Gender is not accurately captured by the traditional male and female dichotomy of sex. Instead, it is a complex social system that structures the life experience of all human beings. This paper, the first in a Series of five papers, investigates the relationships between gender inequality, restrictive gender norms, and health and wellbeing. Building upon past work, we offer a consolidated conceptual framework that shows how individuals born biologically male or female develop into gendered beings, and how sexism and patriarchy intersect with other forms of discrimination, such as racism, classism, and homophobia, to structure pathways to poor health. We discuss the ample evidence showing the far-reaching consequences of these pathways, including how gender inequality and restrictive gender norms impact health through differential exposures, health-related behaviours and access to care, as well as how gender-biased health research and health-care systems reinforce and reproduce gender inequalities, with serious implications for health. The cumulative consequences of structured disadvantage, mediated through discriminatory laws, policies, and institutions, as well as diet, stress, substance use, and environmental toxins, have triggered important discussions about the role of social injustice in the creation and maintenance of health inequities, especially along racial and socioeconomic lines. This Series paper raises the parallel question of whether discrimination based on gender likewise becomes embodied, with negative consequences for health. For decades, advocates have worked to eliminate gender discrimination in global health, with only modest success. A new plan and new political commitment are needed if these global health aspirations and the wider Sustainable Development Goals of the UN are to be achieved.

Despite global commitments to achieving gender equality and improving health and wellbeing for all, quantitative data and methods to precisely estimate the effect of gender norms on health inequities are underdeveloped. Nonetheless, existing global, national, and subnational data provide some key opportunities for testing associations between gender norms and health. Using innovative approaches to analysing proxies for gender norms, we generated evidence that gender norms impact the health of women and men across life stages, health sectors, and world regions. Six case studies showed that: (1) gender norms are complex and can intersect with other social factors to impact health over the life course; (2) early gender-normative influences by parents and peers can have multiple and differing health consequences for girls and boys; (3) non-conformity with, and transgression of, gender norms can be harmful to health, particularly when they trigger negative sanctions; and (4) the impact of gender norms on health can be context-specific, demanding care when designing effective gender-transformative health policies and programmes. Limitations of survey-based data are described that resulted in missed opportunities for investigating certain populations and domains. Recommendations for optimising and advancing research on the health impacts of gender norms are made.

Evidence that gender inequalities and restrictive norms adversely affect health is extensive; however, far less research has focused on testing solutions. We first comprehensively reviewed the peer-reviewed and grey literature for rigorously evaluated programmes that aimed to reduce gender inequality and restrictive gender norms and improve health. We identified four mutually reinforcing factors underpinning change: (1) multisectoral action, (2) multilevel, multistakeholder involvement, (3) diversified programming, and (4) social participation and empowerment. Following this review, because little research has investigated the effects of national-level law and policy reforms, we conducted original quasi-experimental studies on laws and policies related to education, work, and income, all social determinants of health in which deep gender inequalities exist. We examined whether the laws and policies significantly affected health outcomes and gender norms, and whether law-induced and policy-induced changes in gender norms mediated the health effects, in areas for which longitudinal data existed. Laws and policies that made primary education tuition-free (13 intervention countries with the law and/or policy and ten control countries without) and that provided paid maternity and parental leave (seven intervention and 15 control countries) significantly improved women's and their children's health (odds ratios [OR] of 1·16-2·10, depending on health outcome) and gender equality in household decision making (OR 1·46 for tuition-free and 1·45 for paid maternity and parental leave) as a proxy indicator of gender norms. Increased equality partially mediated the positive effects on health outcomes. We conclude by discussing examples of how improved governance can support gender-equitable laws, policies, and programmes, immediate next steps, and future research needs.

Restrictive gender norms and gender inequalities are replicated and reinforced in health systems, contributing to gender inequalities in health. In this Series paper, we explore how to address all three through recognition and then with disruptive solutions. We used intersectional feminist theory to guide our systematic reviews, qualitative case studies based on lived experiences, and quantitative analyses based on cross-sectional and evaluation research. We found that health systems reinforce patients' traditional gender roles and neglect gender inequalities in health, health system models and clinic-based programmes are rarely gender responsive, and women have less authority as health workers than men and are often devalued and abused. With regard to potential for disruption, we found that gender equality policies are associated with greater representation of female physicians, which in turn is associated with better health outcomes, but that gender parity is insufficient to achieve gender equality. We found that institutional support and respect of nurses improves quality of care, and that women's empowerment collectives can increase health-care access and provider responsiveness. We see promise from social movements in supporting women's reproductive rights and policies. Our findings suggest we must view gender as a fundamental factor that predetermines and shapes health systems and outcomes. Without addressing the role of restrictive gender norms and gender inequalities within and outside health systems, we will not reach our collective ambitions of universal health coverage and the Sustainable Development Goals. We propose action to systematically identify and address restrictive gender norms and gender inequalities in health systems.

Stroke thrombolysis with alteplase is currently recommended 0-4·5 h after stroke onset. We aimed to determine whether perfusion imaging can identify patients with salvageable brain tissue with symptoms 4·5 h or more from stroke onset or with symptoms on waking who might benefit from thrombolysis.

Refractive surgery has evolved beyond laser refractive techniques over the past decade. Laser refractive surgery procedures (such as laser in-situ keratomileusis), surface ablation techniques (such as laser epithelial keratomileusis), and photorefractive keratectomy have now been established as fairly safe procedures that produce excellent visual outcomes for patients with low-to-moderate amounts of ametropia. Additionally, a broader selection of options are now available to treat a wider range of refractive errors. Small incision lenticule extraction uses a femtosecond laser to shape a refractive lenticule, which is removed through a small wound. The potential advantages of this procedure include greater tectonic strength and less dry eye. In the future, intracorneal implants could be used to treat hyperopia or presbyopia. Phakic intraocular implants and refractive lens exchange might be useful options in carefully selected patients for correcting high degrees of ametropia. Thus, physicians are now able to provide patients with the appropriate refractive corrective option based on the individual's risk-benefit profile.

Mass gathering events are associated with major public health challenges. The 2014 Lancet Series on the new discipline of mass gatherings medicine was launched at the World Health Assembly of Ministers of Health in Geneva in May, 2014. The Series covered the planning and surveillance systems used to monitor public health risks, public health threats, and experiences of health-care providers from mass gathering events in 2012 and 2013. This follow-up Review focuses on the main public health issues arising from planned mass gathering events held between 2013 and 2018. We highlight public health and research data on transmission of infectious diseases and antibiotic-resistant bacteria, mass casualty incidents, and non-communicable diseases, including thermal disorders. In the events discussed in this Review, the combination of a large influx of people, many from countries with outbreak-prone infectious diseases, with a high degree of crowd interactions imposed substantial burdens on host countries' health systems. The detection and transmission of antibiotic-resistant bacteria in pilgrims attending the Kumbh Mela and the Hajj raise concern of possible globalisation from mass-gathering religious events. Priorities for further investments and opportunities for research into prevention, surveillance, and management of these public health issues are discussed.

New-generation drug-eluting stents (DES) have mostly been investigated in head-to-head non-inferiority trials against early-generation DES and have typically shown similar efficacy and superior safety. How the safety profile of new-generation DES compares with that of bare-metal stents (BMS) is less clear.

Being the second-largest country in the Middle East, Iran has a long history of civilisation during which several dynasties have been overthrown and established and health-related structures have been reorganised. Iran has had the replacement of traditional practices with modern medical treatments, emergence of multiple pioneer scientists and physicians with great contributions to the advancement of science, environmental and ecological changes in addition to large-scale natural disasters, epidemics of multiple communicable diseases, and the shift towards non-communicable diseases in recent decades. Given the lessons learnt from political instabilities in the past centuries and the approaches undertaken to overcome health challenges at the time, Iran has emerged as it is today. Iran is now a country with a population exceeding 80 million, mainly inhabiting urban regions, and has an increasing burden of non-communicable diseases, including cardiovascular diseases, hypertension, diabetes, malignancies, mental disorders, substance abuse, and road injuries.

Osteoarthritis is a leading cause of disability and source of societal cost in older adults. With an ageing and increasingly obese population, this syndrome is becoming even more prevalent than in previous decades. In recent years, we have gained important insights into the cause and pathogenesis of pain in osteoarthritis. The diagnosis of osteoarthritis is clinically based despite the widespread overuse of imaging methods. Management should be tailored to the presenting individual and focus on core treatments, including self-management and education, exercise, and weight loss as relevant. Surgery should be reserved for those that have not responded appropriately to less invasive methods. Prevention and disease modification are areas being targeted by various research endeavours, which have indicated great potential thus far. This narrative Seminar provides an update on the pathogenesis, diagnosis, management, and future research on osteoarthritis for a clinical audience.

Oral immunotherapy is an emerging experimental treatment for peanut allergy, but its benefits and harms are unclear. We systematically reviewed the efficacy and safety of oral immunotherapy versus allergen avoidance or placebo (no oral immunotherapy) for peanut allergy.

ABO-incompatible renal transplantation (ABOi-rTx) is increasingly used to overcome organ shortage. Evidence about its non-inferiority in comparison with ABO-compatible renal transplantation (ABOc-rTx) needs to be analysed at early and late timepoints. We aimed to investigate differences in outcome after ABOi-rTX and ABOc-rTX.

Opioids are a mainstay of acute pain management but can have many adverse effects, contributing to problematic long-term use. Opioid tolerance (increased dose needed for analgesia) and opioid-induced hyperalgesia (paradoxical increase in pain with opioid administration) can contribute to both poorly controlled pain and dose escalation. Hyperalgesia is particularly problematic as further opioid prescribing is largely futile. The mechanisms of opioid tolerance and hyperalgesia are complex, involving μ opioid receptor signalling pathways that offer opportunities for novel analgesic alternatives. The intracellular scaffold protein β-arrestin-2 is implicated in tolerance, hyperalgesia, and other opioid side-effects. Development of agonists biased against recruitment of β-arrestin-2 could provide analgesic efficacy with fewer side-effects. Alternative approaches include inhibition of peripheral μ opioid receptors and blockade of downstream signalling mechanisms, such as the non-receptor tyrosine kinase Src or N-methyl-D-aspartate receptors. Furthermore, it is prudent to use multimodal analgesic regimens to reduce reliance on opioids during the perioperative period. In the third paper in this Series we focus on clinical and mechanism-based understanding of tolerance and opioid-induced hyperalgesia, and discuss current and future strategies for pain management.

Worldwide, the use of prescription opioid analgesics more than doubled between 2001 and 2013, with several countries, including the USA, Canada, and Australia, experiencing epidemics of opioid misuse and abuse over this period. In this context, excessive prescribing of opioids for pain treatment after surgery has been recognised as an important concern for public health and a potential contributor to patterns of opioid misuse and related harm. In the second paper in this Series we review the evolution of prescription opioid use for pain treatment after surgery in the USA, Canada, and other countries. We summarise evidence on the extent of opioid overprescribing after surgery and its potential association with subsequent opioid misuse, diversion, and the development of opioid use disorder. We discuss evidence on patient, physician, and system-level predictors of excessive prescribing after surgery, and summarise recent work on clinical and policy efforts to reduce such prescribing while ensuring adequate pain control.

Over the past decade there has been an increasing reliance on strong opioids to treat acute and chronic pain, which has been associated with a rising epidemic of prescription opioid misuse, abuse, and overdose-related deaths. Deaths from prescription opioids have more than quadrupled in the USA since 1999, and this pattern is now occurring globally. Inappropriate opioid prescribing after surgery, particularly after discharge, is a major cause of this problem. Chronic postsurgical pain, occurring in approximately 10% of patients who have surgery, typically begins as acute postoperative pain that is difficult to control, but soon transitions into a persistent pain condition with neuropathic features that are unresponsive to opioids. Research into how and why this transition occurs has led to a stronger appreciation of opioid-induced hyperalgesia, use of more effective and safer opioid-sparing analgesic regimens, and non-pharmacological interventions for pain management. This Series provides an overview of the epidemiology and societal effect, basic science, and current recommendations for managing persistent postsurgical pain. We discuss the advances in the prevention of this transitional pain state, with the aim to promote safer analgesic regimens to better manage patients with acute and chronic pain.

Leonardo da Vinci (1452-1519) contributed to the study of the nervous system. His earliest surviving anatomical drawings (circa 1485-93) included studies of the skull, brain, and cerebral ventricles. These works reflected his efforts to understand medieval psychology, including the localisation of sensory and motor functions to the brain. He was also the first to pith a frog, concluding that piercing the spinal medulla causes immediate death. After a 10-year interval in the early 1500s Leonardo resumed his anatomical studies and developed a method to inject hot wax into the ventricular system, creating a cast that showed the shape and extent of the ventricles. During this period he also progressed in his understanding of the anatomy of the cranial nerves. Besides being the first to identify the olfactory nerve as a cranial nerve, his dissections showed him that contrary to previous theories, the nerves do not converge on the lateral or third ventricles. Leonardo also performed detailed studies of the peripheral nervous system. Although his discoveries had little influence on the development of the field of anatomy, they represent an astonishingly sharp break from the field that had seen little if any progress in the previous 13 centuries. His work reflects the emergence of the modern scientific era and forms a key part of his integrative approach to art and science.

Tetanus is a vaccine-preventable disease that still commonly occurs in many low-income and middle-income countries, although it is rare in high-income countries. The disease is caused by the toxin of the bacterium Clostridium tetani and is characterised by muscle spasms and autonomic nervous system dysfunction. Global vaccination initiatives have had considerable success but they continue to face many challenges. Treatment for tetanus aims to control spasms and reduce cardiovascular instability, and consists of wound debridement, antitoxin, antibiotics, and supportive care. Recent research has focused on intravenous magnesium sulphate and intrathecal antitoxin administration as methods of spasm control that can avoid the need for ventilatory support. Nevertheless, without access to mechanical ventilation, mortality from tetanus remains high. Even with such care, patients require several weeks of hospitalisation and are vulnerable to secondary problems, such as hospital-acquired infections.

Universal and timely access to a caesarean section is a key requirement for safe childbirth. We identified the burden of maternal and perinatal mortality and morbidity, and the risk factors following caesarean sections in low-income and middle-income countries (LMICs).

Epithelial ovarian cancer generally presents at an advanced stage and is the most common cause of gynaecological cancer death. Treatment requires expert multidisciplinary care. Population-based screening has been ineffective, but new approaches for early diagnosis and prevention that leverage molecular genomics are in development. Initial therapy includes surgery and adjuvant therapy. Epithelial ovarian cancer is composed of distinct histological subtypes with unique genomic characteristics, which are improving the precision and effectiveness of therapy, allowing discovery of predictors of response such as mutations in breast cancer susceptibility genes BRCA1 and BRCA2, and homologous recombination deficiency for DNA damage response pathway inhibitors or resistance (cyclin E1). Rapidly evolving techniques to measure genomic changes in tumour and blood allow for assessment of sensitivity and emergence of resistance to therapy, and might be accurate indicators of residual disease. Recurrence is usually incurable, and patient symptom control and quality of life are key considerations at this stage. Treatments for recurrence have to be designed from a patient's perspective and incorporate meaningful measures of benefit. Urgent progress is needed to develop evidence and consensus-based treatment guidelines for each subgroup, and requires close international cooperation in conducting clinical trials through academic research groups such as the Gynecologic Cancer Intergroup.