Schizophrenia: the new etiological synthesis

Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss the constellation of evolutionary hypotheses for schizophrenia, highlighting the lack of empirical support for most existing evolutionary hypotheses-with the exception of the relatively well supported evolutionary mismatch hypothesis. It posits that evolutionarily novel features of contemporary environments, such as chronic stress, low-grade systemic inflammation, and gut dysbiosis, increase susceptibility to schizophrenia. Environmental factors such as microbial infections (e.g., Toxoplasma gondii) can better predict the onset of schizophrenia than polygenic risk scores. However, researchers have not been able to explain why only a small minority of infected people develop schizophrenia. The new etiological synthesis of schizophrenia indicates that an interaction between host genotype, microbe infection, and chronic stress causes schizophrenia, with neuroinflammation and gut dysbiosis mediating this etiological pathway. Instead of just alleviating symptoms with drugs, the parasite x genotype x stress model emphasizes that schizophrenia treatment should focus on detecting and treating possible underlying microbial infection(s), neuroinflammation, gut dysbiosis, and chronic stress.

Self-Perceived Facial Attractiveness, Fluctuating Asymmetry, and Minor Ailments Predict Mental Health Outcomes

Objective

Phenotypic markers associated with developmental stability such as fluctuating asymmetry, facial attractiveness, and reports of minor ailments can also act as indicators of overall physical health. However, few studies have assessed whether these markers might also be cues of mental health. We tested whether self- and other-perceived facial attractiveness, fluctuating asymmetry, and minor ailments are associated with psychopathological symptoms in a mixed sample of 358 college students, controlling for the effects of body mass index, age, and sex.

Methods

We applied the Symptom Checklist-90-Revised (SCL-90-R) questionnaire to assess psychopathological symptoms, a battery of questionnaires about self-perceptions of facial attractiveness, and gathered information about the number of previous minor ailments as well as demographic data. Other-perceived attractiveness was assessed by an independent mixed sample of 109 subjects. Subjects’ facial fluctuating asymmetry was determined by geometric morphometrics.

Results

The results revealed that in both men and women, higher self-perceived attractiveness and fewer minor ailments predicted lower scores of Somatization, Obsessive–Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Phobic Anxiety, Paranoid Ideation, Psychoticism, and a General Psychopathology Index. Higher facial fluctuating asymmetry was associated with higher Interpersonal Sensitivity, but did not contribute to its prediction when controlling for the other studied variables.

Conclusions

The observed strong associations between self-perceived attractiveness, minor ailments, and psychopathology indicate common developmental pathways between physiological and psychological symptomatology which may reflect broader life history (co)variation between genetics, developmental environment, and psychophysiological functioning.

Ecological traps: evidence of a fitness cost in a cavity-nesting bird

Habitat quality has direct effects on the evolutionary fitness of breeding organisms, which is why it is believed that animals tend to have an evolved preference for the best possible habitats. However, some animals may mistakenly choose to reproduce in habitats that decrease their fitness, resulting in 'ecological traps'. In this study, we tested whether great tits (Parus major) attracted to areas affected by outbreaks of the great web-spinning sawfly (Acantholyda posticalis) had fitness detriments characteristic of ecological traps. Sawfly larvae consume pine needles, which decreases resource availability for birds co-habiting the forest. Using artificial nesting sites, we found that great tits inhabiting areas of sawfly outbreaks had similar clutch sizes as tits breeding in healthy forest patches; however, the fledgling number was significantly lower, and fledgling condition was worse in the damaged forests. While moth larvae are the most important food for bird nestlings, the forest patches damaged by sawflies had lower larval biomass. Although most ecological traps occur in environments altered by humans, this study shows that pest insects can lower habitat quality, forming ecological traps. Our results indicate that attracting cavity-nesting birds should be done with caution because it may negatively impact birds' nutritional status and reproductive fitness.

Sexual Dimorphism in Language, and the Gender Shift Hypothesis of Homosexuality

Psychological sex differences have been studied scientifically for more than a century, yet linguists still debate about the existence, magnitude, and causes of such differences in language use. Advances in psychology and cognitive neuroscience have shown the importance of sex and sexual orientation for various psychobehavioural traits, but the extent to which such differences manifest in language use is largely unexplored. Using computerised text analysis (Linguistic Inquiry and Word Count: LIWC 2015), this study found substantial psycholinguistic sexual dimorphism in a large corpus of English-language novels (n = 304) by heterosexual authors. The psycholinguistic sex differences largely aligned with known psychological sex differences, such as empathising–systemising, people–things orientation, and men’s more pronounced spatial cognitive styles and abilities. Furthermore, consistent with predictions from cognitive neuroscience, novels (n = 158) by lesbian authors showed minor signs of psycholinguistic masculinisation, while novels (n = 167) by homosexual men had a female-typical psycholinguistic pattern, supporting the gender shift hypothesis of homosexuality. The findings on this large corpus of 66.9 million words indicate how psychological group differences based on sex and sexual orientation manifest in language use in two centuries of literary art.

Socioeconomic position, immune function, and its physiological markers

The development of costly traits such as immune function and secondary sexual traits is constrained by resource availability. The quality of developmental conditions and the availability of resources in ontogeny may therefore influence immune system functions and other biological traits. We analyzed causal pathways between family socioeconomic position, strength of immune response, and five physiological biomarkers in young Latvian men (n = 93) using structural equation modeling. Men from wealthier families had higher testosterone levels (r_s = 0.280), stronger immune response (r_s = 0.551), and higher facial attractiveness (r_s = 0.300). There were weak, non-significant correlations between family income, body fat percentage (r_s = -0.147), and fluctuating asymmetry (r_s = -0.159). Testosterone partially (33.8%) mediated the effect of family income on facial masculinity. Testosterone (positively) and adiposity (negatively) partially (4%) mediated the relationship between family income and immune function. Higher facial masculinity, higher facial symmetry, and lower adiposity were reliable and independent cues of better immune function (R² = 0.238) in a larger sample of young Latvian men (N = 146). Resource availability in ontogeny has an important role for the development of immune function and physical appearance, and it is a key parameter to be included in human eco-immunological research.

COVID-19 Pandemic on Fire: Evolved Propensities for Nocturnal Activities as a Liability Against Epidemiological Control

Humans have been using fire for hundreds of millennia, creating an ancestral expansion toward the nocturnal niche. The new adaptive challenges faced at night were recurrent enough to amplify existing psychological variation in our species. Night-time is dangerous and mysterious, so it selects for individuals with higher tendencies for paranoia, risk-taking, and sociability (because of security in numbers). During night-time, individuals are generally tired and show decreased self-control and increased impulsive behaviors. The lower visibility during night-time favors the partial concealment of identity and opens more opportunities for disinhibition of self-interested behaviors. Indeed, individuals with an evening-oriented chronotype are more paranoid, risk-taking, extraverted, impulsive, promiscuous, and have higher antisocial personality traits. However, under some circumstances, such as respiratory pandemics, the psychobehavioral traits favored by the nocturnal niche might be counter-productive, increasing contagion rates of a disease that can evade the behavioral immune system because its disease cues are often nonexistent or mild. The eveningness epidemiological liability hypothesis presented here suggests that during the COVID-19 pandemic, the evening-oriented psychobehavioral profile can have collectively harmful consequences: there is a clash of core tendencies between the nocturnal chronotype and the recent viral transmission-mitigating safety guidelines and rules. The pandemic safety protocols disrupt much normal social activity, particularly at night when making new social contacts is desired. The SARS-CoV-2 virus is contagious even in presymptomatic and asymptomatic individuals, which enables it to mostly evade our evolved contagious disease avoidance mechanisms. A growing body of research has indirectly shown that individual traits interfering with social distancing and anti-contagion measures are related to those of the nocturnal chronotype. Indeed, some of the social contexts that have been identified as superspreading events occur at night, such as in restaurants, bars, and nightclubs. Furthermore, nocturnal environmental conditions favor the survival of the SARS-CoV-2 virus much longer than daytime conditions. We compare the eveningness epidemiological liability hypothesis with other factors related to non-compliance with pandemic safety protocols, namely sex, age, and life history. Although there is not yet a direct link between the nocturnal chronotype and non-compliance with pandemic safety protocols, security measures and future empirical research should take this crucial evolutionary mismatch and adaptive metaproblem into account, and focus on how to avoid nocturnal individuals becoming superspreaders, offering secure alternatives for nocturnal social activities.

Pandemic Leadership: Sex Differences and Their Evolutionary-Developmental Origins

The COVID-19 pandemic has caused a global societal, economic, and social upheaval unseen in living memory. There have been substantial cross-national differences in the kinds of policies implemented by political decision-makers to prevent the spread of the virus, to test the population, and to manage infected patients. Among other factors, these policies vary with politicians' sex: early findings indicate that, on average, female leaders seem more focused on minimizing direct human suffering caused by the SARS-CoV-2 virus, while male leaders implement riskier short-term decisions, possibly aiming to minimize economic disruptions. These sex differences are consistent with broader findings in psychology, reflecting women's stronger empathy, higher pathogen disgust, health concern, care-taking orientation, and dislike for the suffering of other people-as well as men's higher risk-taking, Machiavellianism, psychopathy, narcissism, and focus on financial indicators of success and status. This review article contextualizes sex differences in pandemic leadership in an evolutionary framework. Evolution by natural selection is the only known process in nature that organizes organisms into higher degrees of functional order, or counteracts the unavoidable disorder that would otherwise ensue, and is therefore essential for explaining the origins of human sex differences. Differential sexual selection and parental investment between males and females, together with the sexual differentiation of the mammalian brain, drive sex differences in cognition and behavioral dispositions, underlying men's and women's leadership styles and decision-making during a global pandemic. According to the sexually dimorphic leadership specialization hypothesis, general psychobehavioral sex differences have been exapted during human evolution to create sexually dimorphic leadership styles. They may be facultatively co-opted by societies and/or followers when facing different kinds of ecological and/or sociopolitical threats, such as disease outbreaks or intergroup aggression. Early evidence indicates that against the invisible viral foe that can bring nations to their knees, the strategic circumspection of empathic feminine health "worriers" may bring more effective and humanitarian outcomes than the devil-may-care incaution of masculine risk-taking "warriors".

The Obesity Paradox Predicts the Second Wave of COVID-19 to Be Severe in Western Countries

While COVID-19 infection and mortality rates are soaring in Western countries, Southeast Asian countries have successfully avoided the second wave of the SARS-CoV-2 pandemic despite high population density. We provide a biochemical hypothesis for the connection between low COVID-19 incidence, mortality rates, and high visceral adiposity in Southeast Asian populations. The SARS-CoV-2 virus uses angiotensin-converting enzyme 2 (ACE2) as a gateway into the human body. Although the highest expression levels of ACE2 are found in people’s visceral adipose tissue in Southeast Asia, this does not necessarily make them vulnerable to COVID-19. Hypothetically, high levels of visceral adiposity cause systemic inflammation, thus decreasing the ACE2 amount on the surface of both visceral adipocytes and alveolar epithelial type 2 cells in the lungs. Extra weight gained during the pandemic is expected to increase visceral adipose tissue in Southeast Asians, further decreasing the ACE2 pool. In contrast, weight gain can increase local inflammation in fat depots in Western people, leading to worse COVID-related outcomes. Because of the biological mechanisms associated with fat accumulation, inflammation, and their differential expression in Southeast Asian and Western populations, the second wave of the pandemic may be more severe in Western countries, while Southeast Asians may benefit from their higher visceral fat depots.

Toxoplasma gondii and Psychopathology: Latent Infection Is Associated with Interpersonal Sensitivity, Psychoticism, and Higher Testosterone Levels in Men, but Not in Women

Objective

The ability of parasites to hijack the nervous system, manipulating the host’s physiology and behavior in ways that enhance the parasite’s fitness while damaging host fitness, is a topic of ongoing research interest in evolutionary biology, but is largely overlooked in mental health research. Nevertheless, recent evidence has shown that Toxoplasma gondii infection can change host testosterone levels and influence the development of some psychiatric disorders. Here, we tested this hypothesis in a mixed sample of 213 non-clinical subjects.

Methods

Participants (nmales = 108, nfemales = 105) provided 5 ml of blood to quantify testosterone levels and Toxoplasma gondii antibodies. The Symptom Checklist-90-Revised was used to assess psychopathological symptoms.

Results

The results showed that Toxoplasma-infected men had higher testosterone levels and scored higher in Interpersonal Sensitivity and Psychoticism symptoms than non-infected men. Toxoplasma-infected women did not differ from control women.

Conclusions

Framed in an evolutionary framework, the findings suggest that the elevated testosterone levels and the expression of psychopathological symptoms can be seen as the result of the manipulation exerted by Toxoplasma gondii either to reach its definitive host or to increase its spread. Future research can benefit from integrating insights from evolutionary biology and parasite-host interactions with physiology, immunology, and mental health to develop a better understanding of mental health etiology.

Psycholinguistic dataset on language use in 1145 novels published in English and Dutch

This dataset includes psycholinguistic data on 694 English-language and 451 Dutch-language novels, acquired with computerised analysis of digitised novels published mainly between 1800 and 2018. The English-language novels have a total word count of 66.9 million words, while the Dutch-language novels comprise 49.6 million words, therefore offering large, representative samples for both languages. The data provided in this article include 93 linguistic and psycholinguistic outcome variables for the English-language novels, acquired using Linguistic Inquiry and Word Count (LIWC) version 2015, and 68 linguistic and psycholinguistic outcome variables for the Dutch-language novels, acquired using Linguistic Inquiry and Word Count (LIWC) version 2001. The dataset also includes word frequencies (unigram and bigram) for each novel. The metadata for each novel include year of publication, authors’ nationality, sex, age at publication, and sexual orientation (the latter only in the English-language dataset), making it possible for researchers to study the data along these parameters. The use of these data can help researchers illuminate how word use reflects psychological processes in more than two centuries of literary art in English and in contemporary Dutch novels.

Developmental speed affects ecological stoichiometry and adult fat reserves in Drosophila melanogaster

The elemental composition of organisms belongs to a suite of functional traits that change during development in response to environmental conditions. However, associations between adaptive variations in developmental speed and elemental body composition are not well understood. We compared body mass, elemental body composition, food uptake and fat metabolism of Drosophila melanogaster male fruit flies in relation to their larval development speed. Slowly developing flies had higher body carbon concentration than rapidly developing and intermediate flies. Rapidly developing flies had the highest body nitrogen concentration, while slowly developing flies had higher body nitrogen levels than flies with intermediate speed of development. The carbon-to-nitrogen ratio was therefore lower in rapidly developing flies than in slow and intermediate flies. We also had a group of flies grown individually and their body mass and elemental body composition were similar to those of rapidly developing individuals grown in groups. This suggests that rapid growth is not suppressed by stress. Feeding rates were lowest in the slowly developing flies. The amount of triacylglycerides was highest in the flies with intermediate developmental speed which optimizes development under many climatic conditions. Although low food intake slows down developmental speed and the accumulation of body fat reserves in slowly developing flies, their phenotype conceivably facilitates survival under higher stochasticity of their environments. Rapidly developing flies grew with less emphasis on storage build-up. Overall, this study shoes that a combination of bet-hedging, adaptive tracking and developmental plasticity enables fruit flies to respond adaptively to environmental uncertainty.

Women's socioeconomic position in ontogeny is associated with improved immune function and lower stress, but not with height

Immune function, height and resource accumulation comprise important life history traits in humans. Resource availability models arising from life history theory suggest that socioeconomic conditions influence immune function, growth and health status. In this study, we tested whether there are associations between family income during ontogeny, adult height, cortisol level and immune response in women. A hepatitis B vaccine was administered to 66 young Latvian women from different socioeconomic backgrounds, and blood samples were then collected to measure the level of antibodies that the women produced in response to the vaccination. Cortisol levels were measured from plasma samples pre- and post-vaccination. Women from wealthier families had lower cortisol levels, and women from the highest family income group had the highest levels of antibody titers against hepatitis B vaccine. No significant relationships were observed between cortisol level and immune function, nor between family income and height. The results show that income level during ontogeny is associated with the strength of immune response and with psychoneuroendocrine pathways underlying stress perception in early adulthood. The findings indicate that the quality of the developmental niche is associated with the condition-dependent expression of immune function and stress response.

Eating Disorders: An Evolutionary Psychoneuroimmunological Approach

Eating disorders are evolutionarily novel conditions. They lead to some of the highest mortality rates of all psychiatric disorders. Several evolutionary hypotheses have been proposed for eating disorders, but only the intrasexual competition hypothesis is extensively supported by evidence. We present the mismatch hypothesis as a necessary extension to the current theoretical framework of eating disorders. This hypothesis explains the evolutionarily novel adaptive metaproblem that has arisen when mating motives conflict with the large-scale and easy availability of hyper-rewarding but obesogenic foods. This situation is exacerbated particularly in those contemporary environments that are characterized by sedentary lifestyles, ever-present junk foods, caloric surplus and the ubiquity of social comparisons that take place via social media. Our psychoneuroimmunological model connects ultimate-level causation with proximate mechanisms by showing how the adaptive metaproblem between mating motives and food rewards leads to chronic stress and, further, to disordered eating. Chronic stress causes neuroinflammation, which increases susceptibility to OCD-like behaviors that typically co-occur with eating disorders. Chronic stress upregulates the serotonergic system and causes dysphoric mood in anorexia nervosa patients. Dieting, however, reduces serotonin levels and dysphoric mood, leading to a vicious serotonergic-homeostatic stress/starvation cycle whereby cortisol and neuroinflammation increase through stringent dieting. Our psychoneuroimmunological model indicates that between-individual and within-individual variation in eating disorders partially arises from (co)variation in gut microbiota and stress responsivity, which influence neuroinflammation and the serotonergic system. We review the advances that have been made in recent years in understanding how to best treat eating disorders, outlining directions for future clinical research. Current evidence indicates that eating disorder treatments should aim to reduce the chronic stress, neuroinflammation, stress responsivity and gut dysbiosis that fuel the disorders. Connecting ultimate causes with proximate mechanisms and treating biopsychosocial causes rather than manifest symptoms is expected to bring more effective and sophisticated long-term interventions for the millions of people who suffer from eating disorders.

Storytelling, business analytics and big data interpretation

Purpose

The purpose of this paper is to explore the role of storytelling in data interpretation, decision-making and individual-level adoption of business analytics (BA).

Design/methodology/approach

Existing theory is extended by introducing the concept of BA data-driven storytelling and by synthesizing insights from BA, storytelling, behavioral research, linguistics, psychology and neuroscience. Using theory-building methodology, a model with propositions is introduced to demonstrate the relationship between storytelling, data interpretation quality, decision-making quality, intention to use BA and actual BA use.

Findings

BA data-driven storytelling is a narrative sensemaking heuristic positively influencing human behavior towards BA use. Organizations deliberately disseminating BA data-driven stories can improve the quality of individual data interpretation and decision-making, resulting in increased individual utilization of BA on a daily basis.

Research limitations/implications

To acquire a deeper understanding of BA data-driven storytelling in behavioral operational research (BOR), future studies should test the theoretical model of this study and focus on exploring the complexity and diversity in individual attitudes toward BA.

Practical implications

This study provides practical guidance for business practitioners who struggle with interpreting vast amounts of complex data, making data-driven decisions and incorporating BA into daily operations.

Originality/value

This cross-disciplinary study develops existing BOR, storytelling and BA literature by showing how a novel BA data-driven storytelling approach can facilitate BA adoption in organizations.

A Life History Approach to the Female Sexual Orientation Spectrum: Evolution, Development, Causal Mechanisms, and Health

Women's capacity for sexual fluidity is at least as interesting a phenomenon from the point of view of evolutionary biology and behavioral endocrinology as exclusively homosexual orientation. Evolutionary hypotheses for female nonheterosexuality have failed to fully account for the existence of these different categories of nonheterosexual women, while also overlooking broader data on the causal mechanisms, physiology, ontogeny, and phylogeny of female nonheterosexuality. We review the evolutionary-developmental origins of various phenotypes in the female sexual orientation spectrum using the synergistic approach of Tinbergen's four questions. We also present femme-specific and butch-specific hypotheses at proximate and ultimate levels of analysis. This review article indicates that various nonheterosexual female phenotypes emerge from and contribute to hormonally mediated fast life history strategies. Life history theory provides a biobehavioral explanatory framework for nonheterosexual women's masculinized body morphology, psychological dispositions, and their elevated likelihood of experiencing violence, substance use, obesity, teenage pregnancy, and lower general health. This pattern of life outcomes can create a feedback loop of environmental unpredictability and harshness which destabilizes intrauterine hormonal conditions in mothers, leading to a greater likelihood of fast life history strategies, global health problems, and nonheterosexual preferences in female offspring. We further explore the potential of female nonheterosexuality to function as an alloparental buffer that enables masculinizing alleles to execute their characteristic fast life history strategies as they appear in the female and the male phenotype. Synthesizing life history theory with the female sexual orientation spectrum enriches existing scientific knowledge on the evolutionary-developmental mechanisms of human sex differences.

Ecological Stoichiometry: A Link Between Developmental Speed and Physiological Stress in an Omnivorous Insect

The elemental composition of organisms belongs to a suite of functional traits that may adaptively respond to fluctuating selection pressures. Life history theory predicts that predation risk and resource limitations impose selection pressures on organisms’ developmental time and are further associated with variability in energetic and behavioral traits. Individual differences in developmental speed, behaviors and physiology have been explained using the pace-of-life syndrome (POLS) hypothesis. However, how an organism’s developmental speed is linked with elemental body composition, metabolism and behavior is not well understood. We compared elemental body composition, latency to resume activity and resting metabolic rate (RMR) of western stutter-trilling crickets (Gryllus integer) in three selection lines that differ in developmental speed. We found that slowly developing crickets had significantly higher body carbon, lower body nitrogen and higher carbon-to-nitrogen ratio than rapidly developing crickets. Slowly developing crickets had significantly higher RMR than rapidly developing crickets. Male crickets had higher RMR than females. Slowly developing crickets resumed activity faster in an unfamiliar relative to a familiar environment. The rapidly developing crickets did the opposite. The results highlight the tight association between life history, physiology and behavior. This study indicates that traditional methods used in POLS research should be complemented by those used in ecological stoichiometry, resulting in a synthetic approach that potentially advances the whole field of behavioral and physiological ecology.

Linking organismal growth, coping styles, stress reactivity, and metabolism via responses against a selective serotonin reuptake inhibitor in an insect

Evidence suggests that brain serotonin (5-HT) is one of the central mediators of different types of animal personality. We tested this assumption in field crickets Gryllus integer using a selective serotonin reuptake inhibitor (SSRI). Crickets were selected for slow and rapid development and tested for their coping styles under non-stressful conditions (time spent exploring a novel object). Resting metabolic rate, maximum metabolic rate and latency to resume activity were measured under stressful conditions (stress reactivity). Measurements were taken (i) before and (ii) during the SSRI treatment. Before the SSRI treatment, a strong negative correlation was observed between coping style and stress reactivity, which suggests the existence of a behavioral syndrome. After the SSRI treatment, the syndrome was no longer evident. The results of this study show that 5-HT may be involved in regulating behavior not only along a stress reactivity gradient but also along a coping styles axis. The relationship between personality and the strength and direction of 5-HT treatment on observed behaviors indicates trait-like individual differences in 5-HT signaling. Overall, these findings do not support recent ideas arising from the pace-of-life syndrome (POLS) hypothesis, which predict higher exploration and metabolic rates in rapidly developing bold animals.

Effectiveness of three interventions for secondary prevention of low back pain in the occupational health setting - a randomised controlled trial with a natural course control

BACKGROUND

We assessed the effectiveness of three interventions that were aimed to reduce non-acute low back pain (LBP) related symptoms in the occupational health setting.

METHODS

Based on a survey (n = 2480; response rate 71%) on LBP, we selected a cohort of 193 employees who reported moderate LBP (Visual Analogue Scale VAS > 34 mm) and fulfilled at least one of the following criteria during the past 12 months: sciatica, recurrence of LBP ≥ 2 times, LBP ≥ 2 weeks, or previous sickness absence. A random sample was extracted from the cohort as a control group (Control, n = 50), representing the natural course of LBP. The remaining 143 employees were invited to participate in a randomised controlled trial (RCT) of three 1:1:1 allocated parallel intervention arms: multidisciplinary rehabilitation (Rehab, n = 43); progressive exercises (Physio, n = 43) and self-care advice (Advice, n = 40). Seventeen employees declined participation in the intervention. The primary outcome measures were physical impairment (PHI), LBP intensity (Visual Analogue Scale), health related quality of life (QoL), and accumulated sickness absence days. We imputed missing values with multiple imputation procedure. We assessed all comparisons between the intervention groups and the Control group by analysing questionnaire outcomes at 2 years with ANOVA and sickness absence at 4 years by using negative binomial model with a logarithmic link function.

RESULTS

Mean differences between the Rehab and Control groups were - 3 [95% CI -5 to - 1] for PHI, - 13 [- 24 to - 1] for pain intensity, and 0.06 [0.00 to 0.12] for QoL. Mean differences between the Physio and Control groups were - 3 [95% CI -5 to - 1] for PHI, - 13 [- 29 to 2] for pain intensity, and 0.07 [0.01 to 0.13] for QoL. The main effects sizes were from 0.4 to 0.6. The interventions were not effective in reducing sickness absence.

CONCLUSIONS

Rehab and Physio interventions improved health related quality of life, decreased low back pain and physical impairment in non-acute, moderate LBP, but we found no differences between the Advice and Control group results. No effectiveness on sickness absence was observed.

TRIAL REGISTRATION

Number NCT00908102 Clinicaltrials.gov.

Metabolic rate associates with, but does not generate covariation between, behaviours in western stutter-trilling crickets, Gryllus integer

The causes and consequences of among-individual variation and covariation in behaviours are of substantial interest to behavioural ecology, but the proximate mechanisms underpinning this (co)variation are still unclear. Previous research suggests metabolic rate as a potential proximate mechanism to explain behavioural covariation. We measured the resting metabolic rate (RMR), boldness and exploration in western stutter-trilling crickets, Gryllus integer, selected differentially for short and fast development over two generations. After applying mixed-effects models to reveal the sign of the covariation, we applied structural equation models to an individual-level covariance matrix to examine whether the RMR generates covariation between the measured behaviours. All traits showed among-individual variation and covariation: RMR and boldness were positively correlated, RMR and exploration were negatively correlated, and boldness and exploration were negatively correlated. However, the RMR was not a causal factor generating covariation between boldness and exploration. Instead, the covariation between all three traits was explained by another, unmeasured mechanism. The selection lines differed from each other in all measured traits and significantly affected the covariance matrix structure between the traits, suggesting that there is a genetic component in the trait integration. Our results emphasize that interpretations made solely from the correlation matrix might be misleading.

Microbiome symbionts and diet diversity incur costs on the immune system of insect larvae

Communities of symbiotic microorganisms that colonize the gastrointestinal tract play an important role in food digestion and protection against opportunistic microbes. Diet diversity increases the number of symbionts in the intestines, a benefit that is considered to impose no cost for the host organism. However, less is known about the possible immunological investments that hosts have to make in order to control the infections caused by symbiont populations that increase because of diet diversity. Using taxonomical composition analysis of the 16S rRNA V3 region, we show that enterococci are the dominating group of bacteria in the midgut of the larvae of the greater wax moth (Galleria mellonella). We found that the number of colony-forming units of enterococci and expressions of certain immunity-related antimicrobial peptide (AMP) genes such as Gallerimycin, Gloverin, 6-tox, Cecropin-D and Galiomicin increased in response to a more diverse diet, which in turn decreased the encapsulation response of the larvae. Treatment with antibiotics significantly lowered the expression of all AMP genes. Diet and antibiotic treatment interaction did not affect the expression of Gloverin and Galiomicin AMP genes, but significantly influenced the expression of Gallerimycin, 6-tox and Cecropin-D Taken together, our results suggest that diet diversity influences microbiome diversity and AMP gene expression, ultimately affecting an organism's capacity to mount an immune response. Elevated basal levels of immunity-related genes (Gloverin and Galiomicin) might act as a prophylactic against opportunistic infections and as a mechanism that controls the gut symbionts. This would indicate that a diverse diet imposes higher immunity costs on organisms.

Short-term exposure to predation affects body elemental composition, climbing speed and survival ability in Drosophila melanogaster

Factors such as temperature, habitat, larval density, food availability and food quality substantially affect organismal development. In addition, risk of predation has a complex impact on the behavioural and morphological life history responses of prey. Responses to predation risk seem to be mediated by physiological stress, which is an adaptation for maintaining homeostasis and improving survivorship during life-threatening situations. We tested whether predator exposure during the larval phase of development has any influence on body elemental composition, energy reserves, body size, climbing speed and survival ability of adult Drosophila melanogaster. Fruit fly larvae were exposed to predation by jumping spiders (Phidippus apacheanus), and the percentage of carbon (C) and nitrogen (N) content, extracted lipids, escape response and survival were measured from predator-exposed and control adult flies. The results revealed predation as an important determinant of adult phenotype formation and survival ability. D. melanogaster reared together with spiders had a higher concentration of body N (but equal body C), a lower body mass and lipid reserves, a higher climbing speed and improved adult survival ability. The results suggest that the potential of predators to affect the development and the adult phenotype of D. melanogaster is high enough to use predators as a more natural stimulus in laboratory experiments when testing, for example, fruit fly memory and learning ability, or when comparing natural populations living under different predation pressures.

A dark cuticle allows higher investment in immunity, longevity and fecundity in a beetle upon a simulated parasite attack

Cuticle melanism in insects is linked to a number of life history traits: a positive relationship is hypothesized between melanism, immune function, fecundity and lifespan. However, it is not clear how activation of the immune system affects trade-offs between life history traits in female mealworm beetles (Tenebrio molitor) differing in cuticle melanization. The females with tan, brown and black cuticles examined in the present study did not differ in the intensity of encapsulation response, fecundity and longevity when their immune system was not activated. However, we found that immune activation and cuticle melanization have a significant effect on life history traits. Offspring number and lifespan decreased in females with tan and brown cuticles, while the fecundity and lifespan of black females were not affected. Importantly, we inserted the implants again and found a significant decrease in the strength of encapsulation response in females with tan and brown cuticles. In contrast, black females increased melanotic reactions against the nylon implant, suggesting immunological priming. The results show that cuticle melanization plays an important adaptive role under the risk of being infected, while the lack of these benefits before the insertion of nylon monofilaments suggests that there are costs associated with an activated immunity system.

Cost-effectiveness of providing patients with information on managing mild low-back symptoms in an occupational health setting

BACKGROUND

Evidence shows that low back specific patient information is effective in sub-acute low back pain (LBP), but effectiveness and cost-effectiveness (CE) of information in early phase symptoms is not clear. We assessed effectiveness and CE of patient information in mild LBP in the occupational health (OH) setting in a quasi-experimental study.

METHODS

A cohort of employees (N = 312, aged <57) with non-specific, mild LBP (Visual Analogue Scale between 10-34 mm) was selected from the respondents of an employee survey (N = 2480; response rate 71 %). A random sample, representing the natural course of LBP (NC, N = 83; no intervention), was extracted as a control group. Remaining employees were invited (181 included, 47 declined, one excluded) into a randomised controlled study with two 1:1 allocated parallel intervention arms ("Booklet", N = 92; "Combined", N = 89). All participants received the "Back Book" patient information booklet and the Combined also an individual verbal review of the booklet. Physical impairment (PHI), LBP, health care (HC) utilisation, and all-cause sickness absence (SA) were assessed at two years. CE of the interventions on SA days was analysed by using direct HC costs in one year, two years from baseline. Multiple imputation was used for missing values.

RESULTS

Compared to NC, the Booklet reduced HC costs by 196€ and SA by 3.5 days per year. In 81 % of the bootstrapped cases the Booklet was both cost saving and effective on SA. Compared to NC, in the Combined arm, the figures were 107€, 0.4 days, and 54 %, respectively. PHI decreased in both interventions.

CONCLUSIONS

Booklet information alone was cost-effective in comparison to natural course of mild LBP. Combined information reduced HC costs. Both interventions reduced physical impairment. Mere booklet information is beneficial for employees who report mild LBP in the OH setting, and is also cost saving for the health care system.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00908102.

The effectiveness of two active interventions compared to self-care advice in employees with non-acute low back symptoms: a randomised, controlled trial with a 4-year follow-up in the occupational health setting

OBJECTIVE

Evaluate the effectiveness of two active interventions, aimed at secondary prevention of low back pain (LBP), in occupational health.

METHODS

We performed a survey of LBP (n=2480; response rate 71%) and randomized 143 employees (66% males, 45 years) with LBP over 34 mm on VAS into Rehabilitation (n=43), Exercise (n=43) or self-care (n=40) groups. Primary outcomes were LBP, physical impairment (PI) and health-related quality of life (HRQoL) for two years and sickness absence (SA) days during four years (LBP specific, total).

RESULTS

Compared to self-care, exercise reduced LBP at 12 months (mean difference (MD) -12 mm; 95% CI -21 to -2) and improved HRQoL at 12 and 24 months (0.03; 0.00 to 0.05), but did not reduce PI. The MDs of SA days in four years were -17 (-70 to 35, total) and -15 (-47 to 13, LBP specific). Exercise reduced the probability of LBP specific SA during the third and fourth year. Compared to self-care, Rehabilitation reduced LBP at 3 months (-10 mm; -19 to -1) and 6 months (-10 mm; -20 to - 1), but was not effective in HRQoL or PI. The MDs of SA days in four years were -41 (-93 to 8; total) and 5 (-30 to 47; LBP specific). Rehabilitation reduced the probability of total SA during first and second year and amount of total SA days in the fourth year.

CONCLUSIONS

Among employees with relatively mild LBP, both interventions reduced pain, but the effects on SA and PI were minor. Exercise improved HRQoL. The effect sizes were rather small.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT00908102.

Traumatic spinal cord injury as a complication to ankylosing spondylitis. An extended report

OBJECTIVE

Käpylä Rehabilitation Centre is in Finland the only unit taking care of the subacute rehabilitation activities of patients with spinal cord injury (SCI). The annual incidence of new patients with SCI is 55 (1.1 per 100,000 inhabitants). The ankylosed spine (AS) is reported to be at greater risk for fracture and SCI. The aim of the study was to clarify if this higher risk of ankylosing spondylitis (AS) could also be detected among patients with traumatic SCI rehabilitated at Käpylä Rehabilitation Centre. Further, the aim was to evaluate the characteristics of patients with traumatic SCI as a complication to AS in order to develop prevention of SCI in patients with AS.

METHODS

Patient data was gathered from the patient register covering all Finnish patients with traumatic SCI (n = 1,103) rehabilitated at Käpylä Rehabilitation Centre from the year 1979 to 1998. The patient journals were subjected to a detailed and systematic analysis. Data about patients with a history of AS (n = 19; 18 men, 1 woman) was then compared to the data about all the patients with SCI (n = 1,103; 902 men, 201 women).

RESULTS

Based on the national prevalence data, the incidence rate of patients with AS for traumatic SCI was found to be 11.4 times greater than expected for the population at large. The mean age of the patients with AS was clearly higher (55.3 yrs) than the mean age of the whole group of patients (36.4 yrs) with traumatic SCI. The neurologic injury was at the cervical level in 84% of the patients with AS, but only in 48% of the patients with traumatic SCI in general. Among the patients with AS, the SCI was caused by slipping in 53% of the cases, whereas slipping was the reason for SCI only in 7% of the cases in general.

CONCLUSION

Patients with AS seem to run a higher risk of traumatic SCI than the people at large, and the injury levels are higher. In particular, male patients with advanced AS should be instructed to install preventive devices such as night lights and handrails, supports or head rests when driving a car, and they should avoid walking on slippery surfaces, loose carpets etc. They also should be encouraged to avoid excessive use of alcohol and activities involving the risk of physical injury such as contact sports.

The effect of lumbar fatigue on the ability to sense a change in lumbar position. A controlled study

STUDY DESIGN

A cross-sectional study in patients with recurrent/chronic low back trouble and healthy control subjects.

OBJECTIVE

To evaluate the effect of paraspinal muscle fatigue on the ability to sense a change in lumbar position.

SUMMARY OF BACKGROUND DATA

Protection against spinal injury requires proper anticipation of events, appropriate sensation of body position, and reasonable muscular responses. Lumbar fatigue is known to delay lumbar muscle responses to sudden loads. It is not known whether the delay is because of failure in the sensation of position, output of the response, or both.

METHODS

Altogether, 106 subjects (57 patients with low back trouble [27 men and 30 women] and 49 healthy control subjects [28 men and 21 women]) participated in the study. Their ability to sense a change in lumbar position while seated on a special trunk rotation unit was assessed. A motor rotated the seat with an angular velocity of 1 degree per second. The task in the test involved reacting to the perception of lumbar movement (rotation) by releasing a button with a finger movement. The test was performed twice, before and immediately after a fatiguing procedure. During the endurance task, the participants performed upper trunk repetitive extensions against a resistance, with a movement amplitude adjusted between 25 degrees flexion and 5 degrees extension, until exhaustion.

RESULTS

Patients with chronic low back trouble had significantly poorer ability than control subjects on the average to sense a change in lumbar position (P = 0.007), which was noticed before and after the fatiguing procedure. Lumbar fatigue induced significant impairment in the sensation of position change (P < 0.000001).

CONCLUSIONS

Lumbar fatigue impairs the ability to sense a change in lumbar position. This feature was found in patients and control subjects, but patients with low back trouble had poorer ability to sense a change in lumbar position than control subjects even when they were not fatigued. There seems to be a period after a fatiguing task during which the available information on lumbar position and its changes is inaccurate.

Mechanisms explaining the association between low back trouble and deficits in information processing. A controlled study with follow-up

STUDY DESIGN

A controlled study with a 6-month follow-up period.

OBJECTIVES

To find an explanation for the association between impairment in information processing, i.e., slow reaction times, and chronic low back trouble.

SUMMARY OF BACKGROUND DATA

Low back trouble, chronic pain in general, and depression have been associated with impaired cognitive functions and slow reaction times. It is a common phenomenon that the preferred hand performs better than the nonpreferred hand in motor tasks. The authors hypothesized that chronic low back trouble hampers the functioning of short-term memory in a way that leads the preferred hand to loose its advantage over the nonpreferred hand, but that the advantage would be restored during the rehabilitation.

METHODS

Sixty-one healthy control subjects and 68 patients with low back trouble participated in the study. Reaction times for the preferred and nonpreferred upper limbs were tested. A multiway analysis of covariance was used to examine the group, handedness, and rehabilitation effects on reaction times. The hypothesis was specifically tested with a third-degree interaction: group-handedness-rehabilitation.

RESULTS

A significant interaction among group, handedness, and rehabilitation was found (P = 0.05). At the beginning, the reaction times for the preferred hand were faster among the control subjects (P = 0.001), but not among the patients with low back trouble (P = 0.62). After the rehabilitation, the preferred hand was faster both among the control subjects (P = 0.001) and the patients with low back trouble (P = 0.0002). During the rehabilitation, back pain, psychological distress, and general disability decreased significantly among the patients with chronic low back trouble.

CONCLUSIONS

The results support the hypothesis that chronic low back trouble (i.e., pain, psychological distress, and general disability) hampers the functioning of short-term memory, which results in decreased speed of information processing among patients with chronic low back trouble.

Psychomotor speed in chronic low-back pain patients and healthy controls: construct validity and clinical significance of the measure

The effect of ethanol on reaction times was studied in 5 healthy men to test the construct validity of the measure. Reaction times were studied among 61 healthy controls and 99 patients with chronic low-back pain (68 moderate and 31 severe) to evaluate the diagnostic value of reaction time measurements. Analysis of receiver operating characteristics was used to calculate the discriminative power of the reaction time measurements. The severity of low-back pain was associated with slow reaction times but the diagnostic value of a single reaction time measurement was low due to insufficient sensitivity. In conclusion, even though many patients with low-back pain suffer from central impairment of motor function, a single reaction time measurement is not usable in evaluation of the severity of low-back pain.