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Biomedical subjects

D G Cook

Publications and source records attributed to D G Cook.

At least 109 records · Page 6Linked to original sources

A critical review of the effect of factory closures on health.

The dramatic rise in unemployment in the 1970s and 1980s has led to an increase in research into the possible effects of unemployment on health. Studies of the effects of job loss are difficult to interpret because of the difficulty in ruling out selection effects--for example, the least fit may be more likely to be made redundant. The study of factory closures is appealing since all employees are made redundant and all the studies of factory closure recorded in the Index Medicus since 1980 are reviewed. None of the studies fulfil all the criteria for an ideal study, and most fail on several counts. The small sample sizes are often unavoidable, but the lack of awareness of possible selection effects often results in a biased control group of only those people who are economically active. Also, the short duration of follow up restricts the detection of possible long term effects on health. Thus the conclusions that can be drawn about the health effects of factory closures are limited. Whereas there is evidence of short term effects on mental health and of increased use of primary health care, no long term effects have been studied and objective data on physical health are almost non-existent.

Adult↗

Consultation rates among middle aged men in general practice over three years.

OBJECTIVE: To provide data on consultation rates in general practice for middle aged men over three years according to their age and social class. DESIGN: Prospective study of men over eight years. Data on consultation rates during years 6-8 were collected retrospectively from practice records. SETTING: Over 1000 general practices in Great Britain by year 8. Initially (in 1978-80) the men had been selected at random from one practice in each of 24 towns. SUBJECTS: 7013 Men aged 46-65 in the sixth year of follow up. MAIN OUTCOME MEASURE: Number of consultations a year over three years. RESULTS: The mean annual consultation rate over the three years rose steadily with age (7.0 at age 46-50 to 9.7 at age 61-65) and with social class (6.4 in class I to 10.0 in class V) but was potentially misleading as the distribution was skew: 10.5% of men (736) did not consult over the three years and 17.2% (1209) consulted only once or twice, whereas 11.4% (798) of men were seen more than 18 times. The percentage of men who did not consult over three years fell only slightly with age and was unrelated to social class, with roughly a tenth of all age and social class groups not consulting. Two thirds of non-consulters in year 6 (1598/2334) consulted in year 7 or 8. CONCLUSIONS: The mean is not an appropriate summary measure of consultation rates and may conceal important differences among practices or other groups. The new general practitioner contract stipulates that all patients aged 16-74 must be provided with information to promote health and prevent illness at least once every three years. Most practices will have to approach a tenth of their men aged 46-65 specially to provide this service even if one consultation in three years is regarded as sufficient to allow a service to be provided.

Age Factors↗

ABO blood group and ischaemic heart disease in British men.

OBJECTIVE: To establish whether ABO blood group is related to ischaemic heart disease on an individual and geographic basis in Britain. DESIGN: Prospective study of 7662 men with known ABO blood group selected from age-sex registers in general practices in 24 British towns. MEASUREMENTS: ABO blood group, standard cardiovascular risk factors, social class, and presence or absence of ischaemic heart disease determined at entry to study. END POINTS: Eight year follow up of fatal and nonfatal ischaemic heart disease events achieved for 99% of study population. RESULTS: Towns with a higher prevalence of blood group O had higher incidences of ischaemic heart disease. In individual subjects, however, the incidence of ischaemic heart disease was higher in those with group A than in those with other blood groups (relative risk 1.21, 95% confidence limits 1.01 to 1.46). Total serum cholesterol concentration was slightly higher in subjects of blood group A. No other cardiovascular risk factor (including social class) was related to blood group. CONCLUSIONS: Blood group A is related to the incidence of ischaemic heart disease in individual subjects. Geographic differences in the distribution of ABO blood groups do not explain geographic variation in rates of ischaemic heart disease in Britain. The findings do not support the view that ABO blood group and social class are related.

ABO Blood-Group System↗

Geographical variations in blood pressure in British men and women.

Geographical variations in blood pressure have been studied using an automatic sphygmomanometer in 2596 men and women aged 25-29, 40-44 and 55-59 living in nine British towns. In males aged 40-59, systolic blood pressure showed a range in age-adjusted town means of 9.0 mmHg (p less than 0.05); in females the difference of 8.6 mmHg was not significant (p = 0.14). Mean arterial pressure (MAP) and diastolic at age 40-59 were significantly different between towns for both sexes. Differences at age 25-29 were of a similar magnitude, and the mean town blood pressures at 25-29 correlated highly with those at 40-59 [systolic; males r = 0.74 (p less than 0.05), females r = 0.65 (p = 0.059)]. The ranking of town blood pressures in an earlier study was reflected in the present study, but stronger associations were observed with cardiovascular mortality. It is concluded that geographical blood pressure variations in Britain are established by age 25-29 years.

Adult↗

Casual urine concentrations of sodium, potassium, and creatine in population studies of blood pressure.

The relationships between blood pressure and the concentrations of urinary sodium, potassium and creatinine have been examined using casual urine specimens collected from a random sample of 1,556 men aged 40-59. Partial correlations with systolic blood pressure after adjustment for age, body mass index (BMI), alcohol consumption, and town showed that sodium was not significantly associated with BP, but potassium [r = -0.09 (P less than 0.001)] and creatinine [r = -0.07 (P less than 0.01)] were negatively associated. The sodium/creatinine ratio [r = 0.10 (P less than 0.001)] and sodium/potassium ratio [r = 0.11 (P less than 0.001)] were positively correlated with SBP. Comparable results were found throughout for diastolic pressure. Multiple regression analysis suggested that it was creatinine rather than sodium that was the important component of the sodium/creatinine ratio, and raised the possibility that potassium may play a part in this association because of the strong correlation between potassium and creatinine. Similarly, potassium appeared to be the more important component of the sodium/potassium ratio. The regression coefficients for sodium, potassium, and the sodium/potassium ratio in this study of casual urine samples were found to be similar in direction and magnitude to two large studies using 24 hour urine collections. We suggest that causal specimens may be useful for estimating sodium and potassium intake in population studies.

Adult↗

Differences between observers in blood pressure measurement with an automatic oscillometric recorder.

Blood pressure measurements made with a Dinamap oscillometric blood pressure recorder by two observers on a total of 2596 male and female subjects aged between 25 and 59 living in nine British towns were examined for evidence of observer differences. After adjusting for age, body mass index and town, significant differences between the two observers were found for systolic pressure, 3.07 mmHg (P = 0.001) for male subjects and 2.08 mmHg (P = 0.036) for female subjects. Observer differences for mean arterial pressure and diastolic pressure were less than 1 mmHg and were not significant. The magnitude of observer differences also varied between towns and, when tested statistically, was significant in male subjects for systolic (P = 0.011), mean arterial (P = 0.009) and diastolic pressure (P = 0.002); for female subjects it was significant only for diastolic pressure (P = 0.023). We conclude that although the highly automated Dinamap has kept observer variation within acceptably low limits in field study conditions, the problem has not been altogether eliminated.

Adult↗

Early influences on blood pressure: a study of children aged 5-7 years.

OBJECTIVE: To examine factors that influence blood pressure in children. DESIGN: Cross sectional study of children aged 5.0-7.0 years who had blood pressure measurements and for whom parental questionnaires were completed. SETTING: School based survey. SUBJECTS: 3591 Children aged 5.0-7.5 years selected by stratified random sampling of primary schools in nine British towns (response rate 72%); 3591 were examined and their parental questionnaires were completed. Data were complete for birth rank in 3559, maternal age in 3542, maternal history of hypertension in 3524, and paternal history in 2633. RESULTS: Birth weight was inversely related to mean systolic blood pressure but only when standardised for current weight (weight standardised regression coefficient -1.83 mm Hg/kg (95% confidence interval -1.31 to -2.35). Mean diastolic pressure was similarly related to birth weight. Maternal age, birth rank, and a parental history of hypertension were all related to blood pressure. After standardisation for current weight a 10 year increase in maternal age was associated with a 1.0 mm Hg (0.4 to 1.6) rise in systolic pressure; first born children had systolic blood pressure on average 2.53 mm Hg (0.81 to 4.25) higher than those whose birth rank was greater than or equal to 4; and a maternal history of hypertension was associated with a systolic pressure on average 0.96 mm Hg (0.41 to 1.51) higher than in those with no such history. The effects described were largely independent of one another and of age and social class. The relation for birth rank was, however, closely related to that for family size. CONCLUSIONS: Influences acting in early life may be important determinants of blood pressure in the first decade. The relation between birth weight and blood pressure may reflect the rate of weight gain in infancy. The reasons for the relation with birth rank and maternal age are unknown; if confirmed they imply that delayed motherhood and smaller family size may be associated with higher blood pressure in offspring.

Birth Order↗

Cytomegalovirus infection and progression towards AIDS in haemophiliacs with human immunodeficiency virus infection.

To examine whether cytomegalovirus (CMV) infection could accelerate progression of human immunodeficiency virus (HIV) infection to AIDS, serological studies were done on 108 HIV-infected haemophiliacs. In the 1.3-9 years from time of first recognised HIV seroconversion, the age-adjusted risk of CDC group IV disease in CMV-seropositive patients was 2.5 times that in CMV-seronegative patients. CMV-seropositive patients were also more likely to have detectable p24 antigenaemia. Survival analysis showed that CMV-seropositive patients were at greater risk of HIV disease than CMV-seronegative patients from about 2 years after HIV seroconversion. Thus CMV infection is associated with a more rapid progression to HIV disease.

Acquired Immunodeficiency Syndrome↗

Breathlessness, angina pectoris and coronary artery disease.

The relation of breathlessness to angina was examined in 7,735 middle-aged British men. Among men who did not report breathlessness, the age-standardized prevalence rate of angina was 4%. In men with mild, moderate or severe breathlessness, the prevalence rates of angina were 16, 29 and 41%, respectively. The association between breathlessness and angina was independent of age or cigarette smoking, with similar relations observed in men who had never smoked. The prevalence of electrocardiograms revealing ischemia increased with the severity of breathlessness, even in men without angina or other evidence of coronary artery disease (CAD) at screening. In men with a low forced expiratory volume in 1 second, the prevalence of angina was also increased, but the association was much weaker than that observed between angina and breathlessness. After a 5-year follow-up, 25% of men severely breathless at screening but without any initial evidence of CAD had developed angina, 5% had had a heart attack (half of these were fatal) and 7% were dead from causes other than CAD. The corresponding rates for men not breathless at screening and without evidence of CAD were: 4% angina, 2.5% heart attack and 2% dead from causes other than CAD. Breathlessness appears to be an early indicator of CAD in the absence of either angina or electrocardiographic evidence of ischemia.

Adult↗

Short stature, lung function and risk of a heart attack.

In a large prospective study of cardiovascular disease in 7735 middle-aged men--the British Regional Heart Study--the 443 subjects who experienced a major ischaemic heart disease event within 7.5 years of follow-up were on average 1.6 cm shorter than the other men (p less than 0.001). The risk of heart attack was approximately twice as great in the shortest quintile of men compared with the tallest quintile. When a number of recognized risk factors for ischaemic heart disease were taken into account--age, social class, serum total cholesterol, HDL-cholesterol, systolic blood pressure, cigarette smoking--there was a marked reduction in the risk of heart attack associated with height. When a measure of lung function (FEV1 not standardized for height) was adjusted for in addition to these risk factors, the height-related risk of heart attack disappeared. Indeed, FEV1 alone was sufficient to account for most of the association between height and the risk of heart attack.

Adult↗

Using the WHO (Rose) angina questionnaire in cardiovascular epidemiology.

During 1978-80, 7735 men aged 40-59 took part in a screening examination which included an administered version of the WHO (Rose) questionnaire on chest pain. Those men who had 'possible' angina were as likely to have an ischaemic electrocardiogram at rest as those with 'definite' angina. Furthermore, the heart attack rate over 7.5 years was similar in men with 'definite' and 'possible' angina and did not diminish with length of follow-up. Five years after the initial screening 98% of the surviving men replied to a postal questionnaire which included a self-administered version of the chest pain questionnaire. Age-specific prevalence rates of angina based on the administered questionnaire at screening and on the self-administered postal version five years later, were similar. Men who had angina ('definite' or 'possible') on both occasions had the highest prevalence rate of ischaemic electrocardiograms, men who were positive on only one occasion had intermediate rates and those who were negative on both occasions had the lowest rates. We conclude that in cardiovascular studies of middle-aged men which use the WHO (Rose) questionnaire for the purposes of determining prevalence or assessing risk of a heart attack, angina should include both 'possible' and 'definite' angina.

Adult↗

Blood pressure measurement in children: the importance of cuff bladder size.

The effect of cuff bladder size on blood pressure measurement has been investigated in 838 children aged 5-7 years, using a Dinamap oscillometric automated blood pressure recorder and a Hawksley random zero sphygmomanometer. With both instruments the smallest (infant) cuffs recorded higher pressures than the child cuffs (mean systolic differences: Dinamap 4.6 mmHg, Hawksley 6.6 mmHg), which in turn recorded higher pressures than the largest (adult) cuffs (mean systolic differences: Dinamap 5.5 mmHg, Hawksley 8.1 mmHg). These differences in measurement between cuffs are sufficiently large as to be of concern in both clinical and epidemiological studies. Since they are little affected by arm circumference, their occurrence cannot be prevented simply by following current guidelines for selection of cuff size. Methods of dealing with these problems are discussed.

Blood Pressure Determination↗

Bronchodilator action of inhaled fenoterol and ipratropium in normal subjects: a teaching exercise for medical students.

1. A pharmacology practical class for preclinical medical students was designed as a placebo-controlled, double-blind trial of two bronchodilator drugs. 2. Fenoterol hydrobromide (800 micrograms), ipratropium bromide (80 micrograms) and placebo (propellant only) were given by metered dose inhaler to 79 non-asthmatic volunteers. Their effects on FEV1, heart rate and tremor (assessed by the time taken to thread five sewing needles) were compared. 3. Both drugs caused a significant increase in FEV1: the largest group mean increase was 77 ml, recorded 15 min after fenoterol, and 103 ml, recorded 60 min after ipratropium. 4. Fenoterol also caused a mean increase of 8.7 beats min-1 in heart rate, 5 min after inhalation. This effect was still apparent after 60 min. 5. Fenoterol appeared to prolong needle threading time in some individuals. 6. In subjects who inhaled fenoterol, there were no correlations between the increase in FEV1, the increase in heart rate, or the development of tremor. 7. It is concluded that inhaled fenoterol and ipratropium both cause bronchodilation in normal subjects. Systemic absorption of fenoterol is indicated by the rapid increase in heart rate. The bronchodilator effect of ipratropium suggests that resting airway calibre is governed partly by parasympathetic tone in normal subjects. 8. The bronchodilator and systemic effects of these drugs can be used to demonstrate pharmacological, therapeutic and statistical principles to medical students.

Administration, Inhalation↗

Operant conditioning of head-waving in Aplysia. I. Identified muscles involved in the operant response.

A basic goal in the neurosciences is to understand the cellular mechanisms underlying associative learning. The 2 major forms of associative learning are classical conditioning and operant conditioning. In recent years considerable progress has been made towards a cellular analysis of classical conditioning in a number of different preparations. In contrast, the cellular mechanisms underlying operant conditioning are poorly understood. Since the marine mollusc Aplysia has proved to be a powerful preparation for studying cellular and molecular mechanisms of a variety of forms of learning, including classical conditioning, we asked whether Aplysia might also be capable of exhibiting operant conditioning. In previous experiments we found that a naturally occurring behavior, the head-waving response of Aplysia, could be operantly conditioned (Cook and Carew, 1986). In the present paper we have carried out a quantitative analysis of the horizontal and vertical components of the head-waving response at the level of individual muscle groups. We have identified a discrete, bilateral band of neck muscles, the lateral columellar muscles (LCMs), whose electromyographic (EMG) activity is significantly correlated with the horizontal component of head-waving, the component modified by operant conditioning. Since head-waving is a complex behavioral response involving a variety of different muscle groups, using a restricted system such as the LCMs as an analog of the head-waving response will greatly facilitate a cellular analysis of operant conditioning in Aplysia.

Animals↗