Biochemical changes in muscles following denervation.
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Animals↗
Biomedical subjects
S Mazumdar
Publications and source records attributed to S Mazumdar.
Effect of continuation treatment on residual symptoms in late-life depression: how well is "well"?
UNLABELLED: The objectives of this report were (1) to describe residual depressive symptoms in elderly patients during continuation therapy with combined nortriptyline and interpersonal psychotherapy; (2) to determine which symptoms were persistent; (3) to determine the clinical correlates of residual depressive symptoms; and (4) to document distinct response pattern clusters during combined continuation therapy. METHOD: Box plot analyses of Hamilton depression scores and Global Assessment Scale scores, repeated twice monthly over 4 months, were conducted using data from 105 elderly depressives. Temporal trends in the data were examined via random regression analysis. Individual trajectories for each of the 105 patients were examined for patterns of response during continuation therapy. RESULTS: We observed a low mean Hamilton rating of 7 (SD = 2.3) at the start of continuation therapy and 5 (SD = 3.0) at the end. Both Hamilton and GAS scores showed modest but significant improvement over time. Hamilton variability was most apparent in symptoms of mood lowering, apathy, anxiety (psychological and somatic), feelings of guilt, anergia, insomnia, and loss of libido; other symptoms (retardation, agitation, hypochondriasis, loss of appetite, loss of weight, suicidal ideation, and loss of insight) showed clear resolution. A diagnosis of RDC situational depression was associated with higher levels of residual symptoms, while level of chronic medical burden, personality dysfunction, and social support were not. Examination of response patterns showed that a quarter of patients experienced one or more brief symptomatic exacerbations. CONCLUSION: On average, an excellent level of symptom resolution was achieved for most patients with Hamilton scores comparable to those seen in healthy elderly controls. These data support a position of therapeutic optimism in late-life depression and underscore full remission as an achievable therapeutic goal.
Aged↗
Accounting for covariate measurement error in a Cox model analysis of recurrence of depression.
When a covariate measured with error is used as a predictor in a survival analysis using the Cox model, the parameter estimate is usually biased. In clinical research, covariates measured without error such as treatment procedure or sex are often used in conjunction with a covariate measured with error. In a randomized clinical trial of two types of treatments, we account for the measurement error in the covariate, log-transformed total rapid eye movement (REM) activity counts, in a Cox model analysis of the time to recurrence of major depression in an elderly population. Regression calibration and two variants of a likelihood-based approach are used to account for measurement error. The likelihood-based approach is extended to account for the correlation between replicate measures of the covariate. Using the replicate data decreases the standard error of the parameter estimate for log(total REM) counts while maintaining the bias reduction of the estimate. We conclude that covariate measurement error and the correlation between replicates can affect results in a Cox model analysis and should be accounted for. In the depression data, these methods render comparable results that have less bias than the results when measurement error is ignored.
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Intent-to-treat analysis for longitudinal clinical trials: coping with the challenge of missing values.
Drop-out is a common phenomenon in clinical trials of drug treatments involving longitudinal assessments for a fixed duration of follow-up. For these trials intent-to-treat (IT) analysis is usually preferred because time effects are seen in practice. The IT analysis mandates that all subjects randomized to a treatment arm should be included in the analysis. The purpose of the present paper is to acquaint both clinicians and statisticians with recent statistical methodological advances in handling drop-outs and their usage for IT analysis. We discuss a sensitivity analysis of 12-month outcome data to investigate the efficacy of drug therapy from a longitudinal double-blind placebo-controlled clinical trial in the maintenance therapy of geriatric major depressive illness. Outcome measures consist of monthly Hamilton depression scores. The sensitivity analysis includes endpoint analysis, last observation carried forward analysis, repeated measures models and imputation models. Imputation models are based on multiple imputations of missing responses deriving from an 'as-treated' model. The model used imputed doses from a plausible treatment scenario after drop-out and a 'propensity-adjusted' model where the imputations for the drop-outs were obtained from the adhering subjects with the same probability to remain on study (propensity) given the observed trajectory prior to withdrawal. Issues related to bias and efficiency of the estimates obtained by different analyses are discussed. We recommend a more widespread use of imputation models for the IT analysis.
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Relation of daily mortality to air pollution: an analysis of 14 London winters, 1958/59-1971/72.
The relationship between daily deaths and daily concentrations of Smoke and SO2 in London, England for 14 winters during the years 1958-1959 through 1971-1972 has been explored. Three types of analyses were used: (1) year-by-year multiple regression; (2) stratification using nested quartiles of one pollutant within quartiles of the other; and (3) multiple regression of a special subset of high pollution days. An association was found with Smoke, but not with SO2. Whether a linear model with zero threshold or a threshold model best fits could not be determined unambiguously because of a statistical artifact. Reasons for preferring a threshold-type quadratic model are given.
Air Pollutants↗
Relationships of air pollution to health: results from the Pittsburgh study.
The evaluation of adverse health effects resulting from exposure to relatively low levels of regulated air pollutants is currently of major concern. The determination of short-term or acute effects is necessary for this evaluation. By using methodology that directly addressed the time series nature of the data, this study investigated acute health effects of daily levels of air pollution in Allegheny County, Pennsylvania, using both mortality and morbidity events as the adverse health response to ambient pollution. Health effects were determined using the air quality data for sulfur dioxide (SO2) and particulates as measured by the Coefficient of Haze from three monitoring stations located within the county. The mortality analysis provided a replication of a previous study performed in the New York area. The analysis was limited to the investigation of same day effects. Results indicated a possible association between heart disease mortality/morbidity and same day particulate levels. No association between SO2 and mortality/morbidity was seen at the present level of SO2. These findings were in agreement with those obtained in the New York City study and in a re-analysis of London winter data. The need for investigations of delayed effects and weather-mortality/morbidity relationships, as well as evaluation of hospital discharge record information, was stressed.
Air Pollutants↗
Receiver operating characteristic analysis for validating EEG sleep discrimination of elderly depressed and demented patients.
Receiver operating characteristic analysis is a useful tool in validating a diagnostic marker. This technique was applied to a discriminant function model using selected electroencephalographic sleep measures (sleep maintenance, percentage of rapid-eye-movement sleep, and percentage of indeterminate non-rapid-eye-movement sleep) in elderly patients with major depression or dementia of the Alzheimer type. The diagnostic model correctly classified 79.8% of elderly depressed and demented patients. The area under the curve was 0.86, statistically different from 0.5, which would be expected by chance (P less than .0001) and indicating good predictive power of the model. A logistic regression analysis demonstrated the reliability and stability of the diagnostic equation.
Aged↗
Renaturation of alkali-denatured T7 DNA molecules complexed with ethidium bromide.
Free and ethidium bromide (EB) complexed alkali denatured T7 DNA molecules were renatured at 58 and 62 degrees C respectively for 1--3 h. The structures of the renaturation products of the free candidates were as usual showing native like, branched and unrenatured DNA whereas the structures of the ethidium bromide complexed one were somewhat different, showing non-renatured loop-like and entangled regions present inbetween the renatured segments. On the basis of the linear base sequence of T7 DNA, these non-renatured parts are indicative of the inhibition of renaturation by the complexed EB molecules. Mapping of the non-renatured regions showed that they were present at some specific sites, which inturn suggested that the EB-binding has some base sequence specificity.
Base Sequence↗
Mortality of steelworkers employed in hot jobs.
This paper investigates possible relationships between heat stress of steelworkers and cause-specific mortality patterns. Prior to field investigation, jobs were identified which appeared to involve heat stress exposure. A selected sample of these jobs was surveyed for assessing the workers' environmental and metabolic heat load. These data were utilized to form different categories of heat stress. Mortality patterns of workers in jobs falling in each of the heat stress categories were analyzed by length of exposure for those workers from a cohort of 59,000 steelworkers who held one of the surveyed jobs. The comparison group consisted of workers who never worked in any of the work areas in which job were surveyed but were members of the same cohort. Findings of interest are: a deficit in mortality from cardiovascular disease for workers in jobs involving higher levels of environmental heat exposure; a high risk of death from cardiovascular disease for workers with less than 6 months of exposure and a downward trend in mortality for workers who remained on the job, indicating a possible relationship between inability to work in jobs involving heat stress and health; and, increased risks of digestive disease mortality among workers exposed to higher levels of environmental heat.
Adult↗
Benzodiazepines and zolpidem for chronic insomnia: a meta-analysis of treatment efficacy.
OBJECTIVE: To evaluate the efficacy of benzodiazepines and zolpidem tartrate in chronic insomnia based on a quantitative review of literature. DATA SOURCES: Articles from 1966 to 1996 were identified using MEDLINE, by a manual review of relevant journals, and from bibliographies of identified articles. STUDY SELECTION: Studies using randomized, double-blind, placebo-controlled, parallel or crossover designs with benzodiazepines or zolpidem in adults younger than 65 years with chronic insomnia (modified Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for primary insomnia) were selected for review. Self-report and polysomnographic measures of sleep-onset latency, total sleep time, number of awakenings, and sleep quality were selected as outcomes. DATA EXTRACTION: Twenty-two studies met the selection criteria. A combined test of Pvalues was performed, pooling broadly from the 22 studies to determine whether medication was superior to placebo. A combined test of effect sizes was performed on the subset of studies that reported effect size information to determine the magnitude of medication effect. DATA SYNTHESIS: A homogeneous sample of studies summarized 1894 patients treated for a median duration of 7 days. The combined test of P values demonstrated that medication was superior to placebo in all 4 outcome measures. Treatment response was moderate in magnitude by the combined test of effect sizes. CONCLUSIONS: Benzodiazepines and zolpidem produced reliable improvements in commonly measured parameters of sleep in patients with chronic insomnia. Relative to the chronic and recurring course of insomnia, both the limited duration of treatments studied and the lack of follow-up data from controlled trials represent challenges for developing evidence-based guidelines for the use of hypnotics in the management of chronic insomnia.
Adult↗