Rhesus factor modulation of effects of smoking and age on psychomotor performance, intelligence, personality profile, and health in Czech soldiers

Cognitive Effects of Toxoplasma and CMV Infections: A Cross-Sectional Study of 557 Young Adults Considering Modulation by Sex and Rh Factor

One-third of humanity harbors a lifelong infection with Toxoplasma gondii, and probably about 80% are infected with human cytomegalovirus (CMV). This study aims to delineate the associations between toxoplasmosis and cognitive abilities and compare these to the associations with CMV. We evaluated the cognitive performance of 557 students, who had been examined for Toxoplasma and CMV infections, using intelligence, memory, and psychomotor tests. The results indicated cognitive impairments in seropositive individuals for both pathogens, with variations in cognitive impact related to sex and the Rh factor. Specifically, Toxoplasma infection was associated with lower IQ in men, whereas CMV was predominantly associated with worse performance by women when testing memory and reaction speeds. Analysis of the antibody concentrations indicated that certain Toxoplasma-associated cognitive detrimental effects may wane (impaired intelligence) or worsen (impaired reaction times) over time following infection. The findings imply that the cognitive impairments caused by both neurotropic pathogens are likely due to pathological changes in the brain rather than from direct manipulative action by the parasites.

Toxoplasma infection and Rhesus blood group system: A systematic review and meta-analysis

BACKGROUND

Toxoplasmosis is one of the most common infections in humans and animals, which is caused by an obligate intracellular opportunistic parasite known as Toxoplasma gondii (T. gondii). Some data have shown that both Rhesus (Rh)-positive and Rh-negative individuals differ in response to biological factors, including Toxoplasma infection. Therefore, this systematic review and meta-analysis was conducted to investigate the scientific evidence regarding the possible association between the Rh blood group and Toxoplasma infection and to determine the seroprevalence of T. gondii in the Rh blood group system.

METHODS

The research was conducted on PubMed, ScienceDirect, ProQuest, and Google Scholar databases until January 2023. Twenty-one cross-sectional studies were included with a total of 10910 people. The data were synthesized using a random effect model with 95% confidence intervals (CIs).

RESULTS

The overall prevalence of T. gondii was calculated at 32.34% (CI 95%: 28.23-36.45%) and 33.35% (CI 95%: 19.73-46.96%) in Rh-positive and Rh-negative blood groups. In addition, the pooled OR for the relationship between the Rh blood group and the seroprevalence of T. gondii was 0.96 (95% CI: 0.72-1.28).

CONCLUSIONS

This meta-analysis showed a high prevalence of Toxoplasma infection in both Rh-negative and positive blood groups. This systematic review and meta-analysis revealed that no significant association was found between toxoplasmosis and Rh factor. Because of the limited number of studies in this field, more research is recommended to determine the exact relationship between toxoplasmosis and the Rh factor.

Associated factors with Premenstrual syndrome and Premenstrual dysphoric disorder among female medical students: A cross-sectional study

AIM

The study aimed to determine potential risk factors associated with Premenstrual Syndrome and Premenstrual Dysphoric Disorder.

METHODS

Three hundred two female student participants who were 18-45 years old completed a questionnaire including demographic characteristics, lifestyle factors, and a Vietnamese Premenstrual Syndrome Screening Tool. We then followed up participants during at least two menstrual cycles using the Daily Record of Severity of Problems. The Premenstrual Syndrome and Premenstrual Dysphoric Disorder diagnosis was established using The Carolina Premenstrual Assessment Scoring System, based on the American College of Obstetrics and Gynecology and Diagnostic and Statistical Manual of Mental Disorders.

RESULTS

According to the Carolina Premenstrual Assessment Scoring System, 35 out of 302 students (11.6%; 95%CI: 8.2-15.7%) met the diagnosis of PMS (31 students) or PMDD (4 students). We found that age at menarche (PR = 0.77, 95%CI: 0.63-0.96), having negative Rh blood type (PR = 4.43, 95%CI: 1.95 to 10.08), being moderately depressed or higher (PR = 2.81, 95%CI: 1.24 to 6.36), and consuming caffeine more than three times per week were statistically associated with having Premenstrual Syndrome or Premenstrual Dysphoric Disorder after adjusting for other variables.

CONCLUSION

The prominent risk factors for Premenstrual Syndrome and Premenstrual Dysphoric Disorder were negative Rhesus blood type, menarche age, caffeine consumption, and self-reported depression.

Association between ABO and RH blood groups and Hepatitis B virus infection among young Nigerian adults

BACKGROUND

Several diseases are reported to be associated with ABO/Rh blood groups. Data on the association between ABO and Rh D blood group antigens in the Nigerian population is sparse. This study aimed at determining the prevalence of Hepatitis B Virus (HBV) infection as well as its association with ABO and Rh D antigens among young Nigerian adults.

METHODS

Whole blood was collected from 496 students and screened for the presence of HBsAg using an immuno-chromatographic technique. The ABO and Rh D antigen status of participants were also determined using standard techniques.

RESULTS

In this study, the prevalence of HBV infection was 10/496 (2.10%). Of all factors assessed, only age of participants was identified as a risk factor (P < 0.05) for HBV seropositivity. Over half 257/496 (51.5%) of subjects were of the blood group O type, while 18/496 (3.6%) were of the AB blood type which was the least in occurrence. Rh D negative blood group was observed among 24/496 (4.8%) subjects. Those with the B blood type were observed to have an insignificantly (P > 0.05) higher prevalence of HBV infection. However, with respect to Rh D antigen alone, participants negative for the antigen were observed to have a five times higher risk of acquiring HBV infection than those positive for it (OR = 5.273, 95% CI = 1.056, 26.321, P > 0.05). Combining the ABO and Rh blood group systems, an association (OR = 20.174; P > 0.05) was found to exist between B Rh D negative status and HBV infection.

CONCLUSION

Possession of B antigen without Rh D antigen is associated with increased risk of acquiring HBV infection.

Psychomotor abilities of candidates for Polish Special Forces

Combat tasks involving special units often put a mental and physical strain on the soldiers. During the military operation, soldiers may struggle with multiple difficulties such as extreme physical effort, sleep deprivation, weather conditions, limited access to food and stress. These circumstances require a high level of cognitive ability (including psychomotor abilities) to overcome the physiological stress response and to be able to quickly and efficiently make decisions under stressful situations, especially in combat. The aim of the study was to assess the level of the psychomotor abilities of candidates for the Polish Special Forces. The study comprised 48 candidates for the Polish Special Forces (age: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30.06 \pm 2.87$$\end{document}30.06±2.87), 40 athletes (age: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$27.93 \pm 3.91$$\end{document}27.93±3.91) and 40 non-athletes (age: 24). The study was performed using Test2Drive software. Four computer-based tests were used to assess the following psychomotor abilities: simple reaction time, choice reaction time, hand-eye coordination and two-dimensional visuomotor coordination/spatial orientation test (SPANT). The analysis demonstrated statistically significant differences in reaction time and motor time between the study groups. The shortest reaction time in each test was observed in athletes, while the shortest motor time was observed in soldiers. All the psychomotor tests, except for the number of correct answers in SPANT, demonstrated statistically significant differences between the studied groups. It was also found that military training had a positive effect on the motor time in every psychomotor test. As regards the reaction time, it was observed that the athletes were characterised with better reaction times than the special forces candidates. The study has confirmed that military training and sports training have a positive effect on the level of psychomotor abilities, especially motor time.

Faster life history strategy manifests itself by lower age at menarche, higher sexual desire, and earlier reproduction in people with worse health

Factors which indicate lower life expectancy also induce switching to a faster life strategy, that is, a higher investment in current reproduction at the expense of future reproduction and body maintenance. We tested a hypothesis according to which impairment of individual health serves as a signal for switching to a faster life strategy using online-gathered data from 32,911 subjects. Worse health was associated with lower age at menarche and earlier initiation of sexual life in women and higher sexual desire and earlier reproduction in both sexes. Individuals with worse health also exhibited lower sexual activity, lower number of sexual partners, and lower total number of children. These results suggest that impaired health shifts individuals towards a faster life strategy but also has a negative (physiological) effect on behaviours related to sexual life. Signs of a faster life strategy were also found in Rh-negative men in good health, indicating that even just genetic predisposition to worse health could serve as a signal for switching to a faster life strategy. We suggest that improved public health in developed countries and the resulting shift to a slower life strategy could be the ultimate cause of the phenomenon of demographic transition.

The role of balancing selection in maintaining human RhD blood group polymorphism: A preregistered cross-sectional study

Maintenance of genetic polymorphism remains one of the big questions of evolutionary biology, which for a long time tended to be explained by balancing selection. This explanation was later criticized, but now is again accepted as an important mechanism in evolution. Human blood group systems seem affected by balancing selection especially strongly. In this preregistered study, we focused on stable coexistence of RhD-positive and RhD-negative subjects in a population. This is an evolutionary conundrum, because carriers of the less frequent negative allele suffer from lower fecundity due to haemolytic disease of the newborn affecting RhD-positive infants born to RhD-negative women. One explanation of persisting stability of RhD polymorphism points to heterozygote advantage. Over the past decade, numerous studies demonstrated that RhD-positive subjects score better than RhD-negative homozygotes in psychomotor tests and physical health-related variables. Still, evidence of better health and performance of heterozygotes is scarce and merely indirect. We compared the physical and mental health of 2,539 subjects whose RhD genotype was estimated based on their and their parents' RhD phenotype. We confirmed that RhD-negative homozygotes fare worse in terms of physical and mental health than subjects with RhD-positive phenotype and that RhD-positive heterozygotes enjoy better health than both homozygotes. For the first time, we demonstrated that RhD-positive homozygotes might suffer from worse health than RhD-negative homozygotes. Our results strongly support the hypothesis that RhD polymorphism is maintained by heterozygote advantage and that balancing selection may have played an important role in human evolution in this context and in general.

Rhesus-minus phenotype as a predictor of sexual desire and behavior, wellbeing, mental health, and fecundity

Background

Since its discovery in the 1930s, the effects of Rh phenotype on human health and wellbeing, with the exception of the effects of Rh-negativity of a mother on the risk of hemolytic anemia of Rh-positive children, has only rarely been studied. In the last few years, however, several studies have shown that Rh-negative subjects have worse health and performance in certain tests than their Rh-positive peers. Nothing is known about the effect of Rh phenotype on the quality of life of subjects as measured by a standard instrument.

Methods

We hereby analyzed the data of 1768 male (24% Rh-negative) and 3759 female participants (23% Rh-negative) of an anonymous internet study using the partial Kendall test with the age and the population of the hometown of subjects controlled.

Results

The results showed that the Rh-negative women, but not men, scored worse in wellbeing measured with the WHO-BREFF. The Rh-negative men scored worse in mental health-related variables and in their reported economic situation and the Rh-negative women scored better in physical health-related variables. Both the Rh-negative men and women reported higher sexual activity than their Rh-positive peers.

Conclusions

The effects of the Rh phenotype were significant after the correction for multiple tests. However, they were usually weaker and less numerous than those of smoking, consuming alcohol, and high body mass index, which were used as a sort of internal control.

Maternal RhD heterozygous genotype is associated with male biased secondary sex ratio

BACKGROUND

Previous studies suggest that RhD positive heterozygotes express better health status than RhD positive homozygotes and especially RhD negative subjects. This also applies to pregnant women. According to the Trivers-Willard hypothesis, women in better physical condition should have more sons.

AIM

To test the hypothesis that RhD positive heterozygous mothers have a male-skewed sex ratio.

STUDY DESIGN

Cross-sectional study. The data was analysed using Chi-Square test for all women, separately for RhD positive and RhD negative women, and separately for primiparous and multiparous women. The effects of maternal weight as a continuous predictor and the RhD phenotype of newborn as a categorical predictor of newborn sex were evaluated by the generalized linear model (GLZ) separately for RhD positive and RhD negative women using binomial distribution and logit link function.

OUTCOME MEASURES

Clinical records comprised maternal weight before pregnancy, number of previous deliveries, sex of the newborn, maternal RhD phenotype, and RhD phenotype of the newborn.

SUBJECTS

We analysed data from 5655 women who gave birth between 2008 and 2012 in General University Hospital in Prague.

RESULTS

Secondary sex ratio was significantly higher (P = 0.028) in RhD positive mothers who had RhD negative newborns, i.e., in heterozygotes (SR = 1.23), than in RhD positive mothers who had RhD positive newborns, i.e., in a mixed population of heterozygotes and homozygotes (SR = 1.00), especially in primiparous women (P = 0.013; SR = 1.37 and 0.99 resp.).

CONCLUSION

The sex ratio at birth was significantly higher in RhD positive mothers who had RhD negative newborns than in RhD positive mothers who had RhD positive newborns.

Lower performance of Toxoplasma-infected, Rh-negative subjects in the weight holding and hand-grip tests

BACKGROUND

Toxoplasma, a protozoan parasite of cats, infects many species of intermediate and paratenic hosts, including about one-third of humans worldwide. After a short phase of acute infection, the tissue cysts containing slowly dividing bradyzoites are formed in various organs and toxoplasmosis proceeds spontaneously in its latent form. In immunocompetent subjects, latent toxoplasmosis was considered asymptomatic. However, dozens of studies performed on animals and humans in the past twenty years have shown that it is accompanied by a broad spectrum of specific behavioural, physiological and even morphological changes. In human hosts, the changes often go in the opposite direction in men and women, and are mostly weaker or non-existent in Rh-positive subjects.

METHODS

Here, we searched for the indices of lower endurance of the infected subjects by examining the performance of nearly five hundred university students tested for toxoplasmosis and Rh phenotype in two tests, a weight holding test and a grip test.

RESULTS

The results confirmed the existence of a negative association of latent toxoplasmosis with the performance of students, especially Rh-negative men, in these tests. Surprisingly, but in an accordance with some already published data, Toxoplasma-infected, Rh-positive subjects expressed a higher, rather than lower, performance in our endurance tests.

DISCUSSION

Therefore, the results only partly support the hypothesis for the lower endurance of Toxoplasma infected subjects as the performance of Rh-positive subjects (representing majority of population) correlated positively with the Toxoplasma infection.

Eye Movements and Cognitive Strategy in a Fluid Intelligence Test: Item Type Analysis

Eye movements help to infer the cognitive strategy that a person uses in fluid intelligence tests. However, intelligence tests demand different relations/rules tokens to be solved, such as rule direction, which is the continuation, variation or overlay of geometric figures in the matrix of the intelligence test. The aim of this study was to understand whether eye movements could predict the outcome of an intelligence test and in the rule item groups. Furthermore, we sought to identify which measure is best for predicting intelligence test scores and to understand if the rule item groups use the same strategy. Accordingly, 34 adults completed a computerized intelligence test with an eye-tracking device. The toggling rate, that is, the number of toggles on each test item equalized by the item latency explained 45% of the variance of the test scores and a significant amount of the rule tokens item groups. The regression analyses also indicated toggling rate as the best measure for predicting the score and that all the rule tokens seem to respect the same strategy. No correlation or difference were found between baseline pupil size and fluid intelligence. Wiener Matrizen-Test 2 was demonstrated to be a good instrument for the purpose of this study. Finally, the implications of these findings for an understanding of cognition are discussed.

Differences in cognitive functions between cytomegalovirus-infected and cytomegalovirus-free university students: a case control study

Cytomegalovirus (CMV) is the herpetic virus, which infects 45–100% people worldwide. Many reports suggest that CMV could impair cognitive functions of infected subjects. Here we searched for indices of effects of CMV on infected subjects’ intelligence and knowledge. The Intelligence Structure Test I-S-T 2000 R was used to compare IQ of 148 CMV-infected and 135 CMV-free university students. Infected students expressed higher intelligence. Paradoxically, their IQ decreased with decreasing concentration of anti-CMV antibodies, which can be used, statistically, as a proxy of the time passed from the moment of infection in young subjects when the age of subjects is statistically controlled. The paradox of seemingly higher intelligence of CMV infected subjects could be explained by the presence of the subpopulation of about 5–10% CMV-positive individuals in the population of “CMV-negative students”. These false negative subjects had probably not only the oldest infections and therefore the lowest concentration of anamnestic antibodies, but also the lowest intelligence among the infected students. Prevalence of CMV infection in all countries is very high, approaching sometimes 90%. Therefore, the total impact of CMV on human intelligence may be large.

Heterozygote Advantage Probably Maintains Rhesus Factor Blood Group Polymorphism: Ecological Regression Study

Rhesus factor polymorphism has been an evolutionary enigma since its discovery in 1939. Carriers of the rarer allele should be eliminated by selection against Rhesus positive children born to Rhesus negative mothers. Here I used an ecologic regression study to test the hypothesis that Rhesus factor polymorphism is stabilized by heterozygote advantage. The study was performed in 65 countries for which the frequencies of RhD phenotypes and specific disease burden data were available. I performed multiple multivariate covariance analysis with five potential confounding variables: GDP, latitude (distance from the equator), humidity, medical care expenditure per capita and frequencies of smokers. The results showed that the burden associated with many diseases correlated with the frequencies of particular Rhesus genotypes in a country and that the direction of the relation was nearly always the opposite for the frequency of Rhesus negative homozygotes and that of Rhesus positive heterozygotes. On the population level, a Rhesus-negativity-associated burden could be compensated for by the heterozygote advantage, but for Rhesus negative subjects this burden represents a serious problem.

Worse Health Status and Higher Incidence of Health Disorders in Rhesus Negative Subjects

Rhesus-positive and Rhesus-negative persons differ in the presence-absence of highly immunogenic RhD protein on the erythrocyte membrane. The biological function of the RhD molecule is unknown. Its structure suggests that the molecular complex with RhD protein transports NH₃ or CO₂ molecules across the erythrocyte cell membrane. Some data indicate that RhD positive and RhD negative subjects differ in their tolerance to certain biological factors, including, Toxoplasma infection, aging and fatique. Present cross sectional study performed on 3,130 subjects) showed that Rhesus negative subjects differed in many indices of their health status, including incidences of many disorders. Rhesus negative subjects reported to have more frequent allergic, digestive, heart, hematological, immunity, mental health, and neurological problems. On the population level, a Rhesus-negativity-associated burden could be compensated for, for example, by the heterozygote advantage, but for Rhesus negative subjects this burden represents a serious problem.

No Evidence of Association between Toxoplasma gondii Infection and Financial Risk Taking in Females

Background

Past research linked Toxoplasma gondii (TG) infection in humans with neurological and mental disorders (e.g., schizophrenia, Alzheimer’s disease and attention disorders), irregularities of the dopaminergic and testosterone system, and increased likelihood of being involved in traffic accidents.

Methodology/Principal Findings

We test for an association between TG infection and financial decision-making (DM) using a case-control design in a sample of female Czech students (n = 79). We estimate each subject's risk attitude and loss aversion using an experimental economic task involving real monetary incentives. We find no significant evidence that either measure of decision-making is associated with TG infection.

Conclusion

We were unable to find evidence of an association between TG infection and financial decision-making in females.

Toxoplasmosis-associated difference in intelligence and personality in men depends on their Rhesus blood group but not ABO blood group

Background

The parasite Toxoplasma gondii influences the behaviour of infected animals and probably also personality of infected humans. Subjects with a Rhesus-positive blood group are protected against certain behavioural effects associated with Toxoplasma infection, including the deterioration of reaction times and personality factor shift.

Methodology/Principal Findings

Here, we searched for differences in the toxoplasmosis-associated effects between RhD-positive and RhD-negative subjects by testing 502 soldiers with two personality tests and two intelligence tests. The infected subjects expressed lower levels of all potentially pathognomic factors measured with the N-70 questionnaire and in neurasthenia measured with NEO-PI-R. The RhD-positive, Toxoplasma-infected subjects expressed lower while RhD-negative, Toxoplasma-infected subjects expressed higher intelligence than their Toxoplasma-free peers. The observed Toxoplasma-associated differences were always larger in RhD-negative than in RhD-positive subjects.

Conclusions

RhD phenotype plays an important role in the strength and direction of association between latent toxoplasmosis and not only psychomotor performance, but also personality and intelligence.