Hg (confidence interval [CI] = 7.91-8.43 ms/mm Hg) in low-educated to 14.00 ms/mm Hg (CI = 13.53-14.48 ms/mm Hg) in highly educated women, and from 8.32 ms/mm Hg (CI, 7.97-8.69 ms/mm Hg) in low-educated to 12.25 ms/mm Hg (CI = 11.86-12.66 ms/mm Hg) in highly educated men. High education and occupation were statistically significantly associated with higher BRS and standard deviation of the interbeat interval. Compared with the participants of Dutch origin, a pattern of weaker associations was found in the Surinamese and Ghanaian ethnic groups, but not the Turkish and Moroccan groups. CONCLUSIONS: There is a clear socioeconomic gradient in measures of sympathovagal balance, indicating that sympathovagal balance may play a role in socioeconomic disparities in cardiovascular morbidity and mortality.

Association Between Income and Risk of Out-of-Hospital Cardiac Arrest: A Retrospective Cohort Study.

BACKGROUND: Previous studies have observed a higher out-of-hospital cardiac arrest (OHCA) risk among lower socioeconomic groups. However, due to the cross-sectional and ecological designs used in these studies, the magnitude of these inequalities is uncertain. This study is the first to assess the individual-level association between income and OHCA using a large-scale longitudinal study. METHODS: This retrospective cohort study followed 1 688 285 adults aged 25 and above, living in the catchment area of an OHCA registry in a Dutch province. OHCA cases (n=5493) were linked to demographic and income registries. Cox proportional hazard models were conducted to determine hazard ratios of OHCA for household and personal income quintiles, stratified by sex and age. RESULTS: The total incidence of OHCA per 100 000 person years was 30.9 in women and 87.1 in men. A higher OHCA risk was observed with lower household and personal income. Compared with the highest household income quintile, the adjusted hazard ratios from the second highest to the lowest household income quintiles ranged from 1.24 (CI=1.01-1.51) to 1.75 (CI=1.46-2.10) in women and from 0.95 (CI=0.68-1.34) to 2.30 (CI=1.74-3.05) in men. For personal income, this ranged from 0.95 (CI=0.68-1.34) to 2.30 (CI=1.74-3.05) in women and between 1.28 (CI=1.16-1.42) and 1.68 (CI=1.48-1.89) in men. Comparable household and personal income gradients were found across age groups except in the highest (>84 years) age group. For example, household income in women aged 65 to 74 ranged from 1.25 (CI=1.02-1.52) to 1.65 (CI=1.36-2.00). Sensitivity analyses assessing the prevalence of comorbidities at baseline and different lengths of follow-up yielded similar estimates. CONCLUSIONS: This study provides new evidence for a substantial increase in OHCA risk with lower income in different age and sex groups. Low-income groups are likely to be a suitable target for intervention strategies to reduce OHCA risk.

Is there an association between socioeconomic status and the degree of diurnal variation in heart rate?

BACKGROUND: Disruption in circadian rhythms is associated with cardiovascular disease and may play a role in socioeconomic differences in cardiovascular disease prevalence. However, it is unclear whether low SES is associated with a lower diurnal rhythm in autonomic activity markers. We investigated the association between SES and the amplitude of the daily fluctuation of heart rate. METHODS: We included data of 450 participants of a HELIUS sub-study in Amsterdam, the Netherlands. Participants wore an Actiheart monitor (CamNtech), a chest-worn monitor which measures heart rate every 15 s for several days. Cosinor analysis was performed on the time series of heart rate within each participant. We analyzed the association between the cosinor parameters (amplitude, midline and peak time of the diurnal HR rhythm) and SES indicators (education, occupational class and a proxy of income) in multivariate linear regression models, adjusting for age, sex and ethnicity. RESULTS: There was a clear diurnal rhythm in the average heart rates, with a peak between noon and 18:00 and a trough between 04:00 and 06:00. This rhythm was present for all categories of education, occupation and income proxy. The estimates for the cosinor parameters did not differ consistently and significantly between categories of education, occupation or income proxy. CONCLUSIONS: We did not find any consistent evidence to support our hypothesis of a diminished amplitude in the diurnal variation of heart rate in individuals with lower SES. Future studies should explore SES differences in the diurnal variation in markers of autonomic activity other than heart rate.

Socio-economic differences in incidence, bystander cardiopulmonary resuscitation and survival from out-of-hospital cardiac arrest: A systematic review.

BACKGROUND: Individuals with a low socioeconomic status (SES) may have a greater mortality rate from out of hospital cardiac arrest (OHCA) than those with a high SES. We explored whether SES disparities in OHCA mortality manifest in the incidence of OHCA, the chance of receiving bystander cardiopulmonary resuscitation (CPR) or in the chance of surviving an OHCA. We also studied whether sex and age differences exist in such SES disparities. METHODS: The Medline, Embase and Scopus databases were searched from 01-01-1993 until 31-01-2019. Studies utilising any study design or population were included. Studies were included if the exposure was SES of the OHCA victim or the OHCA location and the outcome was either OHCA incidence, CPR provision and/or survival rate after OHCA. Study selection and quality assessment were conducted by two reviewers independently. Descriptive data and measures of association were extracted, both in the total study population and in subgroups stratified by age and/or sex. This review was carried out following the PRISMA guidelines. RESULTS: Overall 32 studies were included. Twelve studies reported on OHCA incidence, thirteen on bystander CPR provision and fourteen on survival. Some evidence for SES differences was found in each identified stage. In all the studies on incidence, SES was measured over the area of the OHCA victims' residence and was consistently associated with OHCA. In studies on bystander CPR, SES of the area in which the OHCA occurred was associated with bystander CPR, while evidence on individual SES was lacking. In studies on OHCA survival, SES of the victim measured at the individual level and SES of the area in which the OHCA occurred were associated, while SES of the victim, measured at the area of residence was not. Studies reporting age and sex differences in the SES trends were scarce. CONCLUSION: SES disparities in OHCA mortality likely manifest in OHCA incidence, bystander CPR provision and survival rate after OHCA. However, there is a distinct lack of data on SES measured at the individual level and on differences within subgroups, e.g. by sex and age.