Epidemiological studies are essential in medicine and public health as they help identify risk factors and causes of diseases. Additionally, they are key to planning, implementing, and evaluating health interventions aimed at preventing and controlling the spread of diseases. Among these studies, analytical observational studies, such as cross-sectional, case-control, and cohort studies, are the most used. The validity of their results largely depends on the robustness of the design, execution, and statistical analysis. Objective: The objective of this study is to examine the most common errors in the selection of methodological design and statistical tests in analytical observational studies and to provide recommendations to correct them. Methodology: A comprehensive review of the available literature on methodology in epidemiological observational studies was conducted, focusing on cross-sectional, case-control, and cohort studies. Common errors in the selection of designs and statistical tests were identified and analyzed. Results and Conclusions: Errors in the selection of methodological design and statistical tests are common in epidemiological observational studies. Based on the identified errors, a series of recommendations is provided to improve the selection of methodological design and statistical tests, thereby increasing the reliability of the results in cross-sectional, case-control, and cohort studies.

Objective: The aim of this study was to test the hypothesis that the duration of breastfeeding in infancy reduces the risk of childhood leukemia or lymphoma, and modifies the risk of developing functional gastrointestinal disorders (FGIDs). Subjects and Methods: This case-control study involved the recruitment of children with lymphoid malignancy and functional gastrointestinal symptoms with healthy children as controls. Focused questionnaires were used to collect data on breastfeeding history and other key risk factors. Univariate and multivariate analyses were undertaken. Results: Of the 334 children with lymphoid malignancy, 65% were male. The control group included 334 age- and sex-matched participants. Most (n = 189; 56.6%) of the children with leukemia were <10 years of age. Differences between cases and controls included the duration of breastfeeding (p < 0.0001), mean birthweight (p < 0.001), maternal age (p < 0.001), paternal age (p < 0.001), birth order (p < 0.001), mean number of children (p < 0.001), BMI percentile (p = 0.042), and maternal smoking (p = 0.012). Breastfeeding duration of up to 6 months\' duration, when compared with feeding of longer than 6 months, was associated with increased odds ratios (OR) for acute lymphoblastic leukemia (OR = 3.43, 95% confidence interval [CI] 2.37-4.98; p < 0.001), Hodgkin\'s lymphoma (OR = 1.58, 95% CI: 0.88-2.84, p = 0.120), Non-Hodgkin\'s lymphoma (OR = 2.14, 95% CI: 1.25-3.65, p = 0.005), and overall (OR = 1.95, 95% CI: 1.40-2.71, p < 0.001). Cases also differed from controls with regard to FGIDs, such as stomach ache (p < 0.001), dyspepsia (p < 0.001), early satiety (p = 0.017), bowel satisfaction (p < 0.001), bloating (p < 0.001), nausea (p = 0.005), vomiting (p = 0.039), constipation (p = 0.003), diarrhea (p = 0.010), gastrointestinal canal congestion (p =0.039), muscle aches pains (p = 0.008), fecal incontinence (p = 0.021), and indigestion (p = 0.003). A multivariate stepwise regression analysis revealed that maternal smoking (p < 0.001), formula feeding (p < 0.001), duration of breastfeeding (p < 0.001), birth order (p = 0.002), mother\'s age (p = 0.004) and the child\'s birthweight (p = 0.009) were predictors for leukemia. Further analysis showed that dyspepsia (p < 0.001), gastrointestinal tract canal congestion (p < 0.001), constipation (p = 0.009), diarrhea (p = 0.013), bowel satisfaction (p = 0.021), bloating (p = 0.022), duration of breastfeeding (p < 0.001), and stomach ache (p = 0.025) were significant predictors for developing FGID symptoms after adjusting for age, gender, and other confounding variables. Conclusion: This study confirmed that breastfeeding has some effect on reducing possible risk of childhood lymphoma and leukemia and FGID symptoms compared with healthy control children.

BACKGROUND: The matched case-control design, up until recently mostly pertinent to epidemiological studies, is becoming customary in biomedical applications as well. For instance, in omics studies, it is quite common to compare cancer and healthy tissue from the same patient. Furthermore, researchers today routinely collect data from various and variable sources that they wish to relate to the case-control status. This highlights the need to develop and implement statistical methods that can take these tendencies into account.
RESULTS: We present an R package penalizedclr, that provides an implementation of the penalized conditional logistic regression model for analyzing matched case-control studies. It allows for different penalties for different blocks of covariates, and it is therefore particularly useful in the presence of multi-source omics data. Both L1 and L2 penalties are implemented. Additionally, the package implements stability selection for variable selection in the considered regression model.
CONCLUSIONS: The proposed method fills a gap in the available software for fitting high-dimensional conditional logistic regression models accounting for the matched design and block structure of predictors/features. The output consists of a set of selected variables that are significantly associated with case-control status. These variables can then be investigated in terms of functional interpretation or validation in further, more targeted studies.

Objective: Previous studies have reported controversial results on the association between gout and the risk of cancer. This study aimed to investigate the relationship between gout and the incidence of head and neck cancer (HNC). Methods: The data of participants who underwent health checkups in 2009 were analyzed using the National Health Insurance Database in South Korea. A total of 14,348 HNC patients and 57,392 control participants were analyzed for a prior history of gout. Overlap weighting was applied, and odds ratios (ORs) of gout for HNC patients were analyzed. The overlap-weighted model adjusted for demographic, socioeconomic, and lifestyle factors and comorbidities. HNC sites were classified as oral cavity cancer, oropharyngeal cancer, nasopharyngeal cancer, hypopharyngeal cancer, nasal cavity/sinus cancer, larynx cancer, or salivary gland cancer, and the ORs of gout were estimated for each site. Results: Overall, patients with HNC had 1.12-fold greater odds of having gout (95% confidence intervals [CIs] = 1.04-1.20). According to the site of HNC, oral cavity cancer, oropharynx cancer, and larynx cancer demonstrated high odds of having gout (OR = 1.25, 95% CI = 1.16-1.34 for oral cavity cancer; OR = 1.08, 95% CI = 1.01-1.15 for oropharynx cancer; and OR = 1.12, 95% CI = 1.06-1.20 for larynx cancer). On the other hand, nasal cavity/sinus cancer, nasopharynx cancer, and salivary gland cancer presented low odds of having gout (OR = 0.78, 95% CI = 0.72-0.84 for nasal cavity/sinus cancer; OR = 0.89, 95% CI = 0.83-0.96 for nasopharynx cancer; and OR = 0.88, 95% CI = 0.81-0.96 for salivary gland cancer). Conclusions: A prior history of gout was associated with a high overall incidence of HNC. Oral cavity cancer, oropharynx cancer, and larynx cancer have a high incidence in gout patients. However, nasal cavity/sinus cancer, nasopharyngeal cancer, and salivary gland cancer have low incidences in gout patients. The impact of gout on HNC risk should be specifically considered according to the site of the HNC.

BACKGROUND: Fatigue is a common symptom that negatively affects the outcomes and functions of rheumatoid arthritis (RA) patients. This study aimed to assess the fatigue by two scales and validate their consistency, also to comprehensively evaluate fatigue-related risk factors in RA patients.
METHODS: In this case-control study, the fatigue of 160 RA patients and 60 healthy controls was evaluated by the Bristol Rheumatoid Arthritis Fatigue Multi-Dimensional Questionnaire (BRAF-MDQ) and the Chinese version of the Brief Fatigue Inventory (BFI-C). The 28-joint disease activity score using erythrocyte sedimentation rate of RA patients was assessed.
RESULTS: The BRAF-MDQ and BFI-C scores were elevated in RA patients versus healthy controls (all p < .001). Interestingly, BRAF-MDQ global fatigue score positively correlated with BFI-C global fatigue score in both RA patients (r = .669, p < .001) and healthy controls (r = .527, p < .001); meanwhile, Kendall\'s tau-b test showed a high consistency between BRAF-MDQ and BFI-C global fatigue scores in RA patients (W = 0.759, p < .001) and healthy controls (W = 0.933, p < .001). Notably, higher education level (В = -4.547; 95% confidence interval: -7.065, -2.029; p < .001) and swollen joint count (В = 1.965; 95% confidence interval: 1.375, 2.554; p < .001) independently related to BRAF-MDQ global fatigue score; higher education level (В = -0.613; 95% confidence interval: -0.956, -0.269; p = .001) and clinical disease activity index (В = 0.053; 95% confidence interval: 0.005, 0.102; p = .032) independently linked with BFI-C global fatigue score.
CONCLUSIONS: Fatigue commonly occurs in RA patients, which independently relates to education level and disease activity. Furthermore, BRAF-MDQ and BFI-C scales exhibit a high consistency in assessing fatigue.

BACKGROUND: Previous studies that have assessed social cognition in Attention-Deficit/Hyperactivity Disorder (ADHD) have produced inconsistent findings. To summarize these data and shed light upon moderators that may explain observed inconsistencies, we conducted a systematic review and meta-analysis exploring social cognition (Theory of Mind (ToM), Empathy, Facial and Non-Facial Emotion Recognition) and Everyday Social Skills in children and adolescents with ADHD.
METHODS: The current meta-analysis involved 142 studies including 652 effect sizes. These studies compared children and adolescents with ADHD (n = 8,300) and with typical development (n = 7,983).
RESULTS: Participants with ADHD exhibited moderate to very large deficits in ToM (SMD = 0.84, 95% CI = 0.68-0.99), Facial Emotion Recognition (SMD = 0.63, 95% CI = 0.46-0.81), and Everyday Social Skills (SMD = 1.23, 95% CI = 1.08-1.37). The magnitude of these impairments was similar when considering effect sizes adjusted for some covariates and the methodological quality of the studies. Few studies have investigated Empathy and Non-Facial Emotion Recognition, which precludes definitive conclusions.
CONCLUSIONS: Children and adolescents with ADHD experience robust impairments in ToM, Facial Emotion Recognition and Everyday Social Skills. Future studies should explore whether these deficits are a consequence of difficulties in other areas of cognition (e.g., executive functioning). We have made all our raw data open access to facilitate the use of the present work by the community (e.g., clinicians looking for tools, assessing social impairments, or researchers designing new studies).

In September 2023, France was one of the first countries that started a national immunisation campaign with nirsevimab, a new monoclonal antibody against respiratory syncytial virus (RSV). Using data from a network of paediatric intensive care units (PICUs), we aimed to estimate nirsevimab effectiveness against severe cases of RSV bronchiolitis in France. We conducted a case-control study based on the test-negative design and included 288 infants reported by 20 PICUs. We estimated nirsevimab effectiveness at 75.9% (48.5-88.7) in the main analysis and 80.6% (61.6-90.3) and 80.4% (61.7-89.9) in two sensitivity analyses. These real-world estimates confirmed the efficacy observed in clinical studies.

OBJECTIVE: To identify sexual/sex-associated risk factors for hepatitis C transmission among men who have sex with men (MSM) and visualise behavioural trajectories from 2019 to 2021.
METHODS: We linked a behavioural survey to a hepatitis C cohort study (NoCo), established in 2019 across six German HIV/hepatitis C virus (HCV) treatment centres, and performed a case-control analysis. Cases were MSM with recent HCV infection, and controls were matched for HIV status (model 1) or proportions of sexual partners with HIV (model 2). We conducted conditional univariable and multivariable regression analyses.
RESULTS: In all, 197 cases and 314 controls completed the baseline questionnaire and could be matched with clinical data. For regression models, we restricted cases to those with HCV diagnosed since 2018 (N = 100). Factors independently associated with case status included sex-associated rectal bleeding, shared fisting lubricant, anal douching, chemsex, intravenous and intracavernosal injections, with population-attributable fractions of 88% (model 1) and 85% (model 2). These factors remained stable over time among cases, while sexual partner numbers and group sex decreased during COVID-19 measures.
CONCLUSIONS: Sexual/sex-associated practices leading to blood exposure are key factors in HCV transmission in MSM. Public health interventions should emphasize the importance of blood safety in sexual encounters. Micro-elimination efforts were temporarily aided by reduced opportunities for sexual encounters during the COVID-19 pandemic.

OBJECTIVE: To assess clinical-causal validity evidence of the nursing diagnosis, risk for unstable blood glucose level (00179), in individuals with type 2 diabetes mellitus.
METHODS: A case-control study was conducted in 5 primary healthcare units, involving 107 subjects with type 2 diabetes mellitus, 60 in the case group and 47 in the control group. Causality was determined by the association between sociodemographic and clinical factors, risk factors related to the nursing diagnosis, and the occurrence of unstable blood glucose level. An association was considered when the risk factor had a p-value of <0.05 and odds ratio >1.
RESULTS: Risk factors, such as stress, inadequate physical activity, and low adherence to therapeutic regimen, were prevalent in the sample. Time since diagnosis between 1-5 and 6-10 years, multiracial ethnicity, and the risk factor of low adherence to therapeutic regimen increased the likelihood of the outcome. Completion of high school education was identified as a protective factor.
CONCLUSIONS: The clinical validation of the nursing diagnosis, risk for unstable blood glucose level, has been successfully established, revealing a clear association between sociodemographic and clinical factors and the risk factors inherent to the nursing diagnosis.
CONCLUSIONS: The results contribute to advancing scientific knowledge related to nursing education, research, and practice and provide support for the evolution of nursing care processes for individuals with type 2 diabetes mellitus.
OBJECTIVE: Avaliar a evidência de validade clínico‐causal do diagnóstico de enfermagem, risco para nível instável de glicose no sangue (00179), em indivíduos com diabetes mellitus tipo 2. MÉTODO: Foi realizado um estudo caso‐controle em cinco unidades básicas de saúde, envolvendo 107 indivíduos com diabetes mellitus tipo 2, 60 no grupo caso e 47 no grupo controle. A causalidade foi determinada pela associação entre fatores sociodemográficos e clínicos, fatores de risco relacionados ao diagnóstico de enfermagem e a ocorrência de nível instável de glicose no sangue. Uma associação foi considerada quando o fator de risco tinha um valor de p < 0.05 e odds ratio > 1.
RESULTS: Fatores de risco como estresse, atividade física inadequada e baixa adesão ao regime terapêutico foram predominantes na amostra. O tempo desde o diagnóstico entre 1 e 5 anos e 6 a 10 anos, a etnia parda e o fator de risco baixa adesão ao regime terapêutico aumentaram a probabilidade do resultado. A conclusão do ensino médio foi identificada como um fator de proteção. CONCLUSÕES: A validação clínica do diagnóstico de enfermagem, risco para nível instável de glicose no sangue, foi estabelecida com sucesso, revelando uma clara associação entre fatores sociodemográficos e clínicos e os fatores de risco inerentes ao diagnóstico de enfermagem. IMPLICAÇÕES PARA A PRÁTICA DE ENFERMAGEM: Os resultados contribuem para o avanço do conhecimento científico relacionado à educação, à pesquisa e à prática de enfermagem e fornecem suporte para a evolução dos processos de cuidados de enfermagem para indivíduos com diabetes.

OBJECTIVE: The rate of readmission after hospitalisation for respiratory diseases has become a common and challenging clinical problem. Social and functional patient variables could help identify cases at high risk of readmission. The aim was to identify the nursing diagnoses that were associated with readmission after hospitalisation for respiratory disease in Spain.
METHODS: Case-control study within the cohort of patients admitted for respiratory disease during 2016-19 in a tertiary public hospital in Spain (n = 3781).
METHODS: Cases were patients who were readmitted within the first 30 days of discharge, and their controls were the remaining patients. All nursing diagnoses (n = 130) were collected from the electronic health record. They were then grouped into 29 informative diagnostic categories. Clinical confounder-adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using logistic regression models.
RESULTS: The readmission rate was 13.1%. The nursing diagnoses categories \'knowledge deficit\' (OR: 1.61; 95%CI: 1.13-2.31), \'impaired skin integrity and risk of ulcer infection\' (OR: 1.45; 95%CI: 1.06-1.97) and \'activity intolerance associated with fatigue\' (OR: 1.56; 95%CI: 1.21-2.01) were associated with an increased risk of suffering an episode of hospital readmission rate at 30% after hospital discharge, and this was independent of sociodemographic background, care variables and comorbidity.
UNASSIGNED: The nursing diagnoses assigned as part of the care plan of patients during hospital admission may be useful for predicting readmissions.