What prevents professional drivers from following physicians' cardiologic advice?

BACKGROUND: There is a scarcity of published studies of the effects of cardiac counselling among professional drivers (PD). Aims of the study were: (1) to examine explanatory variables for two classical 'driver' risk factors - body mass index (BMI), and smoking - and to analyse the interrelations among smoking cessation, losing weight and work-related life changes; (2) to assess the effectiveness of risk factor counselling after 6 months, and (3) to gain insight into possible discrepancies between PD perception of needed changes and compliance with the physician's advice. METHODS: There were 4 groups of male PD: 13 with ischemic heart disease, 12 hypertensives, 10 borderline hypertensives and 34 normotensives. Baseline cardiovascular risk factors as well as occupational and behavioral data were assessed via questionnaire. The counselling was aimed at smoking cessation, weight loss and promoting leisure-time physical activity. Qualitative methods were used to assess PD perceptions about the work environment and health promotion. RESULTS: Baseline smoking intensity was best predicted by the total burden of occupational stress and number of smoking years. Baseline BMI was best predicted by long work hours behind the wheel, low availability of attachment outside work and low self-reported job strain. Self-initiated smoking cessation was best predicted by few smoking years, low coffee intake and admitting fear during driving. Physical activity was significantly increased after 6 months. Losing weight was associated with: quitting or diminishing smoking and making other, work-related, life changes. None of the heavy smokers decreased their daily number of cigarettes after 6 months, although expressing the need to do so in self-generated statements. CONCLUSIONS: Exposure to occupational stressors, mainly, long work hours and the concomitant denial of job strain, in combination with low availability of social attachment outside work, could contribute to maintenance of maladaptive behavior in PD. These findings could serve as a basis for designing standardized intervention trials and suggest that modification of the work environment, with participation of the drivers, is a needed component of such trials. Particular attention should be paid to the length and scheduling of work shifts.

Psychophysiologic sensitization to headlight glare among professional drivers with and without cardiovascular disease.

Previous studies have shown that young, healthy professional drivers show heightened central nervous system arousal and cardiovascular hyperreactivity to simulated headlight glare. Electroencephalographic and cardiovascular response and recovery to simulated headlight glare (the glare pressor test) were examined in 4 groups of male professional drivers (age 25-52 years)--12 with ischemic heart disease (IHD), 12 with hypertension (HTN), 10 with borderline hypertension (BHTN), and 34 who were healthy--and in 23 non-professional driver controls--with the aim of assessing sensitization to this night driving stressor in relation to degree of cardiovascular disease severity. After glare exposure the IHD drivers showed the most pronounced alpha blockade, a rise in diastolic blood pressure (DBP; p < .05), and, unlike the other groups, a persistent fall in finger pulse volume (p < .02). The BHTN group reacted initially with DBP rise and finger pulse drop (ps < .05 and .02, respectively), mainly without central nervous system arousal. The DBP remained constant in normotensive professional drivers older than 40. The drivers' cardiovascular responses to glare were inversely related to reported stressors and subjective experience. Anxiety trait and long work hours were associated with heightened central arousal to glare in professional drivers. The results suggest that there may be progressive degrees of sensitization to glare exposure in these samples, with the least among normotensive professional drivers older than 40, moderate levels in borderline hypertensives, and the most severe in drivers with IHD.

Electrocortical responses to ecologically relevant visual stimuli among professional drivers with and without cardiovascular disease.

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.

Atrial natriuretic peptide concentrations and hemodynamic effects of acute plasma volume expansion in normal pregnancy and preeclampsia.

Plasma atrial natriuretic peptide (ANP) and circulatory responses were studied during rapid plasma volume expansion with crystalloid solutions. Sixteen women with preeclampsia and 16 healthy controls in the third trimester were compared. Basal mean (+/- standard error of the mean) ANP levels were not significantly higher in the preeclamptics than in controls (13.6 +/- 3.5 versus 6.4 +/- 1.1 pmol/L; not significant), but the increment following volume expansion was more pronounced (12.9 +/- 2.6 versus 6.1 +/- 2.3 pmol/L; P less than .05). The mean plasma volume expansion was less in the preeclamptic group (6.1 +/- 0.8 versus 9.3 +/- 1.1%; P less than .05), reflecting a higher capillary permeability in this disease. Left ventricular posterior-wall thickness in diastole was increased in the preeclamptics under basal conditions as compared with the controls (9.8 +/- 0.3 versus 8.9 +/- 0.3 mm; P less than .05), as was the thickness of the interventricular septum in systole (14.3 +/- 0.5 versus 12.3 +/- 0.6 mm; P less than .05). Systemic vascular resistance was higher in the preeclamptic group (19.7 +/- 0.8 versus 15.1 +/- 1.1 peripheral resistance units; P less than .01). In the controls, cardiac output increased by 23 +/- 4% and systemic vascular resistance decreased by 17 +/- 3%. The preeclamptic women reacted in a similar way. Our results indicate that preeclampsia is associated with an enhanced ANP response despite a less pronounced increase in plasma volume during acute fluid challenge.

Repetitive static muscle contractions in humans--a trigger of metabolic and oxidative stress?

Repetitive static exercise (RSE) is a repetitive condition of partial ischaemia/reperfusion and may therefore be connected to the formation of oxygen-derived free radicals and tissue damage. Seven subjects performed two-legged intermittent knee extension exercise repeating at 10 s on and 10 s off at a target force corresponding to about 30% of the maximal voluntary contraction force. The RSE was continued for 80 min (n = 4) or to fatigue (n = 3). Four of the subjects also performed submaximal dynamic exercise (DE) at an intensity of about 60% maximal oxygen uptake (VO2max) for the same period. Whole body oxygen uptake (VO2) increased gradually with time during RSE (P less than 0.05), indicating a decreased mechanical efficiency. This was further supported by a slow increase in leg blood flow (P less than 0.05) and leg oxygen utilization (n.s.) during RSE. In contrast, prolonged RSE had no effect on VO2 during submaximal cycling. Maximal force (measured in six additional subjects) declined gradually during RSE and was not completely restored after 60 min of recovery. After 20 and 80 min (or at fatigue) RSE phosphocreatine (PC) dropped to 74% and 60% of the initial value, respectively. A similar decrease in PC occurred during DE. Muscle and arterial lactate concentrations remained low during both RSE and DE. The three subjects who were unable to continue RSE for 80 min showed no signs of a more severe energy imbalance than the other subjects. A continuous release of K+ occurred during both RSE and DE.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in plasma hypoxanthine and free radical markers during exercise in man.

Eight men cycled for about 6 minutes at workloads corresponding to 44 and 72% of maximal oxygen uptake and to fatigue at 98% maximal oxygen uptake. Blood samples from a brachial artery and a femoral vein were taken at rest and during exercise. Hypoxanthine, xanthine and urate in plasma were significantly elevated at fatigue and after 10 minutes of recovery. Only hypoxanthine showed a significant arterio-femoral venous difference. The release of hypoxanthine from the legs increased during the recovery period and was three-fold higher 10 minutes post exercise than at the end of exercise. It is concluded that the marked increase in plasma hypoxanthine which occurs during intensive exercise originates from the working muscle whereas the transformation to xanthine and urate may occur in other tissues. Glutathione, methemoglobin and malondialdehyd (MDA) were used as plasma markers of free radicals. Total glutathione (glutathione + glutathionedisulfide) in blood and plasma increased during intensive exercise and may be indicative of free radical formation. However, MDA was not detectable in plasma during any conditions (less than 0.1 mumol x l-1 plasma) and methemoglobin decreased slightly during exercise. Further studies using more specific techniques are required to determine whether the formation of free radicals is increased after brief intensive exercise.