PubMed Health⌕ Search

Biomedical subjects

N R Cook

Publications and source records attributed to N R Cook.

At least 55 records · Page 3Linked to original sources

Self-reported breast implants and connective-tissue diseases in female health professionals. A retrospective cohort study.

OBJECTIVE: To evaluate the association of breast implants with connective-tissue diseases. DESIGN AND PARTICIPANTS: Retrospective cohort study of 395,543 female health professionals who completed mailed questionnaires for potential participation in the Women's Health Study. A total of 10,830 women reported breast implants and 11,805 reported connective-tissue diseases between 1962 and 1991. Cox proportional hazards regression models were used in analyses. MAIN OUTCOME MEASURE: Self-reported connective-tissue diseases. RESULTS: Compared with women who did not report breast implants, the relative risk (RR) of the combined end point of any connective-tissue disease among those who reported breast implants was 1.24 (95% confidence interval, 1.08 to 1.41, P = .0015). With respect to the individual diseases, the finding for other connective-tissue diseases (including mixed) was statistically significant (P = .017), the findings for rheumatoid arthritis, Sjogren's syndrome, dermatomyositis or polymyositis, or scleroderma were of borderline statistical significance (.05 < P < .10), and the finding for systemic lupus erythematosus was not statistically significant (P = .44). There were no clear trends in RR with increasing duration of breast implants. CONCLUSION: These self-reported data from female health professionals are compatible with prior reports from other cohort studies that exclude a large hazard, but do suggest small increased risks of connective-tissue diseases among women with breast implants. The very large sample size makes chance an unlikely explanation for the results, but bias due to differential overreporting of connective-tissue diseases or selective participation by affected women with breast implants remains a plausible alternative explanation. The major contribution of this and other observational analytic studies has been to exclude large risks of connective-tissue diseases following breast implants.

Adult↗

Blood pressure measurement in childhood epidemiological studies.

BACKGROUND: Accurate measurement of blood pressure in childhood epidemiological studies requires standardized conditions, valid instruments, and multiple measurements. METHODS AND RESULTS: We used published literature and our own data to make recommendations on the reduction of biases caused by various technical factors, to discuss the advantages and disadvantages of selected measurement devices, and to evaluate the optimal number of visits and measurements per visit for accurate estimation of a child's blood pressure level. The conditions under which blood pressure is measured should be standardized. This includes training and certification to minimize observer biases; equipment factors such as use of an appropriate cuff bladder size, subject factors such as minimizing activities before and during the reading, environmental factors such as accounting for the time of day and ambient temperature, and technique factors such as recording both the fourth and fifth Korotkoff sounds. The choice of instrument for measuring blood pressure depends on the goals of the study and the resources available to the investigators. CONCLUSIONS: Although relatively economical and easy to use, the standard mercury sphygmomanometer is subject to the bias resulting from knowledge of earlier readings. The random-zero sphygmomanometer overcomes this bias, but it is more expensive and difficult to use and may underestimate blood pressure levels. In contrast to auscultatory devices, automated oscillometric devices are not subject to observer biases. They are gaining wider use and may be especially appropriate for younger children. However, they are expensive, and each model requires validation before use in epidemiological studies. Ambulatory blood pressure monitoring represents a potentially useful technique for future epidemiological studies. Multiple measurements are vital in estimating a child's blood pressure, and the number of visits, days or weeks apart, is at least as important as the number of measurements per visit.

Blood Pressure Determination↗

Implications of small reductions in diastolic blood pressure for primary prevention.

OBJECTIVES: To estimate the impact of small reductions in the population distribution of diastolic blood pressure (DBP), such as those potentially achievable by population-wide lifestyle modification, on incidence of coronary heart disease (CHD) and stroke. DESIGN: Published data from the Framingham Heart Study, a longitudinal cohort study, and from the National Health and Nutrition Examination Survey II, a national population survey, were used to examine the impact of a population-wide strategy aimed at reducing DBP by an average of 2 mm Hg in a population including normotensive subjects. SETTING/PARTICIPANTS: White men and women aged 35 to 64 years in the United States. MAIN OUTCOME MEASURES: Incidence of CHD and stroke, including transient ischemic attacks (TIAs). RESULTS: Data from overviews of observational studies and randomized trials suggest that a 2-mm Hg reduction in DBP would result in a 17% decrease in the prevalence of hypertension as well as a 6% reduction in the risk of CHD and a 15% reduction in risk of stroke and TIAs. From an application of these results to US white men and women aged 35 to 64 years, it is estimated that a successful population intervention alone could reduce CHD incidence more than could medical treatment for all those with a DBP of 95 mm Hg or higher. It could prevent 84% of the number prevented by medical treatment for all those with a DBP of 90 mm Hg or higher. For stroke (including TIAs), a population-wide 2-mm Hg reduction could prevent 93% of events prevented by medical treatment for those with a DBP of 95 mm Hg or higher and 69% of events for treatment for those with a DBP of 90 mm Hg or higher. A combination strategy of both a population reduction in DBP and targeted medical intervention is most effective and could double or triple the impact of medical treatment alone. Adding a population-based intervention to existing levels of hypertension treatment could prevent an estimated additional 67,000 CHD events (6%) and 34,000 stroke and TIA events (13%) annually among all those aged 35 to 64 years in the United States. CONCLUSIONS: A small reduction of 2 mm Hg in DBP in the mean of the population distribution, in addition to medical treatment, could have a great public health impact on the number of CHD and stroke events prevented. Whether such DBP reductions can be achieved in the population through lifestyle interventions, in particular through sodium reduction, depends on the results of ongoing primary prevention trials as well as the cooperation of the food industry, government agencies, and health education professionals.

Adult↗

Does weight loss from middle age to old age explain the inverse weight mortality relation in old age?

The authors examined body mass index at middle age, body mass index in old age, and weight change between age 50 years and old age in relation to mortality in old age. The study population from the Established Populations for Epidemiologic Studies of the Elderly consisted of 6,387 whites age 70 years or older who experienced 2,650 deaths during the period 1982-1987. Mortality risk was highest for persons in the heaviest quintile of body mass index at age 50 (men, relative risk (RR) = 1.33, 95% confidence interval (CI) 1.13-1.57; women, RR = 1.31, 95% CI 1.12-1.53) compared with persons in the middle quintile. This pattern was reversed for body mass index in old age, with persons in the lowest quintile having the highest mortality risk (men, RR = 1.40, 95% CI 1.19-1.65; women, RR = 1.38, 95% CI 1.17-1.63) relative to persons in the middle quintile. This reversal was explained, in part, by weight change. Compared with persons with stable weight, those who lost 10 percent or more of body weight between age 50 and old age had the highest risk of mortality (men, RR = 1.69, 95% CI 1.45-1.97; women, RR = 1.62, 95% CI 1.38-1.90). Exclusion of participants who lost 10 percent or more of their weight and adjustment for health status eliminated the higher risk of death associated with low weight. The inverse association of weight and mortality in old age appears to reflect illness-related weight loss from heavier weight in middle-age. Weight history may be critical to understanding weight and mortality relations in old age.

Aged↗

Design of a multicenter trial to evaluate long-term life-style intervention in adults with high-normal blood pressure levels. Trials of Hypertension Prevention (phase II). Trials of Hypertension Prevention (TOHP) Collaborative Research Group.

Phase II of the Trials of Hypertension Prevention (TOHP) is a multicenter, randomized trial sponsored by the National Heart, Lung, and Blood Institute designed to test whether weight loss alone, sodium reduction alone, or the combination of weight loss and sodium reduction will decrease diastolic (DBP) and systolic blood pressure (SBP) as well as the incidence of hypertension (DBP > or = 90 mm Hg, SBP > or = 140 mm Hg, and/or use of antihypertensive medications) in subjects with high-normal DBP (83 to 89 mm Hg) and SBP less than 140 mm Hg at entry. These interventions were chosen for longer-term testing with end points including hypertension prevention as well as blood pressure (BP) change based on their demonstrated short-term efficacy in reducing BP in phase I of TOHP. The phase II study population is comprised of 2382 participants (1566 men and 816 women) who are 110 to 165% of desirable body weight, allocated at random to the four treatment arms using a 2 x 2 factorial design. The trial has 80% power to detect an overall treatment effect on DBP of 1.2 mm Hg for weight loss or sodium reduction and a difference of 1.6 mm Hg between the combined intervention and placebo groups. BP observers are blinded to participant treatment assignments. Participants will be followed for 3 to 4 years. This trial may have important public policy implications concerning the ability of life-style modifications to reduce BP and prevent the development of hypertension over the long term, thereby avoiding the need for drug therapy which while effective is costly and may have side effects.

Adult↗

A secondary prevention trial of antioxidant vitamins and cardiovascular disease in women. Rationale, design, and methods. The WACS Research Group.

The evidence for a potential benefit of antioxidant vitamins in the prevention and therapy of atherosclerotic disease is derived from laboratory, clinical, and observational epidemiologic studies but remains inconclusive. Data from randomized clinical trials are sparse, particularly for women. Therefore, it is both timely and important to conduct large-scale primary and secondary prevention trials of antioxidants and cardiovascular disease (CVD). The Women's Antioxidant and Cardiovascular Study (WACS) is a randomized, double-blind, placebo-controlled secondary prevention trial of the balance of benefits and risks of antioxidant vitamins (vitamins E and C, and beta-carotene) among 8000 women with preexisting CVD. This secondary prevention trial will be conducted as a companion to the recently started Women's Health Study, a primary prevention trial of vitamin E and beta-carotene, as well as aspirin. In the WACS, US female health professionals aged 40 years and older with a history of myocardial infarction, angina pectoris, coronary revascularization, stroke, transient cerebral ischemia, carotid endarterectomy, or peripheral artery surgery will be randomly assigned, utilizing a 2 x 2 x 2 factorial design, to receive vitamin E, vitamin C, beta-carotene, and/or placebo. Cardiovascular end points include nonfatal myocardial infarction, nonfatal stroke, coronary revascularization procedures, and total CVD mortality. The present article describes the rationale, design, and methods of the trial.

Antioxidants↗

Interrelationships of peak expiratory flow rate with physical and cognitive function in the elderly: MacArthur Foundation studies of aging.

BACKGROUND: Peak expiratory flow rate (PEFR) is correlated with several measures of health in the elderly, including physical and cognitive function. It is unclear, however, whether these relationships persist among the non-frail. METHODS: The Community-based Studies of the MacArthur Foundation Research Network on Successful Aging included measures of PEFR using a mini-Wright peak flow meter on a sample of 1,354 subjects selected from those aged 70-79 in three population samples. Subjects were chosen on the basis of simple measures of physical and cognitive function (high = 1192; medium = 80; low = 82), and were given a series of more detailed tests. RESULTS: Residual PEFR, adjusted for age, sex, height, weight, and smoking, was highly correlated (p < .001) with several physical performance measures, including number of steps in a tandem walk, number of seconds in a single leg stand, times to turn in a circle, write one's name, and walk 10 feet at a fast pace, foot-tapping (time per tap), and hand grip strength. The strongest association was evident for a combination of six physical function items. Residual PEFR was also correlated with cognitive performance, including tests of similarities, naming, spatial recognition, memory, and figure drawing. The strongest association was present for a combined measure. These associations persisted in analyses restricted to those in the "high" function group as well as with no history of previous myocardial infarction, stroke, or cancer. Residual PEFR also exhibited a strong independent association with urinary norepinephrine, as measured in 12-hour overnight urine specimens. This relation did not appear to be mediated by smoking or medication use.

Aged↗

Relationship of alcohol intake with blood pressure in young adults.

The objective of this study was to examine the relationship of usual current alcohol intake with systolic and diastolic pressures among young adults. Participants were 316 men and women, aged 18 to 26 years, from East Boston, Mass. At each of three weekly visits we obtained three blood pressure measurements on each subject using a random-zero sphygmomanometer. Using an interviewer-administered questionnaire, we obtained information about quantity and frequency of alcohol intake during the previous month. The lowest systolic pressure levels were in subjects consuming 1 to < 2 drinks per day. Adjusted for age, sex, and body mass index, systolic pressure was higher by 4.0 mm Hg (95% confidence interval [CI], 0.5 to 7.6 mm Hg) in abstainers, 3.6 mm Hg (95% CI, 0.5 to 6.6 mm Hg) in those who drank < 1 drink per day, 0.4 mm Hg (95% CI, -4.7 to 5.5 mm Hg) in those who drank 2 to < 3 drinks per day, and 8.1 mm Hg (95% CI, 2.9 to 13.4 mm Hg) in those who drank > or = 3 drinks per day. Levels of diastolic pressure were lowest in those consuming 2 to < 3 drinks per day. Adjustment for pulse rate, smoking, medication use, and family history of hypertension did not alter the results. These results suggest a J-shaped association of alcohol intake with blood pressure level in young adults, with the lowest levels in consumers of 1 to 3 drinks per day.

Adolescent↗

Height, lung function, and mortality from cardiovascular disease among the elderly.

The relation between height and death from cardiovascular disease was studied in a cohort of 3,809 persons aged 65 years or older (85% of eligible individuals) enrolled in a population survey in 1982-1983 in East Boston, Massachusetts. Self-reported height and weight were obtained, and peak expiratory flow rate (PEFR) was measured using a mini-Wright peak flow meter (Armstrong Industries, North Brook, Illinois). Vital status and cause of death were obtained through 1988. The median height was 62 inches in women and 66 inches in men. After adjustment for age, body mass index, and cigarette smoking, the risk of cardiovascular death decreased with quintile of height in women, with relative risks of 1.65, 1.16, 1.15, 0.76, and 1.00 over successive quintiles, with the tallest as the referent (p trend = 0.015). The trend in men was not as strong, with relative risks of 1.22, 0.77, 0.90, 0.98, and 1.00 from the shortest to the tallest quintiles (not significant). In both men and women, the strongest association was found with height and height squared, indicating a curvilinear relation. Height remained a predictor in women after adjustment for PEFR and other risk factors. These data suggest that a relation between height and cardiovascular death that is not mediated by lung function exists in the elderly, at least among women.

Age Factors↗

An optimal rule for screening subjects for clinical trials in the presence of within-person variability.

In screening subjects for a continuous variable, such as blood pressure (BP), for eligibility for clinical trials, multistage rules are often used to select subjects within a target range. Multiple readings may be taken over successive visits, and the subject must meet eligibility criteria at each visit. We present an optimal rule that minimizes the number of clinic visits needed per eligible subject or the overall number of screening visits needed to achieve a given sample size of eligible subjects. We illustrate these methods with the design of phase I of the Trials of Hypertension Prevention (TOHP), which attempts to identify subjects with mean diastolic BP in the range 80- < 90 mm Hg over three screening visits. The optimal rule requires only 73% of the visits needed with a no-screening rule in which all subjects are examined at each visit, and the average BP at all screening visits is used as a criterion. The optimal rule requires only 36% of visits needed in a more standard approach in which a subject must have an observed mean diastolic BP of 80- < 90 mm Hg on each of three consecutive visits. Alternatively, one may minimize the expected cost of screening per eligible subject when screening visits differ in cost. Examples are given of optimal rules with differing relative costs per visit.

Adult↗

Screening rules for determining blood pressure status in clinical trials. Application to the trials of hypertension prevention.

Multistage blood pressure screening rules are often used to select subjects for clinical trials. Multiple blood pressure readings are taken over successive visits, and the subject must meet eligibility criteria at each visit. In this paper, the authors present methods which depend on the distribution of the subject's underlying blood pressure values (the predictive value approach) or, alternatively, the subject's observed mean over all screening visits (the empirical predictive value approach) given the observed mean after one or more visits. The authors apply these methods to data from Phase I of the Trials of Hypertension Prevention, which attempts to identify subjects with mean diastolic blood pressures in the range 80-89 mmHg over three screening visits. The estimated efficiency of these rules is evaluated in terms of the number of clinic screening visits needed per eligible subject. Relative to reexamining all subjects at each visit (no screening), these approaches can reduce the number of visits required by 27%. This is in contrast to the standard rule in which a subject must have an observed mean diastolic blood pressure of 80-89 mmHg on each of three consecutive visits, which requires twice as many clinic visits per eligible subject as not screening. Thus, the approach presented is useful in identifying eligible subjects for clinical trials in an efficient manner.

Adult↗

Weight loss intervention in phase 1 of the Trials of Hypertension Prevention. The TOHP Collaborative Research Group.

BACKGROUND: Phase 1 of the Trials of Hypertension Prevention was a collaborative, randomized controlled clinical trial designed to determine the feasibility and efficacy of selected nonpharmacologic interventions in reducing or preventing an increase in diastolic blood pressure. METHODS: Participants aged 30 to 54 years who had a high-normal diastolic blood pressure (80 to 89 mm Hg), and were between 115% and 165% of their desirable body weight, were randomly assigned to either an 18-month weight loss intervention (n = 308) or a usual-care control condition (N = 256). Intervention consisted of 14 weekly group meetings followed by monthly maintenance sessions. Intervention participants received training in behavioral self-management technique and were asked to make life-style changes aimed at achieving a moderate reduction in energy intake and an increase in physical activity. RESULTS: The average weight losses in the intervention group at 6, 12, and 18 months of follow-up were 6.5, 5.6, and 4.7 kg for men and 3.7, 2.7, and 1.6 kg for women. The mean (+/- SE) change in diastolic blood pressure for intervention participants compared with controls at termination was -2.8 +/- 0.6 mm Hg for men and -1.1 +/- 0.9 mm Hg for women. For systolic blood pressure, the corresponding change was -3.1 +/- 0.7 mm Hg for men and -2.0 +/- 1.3 mm Hg for women. Blood pressure reductions were greater for those who lost larger amounts of weight. Sex-related differences in blood pressure response were largely due to the smaller amount of weight lost by women, and sex differences in weight loss could be accounted for by differences in baseline body weight. CONCLUSIONS: During an 18-month follow-up period, this weight reduction program was shown to be an effective nonpharmacologic intervention for reducing blood pressure in overweight adults with high-normal blood pressure.

Adult↗

Extrapyramidal signs and other neurologic findings in clinically diagnosed Alzheimer's disease. A community-based study.

The association between findings on the neurologic examination and the clinical diagnosis of Alzheimer's disease was investigated among 467 individuals from a geographically defined community population. Participants were selected by stratified random sampling based on their memory performance in a population survey of community residents 65 years of age and older. Each participant underwent a structured medical, psychiatric, neurologic, and neuropsychologic examination. Of the 467 persons examined there were 134 cases of probable Alzheimer's disease and 167 control subjects. Multiple logistic regression analysis was used to estimate the degree to which the presence of each of several neurologic examination findings affected the age- and sex-adjusted relative odds of having clinically diagnosed Alzheimer's disease. The most striking associations with the diagnosis of Alzheimer's disease were seen with various measures of extrapyramidal dysfunction. These increased relative odds were not markedly affected by excluding from the analysis cases with severe cognitive impairment. The results suggest that involvement of the extrapyramidal system is a common finding in Alzheimer's disease.

Aged↗

Identifying children at high risk for the development of essential hypertension.

BACKGROUND AND OBJECTIVES: Because blood pressure (BP) tracks from childhood to adulthood, some have recommended screening to identify children at high risk for the development of essential hypertension as adults. Others, however, have argued against this strategy because they believe that correlations between childhood and adulthood BP levels are too low. To address these issues, we considered prediction of adult BP from childhood levels. DESIGN: Cohort study with follow-up of participants from childhood to early adulthood. SETTING AND PARTICIPANTS: We ascertained BP in 337 schoolchildren from East Boston, Mass., and reexamined 317 (94%) of them 8 to 12 years later, at ages 18 to 26 years. MEASUREMENTS AND DATA ANALYSIS: On each of several visits, 1 week apart (four for children, three for adults), we obtained three BP readings with a random-zero sphygmomanometer. To calculate correlation coefficients (tracking correlations) between childhood and adult BP, we assumed a multivariate normal distribution and used an iterative maximal likelihood approach in a longitudinal model. We then used these correlations in expressions for sensitivity and specificity of childhood BP as a screening test and for positive predictive value for adult BP above specified cutoff points. RESULTS: During the 8- to 12-year interval, tracking correlations, corrected for within-person variability and adjusted for age, sex, smoking, and medication and alcohol use, were 0.55 for systolic BP and 0.44 for diastolic BP. The corresponding positive predictive values indicated that, for example, the probability that a 20-year-old man's true systolic BP will be > 139 mm Hg (> 90th percentile) was 0.44, given that his observed average systolic BP at age 10 years was > 95th percentile (> 117 mm Hg). The sensitivity of a 10-year old boy's systolic BP > 95th percentile to detect systolic BP > 139 mm Hg 10 years later was 0.17. The specificity of his BP < 95th percentile at age 10 years to detect systolic BP < 139 mm Hg at age 20 years was 0.97. For diastolic BP, predictive values and sensitivities were somewhat lower. CONCLUSIONS: After correction for within-person variability, tracking correlations from childhood to early adulthood are higher than previously reported. However, the resulting sensitivities and predictive values for childhood BP as a screening test for adult BP are of only modest magnitude. These data call into question the usefulness of routine BP measurement to identify children at high risk for the development of essential hypertension.

Age Factors↗

Height and incidence of cardiovascular disease in male physicians.

BACKGROUND: An inverse association between height and risk of coronary heart disease (CHD) has been reported in several case-control and cohort studies, but the reasons for the association remain uncertain. We evaluated this association among 22,071 male physicians, a population homogeneous for high educational attainment and socioeconomic status in adulthood. METHODS AND RESULTS: The study population was comprised of participants in the Physicians' Health Study, a randomized, double-blind, placebo-controlled trial of low-dose aspirin and beta-carotene in the primary prevention of cardiovascular disease and cancer among US male physicians, aged 40 to 84 years, in 1982. Participants were classified into five height categories at study entry, from shortest to tallest, and were followed an average of 60.2 months to determine the incidence of myocardial infarction (MI), stroke, and death from cardiovascular disease. Men in the tallest (> or = 73 in. or 185.4 cm) compared with the shortest (< or = 67 in. or 170.2 cm) height category had a 35% lower risk of MI (relative risk, 0.65; 95% confidence interval, 0.44 to 0.99; P = .04), after adjusting for known cardiovascular risk factors. Further, a marginally significant inverse trend (P trend = .05) across the height categories was observed. Although the relationship was not strictly linear, for every inch of added height, there was an approximate 2% to 3% decline in risk of MI. In contrast, men in the tallest compared with the shortest height category had only small and nonsignificant decreases in risk of stroke and cardiovascular death. While no significant trend in risks of these end points across the height categories was observed, the numbers of events for these end points were far less than for MI, and thus the confidence intervals were wide. CONCLUSIONS: These data indicate that height is inversely associated with subsequent risk of MI. At this time, a few mechanisms are plausible, but none are convincing. Other epidemiological and basic research efforts are needed to explore a variety of physiological correlates of height that may be responsible for mediating the height-MI association. In the meantime, while height is not modifiable, it is easy to measure and may be useful to evaluate CHD disease risk profiles and target lifestyle interventions.

Adjuvants, Immunologic↗

Feasibility and efficacy of sodium reduction in the Trials of Hypertension Prevention, phase I. Trials of Hypertension Prevention Collaborative Research Group.

Phase I of the Trials of Hypertension Prevention was a multicenter, randomized trial of the feasibility and efficacy of seven nonpharmacologic interventions, including sodium reduction, in lowering blood pressure in 30- to 54-year-old individuals with a diastolic blood pressure of 80 to 89 mm Hg. Six centers tested an intervention designed to reduce dietary sodium to 80 mmol (1800 mg)/24 h with a total of 327 active intervention and 417 control subjects. The intervention consisted of eight group and two one-to-one meetings during the first 3 months, followed by less-intensive counseling and support for the duration of the study. The mean net decrease in sodium excretion was 43.9 mmol/24 h at 18 months. Women had lower sodium intake at baseline and were therefore more likely to decrease to less than 80 mmol/24 h. Black subjects were less likely to decrease to less than 80 mmol/d, independent of sex or baseline sodium excretion. The mean (95% confidence interval) net decrease associated with treatment was -2.1 (-3.3, -0.8) mm Hg for systolic blood pressure and -1.2 (-2.0, -0.3) mm Hg for diastolic blood pressure at 18 months (both P < .01). Multivariate analyses indicated a larger systolic blood pressure effect in women (-4.44 versus -1.23 mm Hg in men), adjusted for age, race, baseline blood pressure, and baseline 24-hour urinary sodium excretion (P = .02). Dose-response analyses indicated an adjusted decrease of -1.4 mm Hg for systolic blood pressure and -0.9 mm Hg for diastolic blood pressure for a decrease of 100 mmol/24 h in 18-month sodium excretion. These results support the utility of sodium reduction as a population strategy for hypertension prevention and raise questions about possible differences in dose response associated with gender and initial level of sodium intake.

Adult↗