Predictive value of electrocardiographic markers for autonomic nervous system dysfunction in healthy populations: more studies needed

The Association of Work Stress and Glycemic Status Is Partially Mediated by Autonomic Nervous System Function: Cross-Sectional Results from the Mannheim Industrial Cohort Study (MICS)

BACKGROUND

Work stress is associated with an increased risk of pre-diabetes, Type 2 diabetes, and inflammation, as well as decreased autonomic nervous system function as measured, for example, via heart rate variability. We investigated the extent to which the association between work stress and glycemic status is mediated by vagally-mediated heart rate variability (vmHRV) and/or inflammation.

METHODS

Cross-sectional data from the Mannheim Industrial Cohort Study (MICS) with 9,937 participants were analyzed. The root mean squared successive differences (RMSSD) from long-term heart rate monitoring during work and night time periods was used to index vmHRV. Fasting plasma glucose and glycosylated hemoglobin were assessed to determine glycemic status. High sensitive C-reactive protein levels were observed as a measure of systemic inflammation and the Effort-Reward-Imbalance scale was used to evaluate work stress. Mediation models were adjusted for age, sex, and occupational status, and estimations were bootstrapped (5,000 replications).

RESULTS

Effort-Reward-Imbalance was significantly negatively associated with RMSSD and both glycosylated hemoglobin and fasting plasma glucose during both work and night time periods. Effort-Reward-Imbalance was observed to have a significant direct effect on glycosylated hemoglobin and significant indirect effects, through RMSSD, on both glycemic measures during both time periods. Introducing C-reactive protein as a further mediator to the model did not alter the indirect effects observed. C-reactive protein, as an exclusive mediator, was observed to have smaller direct and indirect effects on the glycemic measures as compared to when Effort-Reward-Imbalance was included in the model.

CONCLUSIONS

Our results suggest that the association between work stress and glycemic status is partially mediated through vmHRV independent of systemic inflammation as measured by C-reactive protein. We conclude that work stress may be an additional factor that promotes development of hyperglycemic-metabolic states. If supported by prospective evidence, these results may lead to new approaches for primary prevention of hyperglycemia in the workplace.

Heart rate variability is associated with glycemic status after controlling for components of the metabolic syndrome

OBJECTIVE

To evaluate the relationship between heart rate variability (HRV) and glycemic status after controlling for metabolic syndrome (MetS) in a healthy working cohort.

BACKGROUND

A growing body of literature suggests that reduced HRV, a physiological marker of autonomic nervous system activity, is associated with various pathological conditions including glycemic disorders and cardiovascular diseases. The extent to which this association is confounded by other more traditional markers of cardiovascular risk, such as MetS, is unclear.

METHODS

We recruited 2441 study participants (age 17-65) employed at three sites of an airplane manufacturing plant in southern Germany. All subjects underwent medical examination, blood sampling, and 24-hour ambulatory heart rate recording while on their normal work routine. Indices of HRV were determined from readings made throughout the 24-hour examination period, those during either the day or night only as well as a night to day ratio. Pearson correlations and multivariate-adjusted partial correlation coefficients (PCCs) were calculated.

RESULTS

Pearson correlations suggested inverse associations between HRV measurements and glycemic status (e.g. High frequency r=-0.07, p<0.001; SDNN r=-0.09, p<0.001). After multivariate adjustment of all other components of MetS (triglyceride, blood pressure, waist circumference, high density lipoproteins), medical and demographic variables, these associations persisted (e.g. High frequency PCC=-0.05, p<0.001; SDNN PCC=-0.06, p<0.001).

CONCLUSIONS

We confirm a negative correlation between HRV and glycemic status that appeared to be almost linear in a large cohort of healthy workers. Importantly, we showed that this association was independent of potential confounders, especially all of the MetS components and inflammation.

Quantification of leg oedema in postmenopausal hypertensive patients treated with lercanidipine or amlodipine

OBJECTIVE

Of the study was to compare the leg oedema-forming potential of two different dihydropyridine calcium channel blockers in postmenopausal women.

DESIGN

A total of 92 postmenopausal hypertensive patients [systolic blood pressure (SBP) 150-179 mmHg or diastolic blood pressure (DBP) 95-109 mmHg were randomized to receive a 4-week treatment with either 10 mg/day lercanidipine (n = 48) or 5 mg/day amlodipine (n = 44), with force-titration to 20 and 10 mg/day, respectively for an additional 4 weeks.

METHODS

Leg volume was measured by water displacement volumetry, patients were questioned for symptoms and a physical examination was performed to detect the presence of oedema.

RESULTS

A total of 77 patients completed the study, without a major protocol violation and were included in the primary analysis. Leg volume increase from baseline was significantly higher in the amlodipine than in the lercanidipine group (60.4 +/- 8.6 versus 5.3 +/- 8.1 ml; P < 0.001). The percentage of patients with evidence of oedema on physical examination (33.3 versus 9.8%, P = 0.011) and with symptoms of leg swelling (63.9 versus 22%, P < 0.001) and leg heaviness (47.2 versus 12.2%, P < 0.001) was also greater with amlodipine compared with lercanidipine. A positive correlation was found between leg volume and sign or symptoms of oedema (P < 0.001). Both drugs reduced SBP and DBP, with no significant differences between treatments. No correlation was found between leg volume changes from baseline and the antihypertensive effect of either drug.

CONCLUSIONS

In postmenopausal females with mild to moderate hypertension the oedema formation of Lercanidipine was significantly less than that of Amlodipine, despite no significant differences in the antihypertensive effect.