La dramática pérdida de potencia estadística al dicotomizar variables continuas / The dramatic loss of statistical power when dichotomising continuous variables

Una práctica muy habitual en la investigación médica, durante el proceso de análisis de los datos, es dicotomizar variables numéricas en dos grupos. Dicha práctica conlleva la pérdida de información muy útil que puede restar eficacia a la investigación. A través de varios ejemplos, se muestra cómo con la dicotomización de variables numéricas los estudios pierden potencia estadística. Esto puede ser un aspecto crítico que impida valorar, por ejemplo, si un procedimiento terapéutico es más efectivo o si un determinado factor es de riesgo. Por tanto, se recomienda no dicotomizar las variables continuas si no existe un motivo muy concreto para ello. (AU)

Abstract. A very common practice in medical research, during the process of data analysis, is to dichotomise numerical variables in two groups. This leads to the loss of very useful information that can undermine the effectiveness of the research. Several examples are used to show how the dichotomisation of numerical variables can lead to a loss of statistical power in studies. This can be a critical aspect in assessing, for example, whether a therapeutic procedure is more effective or whether a certain factor is a risk factor. Dichotomising continuous variables is therefore not recommended unless there is a very specific reason to do so. (AU)

Reply to López-Moreno, M. Comment on "Montoro-García et al. Beneficial Impact of Pork Dry-Cured Ham Consumption on Blood Pressure and Cardiometabolic Markers in Individuals with Cardiovascular Risk. Nutrients 2022, 14, 298".

We thank Dr. López-Moreno for the comment [...].

The Impact of Hypopressive Abdominal Exercise on Linea Alba Morphology in Women Who Are Postpartum: A Short-Term Cross-Sectional Study.

OBJECTIVE: The purpose of this study was to determine the acute effect of an abdominal hypopressive exercise (AHE) on linea alba morphology among women who are primiparous and to compare this effect with that of other common abdominal exercise modalities. METHODS: A cross-sectional study of 46 women 3 months after first delivery was conducted. B-mode ultrasound imaging of the interrectus distance (IRD) and linea alba distortion was performed 2 cm below (I-point) and above (S-point) the umbilicus and at the mid-point between the umbilicus and xiphoid process (X-point). Images were recorded at rest and during an AHE performed in a supine position, a semi curl-up (SCU), an abdominal drawing-in maneuver (ADIM), and a SCU performed after an initial ADIM (ADIM+SCU). RESULTS: The SCU exercise narrowed the IRD at the X- and S-points. Compared with SCU, AHE and ADIM widened the IRD at the S- and X-points. No significant differences were found when comparing the IRD at rest, during AHE and during ADIM, but AHE tended to narrow I-point IRD more than ADIM but to widen S-point IRD more than ADIM+SCU. No participant showed linea alba distortion during the AHE or ADIM. When compared, SCU increased the occurrence of distortion with respect to AHE and ADIM. The isolated hypopressive posture did not change the IRD or linea alba distortion. CONCLUSION: Among women who were postpartum, AHE seemed to narrow IRD below the umbilicus compared with ADIM without either of these 2 modalities generating linea alba distortion, as SCU or ADIM+SCU does. Thus, although no significant differences were found when comparing the IRD at rest and during AHE, the AHE could improve the tensile response of the linea alba without increasing the IRD. IMPACT: This is believed to be the first study to describe linea alba changes during AHE in women who are postpartum. AHE and ADIM seem to show different effects on infraumbilical IRD. The lack of distortion suggests that linea alba may undergo tensile loading at all levels.

Beneficial Impact of Pork Dry-Cured Ham Consumption on Blood Pressure and Cardiometabolic Markers in Individuals with Cardiovascular Risk.

BACKGROUND: Evidence suggests that bioactive peptides reduce hypertension and affect certain metabolic pathways. METHODS: Fifty-four volunteers with stage 1 prehypertension and/or hypercholesterolemia and/or basal glucose >100 mg/dL were recruited and randomized to pork dry-cured ham (n = 35) or cooked ham (placebo group; n = 19) for 28 days. After a wash-out period, meat products were changed for 28 additional days. Bioactive peptides composition and enzyme inhibitory activities of both products were characterized. Treatment comparisons for the main effects were made using a two (treatment) × two (times) repeated measures minus the effect of cooked ham (placebo). RESULTS: 24 h mean systolic and diastolic pressures decreased up to 2.4 mmHg in the dry-cured ham period (treatment effect, p = 0.0382 y p = 0.0233, respectively) as well as the number of systolic pressure measures > 135 mmHg (treatment effect, p = 0.0070). Total cholesterol levels also decreased significantly after dry-cured ham intake (p = 0.049). No significant differences were observed between the two treatments for basal glucose, HOMA-IR index and insulin levels (p > 0.05). However, a significant rise of ghrelin levels was observed (treatment effect, p = 0.0350), while leptin plasma values slightly decreased (treatment effect, p = 0.0628). CONCLUSIONS: This study suggested the beneficial effects of regular dry-cured ham consumption on the improvement of systolic/diastolic blood pressures and facilitated the maintenance of metabolic pathways, which may be beneficial in the primary prevention of cardiovascular disease.

Health impact of acute intermittent porphyria in latent and non-recurrent attacks patients.

BACKGROUND: Acute intermittent porphyria (AIP) is a genetic disease characterized by acute neurovisceral attacks. Long-term clinical conditions, chronic symptoms and impaired health related quality of life (HRQoL) have been reported during non-attack periods but mainly in patients with recurrent attacks. Our aim was to investigate these aspects in sporadic AIP (SA-AIP) and latent AIP (L-AIP) patients. Fifty-five participants, 27 SA-AIP (< 4 attacks/year) and 28 L-AIP patients with a prevalent founder mutation from Spain were included. Medical records were reviewed, and individual interviews, physical examinations, biochemical analyses, and abdominal ultrasound scans were conducted. HRQoL was assessed through an EQ-5D-5L questionnaire. A comparative study was made between SA-AIP and L-AIP patients. RESULTS: The earliest long-term clinical condition associated with SA-AIP was chronic kidney disease. Chronic symptoms were reported in 85.2 % of SA-AIP and 46.4 % of L-AIP patients. Unspecific abdominal pain, fatigue, muscle pain and insomnia were significantly more frequent in SA-AIP than in L-AIP patients. The EQ-5D-5L index was lower in SA-AIP (0.809 vs. 0.926, p = 0.0497), and the impact of "pain", "anxiety-depression" and "mobility" was more intense in the EQ-5D-5L domains in SA-AIP than in L-AIP subjects and the general Spanish population. CONCLUSIONS: AIP remains a chronically symptomatic disease that adversely affects health and quality of life, even in patients with low rate of acute attacks. We suggest a regular monitoring of patients with symptomatic AIP regardless of their attack rate or the time since their last attack, with proper pain management and careful attention to kidney function.

High penetrance of acute intermittent porphyria in a Spanish founder mutation population and CYP2D6 genotype as a susceptibility factor.

BACKGROUND: Acute intermittent porphyria (AIP) is a low-penetrant genetic metabolic disease caused by a deficiency of hydroxymethylbilane synthase (HMBS) in the haem biosynthesis. Manifest AIP (MAIP) is considered when carriers develop typical acute neurovisceral attacks with elevation of porphyrin precursors, while the absence of attacks is referred to as latent AIP (LAIP). Attacks are often triggered by drugs, endocrine factors, fasting or stress. Although AIP penetrance is traditionally considered to be around 10-20%, it has been estimated to be below 1% in general population studies and a higher figure has been found in specific AIP populations. Genetic susceptibility factors underlying penetrance are still unknown. Drug-metabolizing cytochrome P450 enzymes (CYP) are polymorphic haem-dependent proteins which play a role in haem demand, so they might modulate the occurrence of AIP attacks. Our aim was to determine the prevalence and penetrance of AIP in our population and analyse the main hepatic CYP genes to assess their association with acute attacks. For this, CYP2C9*2, *3; CYP2C19*2; CYP2D6*4, *5; CYP3A4*1B and CYP3A5*3 defective alleles were genotyped in fifty AIP carriers from the Region of Murcia, a Spanish population with a high frequency of the HMBS founder mutation c.669_698del30. RESULTS: AIP penetrance was 52%, and prevalence was estimated as 17.7 cases/million inhabitants. The frequency of defective CYP2D6 alleles was 3.5 times higher in LAIP than in MAIP. MAIP was less frequent among CYP2D6*4 and *5 carriers (p < 0.05). The urine porphobilinogen (PBG)-to-creatinine ratio was lower in these individuals, although it was associated with a lower prevalence of attacks (p < 0.05) rather than with the CYP2D6 genotype. CONCLUSIONS: AIP prevalence in our region is almost 3 times higher than that estimated for the rest of Spain. The penetrance was high, and similar to other founder mutation AIP populations. This is very relevant for genetic counselling and effective health care. CYP2D6*4 and *5 alleles may be protective factors for acute attacks, and CYP2D6 may constitute a penetrance-modifying gene. Further studies are needed to confirm these findings, which would allow a further progress in clinical risk profile assessment based on the CYP genotype, leading to predictive personalized medicine for each AIP carrier in the future.

Comparación biomecánica de la autoextracción con y sin collarín cervical: estudio de simulación / Self-extraction with and without a cervical collar: a biomechanical simulation study

Objetivos: Comparar la autoextracción (AE) frente a la AE con collarines en sujetos con bajo riesgo de lesión cervical. Método: Estudio de simulación mediante análisis biomecánico con sensores inerciales, determinando la desalineación de la columna cervical durante la AE con y sin collarines cervicales. Resultados: El desequilibrio fue 3,12 (DE 34,62) grados mayor con el collarín STIFNECK (SN) (IC al 95% de -15,33 a 21,57; p =0,7234) que con AE y también 5,95 (DE 31,76) grados mayor con collarín X-COLLAR (XC) (IC al 95% de -10,98 a 22,87; p = 0,4654) que con AE. Cuando comparamos la AE con los diferentes tipos de collarines, observamos que con el collarín XC se produjeron 2,83 (DE 12,10) grados de desalineación más que con el collarín SN (IC al 95% de -3,62 a 9,27; p = 0,3650). Conclusiones: La desalineación de la columna cervical mediante la AE es similar a la provocada cuando se aplican collarines cervicales

Objective: To compare self-extraction with and without a cervical collar in subjects at low risk of cervical spine injuries. Methods: Simulation study analyzing biomechanical data from inertial sensors to detect misalignment of the cervical spine during self-extraction with and without a cervical collar. Results: Misalignment was a mean (SD) 3.12 (34.62) degrees greater during self-extraction with a Stiffneck collar in place (95% CI, -15.33 to 21.57 degrees; P=.7234) than during extraction without a collar. Misalignment was also greater, by 5.95 (31.76) degrees, with an X-collar in place (95% CI, -10.98 to 22.87; P=.4654) than without a collar. The between-collar comparison of differences showed that misalignment was 2.83 (12.10) degrees greater with the X-collar (95% CI, -3.62 to 9.27 degrees; P=.3650). Conclusion: Misalignment of the cervical spinal column is similar during self-extraction with or without a cervical collar in place

Self-extraction with and without a cervical collar: a biomechanical simulation study. / Comparación biomecánica de la autoextracción con y sin collarín cervical: estudio de simulación.

OBJECTIVES: To compare self-extraction with and without a cervical collar in subjects at low risk of cervical spine injuries. MATERIAL AND METHODS: Simulation study analyzing biomechanical data from inertial sensors to detect misalignment of the cervical spine during self-extraction with and without a cervical collar. RESULTS: Misalignment was a mean (SD) 3.12 (34.62) degrees greater during self-extraction with a Stiffneck collar in place (95% CI, -15.33 to 21.57 degrees; P=.7234) than during extraction without a collar. Misalignment was also greater, by 5.95 (31.76) degrees, with an X-collar in place (95% CI, -10.98 to 22.87; P=.4654) than without a collar. The between-collar comparison of differences showed that misalignment was 2.83 (12.10) degrees greater with the X-collar (95% CI, -3.62 to 9.27 degrees; P=.3650). CONCLUSION: Misalignment of the cervical spinal column is similar during self-extraction with or without a cervical collar in place.

OBJETIVO: Comparar la autoextracción (AE) frente a la AE con collarines en sujetos con bajo riesgo de lesión cervical. METODO: Estudio de simulación mediante análisis biomecánico con sensores inerciales, determinando la desalineación de la columna cervical durante la AE con y sin collarines cervicales. RESULTADOS: El desequilibrio fue 3,12 (DE 34,62) grados mayor con el collarín STIFNECK (SN) (IC al 95% de ­15,33 a 21,57; p =0,7234) que con AE y también 5,95 (DE 31,76) grados mayor con collarín X-COLLAR (XC) (IC al 95% de ­10,98 a 22,87; p = 0,4654) que con AE. Cuando comparamos la AE con los diferentes tipos de collarines, observamos que con el collarín XC se produjeron 2,83 (DE 12,10) grados de desalineación más que con el collarín SN (IC al 95% de ­3,62 a 9,27; p = 0,3650). CONCLUSIONES: La desalineación de la columna cervical mediante la AE es similar a la provocada cuando se aplican collarines cervicales.

Effects of long-term consumption of broccoli sprouts on inflammatory markers in overweight subjects.

BACKGROUND & AIMS: Broccoli sprouts represent an interesting choice of healthy food product as they are rich in glucosinolates and their cognate bioactive metabolites, isothiocyanates able to counteract the negative effects of diverse pathologies. As obesity is linked to an inflammatory component, the aim of the study was to evaluate the anti-inflammatory action of broccoli sprouts in overweight adult subjects. METHODS: An in vivo controlled study was performed in 40 healthy overweight subjects (ClinicalTrials.gov ID NCT 03390855). Treatment phase consisted on the consumption of broccoli sprouts (30 g/day) during 10 weeks and the follow-up phase of 10 weeks of normal diet without consumption of these broccoli sprouts. Anthropometric parameters as body fat mass, body weight, and BMI were determined. Inflammation status was assessed by measuring levels of TNF-α, IL-6, IL-1ß and C-reactive protein. RESULTS: IL-6 levels significantly decreased (mean values from 4.76 pg/mL to 2.11 pg/mL with 70 days of broccoli consumption, p < 0.001) and during control phase the inflammatory levels were maintained at low grade (mean values from 1.20 pg/mL to 2.66 pg/mL, p < 0.001). C-reactive protein significantly decreased as well. CONCLUSIONS: This study represents an advance in intervention studies as the broccoli sprouts were included in a daily dietary pattern in quantities that reflect a real consumption. Further studies are necessary to elucidate the role of this healthy rich and nutritious food product, but these promising results support the current evidence on the healthy properties of Brassica varieties.