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Biomedical subjects

C S Berkey

Publications and source records attributed to C S Berkey.

15 recordsLinked to original sources
PubMed1991

Long-term memory of body weight and past weight satisfaction: a longitudinal follow-up study.

Recalled body weight and self-reported current weight were validated in a longitudinal study population by comparing recalls at 50 y to actual measures taken at ages 18, 30, 40, and 50 y. Recalled body weights were also compared with reported desired weights at these same ages. Self-reported weights at 50 y were equally accurate for both males and females; the mean reporting underestimate was -1.98 kg for males and -1.86 kg for females. Males' self reports at age 50 y were influenced by years of education (P less than 0.005) and current body size (P less than 0.0001) whereas females' were not. Correlations between recall of past weights and measured weights ranged from r = 0.87 at 18 y to 0.95 at 40 y. Recalls of past body weight were not significantly influenced by the passage of time, the number of years of education, or the accuracy of current weight reports. Current body size (wt/ht2) was significantly associated with life-time weight dissatisfaction in both sexes (P less than 0.0005).

Body Image↗
PubMed1991

Modelling adolescent blood pressure patterns and their prediction of adult pressures.

Tracking of blood pressure in adolescent boys is investigated using a mathematical model that corresponds to progression along a constant percentile. A more general analysis, based on the method of principal components, is also proposed that determines various alternative tracks or patterns that are most prevalent in the longitudinal blood pressure data. The degree of tracking along a constant percentile curve for systolic pressure was moderately high, as evidenced by a tracking index of .78 explaining 81% of the variance, but less strong for diastolic (tracking index of .60) where tracking along a percentile explained 66% of the variance. The value of the more general analysis of blood pressure patterns may lie in the assessment of adolescent risk factors for elevated adult blood pressure. Using adolescent patterns determined by either statistical model, adult systolic at age 38 was predicted (R2 = .22) by the concept of a systolic fixed percentile curve in adolescence, and similarly for diastolic (R2 = .21). However, the more general analysis based on longitudinal principal components further suggests that boys who have a larger than usual systolic peak at age 14 years, which is near the time of the adolescent physical growth spurt in these boys, may be more likely to have higher systolic pressures at age 38. Because the adult data were incomplete and highly unbalanced, these findings were obtained using random-effects models for longitudinal data.

Adolescent↗
PubMed1990

Split-mouth and cross-over designs in dental research.

The presence of paired or multiple organs (arches, quadrants, teeth) and the chronic nature of many dental diseases suggest the use of split-mouth (trials in which each subject receives greater than or equal to 2 treatments, each to a separate section of the mouth) and cross-over research designs (trials in which each subject receives greater than or equal to 2 treatments in sequence). While these designs offer potential savings in resources, their usefulness can be negated if several strict scientific and statistical assumptions are not met. The primary prerequisites for the use of split-mouth and cross-over designs are that: (1) the disease to be investigated is relatively stable and uniformly distributed; (2) the effects of the treatments to be evaluated are short-lived or reversible for cross-over studies, or are localized for split-mouth designs. Other important factors that influence the appropriate use of these designs include: the method of treatment sequencing and assignment, and the cross-over rules used; blinding of patient assignment, patients and observers; assessment of order effects including period, carry-over or spill-over effects; the choice of statistical analysis, the sample size utilized, and the special importance of patients lost to study or of faulty data points. The objective of this study was to review 3 journals for studies using split-mouth or cross-over designs to determine how the assumptions underlying these research designs are considered and applied in dental research. The majority of studies used adequate methods for treatment allocation and sequencing; however, many studies failed to take advantage of the research designs in the statistical analysis of data. In addition, very few studies considered the possibility of order effects or reduced bias through blinding procedures.

Clinical Trials as Topic↗
PubMed1990

Statistical methods for comparing dental diagnostic procedures.

In dental diagnosis, there are typically two or more clinical diagnostic procedures which may be used either independently or jointly to reach a conclusion regarding the presence of a particular disease in a patient. To determine which of these diagnostic procedures are more accurate, statistical methods may be applied to research data in which the true health status as well as the diagnosis provided by each clinical procedure are available on each observation. Results arising from this type of analysis can be of great interest to clinicians when the diagnostic procedures themselves are costly, painful, or even potentially harmful to the patient. Considered here is the special situation encountered in dental research in which each patient can have multiple concurrent cases of a certain disease such as caries, for then the statistical evaluation of diagnostic procedures is even further complicated. This report describes several statistical approaches for comparing the efficacy of diagnostic tests and illustrates their application on data from a study of diagnostic radiographs for dental caries.

Adult↗
PubMed1990

The length of uncomplicated human gestation.

By retrospective exclusion of gestations with known obstetric complications, maternal diseases, or unreliable menstrual histories, we found that uncomplicated, spontaneous-labor pregnancy in private-care white mothers is longer than Naegele's rule predicts. For primiparas, the median duration of gestation from assumed ovulation to delivery was 274 days, significantly longer than the predicted 266 days (P = .0003). For multiparas, the median duration of pregnancy was 269 days, also significantly longer than the prediction (P = .019). Moreover, the median length of pregnancy in primiparas proved to be significantly longer than that for multiparas (P = .0032). Thus, this study suggests that when estimating a due date for private-care white patients, one should count back 3 months from the first day of the last menses, then add 15 days for primiparas or 10 days for multiparas, instead of using the common algorithm for Naegele's rule.

Female↗
PubMed1988

Clinical indicators of radiographically detectable dental diseases in the adult patient.

A comprehensive analysis of the relationship between clinical observations in dental patients without symptoms and oral disease as detected by full-mouth and panoramic dental radiographs in a large population of patients has never been reported. Knowledge of these relationships is necessary in the design of a diagnostic decision process (clinical algorithm) that can predict which patients require dental radiographs for the diagnosis of dental caries or periodontal disease to be confirmed or refined. An accurate clinical algorithm could reduce the number of radiographs that are taken of certain routinely seen dental patients without symptoms, thus reducing unnecessary exposure x-radiation as well as potentially reducing health care costs for these patients. A sample of 602 adult men on whom a complete series of panoramic, posterior bitewing, and periapical dental radiographs and an independent oral examination were performed provided the opportunity to evaluate the relationship between clinically observed oral disease indicators and independent radiographic evidence of dental caries and periodontal disease. The analysis suggests that combinations of several clinical indicators can predict with some success which patients without symptoms will benefit most from oral radiographs. The presence of several carious lesions on oral examination was the best predictor of radiographic detection of dental caries. Clinical indicators tht appear to predict radiographic evidence of periodontal disease are clinical measures of pocket depth, mobility, and the patient's denture status. An important finding is that because of the high prevalence of gingivitis and plaque, these indicators were not related to radiographic evidence of periodontal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Longitudinal radiographic analysis of carious lesion progression.

Information on the rate at which carious lesions progress through the enamel of human teeth in an adult population was obtained from dental radiographs taken at 3-yr intervals, over a 10-yr period on 602 men. Clinical measures of calculus deposition, plaque accumulation, gingival inflammation, tooth mobility, periodontal pocket depth, and gingival recession were studied to find predictors that might be of value to the clinician for determining how frequently radiographs should be taken. We estimate that 50% of the enamel lesions on mesial and distal surfaces, if left untreated, would not progress into the dentin until 73 months had elapsed after the lesion was initiated. Significant differences in the progression rate were associated with the arch and tooth type. Patient age, number of decayed or filled surfaces, degree of gingival inflammation, amount of recession, and plaque accumulation were positively associated with more rapid caries progression, while greater numbers of teeth present were predictive of slower disease progression.

Adult↗
PubMed1988

Selecting the optimal threshold for the radiographic diagnosis of interproximal caries.

The declining prevalence of dental caries and changes in understanding about the progressive nature of this disease have led to recommendations that new diagnostic criteria be adopted. Selecting the optimum diagnostic threshold requires consideration of the probability of disease, distribution of true and false diagnoses at different test thresholds, and estimates of the consequences of treatment based on these diagnoses. Data from the Veterans Administration Dental Longitudinal Study were used to determine the distribution of true and false diagnoses at progressively more stringent diagnostic thresholds. Estimates of the consequences of treatment provided on the basis of true and false diagnoses were obtained from a randomly selected group of clinicians. The data were combined in a decision analysis to determine the "expected value" of operative treatment at each threshold under varying assumptions about the prevalence of disease, rate of disease progression, and value of treatment. No single diagnostic threshold consistently maximized the benefits of treatment. While patients with a high caries prevalence who experience infrequent recalls would benefit from a diagnostic threshold that includes early lesions, patients with a low caries prevalence who follow good recall schedules should benefit from a more conservative diagnostic threshold.

Dental Caries↗
PubMed1986

Indoor air pollution and pulmonary function growth in preadolescent children.

Results are reported from a study of the association between exposure to sidestream cigarette smoke or gas stove emissions and pulmonary function level and growth rate of 7,834 children seen at 2-5 annual visits between the ages of 6-10 years. Children whose mothers smoked one pack of cigarettes per day had levels of forced expiratory volume in one second (FEV1) at age eight that were 0.81% lower than children of nonsmoking mothers (p less than 0.0001), and FEV1 growth rates approximately 0.17% per year lower (p = 0.05). For a child of age eight with an FEV1 of 1.62 liters, this corresponds to a deficit in rate of change of FEV1 of approximately 3 ml/annum and a deficit of 13 ml at age eight. Children whose mothers smoked one pack per day had levels of forced vital capacity (FVC) at age eight that were 0.33% higher than children of nonsmokers (p = 0.12); however, their growth rates of FVC were 0.17% per year lower (p = 0.04). Because few mothers changed their smoking habits during the course of the study, it was not possible to determine whether the difference in rate of growth was due to current exposure or to an effect of prenatal and early childhood exposure on the course of development. The magnitude of the effect on FEV1 is consistent with deficits in FEV1 of up to 3% in early adult life due to childhood exposure to sidestream cigarette smoke. The importance of this relatively small effect will be evaluated further through follow-up of these children as they are exposed to other risk factors such as personal active smoking. The data provide some evidence for an association between gas stove exposure and pulmonary function level, especially at younger ages, but no evidence for an effect of gas stove exposure on growth rate.

Air Pollutants↗
PubMed1986

Examiner reliability in dental radiography.

In long-term investigations involving a large number of study participants, it is frequently necessary to employ the use of multiple examiners who must exhibit high levels of inter- and intra-examiner reliability in order to minimize examiner bias, which can distort scientific findings. This report on the calibration of four examiners in a large project investigating the efficacy of dental radiography shows high levels of examiner reliability using various statistical measures of agreement. Levels of intra-examiner agreement using Cohen's Kappa index were 0.75 and higher at baseline, and remained at approximately the same level (0.80) throughout the 24-month period of the study. The Kappa index of inter-examiner agreement among the six pairings of the four examiners ranged from 0.68 to 0.80 for caries and 0.72 and 0.83 for periodontal disease. Values of four statistical measures of agreement (proportional agreement, Kendall's rank correlation, Cohen's Kappa index, and Cohen's weighted Kappa index) were determined to show the importance of using measures, such as the Kappa index, which take chance agreement into account.

Adult↗
PubMed1985

Occupational lead neurotoxicity: improvement in behavioural effects after reduction of exposure.

To evaluate critical exposure levels and the reversibility of lead neurotoxicity a group of lead exposed foundry workers and an unexposed reference population were followed up for three years. During this period, tests designed to monitor neurobehavioural function and lead dose were administered. Evaluations of 160 workers during the first year showed dose dependent decrements in mood, visual/motor performance, memory, and verbal concept formation. Subsequently, an improvement in the hygienic conditions at the plant resulted in striking reductions in blood lead concentrations over the following two years. Attendant improvement in indices of tension (20% reduction), anger (18%), depression (26%), fatigue (27%), and confusion (13%) was observed. Performance on neurobehavioural testing generally correlated best with integrated dose estimates derived from blood lead concentrations measured periodically over the study period; zinc protoporphyrin levels were less well correlated with function. This investigation confirms the importance of compliance with workplace standards designed to lower exposures to ensure that individual blood lead concentrations remain below 50 micrograms/dl.

Behavior↗
PubMed1985

Effects of passive smoking on health of children.

Analysis of data on the effects of passive smoking obtained in preadolescent children from the Harvard Six-Cities Study demonstrates an exposure-response relationship between the number of smokers in the household and the reporting rates for doctor-diagnosed respiratory illness before age 2, history of bronchitis, wheeze most days and nights apart from colds, and a composite of symptoms defined as the lower respiratory index. Similarly, when only the amount currently smoked by the mother was used, the data indicated a relatively uniform increase in each of the reported diseases and symptoms. FEV1 was lower in children with smoking mothers compared to children of nonsmoking mothers. Rate of increases in FEV1 after adjusting for normal growth was significantly smaller in children of smoking mothers and was related also to amount smoked. Notably the effect on level of FVC was not seen and this finding, consistent in several studies, remains unexplained. Although children of smoking mothers were shorter on the average than children of nonsmoking mothers, no on-going passive smoking effect on height growth can be ascertained. All these differences are small and their medical significance remains to be defined.

Body Height↗
PubMedDate not supplied

Nonlinear growth curve analysis: estimating the population parameters.

A model for analysing longitudinal growth data with covariates is proposed. It assumes that the data for each individual follow a nonlinear growth model, with parameters unique to that individual. The parameters of individuals are assumed to vary in the population, with the population mean of each parameter dependent upon covariates. Several simple, two-stage methods of estimation are described and compared for making inferences about the effects of covariates upon growth. We also present a method of model validation for nonlinear models. These two-stage methods solve the inference problem we encounter when performing multiple cross-sectional analyses of the effects of covariates along the age scale. In addition, these two-stage methods permit us to study the effects of covariates upon growth rate, or other, possibly nonlinear, growth parameters. We find that some methods are better than others at reproducing the covariate effects observed in a series of age-specific analyses of the data.

Age Factors↗
PubMedDate not supplied

Longitudinal analysis of incomplete adolescent data.

An approach is illustrated for the analysis of longitudinal variables collected during adolescence. Since the method requires complete data, three techniques are compared for application when some individuals have missing values. These methods are implemented in a study of systolic blood pressures and dietary fat intakes collected longitudinally in adolescent girls. The value of adolescent systolic and fat variables in predicting systolic pressure in adult women is investigated.

Adolescent↗