Tag: statistics

Sports Med. 2022 Oct 8. doi: 10.1007/s40279-022-01766-0. Online ahead of print.

ABSTRACT

BACKGROUND AND OBJECTIVE: Meta-analysis and meta-regression are often highly cited and may influence practice. Unfortunately, statistical errors in meta-analyses are widespread and can lead to flawed conclusions. The purpose of this article was to review common statistical errors in meta-analyses and to document their frequency in highly cited meta-analyses from strength and conditioning research.

METHODS: We identified five errors in one highly cited meta-regression from strength and conditioning research: implausible outliers; overestimated effect sizes that arise from confusing standard deviation with standard error; failure to account for correlated observations; failure to account for within-study variance; and a focus on within-group rather than between-group results. We then quantified the frequency of these errors in 20 of the most highly cited meta-analyses in the field of strength and conditioning research from the past 20 years.

RESULTS: We found that 85% of the 20 most highly cited meta-analyses in strength and conditioning research contained statistical errors. Almost half (45%) contained at least one effect size that was mistakenly calculated using standard error rather than standard deviation. In several cases, this resulted in obviously wrong effect sizes, for example, effect sizes of 11 or 14 standard deviations. Additionally, 45% failed to account for correlated observations despite including numerous effect sizes from the same study and often from the same group within the same study.

CONCLUSIONS: Statistical errors in meta-analysis and meta-regression are common in strength and conditioning research. We highlight five errors that authors, editors, and readers should check for when preparing or critically reviewing meta-analyses.

PMID:36208412 | DOI:10.1007/s40279-022-01766-0

J Dig Dis. 2022 Oct 8. doi: 10.1111/1751-2980.13136. Online ahead of print.

ABSTRACT

BACKGROUND: Population-based prospective studies on the associations of cigarette smoking, alcohol drinking and primary liver cancer are still limited in mainland China, our study was designed to evaluate such relationships in middle-aged Chinese men.

METHODS: Self-reported habits of smoking and alcohol drinking were obtained from all cohort members at the baseline survey. The outcomes were identified through in-person follow-up and annual record linkage to multiple statistics of vital and cancer registration. Age-adjusted and multivariable-adjusted hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) were estimated utilizing the Cox regression model.

RESULTS: After a median follow-up time of 12.31 years, 329 incident cases of primary liver cancer occurred among 45 266 male participants. Compared with never smokers, former smoking was positively associated with liver cancer risk, with a multivariable-adjusted HR of 1.42 (95% CI, 1.02-1.98). Individuals who have smoked for more than 40 years have an increased risk of liver cancer by 49% (HR_{>40 years} = 1.49, 95% CI, 1.04-2.14). The association of alcohol drinking with liver cancer did not show any statistical significance.

CONCLUSION: Our study provided evidence that cigarette smoking was positively associated with an increased liver cancer risk among Chinese men. Attention to such non-viral modifiable risk factors to prevent liver cancer effectively is needed.

PMID:36208410 | DOI:10.1111/1751-2980.13136

Environ Monit Assess. 2022 Oct 8;194(12):857. doi: 10.1007/s10661-022-10543-5.

ABSTRACT

Heavy metals in indoor dust are associated with health risks in humans. However, in Shijiazhuang, a city in northern China with severe haze, no research has been published on this topic. To determine the content, distribution characteristics, and sources of heavy metals in indoor dust in the city of Shijiazhuang, indoor dust samples from 33 sampling points in the main urban area of Shijiazhuang were collected and tested. Concentrations of Cu, Ni, Cr, Zn, Cd, and Pb were 87.0, 35.1, 104.4, 568.0, 1.980, and 187.6 mg·kg^-1, respectively; their levels have been discussed statistically in comparison with the reported values in other cities in China. The sources of heavy metals were analyzed using enrichment factor, correlation coefficient, and principal component analysis. The results showed that the levels of all six elements in indoor dust in Shijiazhuang exceeded the background values of soil in Hebei Province. Among these, Cd, Pb, and Zn were significantly enriched. The enrichment factors of Cu, Ni, and Cr were below 10, and their levels at different sampling points were similar, indicating their geogenic source. The corresponding pollution levels of Cd, Pb, and Zn were relatively high, and their levels at different points were significantly different and correlated, indicating that they were derived mainly from transportation. Additionally, the level of Zn was significantly affected by the indoor environment. Our findings provide a basis for conducting health risk assessments in the future.

PMID:36208397 | DOI:10.1007/s10661-022-10543-5

Forensic Sci Med Pathol. 2022 Oct 8. doi: 10.1007/s12024-022-00536-8. Online ahead of print.

ABSTRACT

Identifying charred human remains poses a challenge to forensic laboratories. High temperature completely incinerates the superficial tissues and partially destroys bones, forcing the forensics to seek an alternative, for bones and teeth, forensic material that should quickly and cheaply deliver DNA of sufficient quantity and quality. We sought, other than rib cartilage, types of cartilages that could serve as a DNA source. DNA was isolated from the fibrous cartilage of a fibrous ring of intervertebral L1-L2 discs sampled from charred cadavers or charred body fragments: 5 victims of car fires, 1 victim of combustion during a residential house gas explosion, and 3 victims of nitroglycerin explosion. DNA was isolated by the column method. DNA quality and concentration were assessed by RT-PCR and multiplex PCR for 23 autosomal and 17 Y chromosome STR loci. STR polymorphism results obtained by capillary electrophoresis served for likelihood ratio (LR) calculations. DNA concentration in relation to the cadaver’s age and post-mortem interval (PMI) were analyzed. All samples (n = 9) yielded good-quality DNA in quantities (0.57-17.51 ng/µL for T. Large autosomal sequence) suitable for STR-based amplification. The isolated DNA characterized a low degradation index (0.80-1.99), and we were able to obtain complete genetic profiles. In each of the nine cases, the genotyping results allowed identifying the victims based on comparative material from the immediate family. The results demonstrate the usefulness of human intervertebral disc fibrocartilage as an alternative DNA source for the genetic identification of charred bodies or charred torso fragments.

PMID:36208368 | DOI:10.1007/s12024-022-00536-8

Lifetime Data Anal. 2022 Oct 8. doi: 10.1007/s10985-022-09579-z. Online ahead of print.

ABSTRACT

The proportional hazards (PH) model is, arguably, the most popular model for the analysis of lifetime data arising from epidemiological studies, among many others. In such applications, analysts may be faced with censored outcomes and/or studies which institute enrollment criterion leading to left truncation. Censored outcomes arise when the event of interest is not observed but rather is known relevant to an observation time(s). Left truncated data occur in studies that exclude participants who have experienced the event prior to being enrolled in the study. If not accounted for, both of these features can lead to inaccurate inferences about the population under study. Thus, to overcome this challenge, herein we propose a novel unified PH model that can be used to accommodate both of these features. In particular, our approach can seamlessly analyze exactly observed failure times along with interval-censored observations, while aptly accounting for left truncation. To facilitate model fitting, an expectation-maximization algorithm is developed through the introduction of carefully structured latent random variables. To provide modeling flexibility, a monotone spline representation is used to approximate the cumulative baseline hazard function. The performance of our methodology is evaluated through a simulation study and is further illustrated through the analysis of two motivating data sets; one that involves child mortality in Nigeria and the other prostate cancer.

PMID:36208362 | DOI:10.1007/s10985-022-09579-z

J Relig Health. 2022 Oct 8. doi: 10.1007/s10943-022-01666-7. Online ahead of print.

ABSTRACT

The Yule-Simpson paradox indicates contradicting statistical outcomes for the pooled sample and for each stratified group separately. The objective of the current study is to demonstrate this paradox. The sample is based on a 2015-2016 longitudinal survey carried out by the Israeli Central Bureau of Statistics. The sample includes 1194 individuals, where the responses of 1140 individuals were assessed twice (in 2015 and 2016) and the responses of 54 individuals were recorded only once. This gives a total sample of 2334 observations × years. The sample includes 609 females and 585 males. We use the limited dependent binary probit regression model. The dependent variable is a dummy variable that equals 1 if the individual is obese (BMI ≥ 30, where BMI = WEIGHT ÷ (HEIGHT²), WEIGHT is measured in kilograms and HEIGHT is measured in meters) and zero otherwise. The independent variables are the denomination (secular vs. ultra-Orthodox) and age in years. Findings suggest that on the one hand, for the pooled sample of 21-50-year-old females and males, results clearly support the conclusion that compared with secular Israeli Jews, projected probability of obesity (BMI ≥ 30) among ultra-Orthodox Israeli Jews is higher (p = 0.0128). On the other hand, when stratified by gender, one cannot reject the opposite conclusion, according to which projected probability of obesity is equal for all cohorts among ultra-Orthodox and secular Israeli Jews. Research findings thus stress the importance of cautious and rigorous statistical analysis and robustness tests prior to statistical inference.

PMID:36208353 | DOI:10.1007/s10943-022-01666-7

Clin Oral Investig. 2022 Oct 8. doi: 10.1007/s00784-022-04736-y. Online ahead of print.

ABSTRACT

OBJECTIVES: To assess and compare the diagnostic performance of CT-like images based on a three- dimensional (3D) T1-weighted spoiled gradient-echo sequence (3D T1 GRE) with CT in patients with acute traumatic fractures of the mandible.

MATERIALS AND METHODS: Subjects with acute mandibular fractures diagnosed on conventional CT were prospectively recruited and received an additional 3 T MRI with a CT-like 3D T1 GRE sequence. The images were assessed by two radiologists with regard to fracture localization, degree of dislocation, and number of fragments. Bone to soft tissue contrast, diagnostic confidence, artifacts, and overall image quality were rated using a five-point Likert-scale. Agreement of measurements was assessed using an independent t-test.

RESULTS: Fourteen subjects and 22 fracture sites were included (26 ± 3.9 years; 4 females, 10 males). All traumatic fractures were accurately detected on CT-like MRI (n = 22, κ 1.00 (95% CI 1.00-1.00)). There was no statistically significant difference in the assessment of the fracture dislocation (axial mean difference (MD) 0.06 mm, p = 0.93, coronal MD, 0.08 mm, p = 0.89 and sagittal MD, 0.04 mm, p = 0.96). The agreement for the fracture classification as well as the inter- and intra-rater agreement was excellent (range κ 0.92-0.98 (95% CI 0.96-0.99)).

CONCLUSION: Assessment of mandibular fractures was feasible and accurate using CT-like MRI based on a 3D T1 GRE sequence and is comparable to conventional CT.

CLINICAL RELEVANCE: For the assessment of acute mandibular fractures, CT-like MRI might become a useful alternative to CT in order to reduce radiation exposure particularly in young patients.

PMID:36208329 | DOI:10.1007/s00784-022-04736-y

J Biol Inorg Chem. 2022 Oct 8. doi: 10.1007/s00775-022-01966-z. Online ahead of print.

ABSTRACT

LPMOs are enzymes which catalyse the oxidation of a C-H bond within polysaccharides, leading to their oxidative cleavage. To achieve this, LPMOs employ highly reactive oxidising intermediates, the generation of which is likely coupled to substrate binding to the enzyme. The nature of this coupling is unknown. Here we report a statistical comparison for four three-dimensional structures of an AA9 LPMO crystallised in the same space group but in different oxidation and substrate-binding states, to determine which significant structural perturbations occur at the enzyme upon either oxidation state change or the binding of substrate. In a novel step, we determine the global random error associated with the positional coordinates of atoms using the method of moments to ascertain the statistical estimators of Gaussian distributions of pairwise RMS differences between individual atoms in different structures. The results show that a change in the oxidation state of the copper leads to no significant structural changes, and that binding of the substrate leads to a single change in the conformation of a tryptophan residue. This tryptophan has previously been identified as part of a charge transfer pathway between the active site and the external surface of the protein, and the structural change identified herein may be part of the substrate-enzyme coupling mechanism.

PMID:36208326 | DOI:10.1007/s00775-022-01966-z

Pediatr Surg Int. 2022 Oct 8. doi: 10.1007/s00383-022-05257-1. Online ahead of print.

ABSTRACT

PURPOSE: Preterm infants are more susceptible to necrotizing enterocolitis (NEC) than term Queryinfants. This may be due to a relative paucity of Lgr5⁺ or Bmi1⁺-expressing intestinal stem cells (ISCs) which are responsible for promoting intestinal recovery after injury. We hypothesized that the cellular markers of Lgr5⁺ and Bmi1⁺, which represent the two distinct ISC populations, would be lower in younger mice compared to older mice. In addition, we hypothesized that experimental NEC would result in a greater loss of Lgr5⁺ expression compared to Bmi1⁺ expression.

METHODS: Transgenic mice with EGFP-labeled Lgr5 underwent euthanasia at 10 different time points from E15 to P56 (n = 8-11/group). Lgr5⁺-expressing ISCs were quantified by GFP ELISA and Bmi1⁺ was assessed by qPCR. In addition, Lgr5^EGFP mice underwent experimental NEC via formula feeding and hypoxic and hypothermic stress. Additional portions of the intestine underwent immunostaining with anti-GFP or anti-Bmi1⁺ antibodies to confirm ELISA and PCR results. For statistical analysis, p < 0.05 was significant.

RESULTS: Lgr5⁺ and Bmi1⁺expression was lowest in embryonal and early postnatal mice and increased with age in all segments of the intestine. Experimental NEC was associated with loss of Lgr5⁺-expressing ISCs but no significant change in Bmi1⁺ expression.

CONCLUSION: Lgr5⁺ and Bmi1⁺ expression increase with age. Lgr5⁺-expressing ISCs are lower following experimental necrotizing enterocolitis while Bmi1⁺ expression remains relatively unchanged. Developing a targeted medical therapy to protect the low population of ISCs in preterm infants may promote tissue recovery and regeneration after injury from NEC.

PMID:36208323 | DOI:10.1007/s00383-022-05257-1

Eur Spine J. 2022 Oct 8. doi: 10.1007/s00586-022-07415-4. Online ahead of print.

ABSTRACT

PURPOSE: Lumbosacral transitional vertebra (LSTV) is a congenital anomaly of the lumbosacral junction. Its prevalence is variable in the literature such as its association with low back pain. The aim of this study was to identify the prevalence of LSTV in a southern European population, and its correlation with low back pain.

METHODS: A retrospective review of 639 thoraco-abdomino-pelvic consecutive CT-scans between January 2019 and November 2020 was performed. The presence of LSTV was classified into type II, III, IV based on Castellvi’s classification. To investigate the association with low back pain, Oswestry Low Back Disability Questionnaire (ODI) and the EuroQol-5D-3L questionnaire was applied.

RESULTS: The prevalence of LSTV was 24.9% (142 of 571). 37,3% were type IIb, 31,0% were type IIa, 13,4% were type IIIa, 9.9% were type IIIb and 8.5% were type IV. Individuals with LSTV were more likely to report low back pain and have a higher ODI score (OR:0.392, 95% CI:0.192-0.802, p = 0.010), (OR: 1050, 95% CI: 1029-1072, p < 0.01). Castellvi’s type IV showed a significantly higher ODI when compared to type II (OR:1059, 95% CI:1019-1100, p = 0,04). There was no statistical difference in the EuroQol-5D-3L score between two groups (OR:1085, 95% CI: 0.459-2.560, p = 0.852).

CONCLUSION: This population-based study adds to the literature the prevalence of LSTV in a southern European population. LSTV was associated with low back pain. However, this difference did not translate into a loss of quality life. Type IV was associated with higher functional disability when compared with type II.

PMID:36208322 | DOI:10.1007/s00586-022-07415-4