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At least 289 records · Page 16Linked to original sources
PubMed2005

Effects of updating linkage evidence across subsets of data: reanalysis of the autism genetic resource exchange data set.

Results of autism linkage studies have been difficult to interpret across research groups, prompting the use of ever-increasing sample sizes to increase power. However, increasing sample size by pooling disparate collections for a single analysis may, in fact, not increase power in the face of genetic heterogeneity. Here, we applied the posterior probability of linkage (PPL), a method designed specifically to analyze multiple heterogeneous data sets, to the Autism Genetic Resource Exchange collection of families by analyzing six clinically defined subsets of the data and updating the PPL sequentially over the subsets. Our results indicate a substantial probability of linkage to chromosome 1, which had been previously overlooked; our findings also provide a further characterization of the possible parent-of-origin effects at the 17q11 locus that were previously described in this sample. This analysis illustrates that the way in which heterogeneity is addressed in linkage analysis can dramatically affect the overall conclusions of a linkage study.

Autistic Disorder↗
PubMed2001

Reanalysis of full-length HIV type 1 group M subtype K and sub-subtype F2 with an MS-DOS bootscanning program.

Five new complete HIV-1 group M genome sequences have been published (Triques et al., AIDS Res Hum Retroviruses 2000;16:139-151). One of these clustered consistently with subtype F sequences, while two others were identified as representatives of a subcluster within the subtype F clade, called F2, and the two remaining sequences were described as a new subtype K. We reanalyzed these sequences by means of bootscanning and phylogeny, using a newly developed MS-DOS bootscanning program. Although our analysis does not contradict the existence of the new subtype K, it also indicates that in some regions the F2 sequences do not cluster with the F1 clade. This suggests that some fragments in the F2 sequences have an uncertain origin, and care should be taken when F2 sequences are used in analyses.

Genetic Techniques↗
PubMed2001

Efficacy of Adderall and methylphenidate in attention deficit hyperactivity disorder: a reanalysis using drug-placebo and drug-drug response curve methodology.

Because methylphenidate (MPH) is currently the most widely prescribed medication for attention deficit hyperactivity disorder (ADHD), several studies have used this as the touch-stone for evaluating the efficacy of a newer stimulant, Adderall. In a parallel-groups study of MPH (n = 20), Adderall (n = 20), and placebo (n = 18), Pliszka et al. (2000) reported that both medications were superior to placebo in improving parent, teacher, and clinician ratings of ADHD and associated behaviors. Compared with MPH, Adderall led to significantly more improvements in teacher and clinician ratings. The present study extends these results by addressing the issue of clinical significance using drug-placebo and drug-drug response curve analyses of the same data. The goal of this method is to answer the following questions about drug-placebo or drug-drug differences: Is the effect clinically meaningful? What does the effect tell us about individual responses? Is the effect due to symptom improvement, the prevention of worsening, or both? Our results show that the efficacy of Adderall to improve functioning is seen throughout the full range of improvement scores. In contrast, MPH showed a substantial effect for "mildly" and "much improved" but not for "very much improved." Our analyses also show that both Adderall and MPH prevent worsening of symptoms. They further suggest that, compared with the Conners Teacher Rating Scale, the Clinical Global Impressions scale may be more sensitive to improvements at the "well end" of the spectrum of functioning.

Algorithms↗
PubMed1980

A reanalysis of the factors influencing basal metabolic rate in normal adults.

A multiple regression analysis of several factors influencing basal metabolic rate (BMR) was performed using data for 223 subjects from the classic metabolism studies published by Harris and Benedict in 1919. These data had previously been analyzed by Kleiber using metabolic body size, the three-fourths power of body mass, as a predictor of BMR. His prediction equations were separated by sex and each contained components for age and height. Factors in the present analysis included sex, age, height, body mass, and estimated lean body mass (LBM). Lean body mass was found to be the single predictor of BMR. A best estimate prediction equation: BMR(cal/day) = 500 + 22 (LBM) is proposed. The previously presumed influences of sex and age are shown to add little to this estimation.

Adolescent↗
PubMed2003

Suggested lower cutoffs of serum zinc concentrations for assessing zinc status: reanalysis of the second National Health and Nutrition Examination Survey data (1976-1980).

BACKGROUND: The risk of zinc deficiency in populations can be estimated by comparing serum zinc data with statistically defined lower cutoffs derived from a presumably healthy population. Serum zinc data are available from a large sample of the US population assessed during the second National Health and Nutrition Examination Survey (NHANES II). Although the original analysis of these data considered fasting status and the time of day of blood sampling, it did not account for potentially confounding variables that may affect the serum zinc concentration, such as age, sex, and health status. OBJECTIVE: The objective was to describe variations in serum zinc concentration by age, sex, and other characteristics and to recommend lower cutoffs for presumably healthy persons. DESIGN: Serum zinc data from NHANES II were analyzed by using analysis of variance and covariance models to identify and describe variables significantly associated with serum zinc concentration; 2.5th percentile curves were produced and used to establish age- and sex-based lower cutoffs. RESULTS: Age and sex were significant confounders of serum zinc concentration, so separate lower cutoffs were derived for children and adolescent and adult males and females. Other minor confounding variables were identified. Tentative lower cutoffs for pregnancy and oral contraceptive use were also derived. CONCLUSIONS: The interpretation of population serum zinc data with the use of lower cutoffs should account for the age and sex of the subjects, pregnancy and oral contraceptive use, and fasting status and time of day of blood collection.

Adolescent↗
PubMed1983

Reanalysis and clarification of the structures of alpha-naphthoflavone dihydrodiols formed by uninduced and induced rat liver microsomes from Charles River CD and Sprague-Dawley rats.

The structures of alpha-naphthoflavone (ANF) dihydrodiols formed by uninduced and induced rat liver microsomes are identified by conversion of the metabolically formed ANF-dihydrodiols to the corresponding phenols. Comparison of these phenols with synthetic standards provides an unambiguous method for structural identification. The results of these studies are that hepatic microsomes from uninduced or phenobarbital, Aroclor-1254, 3-methylcholanthrene, or 5,6-benzoflavone induced Sprague-Dawley or Charles River CD rats each produce a major and a minor ANF-dihydrodiol identified as ANF-7,8-dihydrodiol and ANF-5,6-dihydrodiol, respectively.

Animals↗
PubMed2004

Individual differences in error processing: a review and reanalysis of three event-related fMRI studies using the GO/NOGO task.

Three previous studies using the GO/NOGO task were examined to characterize the pattern of functional activation seen during error-related processing. The large sample size (n = 44) also allowed investigation of the influence of individual differences in age, sex, self-reported absentmindedness and reaction speed on the level of activation. Errors were seen to activate a network of regions including the anterior cingulate cortex (ACC), pre-supplementary motor area (pre-SMA), bilateral insula, thalamus and right inferior parietal lobule. Split-half comparisons performed for each of the individual difference variables indicated greater ACC and pre-SMA activation for older subjects while slower responders showed greater activation in the parietal, lateral PFC, insula and ACC regions. Whereas males and females demonstrated equivalent levels of activation in both the ACC and insula, self-reported absentmindedness related to reduced activation in these regions. Our review of the current imaging literature on error-related activation indicates that, despite the use of a variety of other cognitive paradigms, the network of regions identified here is consistent with these previous studies, suggesting that these regions are critical to a 'general' error-related response. Furthermore, this response is, in part, influenced by individual differences in both demographic characteristics and behavioural performance.

Adolescent↗
PubMed2006

Reanalysis of two studies with contrasting results on the association between statin use and fracture risk: the General Practice Research Database.

BACKGROUND: Two recent case-control studies by Meier et al. and van Staa et al. used the UK General Practice Research Database (GPRD) to examine the association between the use of statins and the risk of fractures, with different results. The objective of the present study was to examine methodological explanations for the discrepant results. METHODS: We created two datasets, which mimicked the previous study designs: a 'selected population' (SP) case-control dataset, with fracture cases matched to controls nested within a selected cohort (Meier et al.), and an 'entire population' (EP) case-control dataset, with both cases and controls sampled from the total GPRD population (van Staa et al.). Cases and controls were matched by gender, age (year of birth or 5 year age bands), and general practice. RESULTS: The study included 131 855 fracture cases. The crude odds ratio (OR) for hip fracture in statin users was 0.37 (95% CI 0.27-0.52) in the SP and 0.54 (95% CI 0.39-0.74) in the EP dataset. This difference was reduced when matching by year of birth, rather than by 5 year age bands: crude ORs were 0.58 (95% CI 0.43-0.79) and 0.61 (95% CI 0.44-0.88), respectively. In the SP dataset, 37% of the cases could be matched by year of birth, while this was achieved for 99% in the 'EP' dataset. The exposure time-window, the selection of confounders, and exclusion of high-risk patients also influenced results. CONCLUSION: Residual confounding by a matching variable and different definitions of the exposure time window explained differences in results. In case-control studies of drug use and fracture risk, broad matching criteria for age should be avoided and the selection of the time-window for exposure should be carefully considered.

Aged↗
PubMed1990

Patterns of transmission and severity of measles infection: a reanalysis of data from the Machakos area, Kenya.

Data on measles from the project in the Machakos District, Kenya, 1974-1981, were reanalyzed. In families with several cases, secondary cases (children infected in the home) had a relative mortality risk of 3.00 (95% confidence interval [CI]: 1.55-5.80) compared with index cases who caught infection from someone outside the home. The case fatality rate (CFR) may be higher among secondary cases exposed to two or more index cases than among those exposed to only one index case (relative risk [RR] = 2.47; 95% CI: 0.93-6.56). The CFR was also higher among secondary cases exposed to a fatal index case than among those exposed to an index case who survived (RR = 4.69; 95% CI: 1.64-13.41). Children aged 12-23 months and those greater than or equal to 5 years were more likely than other age groups to have been infected by someone outside the home. During the course of the project the CFR in families with several cases was reduced from 8.8% to 2.7%. Though there is no general explanation for this tendency, it was observed that the proportion of secondary cases per index case was reduced during the last part of the project (odds ratio = 0.73; 95% CI: 0.56-0.95).

Age Factors↗
PubMed2026

A reanalysis of the Hitachi cohort study evaluating the effectiveness of low-dose CT screening for lung cancer.

The effectiveness of low-dose thoracic computed tomography (CT) screening for lung cancer for non-smokers or light smokers has been unclear. The results of the Hitachi cohort study performed by the conventional multivariable analysis suggested the reduction of lung cancer mortality by thoracic CT screening, but also revealed the lower all-cause mortality in the CT group, which indicated the existence of self-selection bias. Because the background of the subjects in the CT screening group and that in the X-ray screening group were very different, it is critical to adjust appropriately the confounding factors. In this brief report, we describe a re-evaluation of the results of the Hitachi Cohort Study performed by using more flexible methods, propensity score matching and inverse probability weighting.

epidemiology/public health↗
PubMed1989

Cigarette smoking and lung cancer: reanalysis of the British doctors' data.

Attention has focused recently on the recessive oncogenesis model, according to which inactivation of both alleles of specific genes leads to cancer. A mathematical formulation of this model was fitted to the lung cancer incidence data from a cohort study among British doctors. The model described the data well. One implication is that age influences lung cancer risk among smokers independently of duration of smoking. A study of dose-response within the framework of the model shows that the data are consistent with various interpretations regarding the relative importance of daily level of smoking and duration of smoking in determining lung cancer risk.

Adult↗
PubMed2002

Endogenous sex hormones and breast cancer in postmenopausal women: reanalysis of nine prospective studies.

BACKGROUND: Reproductive and hormonal factors are involved in the etiology of breast cancer, but there are only a few prospective studies on endogenous sex hormone levels and breast cancer risk. We reanalyzed the worldwide data from prospective studies to examine the relationship between the levels of endogenous sex hormones and breast cancer risk in postmenopausal women. METHODS: We analyzed the individual data from nine prospective studies on 663 women who developed breast cancer and 1765 women who did not. None of the women was taking exogenous sex hormones when their blood was collected to determine hormone levels. The relative risks (RRs) for breast cancer associated with increasing hormone concentrations were estimated by conditional logistic regression on case-control sets matched within each study. Linear trends and heterogeneity of RRs were assessed by two-sided tests or chi-square tests, as appropriate. RESULTS: The risk for breast cancer increased statistically significantly with increasing concentrations of all sex hormones examined: total estradiol, free estradiol, non-sex hormone-binding globulin (SHBG)-bound estradiol (which comprises free and albumin-bound estradiol), estrone, estrone sulfate, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone. The RRs for women with increasing quintiles of estradiol concentrations, relative to the lowest quintile, were 1.42 (95% confidence interval [CI] = 1.04 to 1.95), 1.21 (95% CI = 0.89 to 1.66), 1.80 (95% CI = 1.33 to 2.43), and 2.00 (95% CI = 1.47 to 2.71; P(trend)<.001); the RRs for women with increasing quintiles of free estradiol were 1.38 (95% CI = 0.94 to 2.03), 1.84 (95% CI = 1.24 to 2.74), 2.24 (95% CI = 1.53 to 3.27), and 2.58 (95% CI = 1.76 to 3.78; P(trend)<.001). The magnitudes of risk associated with the other estrogens and with the androgens were similar. SHBG was associated with a decrease in breast cancer risk (P(trend) =.041). The increases in risk associated with increased levels of all sex hormones remained after subjects who were diagnosed with breast cancer within 2 years of blood collection were excluded from the analysis. CONCLUSION: Levels of endogenous sex hormones are strongly associated with breast cancer risk in postmenopausal women.

Aged↗
PubMed1998

Incidence of dementia and Alzheimer's disease: a reanalysis of data from Rochester, Minnesota, 1975-1984.

For both dementia and Alzheimer's disease (AD), data regarding incidence rates in the oldest old and time trends in incidence are limited. The authors reanalyzed previously reported data on the incidence of dementia and AD in Rochester, Minnesota, from 1975 through 1984, using three new strategies. First, incidence rates were corrected by removing age-, sex-, and calendar year-specific prevalent cases from the census-derived denominator figures. Second, incidence figures for persons above age 84 years were disaggregated. Third, time trends were investigated graphically using age-specific curves and birth cohort curves. Dementia diagnosis and AD diagnosis followed defined ad hoc criteria. Analyses were conducted for men, women, and both sexes combined, and for dementia and AD separately. The age-specific incidence rates were similar in men and women, continued to increase after age 84 years, and remained stable over time for both dementia and AD. No birth cohort effect was present for either dementia or AD. The similar risks seen in men and women, the continuing increase in incidence after age 84 years, and the stability of incidence over time have important implications for etiologic research on AD.

Age Distribution↗