Data quality in epidemiological studies is a basic requirement for good scientific research. The aim of this study was to examine an important indicator of data quality, data completeness, by investigating predictors of missing data.

Baseline data of a cohort study, the population-based Hamburg City Health Study, were used. Missingness was investigated at the levels of a whole research unit, on the two segments of health service utilisation and psychosocial variables, and two sensitive items (income and number of sexual partners). Predictors for missingness were sociodemographic variables, cognitive abilities and the mode of data collection. Associations were estimated using binary and multinomial logistic regression models.

Of 10 000 participants (mean age=62.4 years; 51.1% women), 32.9% had complete data at the unit level, 66.8% had partially missing data and 0.3% missed all items. The highest proportions of missing values were found for income (27.8%) and the number of sexual partners (36.7%). At both the unit, segment and item level, older age, female sex, low education, a foreign mother language and cognitive impairment were significant predictors for missingness.

For analysing population-based data, dealing with missingness is equally important at all levels of analysis. During the design and conduct of the study, the identified groups may be targeted to reach higher levels of data completeness.

Neonatal death and later disability remain common sequelae of hypoxic-ischaemic encephalopathy (HIE) despite the now standard use of therapeutic hypothermia (HT). New therapeutic approaches to brain protection are required. Melatonin is an indolamine hormone with free-radical scavenging, antiapoptotic, anti-inflammatory and gene regulatory neuroprotective properties, which has extensive preclinical evidence of safety and efficacy. Pharmacokinetic (PK) data suggest it is necessary to reach melatonin levels of 15–30 mg/L within 6–8 hours of hypoxia-ischaemia for brain protection. We developed a novel Good Manufacturing Practice (GMP) grade melatonin in ethanol 50 mg/mL solution for intravenous use. In preclinical studies, ethanol is an adjuvant excipient with additional neuroprotective benefit; optimised dosing protocols can achieve therapeutic melatonin levels while limiting blood alcohol concentrations (BACs).

The Acute High Dose Melatonin for Encephalopathy of the Newborn (ACUMEN) Study is a first-in-human, international, multicentre, phase 1 safety study of intravenous melatonin in babies with moderate/severe HIE receiving HT. Sixty babies will be studied over two phases: a dose escalation study including four dose levels to establish the recommended phase 2 dose (RP2D), followed by a 6-month cohort expansion study of RP2D to further characterise PKs and affirm safety. Participants will receive a 2-hour intravenous infusion of melatonin within 6 hours of birth, followed by five maintenance doses every 12 hours to cover the period of HT. Plasma melatonin and BACs will be monitored. The RP2D will be based on the attainment of therapeutic melatonin levels while limiting BACs and the frequency of dose-limiting events (DLEs). A Bayesian Escalation with Overdose Control approach will be used to estimate the risk of DLE per dose level, with a target level of

Approval has been given by the London Central National Health Service Health Research Authority Ethics Committee (25/LO/0170) and UK Clinical Trials Authorisation from the Medicines and Healthcare products Regulatory Agency. Separate approvals have been sought in Ireland and Australia. Dissemination will be via peer-reviewed journals, conference presentations, public registries and plain language summaries for parent/legal guardian(s), in accordance with national requirements.

ISRCTN61218504. EU CT: 2025-520538-49-00.

Publication based on the UK protocol V.3.0, 08 May 2025