Cecilia C. A. Macintyre

Risk of angina pectoris and plasma concentrations of vitamins A, C, and E and carotene

The relation between risk of angina pectoris and plasma concentrations of vitamins A, C, and E and carotene was examined in a population case-control study of 110 cases of angina, identified by the Chest Pain Questionnaire, and 394 controls selected from a sample of 6000 men aged 35-54. Plasma concentrations of vitamins C and E and carotene were significantly inversely related to the risk of angina. There was no significant relation with vitamin A. Smoking was a confounding factor. The inverse relation between angina and low plasma carotene disappeared and that with plasma vitamin C was substantially reduced after adjustment for smoking. Vitamin E remained independently and inversely related to the risk of angina after adjustment for age, smoking habit, blood pressure, lipids, and relative weight. The adjusted odds ratio for angina between the lowest and highest quintiles of vitamin E concentrations was 2.68 (95% confidence interval 1.07-6.70; p = 0.02). These findings suggest that some populations with a high incidence of coronary heart disease may benefit from eating diets rich in natural antioxidants, particularly vitamin E.

LINOLEIC AND EICOSAPENTAENOIC ACIDS IN ADIPOSE TISSUE AND PLATELETS AND RISK OF CORONARY HEART DISEASE

The relation between the fatty-acid composition of adipose tissue and platelet membranes and the estimated relative risk of coronary heart disease (CHD) was examined in a case-control study of new angina pectoris (AP) and first acute myocardial infarction (AMI). There were progressive inverse relations between adipose linoleic acid and platelet-membrane eicosapentaenoic acid and the estimated relative risk of AP. These relations were statistically independent of each other and traditional CHD risk factors. For AMI there was a progressive inverse relation between adipose linoleic acid and the estimated relative risk, but it was confounded by smoking habit. Smokers consume less linoleic acid than non-smokers. Although eicosapentaenoic acid in platelet membranes was lower in AMI patients than in controls, this difference was not significant. The estimated proportionate increase in risk of AP, independent of other CHD risk factors, was 1.2 (1.1-1.3) for a 1% decrease in linoleic acid or a 0.1% decrease in eicosapentaenoic acid.

Low plasma vitamins E and C. Increased risk of angina in Scottish men.

Cross-cultural studies suggest that low plasma antioxidant levels contribute to the high incidence of coronary heart disease (CHD) in Scotland. One hundred twenty-five cases of angina without reported history were identified by a postal WHO chest pain questionnaire from a systemic population sample of 6000 Edinburgh men (35-54 years). Classical CHD risk factors (lipids, blood pressure, smoking, and relative weight), plasma vitamins, and a new independent CHD risk factor, adipose tissue linoleate, were measured in angina (n = 125) and healthy controls (n = 430). Cigarette smoking was common in angina (46% vs. 29%, p less than 0.01), and adipose tissue linoleate was lower (8.77 +/- 0.18% vs. 9.81 +/- 0.14% (p less than 0.01). Classical CHD risk factors were not different. Vitamin E/cholesterol molar ratio (micron/mM) was lower in angina than in controls: 1.58 +/- 0.03 vs. 1.66 +/- 0.02 (p less than 0.01). Plasma vitamin C was also lower in angina than in controls: 23.6 +/- 1.7 vs. 30.5 +/- 1.1 microM (p less than 0.001). The relative risk of angina for those in the lowest versus those in the highest quintile of the vitamin E/cholesterol ratio distribution was 2.2:1, irrespective of other risk factors (p less than 0.009). Adipose tissue linoleate removed the association between vitamin E and angina. The relative risk of angina for those in the lowest versus those in the highest quintile of plasma vitamin C was 2.6:1 (p less than 0.01), and the increased risk was also independent of classical risk factors, but closely related to a smoking habit. Low plasma vitamin E or adipose linoleate predisposes to angina, and smoking may increase the risk of angina by lowering plasma vitamin C levels in Scottish men.

Normal pharyngoesophageal motility

Upper esophageal manometry is technically problematic. Published normal values are, therefore, few and wide ranging, reflecting catheter and recording-system variables, while the reproducibility of measurements and the influence of food consistency have been little studied. In this investigation, 50 healthy volunteers were studied with (1) a 2.8-mm-diameter six-sensor catheter-mounted transducer assembly and (2) a 3.2×7.2-mm sleeve device linked to a computerized recorder with a pressure-sample rate of 32/sec. The study protocol included water, bread, and semisolid swallows. Upper esophageal sphincter (UES) tonic pressures measured with the catheter-mounted assembly were lower and more reproducible than pressures measured with the sleeve system. Compared with water, bread swallows showed greater pharnygeal and sphincter after-contraction pressures, while semisolid swallows had less complete sphincter relaxation. Duration of pharyngoesophageal contractions was greater with bread or semisolid than water. The observations have established normal values for measurements of UES function and, in addition, have shown that (1) catheter variables significantly influence the measurement of upper sphincter tonic pressure, (2) pressures recorded with the catheter-mounted transducer are most reproducible, and (3) pharyngoesophageal motility patterns vary significantly according to the substance swallowed.Upper esophageal manometry is technically problematic. Published normal values are, therefore, few and wide ranging, reflecting catheter and recording-system variables, while the reproducibility of measurements and the influence of food consistency have been little studied. In this investigation, 50 healthy volunteers were studied with (1) a 2.8-mm-diameter six-sensor catheter-mounted transducer assembly and (2) a 3.2×7.2-mm sleeve device linked to a computerized recorder with a pressure-sample rate of 32/sec. The study protocol included water, bread, and semisolid swallows. Upper esophageal sphincter (UES) tonic pressures measured with the catheter-mounted assembly were lower and more reproducible than pressures measured with the sleeve system. Compared with water, bread swallows showed greater pharnygeal and sphincter after-contraction pressures, while semisolid swallows had less complete sphincter relaxation. Duration of pharyngoesophageal contractions was greater with bread or semisolid than water. The observations have established normal values for measurements of UES function and, in addition, have shown that (1) catheter variables significantly influence the measurement of upper sphincter tonic pressure, (2) pressures recorded with the catheter-mounted transducer are most reproducible, and (3) pharyngoesophageal motility patterns vary significantly according to the substance swallowed.

Effects of safflower oil and evening primrose oil in men with a low dihomo-γ-linolenic level.

Low levels of essential polyunsaturated fatty acids of the n − 6 series are associated with coronary heart disease. Linoleic acid, but not γ-linolenic acid requires the activity of Δ6-desaturase for its conversion to dihomo-γ-linolenic and arachidonic acid. Evening primrose oil (EPO) and safflower oil (SO) are rich in linoleic acid, but EPO contains also 9% γ-linolenic acid. The effect of EPO (10, 20 and 30 ml/day) and SO (20 ml/day) for 4 months on the deposition of linoleic acid metabolites in adipose tissue of 4 groups of 6–9 men with low adipose dihomo-γ-linolenic acid was examined. EPO but not SO increased adipose dihomo-γy-linolenic acid level from 0.080 ± 0.005% to 0.101 ± 0.005% (P < 0.01; 20 ml/day for 4 months). Adipose dihomo-γy-linolenic/linoleic acid ratio increased with EPO from 0.99 ± 0.16 × 102 to 1.13 ± 0.14 × 102 and fell on SO from 1.04 ± 0.10 × 102 to 0.90 ± 0.07 × 102 (P < 0.01). Similar qualitative changes in the relative amount of dihomo-γ-linolenic acid in serum triglyceride and cholesteryl ester fractions were observed. At the dose of 20 ml/day, SO and EPO did not differ in their effect on serum cholesterol (7.13 ± 0.43 vs. 7.33 ± 0.42 mmol/l (NS)), LDL-cholesterol (5.10 ± 0.32 vs. 4.88 ± 0.46 mmol/l (NS)) nor did the 2 oils differ in their effect on HDL-cholesterol. These results suggest that linoleic acid is not readily converted to dihomo-y-linolenic acid due to a low activity of Δ6-desaturase in these highly selected men. EPO was not an effective hypocholesterolaemic agent in this study.

Changes in blood lead and water lead in Edinburgh. An eight year follow-up to the Edinburgh lead study

This study aimed to measure changes in household water lead and blood lead in young people living in Edinburgh over a period of 8 years. Two hundred and twenty-three families were eligible and 207 (93%) agreed to participate. A half-hour stagnation sample of kitchen cold water was taken from each household, and 171 young people (aged 14–17 years) provided a blood sample for lead analysis. Information on plumbing changes, exposure to other sources of lead and factors which might influence blood lead was collected by questionnaire. Edinburgh is supplied with water treated in one of two treatment plants. There was a different programme of water treatment in each plant. In one (A) lime and orthophosphate was introduced in the interval between the original and follow-up studies. In the other (F) lime treatment began before the original study and orthophosphate was introduced subsequently. In water from treatment plant A, mean water lead levels fell from 34 to 4.3 μ gL⊃-1 (87%). In water supplied from treatment plant F the corresponding values were 9.3 to 3.6 μ gL⊃-1 (61%). These reductions were due to both water treatment and removal of lead plumbing. Houses with no lead plumbing have water lead levels 89% lower than houses with lead tanks, and 47% lower than houses with lead pipes. About one-third of households with lead tanks are predicted to have water lead levels above the current EC limit of 50 μ gL⊃- 1, though only 3% or less of the remaining households would exceed this limit. If the proposed 10 μ gL⊃-1 limit were introduced, 34% of households supplied from plant A and 25% from plant F would breach the limit. Blood lead levels fell from an average of 11.0 μ gdL⊃-1 to 4.0 μ gdL⊃-1. Males had higher values than females and the main factors influencing levels were water lead and age of house. Our results show substantial reductions in household water lead and blood lead in our sample over a period of 8 years and represent an important achievement in public health. However, more progress will be required if the proposed new limit of 10 μ gL⊃-1 for water lead is to be met. There is a need for the continuing surveillance of household water lead and blood lead levels in representative samples of the population.

Effect of Esophageal Acid Exposure on Upper Esophageal Sphincter Pressure

To investigate the relationship between gastroesophageal reflux and upper esophageal sphincter (UES) pressure, total esophageal acid exposure times on 23‐hour ambulatory pH monitoring were compared with UES manometric results in 98 subjects, 85 with laryngopharyngeal symptoms and 13 asymptomatic controls. There was no correlation of acid exposure time with tonic UES pressure nor with any UES wet swallow parameter. The response of the UES to acute upper esophageal acid infusion was assessed in another 13 patients by a sleeve catheter. There was no significant increase of tonic sleeve UES pressure during acid infusion. In contrast to most previous reports, our results indicate that esophageal acid exposure, whether acute or chronic, has little influence on the UES.