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Biomedical subjects

N R Cook

Publications and source records attributed to N R Cook.

71 records · Page 4Linked to original sources
PubMed1993

Surgical repair of complete atrioventricular canal defects in infancy. Twenty-year trends.

Case histories of 301 patients with complete atrioventricular canal defect presenting to our institution in infancy between January 1972 and January 1992 were reviewed with the purpose of identifying the factors responsible for the observed improvement in perioperative mortality over this time period. A retrospective analysis of hospital records examined 46 patient-related, morphologic, procedure-related, and postoperative variables for associations with perioperative death and reoperation. Operative mortality decreased significantly over the period of the study from 25% before 1976 to 3% after 1987 (p < 0.0001). A number of the 46 variables examined showed trends over time that were similar to that for mortality. Palliative procedures decreased over time. Reoperation for most residual lesions also decreased to the degree that they were essentially eliminated in recent years. The exception to this was reoperation for postoperative left atrioventricular valve regurgitation, which also decreased but remained at 7% in recent years. Both technical and support-related procedural variables showed no trends over time, with the exception of the performance of left atrioventricular valve annuloplasty, which increased over time. Closure of the left-sided cleft was performed in 61% of the patients, with no trend over time. Annuloplasty and cleft closure were not associated with less postoperative left atrioventricular valve regurgitation, fewer reoperations, or lower mortality. Multivariate logistic regression analysis identified only earlier year of operation, the presence of double-orifice left atrioventricular valve, and postoperative residual regurgitation of the left atrioventricular valve as risk factors for death. Experience-related improvements in technical precision achieved over time best account for the reduction in the rate of reoperation for most types of residual lesions and also for the reduction in mortality. The only residual lesion that has not been essentially completely eliminated is left atrioventricular valve regurgitation, with reoperation for this lesion having been reduced in recent years, but not eliminated. Improved understanding of the structural and functional variability of the atrioventricular valve in this lesion may be necessary before postoperative dysfunction of this valve can be completely eliminated.

Child↗
PubMed1993

Repair of truncus arteriosus in the neonate.

From September 1986 through December 1991, 63 patients with truncus arteriosus underwent surgical repair. The management approach evolved over the period of the study from elective primary repair at 3 months of age to elective primary repair in the early neonatal period. Thirty variables were examined as potential risk factors for the outcome events of death, reoperation, and presence of pulmonary vascular morbidity. According to both univariate and multivariate techniques, severe truncal valve regurgitation, interrupted aortic arch, coronary artery anomalies, and age at repair greater than 100 days were important risk factors for perioperative death. In the 33 patients without these risk factors, early survival was 100%. In the 30 patients with one or more of these risk factors, survival was 63%. Pulmonary hypertensive episodes were fewer, and duration of ventilator dependence and pulmonary artery pressure were significantly less in patients undergoing the operation before 30 days of age. Seven patients required reoperation for right ventricular outflow tract obstruction at a mean follow-up time of 23.4 months, with no deaths. In conclusion, interrupted aortic arch, severe truncal valve insufficiency, coronary anomalies, and repair later than 100 days of age were risk factors for death after repair of truncus arteriosus. In the absence of these associations, truncus arteriosus can be repaired with excellent surgical outcome in the neonatal and early infancy period. Repair in the early neonatal period reduces the prevalence of postoperative pulmonary vascular morbidity.

Age Factors↗
PubMed1992

Childhood blood pressure tracking correlations corrected for within-person variability.

The correlation coefficient between initial and subsequent blood pressure (BP) measurements is referred to as the tracking correlation. Childhood BP tracking correlations, although positive, have been considered too low to make accurate predictions for an individual. These correlations, however, can be raised substantially by averaging BP over multiple weekly visits in each year, which partially accounts for within-person variability. In a cohort of 333 school children, we measured BP 3 times on each of 4 successive weekly visits, in each of 4 consecutive years, using a random-zero sphygmomanometer. Approximately 90 per cent of subjects had data for one or more follow-up years, and 75 per cent of subjects who entered in the first year had data for all four years. With a model that allows estimation of correlations and that uses all available longitudinal data, we calculated tracking correlations completely corrected for within-person variability, the statistical equivalent of measuring BP on an infinite number (infinity) of visits and measurements per visit. Age-sex adjusted tracking correlations for 3 years of follow-up based on the means from 1,2,3,4, and infinity visits are, for systolic BP, 0.43, 0.56, 0.62, 0.66, and 0.73, respectively, and for diastolic BP, 0.20, 0.37, 0.46, 0.50, and 0.70, respectively. With longer follow-up, the use of corrected tracking correlations would allow determination of the maximal extent to which childhood BP can predict adult levels, and therefore the usefulness of screening to identify children at high risk of developing hypertension.

Adolescent↗
PubMed1992

Assessing the validity of childhood blood pressure screening: unbiased estimates of sensitivity, specificity, and predictive values.

Blood pressure measurement in childhood can be considered as a screening test for future blood pressure levels. Evaluating this test involves calculating sensitivities, specificities, and predictive values for a blood pressure measurement at an initial time for predicting underlying true blood pressure at a subsequent time. We demonstrate the use of childhood blood pressure tracking correlations that are corrected for within-person variability to calculate unbiased estimates of these test characteristics. In a cohort of 333 schoolchildren, we measured blood pressure on multiple visits in each of 4 successive years. Using these data for within-person variances and corrected tracking correlations, and U.S. population data for means and total variances, we tabulated positive predictive values, sensitivities, and specificities for the case of predicting a 9-year-old male's true systolic blood pressure 3 years later. For example, if a 9-year-old's average blood pressure from 4 visits is 115 mmHg, the probability of his true blood pressure being greater than 116 mmHg (90th percentile) at age 12 is 0.50. With longer follow-up, the use of predictive values, sensitivities, and specificities that incorporate corrected correlations should allow determination of the accuracy of predicting adult blood pressure from childhood values, and therefore the usefulness of screening children for those at high risk of developing hypertension.

Adolescent↗
PubMed1991

Peak expiratory flow rate and 5-year mortality in an elderly population.

During a population survey in 1982-1983 among all community-dwelling elderly aged 65 years and over in East Boston, Massachusetts, measurements of peak expiratory flow rate using the mini-Wright peak flow meter were made on 3,582 participants (80% of those eligible). The average peak flow rate was 315 liters/minute, and a measure of peak flow rate adjusted for age, sex, height, and weight was computed. This was a highly significant (p less than 0.0001) predictor of 5-year total mortality, whose ascertainment was virtually complete. The relative risk was 1.27 (95 percent confidence interval 1.19-1.36) per 100 liters/minute decrease in peak flow rate, using a proportional hazards model including terms for age, sex, and smoking. There was no apparent modification of the effect of this measure in various categories of smoking, with relative risks of 1.24 for nonsmokers, 1.29 for ex-smokers, and 1.26 for current smokers. This finding also persisted after adjustments for other covariates, including respiratory symptoms such as cough, phlegm, and wheeze; cardiovascular risk factors such as history of myocardial infarction and stroke; and systolic and diastolic blood pressures; socioeconomic status; scores on simple tests of cognitive function; measures of physical activity and functional ability; and self-assessed state of health. In a stepwise model including all of these variables, the relative risk was 1.16 (p less than 0.0001) per 100 liters/minute decrease in peak flow rate, indicating that peak flow rate is a strong independent predictor of total mortality in the elderly.

Activities of Daily Living↗
PubMed1989

Prevalence of Alzheimer's disease in a community population of older persons. Higher than previously reported.

Clinically diagnosed Alzheimer's disease and other dementing illnesses were assessed in a geographically defined US community. Of 3623 persons (80.8% of all community residents over 65 years of age) who had brief memory testing in their homes, a stratified sample of 467 persons underwent neurological, neuropsychological, and laboratory examination. Prevalence rates of Alzheimer's disease were calculated for the community population from the sample undergoing clinical evaluation. Of those over the age of 65 years, an estimated 10.3% (95% confidence limits, 8.1% and 12.5%) had probable Alzheimer's disease. This prevalence rate was strongly associated with age. Of those 65 to 74 years old, 3.0% (95% confidence limits, 0.8 and 5.2) had probable Alzheimer's disease, compared with 18.7% (95% confidence limits, 13.2 and 24.2) of those 75 to 84 years old and 47.2% (95% confidence limits, 37.0 and 63.2) of those over 85 years. Other dementing conditions were uncommon. Of community residents with moderate or severe cognitive impairment, 84.1% had clinically diagnosed Alzheimer's disease as the only probable diagnosis. These data suggest that clinically diagnosed Alzheimer's disease is a common condition and that its public health impact will continue to increase with increasing longevity of the population.

Age Factors↗
PubMed1989

Correlates of headache in a population-based cohort of elderly.

Data from a community-based study of 3811 persons aged 65 years and older were used to describe the characteristics of headache in the elderly. Subjects were asked whether they experienced headache in the past year, the frequency and severity of their headaches, and whether they experienced three symptoms of migraine: unilaterality, nausea or vomiting, an aura preceding the headache. Prevalence of headache in those aged more than 65 years declined with age in both men and women; women had a higher prevalence in each age group. The same was true for frequent, severe, and migrainous headache. We examined age- and sex-adjusted correlations of headache with several medical and social factors. Prevalence of any headache was strongly associated with joint pain, depression, bereavement, waking during the night, use of eyeglasses, symptoms of temporomandibular joint dysfunction, and self-assessment of health. Similar variables were associated with frequency, severity, and migrainous symptoms, and thus could not be distinguished among these various types.

Aged↗
PubMed1989

Peak expiratory flow rate in an elderly population.

A population survey was conducted in 1982-1983 among 3,812 persons aged 65 years and older residing in East Boston, Massachusetts, a geographically defined urban community. Three measurements of peak expiratory flow rate were obtained by using calibrated mini-Wright meters. Peak expiratory flow rate was strongly related to age, sex, smoking, and years smoked. After adjustment for these factors, low peak expiratory flow rate was associated with chronic respiratory symptoms (cough, wheeze, shortness of breath, exertional dyspnea, orthopnea, and paroxysmal nocturnal dyspnea; p less than 0.0001) and with certain cardiovascular variables (history of stroke, p = 0.0014; angina, p = 0.05; and high pulse rate, p = 0.004). No significant associations were found with history of myocardial infarction or systolic and diastolic blood pressures. Peak expiratory flow rate was positively related to education (p less than 0.0001) and income (p less than 0.0001). Peak expiratory flow rate also was strongly related (p less than 0.0001) to measures of functional ability and physical activity, self-assessment of health, and simple measures of cognitive function. The correlations of peak expiratory flow rate with pulmonary symptoms and other indices of chronic disease raise the possibility that peak expiratory flow rate will predict mortality in an elderly population.

Age Factors↗
PubMed1988

Correlates of cognitive function in an elderly community population.

In 1982 and 1983, brief, structured performance tests of selected areas of cognitive function were administered to 3,682 (82.1 per cent) of the residents aged 65 years and older of the geographically defined community of East Boston, Massachusetts, a center of the Established Populations for Epidemiologic Studies of the Elderly program. There was a strong inverse relation between age and performance on all four cognitive tests in analyses adjusted for sex only as well as in those adjusted for the effects of other variables. Similarly, fewer years of formal education, increasing level of disability on the modified Katz Activities of Daily Living Scale, and less prestigious occupations, as measured by the modified Duncan Socioeconomic Index, were each independently related to lower performance on all four tests.

Activities of Daily Living↗
PubMed1988

A prospective study of incident comprehensive medical home care use among the elderly.

This prospective study directly examines, in a defined community population, the extent to which a wide array of characteristics predict utilization of an important long-term care (LTC) service--medical home care--over a two-year interval among the cohort of 3,706 people aged 65 or older. The overall age-sex adjusted rate of two-year incident home care use was 3.2 per cent. For both men and women, the rates among the aged 85 or older group were approximately 12 times the rates of those aged 65 to 74. The multivariate predictors of incident home care, adjusted for age and sex, were five: receiving help with at least one activity of daily living (ADL), being dependent in Rosow-Breslau functional health areas, being homebound, more errors in mental status items, and no involvement with social groups. The dominance of indicators of frailty in physical function and cognitive function are consistent with the predictors of another group of LTC clients, those who subsequently enter nursing homes. However, in the present study the ratios of medical home care use were similar for those living alone and for those living with others in the multivariate model, suggesting the possibility of differences between home care and institutional LTC clients.

Activities of Daily Living↗
PubMed1987

Reproducibility and predictive values of routine blood pressure measurements in children. Comparison with adult values and implications for screening children for elevated blood pressure.

A study of the variability of blood pressure was conducted among a total of 780 Massachusetts children, 335 children in East Boston and 445 children in Brookline, ages 8-18 years. All children had their blood pressure measured with a standard mercury sphygmomanometer in a school setting on four visits one week apart with three measurements per visit. In East Boston, repeat measurements were made for the same children for four consecutive years. A nested random effects model was used to estimate between- and within-visit variance components. For children aged 8-12 years, these were, respectively, 33.1, 12.0 in boys and 31.2, 11.1 in girls for systolic blood pressure and 57.7, 21.3 in boys and 56.6, 22.6 in girls for systolic muffling blood pressure (Korotkoff phase 4). For children aged 13-18 years of age, they were, respectively, 41.1, 11.8 in boys and 35.2, 12.2 in girls for blood pressure and 40.6, 15.5 in boys and 36.1, 11.4 in girls for diastolic blood pressure (Korotkoff phase 5). Within-person variability for systolic pressure was comparable to previously published data for 434 white adults ages 30-49 years not on antihypertensive medications; however, within-person variability for diastolic pressure was considerably higher in the children, accounting for over 75% of total variability among 8-12-year-old children, compared with 27% for adults. No meaningful effects of age, sex, or blood pressure level on variability of systolic pressure were found. However, age and level of blood pressure each had a large and independent inverse association with variability of diastolic pressure; variance components for younger children (ages 8-12 years) and children with low diastolic pressure (less than 60 mmHg) were approximately twice as large as for older children (ages 13-18 years) and children with diastolic pressure greater than or equal to 60 mmHg, respectively. Finally, predictive value estimates of blood pressure are provided for particular age-sex groups to enable one to efficiently identify children whose true mean level of blood pressure exceeds the 90th percentile for their age-sex group with minimum misclassification. Because of the substantial variability of diastolic pressure in young children, resulting in relatively low predictive value estimates, systolic pressure (either alone or in combination with diastolic pressure) may be more useful as the primary tool for screening children under age 13 years for high blood pressure.

Adolescent↗
PubMed1985

Regression analysis of changes in blood pressure with oral contraceptive use.

Measurements of blood pressure were obtained on 2,673 women from East Boston, Massachusetts, an urban, working class neighborhood, in surveys conducted in both 1973 and 1976-1977. Of these, 927 women participated in a third survey in 1978. The women were 16 to 49 years of age in 1973, premenopausal throughout the study, and not on blood pressure medication. Regression analyses were performed of blood pressure change between the first and second as well as between the second and third surveys on initial blood pressure, age, weight, and patterns of oral contraceptive use. For systolic pressure the effect of starting oral contraceptive use was an increase of 4.1 mmHg (p less than 0.0001), while the effect of discontinuing use relative to continued use was a 4.4 mmHg decrease (p less than 0.0001). These changes were not affected by duration of use or time since last use among past users. For diastolic pressure the average effect of starting use between surveys was an insignificant 1.0 mmHg increase, but diastolic pressure level seemed to increase with duration of use (0.5 mmHg/year, p = 0.0009). The effect of discontinuing use relative to continued use was a drop of 2.7 mmHg in diastolic pressure (p = 0.0004), which was uninfluenced by time since last use.

Adolescent↗
PubMedDate not supplied

Baseline characteristics of participants in the Women's Health Study.

The Women's Health Study (WHS) is a randomized, double-blind, placebo-controlled trial designed to evaluate the balance of benefits and risks of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer in women. A total of 39,876 female health professionals, age 45 years or older and without a history of cardiovascular disease or cancer (other than nonmelanoma skin cancer), were randomized in a 2x2 factorial design to one of four treatment groups: active aspirin and vitamin E placebo, aspirin placebo and active vitamin E, both active agents, or both placebos. The process of randomization was successful, as evidenced by the equal distribution of a large number of baseline demographic, lifestyle, and health history characteristics among the four treatment groups. Similar distribution of known potential confounders, as well as the large sample size, provides reassuring evidence that unmeasured or unknown potential confounders are also equally distributed. As expected in a clinical trial, the women in the study are healthier in some respects than the general population, but they have very comparable rates of obesity, hypertension, and elevated cholesterol. With adequate duration of treatment and follow-up, this trial will provide important and relevant information on the balance of benefits and risks of aspirin and vitamin E supplementation in the primary prevention of cardiovascular disease and cancer in women.

Aged↗
PubMedDate not supplied

A comparison of elderly participants in a community survey with nonparticipants.

In 1982-83, 4,485 persons ages 65 or older were identified by a household census in East Boston, MA: 3,812 (85 percent) of them responded to a health and social status questionnaire. Data on age, sex, and living arrangements for the 4,485 eligible people were analyzed with respect to final participation status and reason for refusal or reluctance. The health and social status of reluctant and ready self-respondents were compared, and respondents-by-proxy were compared with self-respondents. Total participation rates were similar for both sexes and all ages, but the likelihood of interview by proxy increased with age, as did the likelihood of nonparticipation due to unavailability. Living alone or with other participants favored participation, and living with refusers or other nonrespondents increased the probability of refusal. While reluctant and ready self-respondents differed in only one health variable and two social variables, respondents-by-proxy differed from self-respondents in most variables tested. These analyses suggest an absence of major differences between self-respondents and refusers. Therefore, nonresponse bias is not likely to have a major impact on interpretation of the data obtained from participants in this study.

Aged↗