Biomedical subjects
Publications and source records attributed to J D Lane.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
We studied the relationship between presence of Type A behavior pattern and glycemic response to stress in children with insulin dependent diabetes mellitus (IDDM). Twelve male (six Type A and six Type B) and nine female (four Type A and five Type B) insulin-dependent diabetic patients between the ages of 8 and 16 years received a standard meal and blood glucose values were assessed two hours later. All subjects then played a competitive videogame for 10 minutes following which blood glucose was assessed again. Preprandial and postprandial blood glucose values did not differ between the groups. However, only Type A subjects showed a hyperglycemic response to the videogame stress. Type A subjects also demonstrated significantly higher glycohemoglobin values. In order to assure that this effect was due to a differential response to stress and not simply a difference in metabolic response to a meal, a second study was conducted in which blood glucose values were assessed at one, two and three hours following a standard meal. No significant differences in postprandial blood glucose values were observed between Type A and Type B subjects. These data support previous research which has suggested that some but not all patients with IDDM show a hyperglycemic response to stress.
The mechanisms responsible for the higher incidence of essential hypertension in blacks than in whites are the object of much research attention. One hypothesis is that the development of hypertension in blacks is associated with exaggerated blood pressure reactivity, particularly those responses mediated by vasoconstriction. Racial differences in blood pressure responses to cold stimulation of the forehead, a known alpha-adrenergic vasoconstrictive stimulus, were examined in health, college-age males. Compared to white subjects, black subjects exhibited significantly greater increases in systolic and diastolic blood pressure, as well as increases in forearm vascular resistance, in response to cold stimulation. This preliminary evidence of increased peripheral vascular reactivity in blacks suggests that known racial differences in hypertension prevalence might derive in part from physiological differences in sympathetic nervous system reactivity.
Although habitual caffeine users ingest the drug repeatedly throughout each day, the persistence of caffeine's known cardiovascular effects with such repeated use has not been investigated. Blood pressure and heart rate were measured under resting conditions in 10 healthy, male coffee or tea drinkers for 2 hours following a pretreatment dose of caffeine (125 mg) on two separate days after overnight abstinence. Either a second caffeine dose or placebo was administered and measurements continued for 1.5 hours. Compared to placebo, the second dose of caffeine produced significant increases in heart rate and diastolic and mean arterial, but not systolic, blood pressures. The results suggest that the cardiovascular effects of caffeine may persist throughout the day with repeated administration of moderate amounts of caffeine. Habitual caffeine use does not necessarily lead to complete tolerance, which suggests that caffeine's cardiovascular effects could contribute to an increased risk of cardiovascular disease.
The effects of a moderate dose of caffeine on cardiovascular and neuroendocrine stress reactivity were examined in 25 healthy male subjects selected as habitual or light consumers of caffeine. Measurements were taken under resting conditions before and after administration of caffeine (3.5 mg/kg) or placebo, during a stressful laboratory task, and in a post-stress recovery period. Caffeine elevated blood pressure and plasma norepinephrine levels at rest, effects which added significantly to the effects of stress. Caffeine potentiated stress-related increases in plasma epinephrine and cortisol stress, more than doubling the responses observed in the control condition. These effects were present in both habitual and light consumers and level of habitual caffeine consumption did not affect their magnitude. Results indicate that caffeine can potentiate both cardiovascular and neuroendocrine stress reactivity and that the habitual use of caffeine is not necessarily associated with the development of tolerance to these effects.
The consumption of caffeinated beverages has been linked to elevated serum cholesterol and an increased risk of coronary disease, although the relationships are inconsistent across studies and remain controversial. The effect of caffeine on cholesterol and coronary disease risk may be modulated by other factors. Using cohort data from a subsample of the University of North Carolina Alumni Heart Study, we investigated whether the relationships between caffeinated beverage consumption and serum lipid and lipoprotein levels in middle-aged men and women were modulated by levels of trait hostility. After adjustment for other risk factors, higher caffeinated beverage intake was associated with higher low-density lipoprotein cholesterol levels and a higher ratio of total to high-density lipoprotein cholesterol, both indicative of greater coronary disease risk. The interactive effects of hostility and caffeine intake were ambiguous, although there were trends for caffeine intake to have stronger effects on low-density lipoprotein and on total cholesterol in people with less hostility. Additional studies of personality characteristics and other factors that can modulate the cholesterol-raising effects of coffee drinking may be warranted because they might clarify the health consequences associated with coffee drinking and lead to the identification of individuals who would benefit most from changes in their coffee drinking.
The effect of caffeine on neuroendocrine stress responses in the workplace was studied in 14 habitual coffee drinkers. Urinary catecholamine and cortisol levels were measured on 2 study days, in a 4-hour interval from morning until noon, while participants performed their normal work-related activities. Caffeine (300 mg) or placebo was administered blind at the beginning of study intervals, after overnight caffeine abstinence. Retrospective mood and symptom ratings were collected at the end of each morning. Caffeine elevated urinary epinephrine levels during work by 37% but did not affect norepinephrine or cortisol levels. Subjective reports suggest that caffeine abstinence was associated with symptoms of caffeine withdrawal by the end of the morning. Effects included higher ratings of sleepiness, lethargy, and headache and a reduced desire to socialize. Results suggest caffeine may increase the activity of the sympathetic adrenal-medullary system during everyday activities in the work environment. This action may potentiate psychophysiological responses elicited by occupational stressors.
OBJECTIVE: The study investigated the effects of moderate doses of caffeine on ambulatory blood pressure and heart rate during workday activities. METHODS: Healthy, nonsmoking, habitual coffee drinkers (N = 21) received daily doses of 100 mg and 500 mg of caffeine on 2 days in a crossover design. Treatment order was random and counterbalanced, and administration was double-blind. Ambulatory monitoring was conducted for 6 to 9 hours during normal workday activities and diary entries were completed at each measurement. Ambulatory data were analyzed for the effects of caffeine dose, controlling for variations in posture, physical activity, and perceived stress. RESULTS: The average workday blood pressure and heart rate were significantly higher when the higher dose of caffeine was consumed. Controlling for other factors, dose-related differences were 4 mm Hg for systolic and 3 mm Hg for diastolic blood pressure, and were 3 bpm for heart rate. CONCLUSIONS: Results support earlier evidence that caffeine raises blood pressure at work, and demonstrate that these pressor effects are independent of changes in posture, physical activity, or stress. Daily blood pressure increases associated with caffeine consumption could increase the risk of developing cardiovascular diseases. In addition, caffeine consumption effects might confound ambulatory investigations of the cardiovascular effects of other psychosocial, personality, or health-behavior factors.
OBJECTIVE: The diabetes literature contains conflicting evidence on the relationship between depression and glycemic control. This may be due, in part, to the fact that past studies failed to distinguish between patients with type 1 and type 2 diabetes. Because these are actually completely different diseases that are often treated differently and consequently make different demands on patients, the relationship between glycemic control and depressed mood in type 1 and type 2 diabetes was examined separately. METHODS: The relationship between Beck Depression Inventory (BDI) scores and HbA1c, as an index of long-term glycemic control, was measured in samples of 30 patients with type 1 and 34 patients with type 2 diabetes. RESULTS: Groups of patients with type 1 and type 2 diabetes did not differ in mean BDI score or HbA1c level. Correlation analysis revealed a significant positive relationship between BDI scores and HbA1c in the type 1 group (r = .44, p < .02) but not in the type 2 group (r = -0.06, p > .05). This relationship was evident throughout the entire range of BDI scores and was not restricted to scores indicative of clinical depression. Patients with type 1 diabetes who had higher HbA1c and BDI scores reported a lower frequency of home blood glucose monitoring. CONCLUSIONS: Variations in depressive mood, below the level of clinical depression, are associated with meaningful differences in glycemic control in type 1 but not type 2 diabetes. Preliminary data analysis suggests that this effect may be mediated, at least in part, by decreased self-care behaviors in patients with more depressed mood.
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