Prevalence Of Left-handedness Research Articles

Handedness in schizophrenia and affective disorders: a large-scale cross-disorder study.

While most people are right-handed, a minority are left-handed or mixed-handed. It has been suggested that mental and developmental disorders are associated with increased prevalence of left-handedness and mixed-handedness. However, substantial heterogeneity exists across disorders, indicating that not all disorders are associated with a considerable shift away from right-handedness. Increased frequencies in left- and mixed-handedness have also been associated with more severe clinical symptoms, indicating that symptom severity rather than diagnosis explains the high prevalence of non-right-handedness in mental disorders. To address this issue, the present study investigated the association between handedness and measures of stress reactivity, depression, mania, anxiety, and positive and negative symptoms in a large sample of 994 healthy controls and 1213 patients with DSM IV affective disorders, schizoaffective disorders, or schizophrenia. A series of complementary analyses revealed lower lateralization and a higher percentage of mixed-handedness in patients with major depression (14.9%) and schizophrenia (24.0%) compared to healthy controls (12%). For patients with schizophrenia, higher symptom severity was associated with an increasing tendency towards left-handedness. No associations were found for patients diagnosed with major depression, bipolar disorder, or schizoaffective disorder. In healthy controls, no association between hand preference and symptoms was evident. Taken together, these findings suggest that both diagnosis and symptom severity are relevant for the shift away from right-handedness in mental disorders like schizophrenia and major depression.

Left-handedness in otolaryngology, who is right?

This study aimed to ascertain the prevalence of left-handedness (LH) among otolaryngology-head and neck surgery (ORLHN) practitioners, investigate dexterity's impact on LH trainees, and identify common patterns in their training to improve the training experience. A web-based survey was distributed anonymously via email to members of the Saudi Otorhinolaryngology Society. The survey targeted ORLHN attending consultants, board-certified registrars, and current residents. It consisted of three sections: the first focused on the experience of attending consultants in training LH individuals, the second investigated common maneuvers employed by rhinologists, and the third explored the experiences and impacts reported by LH trainees. The study included 174 participants, and found a 13.2% LH prevalence among them. Rhinologists showed disparities, with 50% advising trainees to stand on the left side of the bed and use their left hand for the scope, whereas the other half asked otherwise. Additionally, 94.4% of the participants had not encountered any courses specifically tailored for LH trainees. Among LH trainees, 57% and 41% reported difficulties in learning and performing side-specific procedures such as functional endoscopic sinus surgery and endoscopic septoplasty, respectively, often attempting to switch to their nondominant hand, and feeling disadvantaged due to their laterality. Left-handedness presents challenges for both LH trainees and their trainers in surgical specialties, particularly in ORLHN, in which specific positioning and instruments are crucial to gain access to the desired surgical field. Despite these challenges, there is insufficient support for LH individuals. We recommend encouraging LH trainees to openly disclose and discuss their left-handedness, provide them with mentors, establish standardized operating room setups and techniques, supply appropriate instruments, and demonstrate flexibility in accommodating their needs. Level 5.

The Italian version of Edinburgh Handedness Inventory: Translation, transcultural adaptation, and validation in healthy subjects

ABSTRACT Lateralization is a key aspect of brain architecture and handedness is its primary manifestation. The Edinburgh Handedness Inventory (EHI) and the laterality quotient (LQ) assess the direction and consistency of handedness and require translation and cross-cultural adaptation to guarantee construct validity. We developed a standardized Italian EHI version. The developed Italian version was tested on 202 Italian subjects, classified into three hand types based on their LQs: right, mixed, and left. The frequency of left-handedness in Italians and other populations was compared to previous data. LQs from the twenty- and the ten-item original inventories were also compared. We conducted a factorial analysis. Mcdonald's Omega tested internal consistency. The prevalence of left-handedness was 6.4%, consistent with prior findings in Italian samples and other EHI translations. Age was the only socio-demographic variable that significantly affected the LQ. The internal consistency of the Italian EHI was excellent. Handedness is a feature of several cognitive functions and some neuropsychological diseases; it is influenced by socio-demographic and cultural factors and the instrument used to assess it. To provide a consistent and comparable evaluation of the construct, we recommend using this validated Italian translation of the EHI.

Difficulties of dental practice among left-handed Tunisian students: a cross-sectional survey.

In dentistry, most equipment is designed for right-handed (RH) individuals. Thus, left-handed (LH) individuals are often forced to adapt to demanding RH working conditions, and therefore, experience difficulties in their practice. The objective of this study was to determine the prevalence of left handedness among dental students at the Dental Clinic of Monastir, Tunisia, and to investigate the difficulties for LH individuals during clinical practice. A cross-sectional study was conducted among dental students during the academic year from September 2019 to March 2020. An adaptation of the Grad-Corllet Diagram and a specific questionnaire on clinical practices were administered to 221 participants. Data were analyzed using SPSS 24.0 statistical software for descriptive statistics and the chi-square test was performed (with a 5% significance level). The study revealed that 18.1% of dental students were LH. Among which, 82.5% of LH students had difficulties using instruments designed for RH dentists, 47.5% of LH students preferred the 3 o'clock working position, and 77.5% of LH students preferred to work in a sitting position. Most LH students (70%) reported that endodontic treatment was the most difficult procedure to perform. All students, whether RH or LH, presented a higher percentage of pain in the lumbar and neck/cervical regions; however, LH students presented higher values (77.5%) with statistically significant differences being reported for lower back pain (p = 0.026) and neck pain (p = 0.012). This study highlights the difficulties that LH dental students face in performing dental work. Dental Schools should provide LH students with appropriate equipment and a proper learning environment.

Born to Score? The Relationship between Left-Handedness and Success from the 7-Meter Line

An asymmetry in the prevalence of left-handedness vs. right-handedness in society has supposedly resulted in negative frequency-dependent advantages for left-handers in interactive sports. The aim of this study was to test whether these advantages apply to handball by examining whether being left-handed is beneficial when executing 7 m shots, a highly unimanual movement. All 1,625 7 m shots at the men’s 2016–2022 European championships were analyzed using a Bayesian two-level analysis. While the results did not indicate that left-handers were more likely to score from any single 7 m shot, left-handers were overrepresented among the designated shooters compared to both the population as a whole (38% vs. 11.6%) and left-handers on any given handball team (38% vs. 25%). The implication here was that handedness plays no role in the outcome of 7 m shots at the world-class level, but handedness does appear to play a role in who becomes a world-class 7 m shooter.

Left-handedness and economic development

This paper studies the interplay between left-handedness and economic development, thereby contributing to our understanding of the relationship between evolutionary forces, human diversity and growth. We propose a novel theoretical framework in which economic development influences the prevalence of left-handedness through structural change and a genetic mechanism driven by differential fertility. In particular, the emergence of the industrial sector puts left-handers at a reproductive disadvantage, because of their lower manual ability and wages. This fertility differential changes sign as soon as the income-fertility relationship is reversed, and eventually fades away when the rise of human capital makes manual skills irrelevant. Our model thus explains the decline and subsequent recovery of left-handedness observed over the last few centuries in the Western world. We further explore the possibility that left-handedness in turn influences growth: despite their lower productivity in manual tasks, left-handers may enhance technological progress through cognitive skills that are conducive to innovation, and through their contribution to the diversity of the workforce. This implies that the link between handedness and economic performance varies across stages of development. We present empirical evidence that lends credence to the core differential-fertility mechanism of our model and suggests that left-handedness can positively contribute to growth, once the economy has reached a sufficiently high level of human capital.

Bilateral differences in handgrip strength in Czech female tennis players aged 11–12 years and injury prevention

The term laterality refers to the preference or dominance of the lateral asymmetry of the human body. The prevalence of left-handedness is reported to be 10–13%, but in some sports (e.g. boxing, ice hockey, tennis), the proportion of left-handers is higher. The left-handedness is considered an advantage in tennis; however, the one-sided load can cause muscular dysbalances leading to injuries. The research aim was to assess bilateral differences in handgrip strength in top Czech female tennis players U12 as to injury prevention. The participants were tennis players (n = 165) aged 11.0–12.9 years taking part in the regular testing by the Czech Tennis Association using the TENDIAG1 test battery between 2000 and 2018. 87.3% of all players were right-handed (RH) and only 12.7% left-handed (LH). Bilateral differences between the right- and left-hand strength of all players were medium significant in favor of the right hand. The assessment of differences between RH and LH players showed only small differences in favor of LH players. There was a medium significant difference between RH and LH players in favor of the dominant hand (DH) over the non-dominant one (NDH). As to injury prevention, it is surprising that a difference between DH and NDH strength >15% was found in 40.91% of RH players and even in 40.06% of LH players. This predicts an increased risk of injury, so it is desirable to pay attention to both sides of the training load and to include compensatory or strengthening exercises.

THE LEFT-HAND DENTAL STUDENTS

The purpose of this study was to evaluate the difficulties faced by LH students of dental faculty and the effect of their training program on the musculo-skeletal system. A survey of 11 questions was used to get the necessary data for further analysis. The results of the study showed that the percentage of LH students in the faculty is 7.32 percent (40 of 546). The prevalence of left-handedness of males (9.59%) is higher than that of females (6.03%). The majority of LH students (85%) confirmed that their sinistrality is of no significance in their life organization. LH students neglect that their sinistrality has a significant effect on their dental practice, this is due to their limited experience in practice. The majority of the LH students (85%) prefer using special dental units designed to fit their needs. 35% of the students approved that they started experiencing symptoms of MSDs during their practical phase of studies. The results of this study suggest that LH dental students require special educational atmosphere which would yield in a more professional undergraduates with high efficiency in the work field.

Left-Handedness and Economic Development

This paper studies the interplay between left-handedness and economic development. To explain the decline and subsequent recovery of left-handedness observed over the last few centuries in the Western world, we propose a theory in which economic development influences the prevalence of left-handedness through structural change and a genetic mechanism driven by differential fertility. We further explore the possibility that the prevalence of left-handedness influences growth, finding that the link between handedness and economic performance varies across stages of development. Consistent with the implications of our model, the analysis of US data suggests that left-handedness can positively contribute to growth, once the economy has reached a sufficiently high level of human capital. Our research provides an example of how economic development can shape evolutionary forces, thus improving our understanding of the growth-diversity link.

Human handedness: A meta-analysis.

Across time and place, right hand preference has been the norm, but what is the precise prevalence of left- and right-handedness? Frequency of left-handedness has shaped and underpinned different fields of research, from cognitive neuroscience to human evolution, but reliable distributional estimates are still lacking. While hundreds of empirical studies have assessed handedness, a large-scale, comprehensive review of the prevalence of handedness and the factors that moderate it, is currently missing. Here, we report 5 meta-analyses on hand preference for different manual tasks and show that left-handedness prevalence lies between 9.3% (using the most stringent criterion of left-handedness) to 18.1% (using the most lenient criterion of nonright-handedness), with the best overall estimate being 10.6% (10.4% when excluding studies assessing elite athletes' handedness). Handedness variability depends on (a) study characteristics, namely year of publication and ways to measure and classify handedness, and (b) participant characteristics, namely sex and ancestry. Our analysis identifies the role of moderators that require taking into account in future studies on handedness and hemispheric asymmetries. We argue that the same evolutionary mechanisms should apply across geographical regions to maintain the roughly 1:10 ratio, while cultural factors, such as pressure against left-hand use, moderate the magnitude of the prevalence of left-handedness. Although handedness appears as a straightforward trait, there is no universal agreement on how to assess it. Therefore, we urge researchers to fully report study and participant characteristics as well as the detailed procedure by which handedness was assessed and make raw data publicly available. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Prevalence and heritability of handedness in a Hong Kong Chinese twin and singleton sample

BackgroundLeft-handedness prevalence has been consistently reported at around 10% with heritability estimates at around 25%. Higher left-handedness prevalence has been reported in males and in twins. Lower prevalence has been reported in Asia, but it remains unclear whether this is due to biological or cultural factors. Most studies are based on samples with European ethnicities and using the preferred hand for writing as key assessment. Here, we investigated handedness in a sample of Chinese school children in Hong Kong, including 426 singletons and 205 pairs of twins, using both the Edinburgh Handedness Inventory and Pegboard Task.ResultsBased on a binary definition of writing hand, we found a higher prevalence of left-handedness (8%) than what was previously reported in Asian datasets. We found no evidence of increased left-handedness in twins, but our results were in line with previous findings showing that males have a higher tendency to be left-handed than females. Heritability was similar for both hand preference (21%) and laterality indexes (22%). However, these two handedness measures present only a moderate correlation (.42) and appear to be underpinned by different genetic factors.ConclusionIn summary, we report new reference data for an ethnic group usually underrepresented in the literature. Our heritability analysis supports the idea that different measures will capture different components of handedness and, as a consequence, datasets assessed with heterogeneous criteria are not easily combined or compared.

The neurophysiological correlates of handedness: Insights from the lateralized readiness potential.

Handedness is the most investigated form of functional hemispheric asymmetries, but its neural correlates remain unclear. Functional imaging studies suggest differences between left- and right-handers in ipsilateral activation during unilateral hand movements, but do not allow for conclusions on the temporal dimension. In the Tapley and Bryden task, subjects have to draw as many dots as possible on a paper within 20 s using either the left or the right hand. We adapted the task for use during EEG in 36 left- and 36 right-handers. Subjects performed a visually guided response task with each trial consisting of eight motor responses. We investigated the lateralized readiness potential (LRP) at the first and last response of the sequence. Overall, increasing complexity of sequences was associated with earlier and less negative LRP peaks. For the last response, right-handers showed more negative LRP peak amplitudes than left-handers. The effect of handedness on LRP peak amplitude in the first response was modulated by task complexity with a more negative LRP peak amplitude in right-handers than left-handers in simple, but not in medium or complex trials. This effect might be due to more symmetrical processing in right-handers with increasing task complexity. These findings complement previous imaging studies and add a new perspective on the relationship between laterality and schizophrenia, associated with less pronounced LRPs and a higher prevalence of left-handedness.

Prevalence of left-handedness in China 2011: small-area estimates

ABSTRACT Nationally representative survey data and small-area estimation techniques are used to assess the geographic prevalence of left-handedness in China 2011. Measures of individuals’ handedness are their self-reported dominant hand and their hand grip strength, which yield four estimates of left-handed prevalence, and these statistics are recorded at the provincial level. These estimates concord with one another. There are several geographic clusters of high-prevalence rates of left-handers located in ethnic minority-designated autonomous areas or historically revolutionary base areas, which may reflect a deep-rooted sense of defiance to authorities and promote such cultural values as individual autonomy and equality among local people.

The Prevalence of Left-Handedness Is Higher Among Individuals With Developmental Coordination Disorder Than in the General Population.

Many medical, psychiatric and neurological conditions have been characterized by a high prevalence of left-handedness or mixed-handedness. Several studies have indicated an elevated frequency of left-handedness in children with Developmental Coordination Disorder (DCD). However, there have been few studies explicitly exploring this relationship. The assumption is that the prevalence of left-handedness in individuals with DCD is higher compared with the prevalence in the general population and resembles the prevalence described in children with other developmental disorders. Computerized searches were conducted in PubMed, PsycInfo and CINAHL databases. Thirty-eight studies were identified and included in the present review, containing handedness distributions across 1071 persons with DCD and 1,045 controls. The distribution of DCD participants across handedness-categories was proved to be significantly different from that of the control group, with 14.7 and 8.1% left-handers, respectively. The prevalence of left-handedness within the DCD-group is lower than that reported for ASD, and larger than in dyslexia. The elevated levels of left-handedness within the different developmental disorders supports the notion of an association between the different diagnoses. However, the present results are not sufficient to conclude anything about a common cause or underlying factor via the male hormone testosterone. The present results could act as a starting point for testing the hypothesis of such a common factor, as one of the requirements is an elevated prevalence of left-handedness, and without such considerable doubt would be cast upon the hypothesis.

Triplets, birthweight, and handedness

The mechanisms behind handedness formation in humans are still poorly understood. Very low birthweight is associated with higher odds of left-handedness, but whether this is due to low birthweight itself or premature birth is unknown. Handedness has also been linked to development, but the role of birthweight behind this association is unclear. Knowing that birthweight is lower in multiple births, triplets being about 1.5 kg lighter in comparison with singletons, and that multiples have a higher prevalence of left-handedness than singletons, we studied the association between birthweight and handedness in two large samples consisting exclusively of triplets from Japan (n = 1,305) and the Netherlands (n = 947). In both samples, left-handers had significantly lower birthweight (Japanese mean = 1,599 g [95% confidence interval (CI): 1,526-1,672 g]; Dutch mean = 1,794 g [95% CI: 1,709-1,879 g]) compared with right-handers (Japanese mean = 1,727 g [95% CI: 1,699-1,755 g]; Dutch mean = 1,903 g [95% CI: 1,867-1,938 g]). Within-family and between-family analyses both suggested that left-handedness is associated with lower birthweight, also when fully controlling for gestational age. Left-handers also had significantly delayed motor development and smaller infant head circumference compared with right-handers, but these associations diluted and became nonsignificant when controlling for birthweight. Our study in triplets provides evidence for the link between low birthweight and left-handedness. Our results also suggest that developmental differences between left- and right-handers are due to a shared etiology associated with low birthweight.

Takotsubo syndrome – A close connection to the brain: A prospective study investigating neuropsychiatric traits

BackgroundTakotsubo syndrome (TTS) is frequently triggered by a stressful event. Overactivation of the sympathetic nervous system has been hypothesized as the underlying mechanism. In a prospective, cross-sectional, single center study we aimed to investigate neuropsychiatric traits in patients with TTS. MethodsTwenty-six patients with TTS with a median latency of 17.5months from their index event underwent detailed medical examination, neuropsychologic examination, and Holter-ECG and were screened for psychiatric comorbidities, chronic stress and personality traits with questionnaires. Results38.5% (10/26) of patients suffered from a neurological disease, and 50.0% (13/26) from at least one mental disorder. In 23.1% (6/26) the hospital anxiety scale (HADS–A) was suspicious for an anxiety disorder. There was a high prevalence of left-handedness (19.2%; 5/26). Despite good performance in cognitive testing, 11 patients had an abnormal score in the fatigue severity scale. Recovery of cardiac function was documented, although symptoms in 69.2% of patients persisted. An increase in the root mean square of the successive differences (RMSSD) (p=0.01) was noted on the Holter-ECG. ConclusionThe study highlights a high prevalence of psychiatric and neurologic comorbidities in patients with TTS, which so far have been under-diagnosed. Future studies will have to show whether these patients might benefit from a combined psychocardiologic rehabilitation.

Incidence and Prevalence of Left handedness in a Nigerian sub-population

Left handedness is controlled by both genetic and environmental factors. Its occurrence has some advantages in the society. There is usually low prevalence of left handedness and variations exist in its frequency from different populations. The present survey is designed to examine the incidence and prevalence of left handedness among different age groups in two geopolitical zones in Nigeria. This study also presents information on difference in incidence between male and female Nigerians sub-population examined. We determine to extend current knowledge on how Nigerians sub-population varies genetically with regards to distribution of left-handedness alleles. A total of 2704 individuals participated in the survey and they include 450 families of which 250 were recruited from Kwara, North-central and 200 from Lagos South-west Nigeria participated in this study. Statistical Package Social Sciences software (SPSS) Version 16 was used to analyse data the overall incidence of left handedness in the two geopolitical zones studied was 12.2%. The incidence of left handedness in Lagos (20.1%) was almost four times higher than what was recorded in Kwara state (5.4%). In Kwara, incidence of left handedness in males (5.8%) was significantly higher than that of females (4.7%) (χ2= 0.706, df= 1 p= 0.401). Similar statistically significant findings was observed in Lagos where incidence of 21.9% and 18.4% were recorded for male and female respectively (χ2=2.32, df= 1 p= 0.128). The findings from this study provide information on left handedness in two geopolitical zones in Nigeria. It will be useful to population geneticists and anthropologists with respect to population studies.

The development of hand preference and dichotic language lateralization in males and females with congenital adrenal hyperplasia

ABSTRACTPeople with congenital adrenal hyperplasia (CAH) are exposed to elevated levels of androgens in utero due to overproduction by the adrenal cortex. In order to test whether high levels of prenatal androgens influence the development of handedness preferences and left-hemisphere language representation, we studied 39 patients with CAH (28 females, 11 males) and 25 unaffected sibling controls (17 females, 8 males). Hand preference for 15 unimanual activities was evaluated via questionnaire and pantomime, and a consonant–vowel dichotic listening test was administered. Contemporary theories disagree as to whether high testosterone is said to increase or decrease the probability of developing a typical right-hand preference. Results showed no significant differences on the handedness inventory. Relative to controls, however, patients with CAH showed a significantly larger right-ear advantage on the dichotic syllables task, indicating stronger left-hemisphere lateralization of language. These results support an emerging body of evidence suggesting that high testosterone may bias lateralized development toward the population norm, but run counter to the Geschwind–Behan–Galaburda model which associates high prenatal testosterone with a greater prevalence of left-handedness.

Higher Prevalence of Left-Handedness in Twins? Not After Controlling Birth Time Confounders.

Pregnancy- and birth-related factors may have an effect on handedness. Compared with singletons, twins have a lower birth weight, shorter gestational age, and are at higher risk for birth complications. We tested whether the prevalence of left-handedness is higher among twins than singletons, and if so, whether that difference is fully explained by pregnancy and birth-related differences between twins and singletons. We analyzed Finnish population-based datasets; included were 8,786 twins and 5,892 singletons with information on birth weight (n = 12,381), Apgar scores (n = 11,129), and gestational age (n = 11,811). Two twin cohorts were involved: FinnTwin12 included twins born during 1983-1987, and FinnTwin16 included twins born during 1974-1979. We had two comparison groups of singletons: 4,101 individuals born during 1986-1988 and enrolled in the Helsinki Ultrasound Trial, and 1,791 individuals who were partners of FinnTwin16 twins. We used logistic regression models with writing hand as the outcome for comparison and evaluating effects of covariates. Left-handedness was more common in twins (9.67%) than in singletons (8.27%; p = .004). However, Apgar scores were associated with handedness, and after controlling for covariates, we found no difference in the prevalence of left-handedness between twins and singletons. Increased left-handedness among twins, often reported by others, was evident in our data, but only among our older twin cohorts, and that association disappeared after removing effects of perinatal covariates.

Human Lateralization among Monozygotic and Dizygotic Twins in Koya Town

At present, we do not understand how human handedness arose. Although much attention has been paid to several genetic theories, some studies involving twins have indicated that the influence of genetic and environmental factors on handedness may be minimal or nonexistent. The incidence of left-handedness amongst males is higher than with females, according to a large body of research. People who are ambidextrous are more likely to start to write with their right hand, even when they are not forced to do this. The left hemisphere of the brain is also lateralized when compared to the right hemisphere and vice versa. Our research examined handedness in dizygotic and identical monozygotic twins in Koya Town/ Erbil governorate. In 2014, we mailed a questionnaire to 100 twins aged between 18 and 50 to survey their handedness. The survey determined whether each subject was a monozygotic or dizygotic twin, and then questioned them about their handedness. We examined whether both twins had the same handedness or different handedness, and whether individual twins have a higher prevalence of left-handedness or right-handedness. The results revealed that in 62% of cases, both monozygotic twins in a pair are right-handed. On the other hand, both dizygotic twins are right-handed only 54% of the time. Furthermore, dizygotic twins are more likely to have one left-handed and one right-handed twin when compared to monozygotic twins. We also found that the prevalence of right handedness in individual monozygotic twins regardless of the handedness of the other twin was 77%, whereas the prevalence of left-handedness was only 21%. The remaining 2% of monozygotic subjects were ambidextrous. These results indicate that unique genetic and environmental factors may account for the majority of variance in that is observed in handedness, although the relationship between the brain, handedness, environmental effects and genetic effects is a complex one. This is a view that is corroborated by a number of recent neuroscientific and genetic studies that are examined in this article.