Null Findings Research Articles

Abstract 4128962: Medicaid Work Requirements and Changes in Insurance Coverage, Employment, Access to Care, and Health Status Overall and Among People with Cardiovascular Disease

Introduction: Medicaid work requirements have been at the forefront of health policy debate. Proponents argue that these policies increase employment, reduce poverty, and improve health. Critics have raised concerns that work requirements lead to loss of coverage and impede access to care. Hypothesis: We hypothesized that Medicaid work requirement implementation would be associated with decreased insurance coverage and healthcare access without impacting employment. Methods: We used the Behavioral Risk Factor Surveillance System (a nationally representative survey administered by the CDC) to estimate the impact of Medicaid work requirements on insurance coverage, employment, access to care, and self-reported health. We used a difference-in-differences (DID) approach to compare changes in outcomes in Arkansas (where work requirements were implemented) versus control states. Outcomes were self-reported and included: 1) insurance coverage, 2) employment, 3) presence of a personal healthcare provider, 4) inability to see a doctor due to cost, and 5) self-reported health. The analysis was conducted among all respondents and among respondents with cardiovascular disease, who were hypothesized to be particularly vulnerable to negative sequelae of insurance loss. Results: The implementation of Medicaid work requirements in Arkansas was associated with decreased insurance coverage compared with control states (adjusted DID estimate -4.3%, CI -8.4%, -0.1%), but no increase in employment rates (-2.2% CI -7.0%, 2.6%). There was a trend toward decreased likelihood of having a personal healthcare provider (-4.7% CI -9.9%, 0.5%). There was no change in inability to see a doctor due to cost or self-reported good health. When this analysis was repeated among participants with cardiovascular disease, work requirement implementation was not associated with changes in any of the outcome variables. Conclusions: The implementation of Medicaid work requirements in Arkansas was associated with decreased insurance coverage and no change in employment. Our findings are particularly relevant given national policy debate about work requirement expansion and the recent implementation of Medicaid work requirements in Georgia. Despite the null findings among respondents with cardiovascular disease (likely the result of a small sample size), this study has important implications for cardiovascular health given the close association between insurance coverage and cardiovascular outcomes.

Academic buoyancy and fear of failure differences among university students: Null findings

Academic buoyancy refers to a student's adaptive response for dealing with academic-related setbacks and challenges that are typical in the ordinary course of school life. Fear of failure, known also as fear avoidance, is the tendency for students to be uncertain about their ability to avoid failures and achieve success. Both constructs have been associated with students' academic outcomes. Herein, we examine whether there were differences in these constructs associated either with students' time in the academic setting (i.e., first generation student or graduate level student) or type of challenges experienced (i.e., as a student of color or primary language other than English). Specifically, in using online surveys, we investigated the relation between academic buoyancy and fear of failure among university students (N = 122) from a public university in the southwestern United States. Supporting earlier research, when examining the association between academic buoyancy and fear of failure across all participating students, we found academic buoyancy was negatively related to fear of failure. When examining whether there were differences in academic buoyancy or fear of failure across either student experience (i.e., degree level or first-generation student status) or types of challenges related to being a student whose primary language is a language other than English or being a student of color, we found insufficient evidence of differences. This suggests that regardless of college-generational status, degree level, primary language, and racial/ethnic backgrounds, students reported similar levels of academic buoyancy and fear of failure. Findings extend the limited literature on academic buoyancy and fear of failure in higher education.

Illusion of control or passive superstition? A comparison of two explanations for irrational gambling beliefs.

The "illusion of control" is a dominant cognitive illusion in disordered gambling, but its role in shaping irrational gambling beliefs has been questioned by recent null experimental findings. Here, we aimed to test this recent work, in a preregistered Bayesian framework, by additionally correlating the dependent variable (nonuniform probabilistic beliefs) with self-reported gambling behavior and by exploring "passive superstition" as an alternative driver of these irrational gambling beliefs. A between-participants online experiment involving three boxes, one of which a $1 prize was randomly assigned to (N = 3,064; 49.1% males, 49.5% females, 1.4% other; Mage = 42.5 years). Participants estimated the likelihood of each box winning, with any estimates outside the 33%-34% interval categorized as irrational "nonuniform" probabilistic beliefs. "Preselection" participants gave estimates prior to box selection, "post-no-choice" participants had their box randomly selected, and participants in the treatment "postchoice" condition selected their own box. Whether participants gambled within the past 12 months (gambling status), Problem Gambling Severity Index (PGSI) score, and passive superstition scores were used as additional predictors. Comparing postchoice participants with post-no-choice participants (95% CI [0.80, 1.22]) and comparing postchoice with preselection participants (95% CI [0.88, 1.34]) yielded substantial support for a null effect. Gambling status supported substantial evidence for a null effect (95% CI [0.92, 1.30]), whereas higher PGSI (95% CI [1.08, 1.13]) and higher passive superstition scores (95% CI [1.08, 1.10]) overwhelmingly predicted our outcome. Active choice elements in illusions of control may have been overemphasized in irrational gambling beliefs compared to passive superstitions. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Measuring Socioeconomic and Stress Disparities in Infant Declarative Memory Using the Visual Paired Comparison Task.

Research suggests that socioeconomic circumstances and stress predict memory skills in adults and older children, yet few studies have addressed this question in infancy. The current study used the visual-paired comparison paradigm to examine whether socioeconomic circumstances, maternal perceived stress, and/or maternal physiological stress, all measured prenatally, predict memory performance among 6-month-old infants. We found no significant associations between infant memory and any measure of socioeconomic circumstance or stress. Potential explanations for these null findings are discussed.

Impact of Adverse Childhood Experiences on Child Development in South America: A Systematic Review

Abstract Background Adverse Childhood Experiences (ACEs) have garnered attention globally for their detrimental effects on children’s development, such as lower communication, gross and fine motor, and personal-social domains. While extensively studied in high-income countries, there remains a gap in understanding their prevalence and impact in low- and middle-income countries (LMICs). This review aimed to identify, evaluate, and summarize the findings of an association between ACEs and children’s developmental and mental health outcomes in South America Methods A systematic review was conducted to investigate the association between ACEs and childhood development in South America. Databases MEDLINE, PsycINFO, Web of Science, Applied Social Sciences Index and Abstracts, Literatura Latino Americana em Ciências da Saúde, IBECS and CINAHL were searched. Selection criteria encompassed studies from Brazil, Colombia, Argentina, Peru, Venezuela, Chile, Ecuador, Bolivia, Paraguay, Uruguay, Guyana and Suriname examining the effects of ACEs on developmental outcomes and mental health disorders in children under 18 years old. Quality assessment aligned with World Health Organization standards was employed. Results Twenty-four studies met the inclusion criteria, with most categorized as low or very low quality. While the majority demonstrated a significant association between ACEs and developmental or mental health outcomes, a few studies reported null findings. Challenges in study quality, such as small sample sizes and selection bias, were identified. Conclusions Despite limitations in study quality, findings underscore the impact of ACEs on child development and mental health in South America. Because of the low quality of the existent studies the next steps should be to grasp a greater understanding of the issue. This review also highlights the urgency for further research and targeted interventions to mitigate the long-term consequences of ACEs in this region. Key messages • ACEs profoundly affect child development and mental health in South America, necessitating urgent attention and intervention. • Addressing the impact of ACEs in South America is critical for fostering healthier developmental trajectories and enhancing public health outcomes.

Measuring and Explaining Situational Fear of Crime: An Experimental Study Into the Effects of Disorder, Using Virtual Reality and Multimodal Measurement

Abstract The current study combines an experimental research design, Virtual Reality (VR) and multimodal (survey and physiological) measurements to measure and explain situational fear of crime. 159 participants completed our VR experiment in which we focused on the role of physical and social disorder in engendering situational fear of crime. Drawing on our survey measures, we find significant effects of disorder on a variety of outcome variables: situationally experienced safety, fear of theft, fear of verbal aggression, fear and physical aggression and fear of sexually transgressive behaviour. Most of our physiological measures rendered null findings. Hence, we also conclude that the results from our two data sources (survey measures vs. physiological measures) diverge in important ways.

Underpowered studies in muscle metabolism research: Determinants and considerations

Biomedical research frequently employs null hypothesis testing to determine whether an observed difference in a sample is likely to exist in the broader population. Null hypothesis testing generally assumes that differences between groups or interventions are non-existent, unless proven otherwise. Because biomedical studies with human subjects are often limited by financial and logistical resources, they tend to have low statistical power, i.e. a low probability of statistically confirming a true difference. As a result, small but potentially clinically important differences may be overseen or ignored simply due to the absence of a statistically significant difference. This absence is often misinterpreted as ‘equivalence’ of treatments. In this educational paper, we will use practical examples related to the effects of exercise and nutrition on muscle protein metabolism to illustrate the most important determinants of statistical power, as well as their implications for both investigators and readers of scientific articles.Changes in muscle mass occur at a relatively slow rate, making it practically challenging to detect differences between treatment groups in a long-term setting. One way to make it ‘easier’ to differentiate between groups and hence increase statistical power is to have a sufficiently long study duration to allow treatment effects to become apparent. This is especially relevant when comparing treatments with relatively small expected differences such as the effect of modest changes in daily protein intake. Secondly, one could try to minimize the variance and response heterogeneity within groups, for example by using strict inclusion criteria and standardization protocols (e.g., meal provision), by using cross-over designs, or even within-subject designs where two interventions are compared simultaneously (e.g., studying an exercised limb vs a contralateral control limb) although this might limit the generalizability of the findings (e.g. such single-limb exercise training is not common in practice). In terms of data interpretation, investigators should obviously refrain from drawing strong conclusions from underpowered studies. Yet, such studies still provide valuable data for meta-analyses. Finally, because muscle protein synthesis rates are highly responsive to anabolic stimuli, acute metabolic studies are more sensitive to detect potentially clinically relevant differences in the anabolic response between treatments. Apart from further elaborating on these topics, this educational article encourages readers to more critically question null findings and scientists to more clearly discuss limitations that may have compromised statistical power.

Antimicrobial Resistance Gene Carriage is not Associated with Uremic Toxin Levels in Chronic Kidney Disease Patients

In chronic kidney disease (CKD), uremic toxin molecules build up and risk of infection increase overtime, making the presence of antimicrobial resistant (AMR) bacteria in the gut more problematic with advancing disease. This study assessed if serum levels of uremic toxins and gut carriage of AMR genes are correlated in individuals with CKD. Whole metagenomic sequencing of stool samples and measured levels of 4 uremic toxins from 21 individuals with CKD were obtained. Multivariable, multivariate linear regression was performed with total abundance of AMR genes and abundance of specific drug classes of AMR genes as outcome variables and serum levels of four uremic toxins as predictor variables. Beta diversity differences of AMR genes were visualized using non-metric multidimensional scaling (NMDS) based on robust Aitchison distances and tested using PERMANOVA. There were no significant associations between uremic toxin levels and AMR gene abundance, or with any of the drug classes of AMR genes. There were no significant differences in beta diversity of AMR genes. These null findings suggest that increased uremic toxin levels are not associated with an increase in AMR carriage, and therefore uremia does not appear to be a direct cause of increased resistant bacteria in patients with more severe CKD.

A study of long-term supraphysiologic-dose anabolic-androgenic steroid use on cognitive function in middle-aged men

ABSTRACT Background: Long-term use of supraphysiologic doses of anabolic-androgenic steroids (AAS) has been associated with impaired visuospatial memory in young men but little is known about its cognitive effects in middle-aged men. Objectives: We compared cognition in middle-aged men with histories of long-term AAS use and age-matched non-users. Methods: We administered cognitive tests from the CANTAB battery to 76 weightlifters aged 37–60 years (mean [SD] 48.5 [6.5] years), of whom 51 reported at least 2 years of cumulative AAS use and 25 reported no AAS exposure. Results: We found no significant AAS user versus non-user group differences on visuospatial, verbal memory, emotional recognition, or executive function tasks (corrected p’s ≥ .00089; effect sizes ≤ .5). Conclusions: Our null visuospatial task findings contrast with our prior younger cohort study (mean age 37.1 [7.1] years), in which we found impaired visuospatial task performance in people who use AAS, and with other reports of cognitive impairments in younger men use AAS. Men who use AAS may develop early visuospatial memory deficits that stabilize by middle age while middle-aged non-users’ performance may “catch up” due to normal age-related visuospatial declines. Similar effects could contribute to our null findings on other tasks. Between-study cohort substance use differences or environmental factor differences that modify cognition, such as study geographical location and time of year, also could contribute to our discordant findings. Since young adult male AAS users experience increased mortality from unnatural causes, improving our understanding of AAS cognitive effects in this age group is important.

Neuroprotective agents ineffective in mitigating autonomic dysreflexia following experimental spinal cord injury

Background and objectivesLoss of supraspinal cardiovascular control and secondary damage following spinal cord injury (SCI) lead to cardiovascular dysfunction, where autonomic dysreflexia (AD), triggered by stimuli below the injury, can cause uncontrolled blood pressure (BP) surges, posing severe health risks such as stroke and seizures. While anti-inflammatory neuroprotective agents have been studied for motor recovery, their impact on cardiovascular function remains under investigated. The objective was to assess the efficacy of four clinically approved neuroprotective agents in promoting cardiovascular recovery following SCI. MethodsMale Wistar rats received contusion at the third thoracic spinal segment (T3). Fluoxetine, Glyburide, Valproic acid, and Indomethacin were first administered at 1 h or 6 h post-SCI, and every 12 h for two weeks thereafter. Four weeks following SCI, hemodynamics were measured at rest and during colorectal distension. Locomotor function was assessed prior to SCI and weekly for four weeks after SCI, using the Basso-Beattie-Bresnahan (BBB) locomotor scale. Quantitative comparisons of lesion area were performed. ResultsContrary to the published literature, Indomethacin and Valproic acid resulted in high morbidity and mortality rates 60 % and 40 % respectively) within 2–3 days of administration. Fluoxetine, and Glyburide were well-tolerated. There were no differences in change in systolic BP with colorectal distension compared to control i.e., all experimental groups experienced severe episodes of AD [F(6, 67) = 0.94, p = 0.47]. There was no significant difference in BBB scores in any experimental group compared to control [F(18, 252) = 0.3, p = 0.99]. No between-group differences were observed in tissue sparing at the lesion epicentre [F(6, 422) = 6.98, p = 0.29]. DiscussionDespite promising beneficial effect reported in previous studies, none of the drugs demonstrated improvement in cardiovascular or motor function. Indomethacin and Valproic acid exhibited unexpected high mortality at doses deemed safe in the literature. This emphasizes the necessity for reproducibility studies in pre-clinical research and underscores the importance of publishing null findings to guide future investigations.

No man’s hand: artificial intelligence does not improve police report writing speed

Abstract Objectives This study examines the potential of artificial intelligence (AI) to reduce the time police officers spend writing reports, a task that consumes a significant portion of their workday. Methods In a pre-registered randomized controlled trial, we test this claim within the patrol division of a medium-sized police department (n = 85) at the individual report level (n = 755). Analyses utilize mixed-effects regression accounting for the nested structure of report-writing. Results AI assistance did not significantly affect the duration of writing police reports. Alternative specifications beyond those specified in the pre-registration, including a difference-in-differences approach observing report duration over a full year (n = 6084), confirm the null findings are robust. Conclusions Our findings contradict marketing expectations for the effect of this technology, suggesting no time savings in report-writing can be expected when using AI-assisted report-writing. Several other potential effects remain possible and untested.

Arsenic exposure and measures of glucose tolerance in Bangladeshi adults: A cross-sectional study.

Arsenic has been associated with diabetes and impaired glucose tolerance in many studies, although some reports have shown null findings. We conducted a cross-sectional study among 300 adults in Bangladesh. Participants were randomly selected from a roster of 1800 people who previously participated in studies of arsenic and skin lesions. We measured fasting glucose and insulin levels. We assessed drinking water arsenic concentration using graphite furnace atomic absorption spectrophotometry (GF-AAS) and toenail arsenic concentration using inductively coupled mass spectrometry (ICP-MS). We ran covariant-adjusted, linear regression and spline models to examine associations of arsenic concentrations with the homeostatic model assessment of insulin resistance (HOMA-IR), a marker of insulin resistance, and HOMA of beta-cell function (HOMA-β), a marker of beta-cell function. Among 285 participants with complete data, the median (IQR) arsenic concentration was 4.0 (6.9) μg/g in toenails and 39.0 (188.5) μg/L in drinking water. Arsenic concentrations were not associated with insulin resistance or beta-cell function. HOMA-IR was 0.67% lower and HOMA-β was 0.28% lower per µg/g increment in toenail arsenic, but these effect estimates were small, and confidence intervals crossed the null value. Although arsenic exposure has been associated with diabetes, we found no evidence of an adverse effect on insulin resistance or beta-cell function.

Incorporating sources of correlation between outcomes: An introduction to mixed models.

Animal research often involves measuring the outcomes of interest multiple times on the same animal, whether over time or for different exposures. These repeated outcomes measured on the same animal are correlated due to animal-specific characteristics. While this repeated measures data can address more complex research questions than single-outcome data, the statistical analysis must take into account the study design resulting in correlated outcomes, which violate the independence assumption of standard statistical methods (e.g. a two-sample t-test, linear regression). When standard statistical methods are incorrectly used to analyze correlated outcome data, the statistical inference (i.e. confidence intervals and p-values) will be incorrect, with some settings leading to null findings too often and others producing statistically significant findings despite no support for this in the data. Instead, researchers can leverage approaches designed specifically for correlated outcomes. In this article, we discuss common study designs that lead to correlated outcome data, motivate the intuition about the impact of improperly analyzing correlated outcomes using methods for independent data, and introduce approaches that properly leverage correlated outcome data.

Breaking free from linear assumptions: Unravelling the relationship between affective polarization and democratic support

AbstractScholars increasingly raise concerns about the alleged detrimental impact of affective polarization on citizens’ democratic attitudes. Yet, prior studies on the relationship between affective polarization and democratic support have yielded mixed results: Whereas some scholars report evidence that affective polarization erodes citizens’ support for democracy, others report null findings. In this research note, we posit that one relevant explanation for these mixed results is that the relationship between affective polarization and democratic support is not linear, but rather negatively curvilinear (i.e., an inverted U‐shape). Though extreme levels of affective polarization may harm citizens’ democratic commitments, a moderate amount of affective polarization can strengthen democratic support by heightening the political stakes and stimulating democratic involvement. Employing generalized additive modelling on data from the CNEP collected in Germany, the United Kingdom, and the United States, we show strong and robust support for this negatively curvilinear pattern. These findings have important implications for our understanding of the dynamics between affective polarization and democratic support, as well as for the recommended estimation strategies of future studies that aim to explore this relationship.

Genetically predicted dietary intake and risks of colorectal cancer: a Mendelian randomisation study

BackgroundEffects of confounders on associations between diet and colorectal cancer (CRC) in observational studies can be minimized in Mendelian randomization (MR) approach. This study aimed to investigate observational and genetically predicted associations between dietary intake and CRC using one-sample MR.MethodsUsing genetic data of over 93 million variants, we performed a genome-wide association study to find genomic risk loci associated with dietary intake in participants from the UK Biobank. Then we calculated genetic risk scores of diet-related variants and used them as instrumental variables in the two-stage least square MR framework to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for associations. We also performed observational analyses using age as a time-scale in Cox proportional hazard models.ResultsAllele scores were calculated from 399 genetic variants associated with the consumption of of red meat, processed meat, poultry, fish, milk, cheese, fruits, vegetables, coffee, tea, and alcohol in participants from the UK Biobank. In MR analysis, genetically predicted fruit intake was significantly associated with a 21% decreased risk of CRC (HR = 0.79, 95% CI = 0.66–0.95), and there was a marginally inverse association between vegetable intake and CRC (HR = 0.85, 95% CI = 0.71–1.02). However, null findings were observed in multivariable analysis, with HRs (95% CIs) of 0.99 (0.98–1.01) and 0.99 (0.98–1.00) per increment of daily servings of fruits and vegetables, respectively.ConclusionDietary habits were attributable to genetic variations, which can be used as instrumental variables in the MR framework. Our study supported a causal relationship between fruit intake and a decreased risk of CRC and suggested an effective strategy of consuming fruits in the primary prevention of CRC.

Re‐evaluating the impact of collective victimhood on conflict attitudes: Results from a natural experiment, a survey experiment, and panel study using Israel's Holocaust Memorial Day

AbstractA significant observational literature identifies a link between collective victimhood and conflict‐enhancing attitudes, though results from experimental work increasing victimhood's salience vary. This article thus revisits this question in two studies in a context in which increased salience is especially likely to shift attitudes. Study 1 exploits the happenstance fielding of 12 surveys over Israel's Holocaust Memorial Day between 1979 and 2021. Using all 192 available estimates assessing hawkishness, preferences for out‐group exclusion, and in‐group solidarity, it fails to detect statistically significant effects of a state‐led effort to increase the salience of Israel's collective victimhood narrative in a natural setting 90% of the time. Study 2 replicates the null findings across multiple comparisons and outcomes in a companion harmonized panel and survey experiment. Substantively, the findings suggest that it may be harder to use short‐term manipulations of collective victimhood to shift attitudes than often assumed.

Estimating the Effect of a Universal Cash Transfer on Birth Outcomes

Babies in the United States fare worse than their peers in other high-income countries, and their well-being is starkly unequal along socioeconomic and racialized lines. Newborn health predicts adult well-being, making these inequalities consequential. Policymakers and scholars seeking to improve newborn health and reduce inequality have recently looked to direct cash transfers as a viable intervention. We examine the only unconditional cash transfer in the United States, the Alaska Permanent Fund Dividend (PFD), to learn if giving pregnant people money improves their newborns’ health. Alaska has paid its residents a significant dividend annually since 1982. The dividend’s size varies yearly and is exogenous to Alaskans and the local economy, permitting us to make causal claims. After accounting for fertility selection, we find that receiving cash during pregnancy has no meaningful effect on newborn health. Current theory focuses on purchasing power and status mechanisms to delineate how money translates into health. It cannot illuminate this null finding. This case illustrates a weakness with current theory: it does not provide clear expectations for interventions. We propose four components that must be considered in tandem to predict whether proposed interventions will work.

Effects of reducing sedentary behaviour by increasing physical activity, on cognitive function, brain function and structure across the lifespan: a systematic review and meta-analysis

ObjectiveTo examine the acute and chronic effects of reducing prolonged sedentary time (ST) with physical activity (PA) on cognitive and brain health.DesignSystematic review and meta-analysis.Data sourcesPubMed, Scopus, CINAHL, PsycINFO, SPORTDiscus,...

Barking up the wrong tree? Voter bias and female underrepresentation in Japanese politics

Abstract Previous studies on gender bias in the evaluation of politicians by voters have reported mixed results. We seek to understand these mixed findings by focusing on Japan, where female political representation is the lowest among advanced democracies and gender stereotypes are prevalent. We consider that gender stereotypes and the dearth of women in politics affect the evaluation of politicians via two distinct mechanisms: biased beliefs and weak priors. The two mechanisms are assumed to run counter to each other, thus leading to the null or mixed findings for gendered evaluation reported by previous studies. To test our argument, we conduct a series of survey experiments in Japan. Our findings conform to neither of the two mechanisms. Even in a society with low female political representation, we find no evidence of the gendered evaluation of candidates by voters. We suggest that rather than biasing voters’ evaluation of candidates, gender stereotypes dissuade women from aspiring to a political career and elite electoral gatekeepers from selecting female candidates.

Risk factors for the development of refeeding syndrome in adults: A systematic review.

Identifying patients with a particularly high risk of refeeding syndrome (RFS) is essential for taking preventive measures. To guide the development of clinical decision-making and risk prediction models or other screening tools for RFS, increased knowledge of risk factors is needed. Therefore, we conducted a systematic review to identify risk factors for the development of RFS. PubMed, EMBASE, Cochrane Library, and Web of Science were searched from January 1990 until March 2023. Studies investigating demographic, clinical, drug use, laboratory, and/or nutrition factors for RFS were considered. The Newcastle-Ottawa Scale was used to appraise the methodological quality of included studies. Of 1589 identified records, 30 studies were included. Thirty-three factors associated with increased risk of RFS after multivariable adjustments were identified. The following factors were reported by two or more studies, with 0-1 study reporting null findings: a previous history of alcohol misuse, cancer, comorbid hypertension, high Acute Physiology and Chronic Health Evaluation II score, high Sequential Organ Failure Assessment score, low Glasgow coma scale score, the use of diuretics before refeeding, low baseline serum prealbumin level, high baseline level of creatinine, and enteral nutrition. The majority of the studies (20, 66.7%) were of high methodological quality. In conclusion, this systematic review informs on several risk factors for RFS in patients. To improve risk stratification and guide development of risk prediction models or other screening tools, further confirmation is needed because there were a small number of studies and a low number of high-quality studies on each factor.