Emdad R, Belcik K, Theorell T, Cizinsky S, Savic C, Olsson K. Work environment, neurophysiologic and psychophysiologic models among professional drivers with and without cardiovascular disease: seeking an integrative neurocardiologic approach. Stress Med 1997; 13:7-21.
ABSTRACT:
Two work environment models, the self-reported job strain model (JSM) and the Occupational Stress Index (OSI) were applied among four groups of professional drivers (PD): 13 with ischaemic heart disease (IHD), 12 with hypertension (HTN), 10 with borderline hypertension (BHTN), 34 health PD and 23 non-PD referents. Neuro- and psychophysiologic models symbolically simulating aspects of the driving environment were applied; behavioral and standard risk factors were assessed. Among the PDs, there were significant correlations between job strain and the total OSI score, implying that both the ratio of demand/control and total OSI measure overall burden of the work environment upon this cohort. There was no significant between-groups effect for job strain. The total OSI scores differed significantly between groups, with significantly greater scores for each PD group compared to controls. The OSI includes a 'potential for disaster' dimension, implicated in cardiac risk, whose score among PDs was over twice that of controls. A logistic regression model was used to find which factors best distinguished normotensive PDs from that of controls. A logistic regression model was used to find which factors best distinguished normotensive PDs from the combined group of borderline plus hypertensive PDs. A greater body mass index, deadline pressure and amplitude of the event N2 component in response to an avoidance task and lower fear of driving score were significant independent indicators of HTN-BHTN status. Professional drivers with IHD had significantly smaller N2 amplitudes to the avoidance task, less activity recovery during the Glare Pressor Test and a greater fall in digital pulse amplitude with repeated glare exposure, compared to hypertensive PDs. Significant independent indicators of IHD as opposed to HTN status were longer work hours and more fear of driving. These findings indicate that the total burden of occupational stress is the backdrop for cardiovascular disease risk among these PDs, but a combination of neuro- and psychophysiologic and behavioral response patterns, together with exacerbating work stressors and standard risk factors, can contribute to this process. Further investigation in the direction of an integrated neurocardiologic approach is warranted.
Orth-Gomer K; Mittleman MA; Schenck-Gustafsson K; Wamala SP; Eriksson M; Belkic K; Kirkeeide R; Svane B; Ryden L. Lipoprotein(a) as a determinant of coronary heart disease in young women. Circulation 1997 Jan 21;95(2):329-34.
ABSTRACT:
BACKGROUND: Lipoprotein(a) [Lp(a)] appears to be a risk factor
for coronary heart disease (CHD) in men. The role of Lp(a) in
women, however, is less clear.
METHODS AND RESULTS: We examined the ability of Lp(a) to predict
CHD in a population-based case-control study of women 65 years
of age or younger who lived in the greater Stockholm area. Subjects
were all patients hospitalized for an acute CHD event between
February 1991 and February 1994. Control subjects were randomly
selected from the city census and were matched to patients by
age and catchment area. Lp(a) was measured 3 months after hospitalization
by use of an immunoturbidometric method (Incstar) calibrated to
the Northwest Lipid Research Laboratories (coefficient of variation
was < 9%). Of the 292 consecutive patients, 110 (37%) were
hospitalized for an acute myocardial infarction, and 182 were
hospitalized (63%) for angina pectoris. The mean age for both
patients and control subjects was 56 +/- 7 years. Of participants,
74 patients (25%) and 84 control subjects (29%) were premenopausal.
The distributions of Lp(a) were highly skewed in both patients
and control subjects, with a range from 0.001 to 1.14 g/L. Age-adjusted
odds ratio for CHD in the highest versus the lowest quartile of
Lp(a) was 2.3 (95% confidence interval [CI], 1.4 to 3.7). After
adjustment for age, smoking, education, body mass index, systolic
blood pressure, total cholesterol, triglycerides, and HDL, the
odds ratio was 2.9 (95% CI, 1.6 to 5.0). The odds ratios were
similar when myocardial infarction and angina patients were compared
with their respective control subjects. The odds ratios were 5.1
(95% CI, 1.4 to 18.4) and 2.4 (95% CI, 1.3 to 4.5) in premenopausal
and postmenopausal women, respectively.
CONCLUSIONS: These results suggest that Lp(a) is a determinant
of CHD in both premenopausal and postmenopausal women.
Ugljesic M; Belkic K; Boskovic D; Boskovic S; Ilic M. Exercise testing of young, apparently healthy professional drivers. Scand J Work Environ Health 1996 Jun;22(3):211-5.
ABSTRACT:
OBJECTIVES: The purpose of this study was to examine the responses
of young, apparently healthy professional drivers to exercise
testing. METHODS: A bicycle exercise test was performed by a randomly
selected group of 42 apparently healthy, male professional drivers
aged 20 to 40 years and a group of 30 building workers, who formed
a reference group. RESULTS: The mean maximal exercise level was
significantly lower for the drivers [139 (SD 32) W] than for the
referents [155 (SD 31) W] (P < 0.05). The mean systolic blood
pressure and heart rate did not differ significantly between the
groups at the end of the exercise, but the mean double product
was significantly higher for the drivers. The mean diastolic blood
pressure at the end of the exercise was 97 (SD 14) mm Hg [12.9
(SD 11.9) kPa] for the drivers and 79 (SD 19) [10.5 (SD 2.5) kPa]
for the referents (P < 0.01). The exercise was stopped due
to diastolic hypertensive reactions [diastolic blood pressure
> 115 mm Hg (> 15.3 kPa)] in 13 (31%) of the drivers and
3 (10%) of the referents (P < 0.05). Eight of the thirteen
drivers with a hypertensive reaction had three or more cardiac
risk factors.
CONCLUSIONS: There seems to be a high occurrence of diastolic
hypertensive reactions to exercise among professional drivers.
These reactions may be associated with risk of ischemic heart
disease and hypertension. Further exercise testing of professional
drivers is warranted. More sensitive methods may be indicated
in selected cases, since the cardiovascular status of this cohort
is a vital concern with respect to traffic safety.
Emdad R; Belkic K; Theorell T; Wennberg A; Hagman M; Johansson L; Savic C; Cizinsky S. Electrocortical responses to ecologically relevant visual stimuli among professional drivers with and without cardiovascular disease. Integr Physiol Behav Sci 1996 Apr-Jun;31(2):96-111.
ABSTRACT:
Electrocortical responses were assessed using two simulated aspects of visual signals encountered in traffic: the Glare Pressor Test (GPT) and Event-Related Potential Avoidance Task (ERPAT) among four groups of male professional drivers: 12 with ischemic heart disease (IHD), 12 hypertensives, 10 borderline hypertensives, 34 who were apparently healthy and 23 nonprofessional driver healthy control subjects. The blood pressure (BP) responses immediately after the ERPAT were also measured. There was a significant between groups effect for the amplitude of the target N2 component in the ERPAT (p = 0.02), with the lowest means among the drivers with IHD and the highest among those with hypertension. Drivers with IHD also showed the highest diastolic BP reactivity to the ERPAT. Significantly more than the expected number of drivers with IHD failed to recover alpha activity after the first glare impulse of the GPT. Professional drivers who failed to recover baseline levels of alpha activity after the GPT showed a significantly smaller N2 amplitude compared to those who recovered (p = 0.01). There was a positive correlation between abundance of alpha activity at rest with P300 amplitude (p = 0.02). An inverse relation was found between number of work hours behind the wheel and the amplitude of the target P300 (p = 0.04). Results are interpreted in light of recent advances concerning integrative mechanisms of defence versus vigilance response patterns. The findings in this study justify further applications of these psychophysiologic methods to assess the relationship between simulated signals of the work environment and mechanisms of cardiac risk in this occupational group.
Belkic K; Savic C; Theorell T; Rakic L; Ercegovac D; Djordjevic M. Mechanisms of cardiac risk among professional drivers. Scand J Work Environ Health 1994 Apr;20(2):73-86.
ABSTRACT:
This literature review indicates that professional drivers have excess cardiac risk that is not fully explained by standard risk factors. The contribution of occupation is suggested by two independent methods and by psychophysiological studies during on the job driving. Driving has been conceptualized as a threat-avoidance task. Stimuli encountered in traffic are not inherently aversive but become so by association with driving experience, a formulation corroborated by laboratory studies in which stimuli such as car headlights elicit cardiovascular hyperreactivity and electroencephalographic signs of arousal in professional drivers. More-advanced neurophysiological methods (event-related potentials) show higher cortical electronegativity to imperative signals among professional drivers than among non-driver referents. These data are viewed in light of reports of possible associations between event-related slow potentials and cardiac risk. A clinically and ecologically relevant neurocardiological model is proposed, and preventive strategies, including workplace interventions, are suggested. Survival in 1,431 pacemaker patients: prognostic factors and comparison with the general population.
Ugljesic M, Belkic K, Boskovic S, Avramovic D, Mickovic L. Rise in arterial blood pressure during work and coronary risk factor profile in high stress occupations. Kardiologija 1992; (13):3-4.
ABSTRACT:
Ambulatory blood pressure (BP) measurement during a work day and standard risk factor (SRF) assessment were performed in clinically healthy males, aged 25 to 50 years with normal resting BP, employed in stressful professions: 30 Belgrade city bus drivers and 30 journalists. This data was compared to 20 matched clerical worker controls. The "ABP-SPACE LABS, MODEL 90202" was used for ambulatory BP measurement. Journalists showed significantly greater mean systolic (S) BP during the entire work shift, as well as during the evening hours (while writing articles for the upcoming day), compared to controls. Mean diastolic (D) BP was significantly higher than in controls during the first 4 hours of work and sparadically during the evening hours. In city bus drivers SBP and DBP were significantly greater compared to controls immediately preceeding, during most of the driving shift and just afterwards. Four journalists, 2 drivers and 1 control exhibited clearly hypertensive BP patterns during the 24th recordings. The presence of individual SRF was higher in drivers and journalists with respect to controls. Hypercholesterolemia was found in 40% of drivers and 63.3% were smokers; the latter of these was significantly more common than in controls. A significantly larger percentage of drivers had at least one SRF than did controls. All the journalists and drivers with hypertensive ambulatory BP recordings had several other SRF present as well. These results indicate that ambulatory BP monitoring during woek and careful scrutiny of risk factor status and work conditions are warranted on a routine basis in order to achieve effective primary cardiac prevention in groups such as these whose occupation is highly stressful.
Jelic V; Belkic K; Djordjevic M; Kocovic. Pacemaker Center, University Clinical Center, Belgrade, Yugoslavia. Pacing Clin Electrophysiol 1992 Feb;15(2):141-7.
ABSTRACT:
A total of 1,431 patients (mean age 63.4 +/- 14.1) with pacemakers (96.2% VVI) primoimplanted between 1967 and 1985 were followed for a mean duration of 78.2 +/- 40 pacing months, with 0.6% loss to follow-up. Cumulative survival for 1, 3, and 10 years was 0.9427, 0.9136, and 0.7536, respectively. There was no significant difference in survival between atrioventricular block (AVB) and sick sinus syndrome (SSS) patients. In addition to age and gender, factors existent prior to implantation that independently affected prognosis included manifest coronary heart disease (CHD), congenital/acquired heart lesions, heart failure, noncardiac internal disease, syncope, and generalized fatigue. After implantation, the most important factor was generalized fatigue, then age, stroke, myocardial infarct (MI), gender (male), heart failure, and syncope. Patients with no underlying disease showed an extremely high cumulative survival (0.9173 at 10 years). Compared to the general population of Yugoslavia, the pacemaker patients showed a similar yearly mortality rate until 1981. After that, elderly males (70+) had a significantly lower yearly mortality than the matched population. Thus, in this large series of pacemaker patients followed into the most recent period with an extremely low loss to follow-up, short- and long-term survival was very high. Pacemaker patients of any age who are otherwise in good health have an excellent prognosis.
Stojanov P; Djordjevic M; Velimirovic D; Belkic K. Assessment of long-term stability of chronic ventricular pacing thresholds in steroid-eluting electrodes. Pacing Clin Electrophysiol 1992 Oct;15(10 Pt 1):1417-20.
ABSTRACT:
Sixteen patients with Medtronic 4003 steroid-eluting electrodes implanted in the ventricular position were followed over 5 years. In each patient a special type of Medtronic 2443 pacemaker was implanted to allow programming of output at 1.35 V. Chronic threshold values in these patients measured at an output of 1.35 V were stable over the first 18 months of follow-up. Mean values were: 0.06 +/- 0.03 msec at 6 months and 0.08 +/- 0.02 msec at 18 months; these did not differ from each other significantly. However, during the period from 18 to 36 months postimplantation, a significant increase in mean pacing threshold was observed: 0.08 +/- 0.02 msec at 18 months postimplantation versus 0.14 +/- 0.05 msec at 36 months (P < 0.01). After 36 months, the chronic pacing threshold remained stable until the end of the 5-year follow-up period. Further long-term study of chronic threshold behavior of steroid-eluting electrodes measured at low amplitudes is warranted.
Belkic K; Ercegovac D; Savic C; Panic B; Djordjevic M; Savic S. EEG arousal and cardiovascular reactivity in professional drivers: the glare pressor test. Eur Heart J 1992 Mar;13(3):304-9.
ABSTRACT:
Patterns of electroencephalographic (EEG) and polygraphically recorded cardiovascular (CV) reactivity to the glare pressor test (GPT) were compared in 19 healthy, young male professional drivers and eight non-driver controls. After the first headlight impulse, 15 drivers showed persistent blockade of spontaneous alpha activity or complete desynchronization. This was accompanied by a significant fall in digital pulse amplitude and a significant rise in diastolic blood pressure (BP) (7.3 +/- 9.5 mmHg). Most drivers recovered baseline alpha activity and showed milder diastolic BP and digital pulse changes after the final (5th) glare impulse. However, in two drivers this last glare stimulus elicited the most pronounced changes: in one case a rapid onset of ventricular extrasystoles and in the other, maximal rise in diastolic BP, together with a persistently desynchronized EEG. No significant effects of the GPT upon central and CV indices were found in the control group. These results indicate that drivers show cardiovascular hyperreactivity to the GPT, with strong central arousal as expected during night driving when an on-coming headlight can represent impending danger and the need for accurate and timely responses to avoid a collision. Once optimal stimulus parameters for routine application are determined, the glare pressor test with EEG and polygraphic recording will offer a clinically useful, standardizable method for evaluating the connection between central mechanisms and CV reactivity in professional drivers, a cohort of patients whose occupational activity epitomizes mentally stressful work, and who are at high cardiac risk.
Belkic K; Savic C; Djordjevic M; Ugljesic M; Mickovic L. Event-related potentials in professional city drivers: heightened sensitivity to cognitively relevant visual signals. Physiol Behav 1992 Sep;52(3):423-7.
ABSTRACT:
Event-related potentials to visual stimuli were recorded in 24 healthy, young subjects: 15 professional Belgrade city drivers and nine nondriver controls (no amateur driving experience) during a tacitly neutral GO:NOGO CNV paradigm and during one which explicitly mimicked heavy traffic conditions. In both paradigms GO S1 was a 30 ms red light, NOGO S1 a green light of equal duration; S2 was, in both cases, a yellow light presented 1.5 s post-S1. Overall, the early and late CNV for GO conditions were significantly larger (more negative) than for NOGO. This GO:NOGO difference was accentuated in drivers, as seen by a significant group-condition interaction using analysis of variance. The mean late CNV was significantly greater in drivers compared to controls: for GO at Cz during the neutral paradigm -12.9 vs. -5.0 microV, respectively, and for the traffic paradigm -14.4 vs. -6.0 microV. There were no significant differences in the CNV between the neutral and the traffic paradigms in either group. The pattern of CNV response seen in these professional Belgrade city drivers seems to suggest a heightened sensitivity to the cognitive significance of visual stimuli. To our knowledge, event-related potentials are applied here for the first time in professional drivers, a cohort known to have a high incidence of psychosomatic disorders, presumably related to the demands made upon them by their occupation. Further investigation using such objective electrophysiologic methods is clearly warranted in this high-risk group.