Sex: A change in our guidelines to authors to ensure that this is no longer an ignored experimental variable

• DOI: 10.1111/bph.14761
• Publication Date: 2019-08-23T08:00:22Z
• Authors: James R. Docherty; S. Clare Stanford; Reynold A. Panett...; Steve P.H. Alexander; Giuseppe Cirino; Christopher H. Ge...; Daniel Hoyer; Angelo A. Izzo; Yong Ji; Elliot Lilley; Christopher G. Sobey; Phil Stanley; Barbara Stefanska; Gary Stephens; Mauro Teixeira; Amrita Ahluwalia
• Keywords: Blame; Suspect; Categorical variable

Precision medicine is a buzz word mentioned frequently in the research world currently. Indeed, initiatives such as UK's 100,000 genomes project are based on premise that better understanding of an individual's biology and genomic profile enables clinicians to serve their patients. In some patients, this approach has led diagnosis rare disease effective treatment was not obvious without genetic information. light these technological advances, it seems unconscionable "sex," which probably most distinguishing characteristic humans, been largely ignored biomedical research. Hitherto, blame for frequent failure translate findings sciences into any human benefit focused issues subjective bias, flawed experimental design, inappropriate statistical analysis, causal factors. By contrast, little consideration given sex differences either efficacy existing therapeutics or implications refinement. Yet increasingly apparent long-established practice studying predominantly one (typically males) could contribute translate. To help rectify problem, editorial outlines rationale policy requires be considered categorical variable all studies submitted publication British Journal Pharmacology. We also offer advice how incorporate optimised design. clear, article, "sex" defined by status subject, whereas "gender" refers social cultural context. Conceptually, interventions animals, castration/ovariectomy, with hormone replacement/substitution, have already provided substantial information about importance hormones anatomical physiological development, well ensuing behavioural traits. The study gender animals possible at present remains clinical endeavour. Interest response harks back far Hippocrates, who noted fever outbreak women were less affected terms symptoms mortality (Hippocrates Kos, ca. 400 BCE). discovery systematic comparisons animals' responses challenge new. For instance, evidence learning behaviour female rats more than males reported 1930s (McNemar & Stone, 1932). Subsequent found higher variability (see, e.g., Broadhurst, 1957). A recent extended processes involved fear conditioning, clearly differ females, especially during extinction (Clark, Drummond, Hoyer, Jacobson, 2019). Likewise, 1947, Boynton Todd both systolic diastolic blood pressures, measured large cohort, young men women—a finding later replicated dogs (Van Liere, Stickney, Marsh, 1949). Despite accumulating leads biology, used rarely reported. Volume 1 Pharmacology (and Chemotherapy) (1946), there 27 papers, 21 did specify sex. majority cases, sexes used, numbers studied. Of remaining six only specified use three only, but two testis. papers included experiments uterine tissue. challenges females perceived justification male even groups had overall (e.g., Sinha, Singh, 1959). 1960, attempts reduce variance data driving investigators single sex, strategy endorsed prominent textbook (Lewis, 1960). section book, dealing amongst recommendation "[in experiments,] from same strain, similar age, weight should used." Meanwhile, world, emerging thalidomide causes congenital abnormalities humans. This preferential order avoid risk exposing novel drugs trials. late 1970s, clear wide range systems (circadian rhythms, feeding, effects localised lesion brain regions, sensory systems, Beatty, 1979). There further depends species animal stage development. reports, strong males, entrenched preclinical experiments, albeit different reasons. Exceptions using non-human primates, where pooled Yanagita Takahashi, 1970). However, motivated need unacceptable waste much drug group "typical" subjects sampled population. Sex now described major fields pathology, physiology, pharmacology humans animals. recognised ischaemic heart result disparities outcome increased morbidity post-myocardial infarction (Aggarwal et al., 2018). Another cohort study, European Prospective Investigation Cancer Nutrition (EPIC), prevalence certain diet-related cancers (Zamora-Ros 2018); attributed activity metabolic enzymes Dellinger, Garcia, Meyskens, 2014). numerous reports inflammatory stimuli confirmed healthy volunteers (Rathod 2017), report indicates genetically dependent incidence irritable bowel syndrome (Bonfiglio These few examples patients provide when investigating pathways disease, identifying targets teasing out therapeutics. tangible growing appreciation within community sex/gender important. PubMed search term "sex difference" 2018 identifies 41 reviews. particular, growth stimulated commissioning BJP Themed Issue topic 2019. themed issue alone, reviews original articles demonstrating important determinant phenotype, diverse body spanning across schizophrenia (Gogos, Ney, Seymour, Van Rheenen, Felmingham, 2019), sensation (Clark 2019) metabolism (Henstridge, Abildgaard, Lindegaard, Febbraio, obesity (Taylor, Ramirez, Musail, Sullivan, focus upon diversity evident literature: Recent include airway smooth muscle, isolated obese manifests greater agonist-induced excitation–contraction coupling those derived lean (Orfanos 2018) thermoregulatory CNS stimulant, cathinone (Alsufyani Docherty, identified. notable complication interest can depend interaction between genotype, case vulnerability strain altered mice (Pillidge, Heal, Stanford, 2016). Unlike 1946, today. consecutive (published Vol 176 3–7), 22 19 improvement. 19, 12 five females. tissues (tissue, blood, cell culture) source. Cell culture lines 16 studies, cultures being None compared sexes. contend whilst reporting encouraging, enough state so, improve our practices further, we encourage researchers Arguably, reason facilitate successful translation science goals well-being, regardless It encouraging new molecular entities, repurposing drugs, risks if supporting only. Furthermore, shows oestrous/menstrual cycle, just affect cardiac electrophysiology; see Salama Bett, Such underpin conventional view males. acknowledged concept challenged recently following meta-analysis (Prendergast, Onishi, Zucker, 2014) (Becker, Prendergast, Liang, 2016), conclusion "intrinsic … least great associated estrous cycle." Nevertheless, potential problems arise intention extrapolate whole population, obvious. Perhaps environment will stimulate much-needed, oestrous cycle actions. meantime, widely agreed problem no longer ignored, extent national funding agencies National Institutes Health (NIH) (USA) Swedish Research Council requiring and/or applications. Importantly, mandate includes cells maintained vitro, (https://orwh.od.nih.gov/sex-gender/nih-policy-sex-biological-variable). aspect critical since, electrophysiological muscle (Lu 2006) assess propensity cause ventricular arrhythmia Torsade de Pointes (Cubeddu, 2003), common level individual cardiomyocytes (Mason MacLeod, 2009; authors (human animal) primary (particularly purchased) mention lines, exceptions Chinese hamster ovary (CHO). address concerns regarding ethical burden surplus breeding. UK 1.81 million non-genetically (91% rats) bred scientific procedures 2017 killed, died, regulated procedure (Gov.uk, Some would collecting tissue post mortem, many stock comprise attrition taken account considering compliance 3Rs (Replacement, Reduction, Refinement), notably respect Reduction (Russell Burch, decided neglect variable, recommend future published journal acknowledge ideal scenario vivo researcher's relevant question, then statement providing required. Obvious reproduction, genitalia, actions hormones, sex-specific diseases immortalised lines. An example article details each Clark al. (2019). economics influence outcomes difficult until grant-funding insist adapt designs, accommodate necessary resources. manuscripts continue BJP. require justify decision gender. conclusions expressed cautiously; experiment, explicit effect work might Even once amended approach, fundamental pharmacological vitro (such receptors enzymes), still BJP, confirmation main sexes, unless doing so. shall review revise continually, ensure consistent funders they move towards mandatory support researchers, considerations, below, designing experiments. evidence, controversial, interest, comply homogeneity assumption must met valid parametric statistics. assumption, simple explained Curtis (2018). suitable transformation logarithm square root) applied responses, necessary, before carrying analysis. Overall and, importantly, interactions (i.e., intervention differs sexes) cannot inferred studied separate time frames. correct fully randomised study. If interventions, lead unequal replication versus groups. imbalance bias comparisons. technique "blocking" stratification so equally often is, randomise what looks like mini-study carried out, intervals, over long period time, subject tested once. appropriate treat "day" blocking factors, equal tested, parallel, day. distribution levels factor treatment) block, counterbalanced (as Williams Latin Square) series test days. conscious confounder close proximity opposite specific deal this, borne mind situation replicate "real world." ask merely consider whether physically separated, sight smell confound results, addressed Obviously, advisable house rooms because undermine exposed environmental factors properly controlled experiment. When vivo, experimenters blind animal. currently journal, blinding place whenever possible. example, samples coded processing them after taking analysis data, other resolve arising introduced earlier stages inevitable consequence used. adopting factorial "Sex" "Treatment" doses) relatively small number sufficient objectives experiment rest comparing pairs means, hoc vs. dose, vehicle sex) then, journal's rubric, sample sizes N ≥ 5 combination Treatment. follows doses (or drugs) plus vehicle, (with receiving treatment), total 40 (see Table 1). design two-way ANOVA analyse implies raw shared levels. As consequence, 40-animal wasting impact measure compromise Russell likely objective solely (across interest. arguing that, representative setting, incorporated interrogated, suggest sometimes adequate. Treatment yields Providing combine proceed illustrates prospective definition objective(s) careful planning size estimation documented manuscript. topic, see: Bate (2014); Percie du Sert (2017); NC3Rs Experimental Design Assistant (https://www.nc3rs.org.uk/experimental-designassistant-eda); Festing (2016). Unless specifically investigate drug-induced record journal. determine moderately stressful stress outcome. aware may particularly cocaine (Calipari 2017; Nicolas wish thank Simon T. his helpful comments early draft article. declare conflicts