Power and sample size calculations

Dupont, William D.; Plummer, W. Dale

doi:10.1016/0197-2456(90)90005-m

Cited by 1,776 publications

(398 citation statements)

References 14 publications

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“…Haplotype analysis was performed in HaploView v.4.2 20. For power analysis, the power and sample size software PS v3.021 was used. With our sample size and a minor allele frequency of 0.33 (http://www.ncbi.nlm.nih.gov/projects/SNP/), we are able to detect true odds ratios (OR) for CH below 0.64 or above 1.51, respectively.…”

Section: Methodsmentioning

confidence: 99%

Screening of Two ADH4 Variations in a Swedish Cluster Headache Case–Control Material

et al. 2016

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BackgroundCluster headache (CH) is a severe neurovascular disorder and an increasing amount of evidence points to a genetic contribution to this disease. When CH was first described, it was observed that alcohol may precipitate an attack during the active phase of the disease. The alcohol dehydrogenase 4 (ADH4) gene encodes an enzyme which contributes to the metabolization of alcohol and is, therefore, an interesting candidate gene for CH. Two Italian groups have reported association of the single nucleotide polymorphism (SNP) rs1126671 located in the ADH4 gene with an increased risk of CH in Italy. In addition, one of the groups found an association between the ADH4 SNP rs1800759 and CH.ObjectiveTo perform a replication study on the ADH4 SNPs rs1126671 and rs1800759 in a large homogeneous Swedish case–control cohort in order to further investigate the possible contribution of ADH4 to CH.MethodsA total of 390 unrelated patients diagnosed with CH and 389 controls representing a general Swedish population were recruited to the study. DNA samples from patients and controls were genotyped for the two ADH4 SNPs rs1126671 and rs1800759 using quantitative real‐time polymerase chain reaction. Statistical analyses of genotype, allele and haplotype frequencies for the two SNPs were performed and compared between patients and controls.ResultsFor rs1126671, the minor allele frequency (A allele) was 32.8% (n = 254) in controls compared with 31.9% (n = 249) in CH patients. The minor allele frequency (A allele) of rs1800759 was 42.3% (n = 324) in controls and 41.9% (n = 327) in CH patients. Statistical analysis showed no significant differences in allele as well as in genotype or haplotype frequencies between the patient and control group for either SNP. This was also seen after stratifying the patient group for experiencing alcohol as a trigger factor.ConclusionsThe data did not support an association of the ADH4 SNPs rs1126671 and rs1800759 with CH. A comparison with previous studies revealed variance in genotype, allele, and haplotype frequencies among the different populations which might contribute to the contradictory results. Although a significant association with CH in Swedish case–control group was not found, ADH4 as a candidate gene for CH could not be excluded.

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Section: Methodsmentioning

confidence: 99%

Screening of Two ADH4 Variations in a Swedish Cluster Headache Case–Control Material

et al. 2016

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“…This lack of association is attributable to either a truly weak relationship or the relatively small sample size of our study. Given these data, there should be 80% power to detect associations if the OR was greater than 1.64 or less than 0.46 26 ; therefore, associations would have to be moderately strong to have a reasonable chance of detection in this study. Nevertheless, the estimated effect was in the anticipated direction for most of risk factors that failed to reach significance, with the possible exceptions of sex (with a higher prevalence in women despite higher clinical stroke incidence rates in men 27 ), triglycerides (with a higher prevalence for lower triglyceride levels), and BMI (with lower prevalence for higher BMI).…”

Section: Discussionmentioning

confidence: 99%

Cigarette Smoking and Other Risk Factors for Silent Cerebral Infarction in the General Population

Howard

Wagenknecht

Cai

et al. 1998

Stroke

206

166

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Background and Purpose-Silent cerebral infarctions (SCIs) have a prevalence between 10% and 40% in the transient ischemic attack population and have been associated with increased mortality and morbidity; however, little is known about the prevalence and risk factors for SCI in the general population. This report focuses on the role of cigarette smoking and other risk factors for SCI in the general population. Methods-MRI scans were performed on 1737 participants selected from the general population as part of the Atherosclerosis Risk in Communities Study. Smoking status and other major cerebrovascular risk factors were assessed, and associations between smoking status and SCIs were established with the use of ANCOVA. Results-Overall, the prevalence of SCI in this population aged 55 to 70 years was 11%. Cigarette smoking had an ordered association (Pϭ0.029) with the presence of SCI, with the odds ratio (OR) of nonsmoking participants exposed to environmental tobacco smoke being 1.06 (95% confidence interval [CI], 0.64 to 1.75) times as great as for nonsmokers not exposed; the OR of past smokers was 1.16 (95% CI, 0.74 to 1.83) times greater, and the OR of current smokers was 1.88 (95% CI, 1.13 to 3.13) times greater. An increased prevalence was also noted among black, older, and hypertensive participants. Conclusions-This report is among the first to examine the risk factors for SCI in the general population and finds a relatively high overall prevalence (11%). There is an ordered relationship between increasing exposure to cigarette smoke and the presence of SCI that parallels the relationship between smoking and carotid atherosclerosis. The magnitude of the association with smoking is substantial compared with the effect of hypertension and other traditional cerebrovascular risk factors. The reduction in prevalence of SCI between current and past smokers and the trend that increased pack-years of smoking is related to increased prevalence of SCI are both additional arguments for smoking avoidance and cessation. (Stroke. 1998;29:913-917.)

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“…This change in joint kinematics represents a large effect size (0.7) relative to the variability of these measures established in a previous study 22 23 Therefore, 20 physically active women from a university campus (age 5 21.0 6 1.3 years, height 5 167.9 6 5.9 cm, mass 5 61.8 6 8.4 kg) were recruited for this study. Being physically active was defined as participating in aerobic or athletic activity at least 3 times per week for at least 30 minutes each time.…”

Section: Participantsmentioning

confidence: 99%

Hip-Abductor Fatigue and Single-Leg Landing Mechanics in Women Athletes

Patrek

Kernozek

Willson

et al. 2011

Journal of Athletic Training

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Context: Reduced hip-abductor strength and muscle activation may be associated with altered lower extremity mechanics, which are thought to increase the risk for anterior cruciate ligament injury. However, experimental evidence supporting this relationship is limited. Objective: To examine the changes in single-leg landing mechanics and gluteus medius recruitment that occur after a hip-abductor fatigue protocol. Design: Descriptive laboratory study. Patients or Other Participants: Twenty physically active women (age = 21.0 ± 1.3 years). Intervention(s): Participants were tested before (prefatigue) and after (postfatigue) a hip-abductor fatigue protocol consisting of repetitive side-lying hip abduction. Main Outcome Measure(s): Outcome measures included sagittal-plane and frontal-plane hip and knee kinematics at initial contact and at 60 milliseconds after initial contact during 5 single-leg landings from a height of 40 cm. Peak hip and knee sagittal-plane and frontal-plane joint moments during this time interval were also analyzed. Measures of gluteus medius activation, including latency, peak amplitude, and integrated signal, were recorded. Results: A small (<1°) increase in hip-abduction angle at initial contact and a small (<1°) decrease in knee-abduction (valgus) angle at 60 milliseconds after contact were observed in the postfatigue landing condition. No other kinematic changes were noted for the knee or hip at initial contact or at 60 milliseconds after initial contact. Peak external knee-adduction moment decreased 27% and peak hip adduction moment decreased 24% during the postfatigue landing condition. Gluteus medius activation was delayed after the protocol, but no difference in peak or integrated signal was seen during the landing trials. Conclusions: Changes observed during single-leg landings after hip-abductor fatigue were not generally considered unfavorable to the integrity of the anterior cruciate ligament. Further work may be justified to study the role of hip-abductor activation in protecting the knee during landing.

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Power and sample size calculations

Cited by 1,776 publications

References 14 publications

Screening of Two ADH4 Variations in a Swedish Cluster Headache Case–Control Material

Screening of Two ADH4 Variations in a Swedish Cluster Headache Case–Control Material

Cigarette Smoking and Other Risk Factors for Silent Cerebral Infarction in the General Population

Hip-Abductor Fatigue and Single-Leg Landing Mechanics in Women Athletes

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