Circadian pattern of emergency calls: implications for ED organization

The Daily Patterns of Emergency Medical Events

This study examines population-level daily patterns of time-stamped emergency medical service (EMS) dispatches to establish their situational predictability. Using visualization, sinusoidal regression, and statistical tests to compare empirical cumulative distributions, we analyzed 311,848,450 emergency medical call records from the US National Emergency Medical Services Information System (NEMSIS) for years 2010 through 2022. The analysis revealed a robust daily pattern in the hourly distribution of distress calls across 33 major categories of medical emergency dispatch types. Sinusoidal regression coefficients for all types were statistically significant, mostly at the p < 0.0001 level. The coefficient of determination ( R 2 ) ranged from 0.84 and 0.99 for all models, with most falling in the 0.94 to 0.99 range. The common sinusoidal pattern, peaking in mid-afternoon, demonstrates that all major categories of medical emergency dispatch types appear to be influenced by an underlying daily rhythm that is aligned with daylight hours and common sleep/wake cycles. A comparison of results with previous landmark studies revealed new and contrasting EMS patterns for several long-established peak occurrence hours-specifically for chest pain, heart problems, stroke, convulsions and seizures, and sudden cardiac arrest/death. Upon closer examination, we also found that heart attacks, diagnosed by paramedics in the field via 12-lead cardiac monitoring, followed the identified common daily pattern of a mid-afternoon peak, departing from prior generally accepted morning tendencies. Extended analysis revealed that the normative pattern prevailed across the NEMSIS data when reorganized to consider monthly, seasonal, daylight-savings versus civil time, and pre-/post-COVID-19 periods. The predictable daily EMS patterns provide impetus for more research that links daily variation with causal risk and protective factors. Our methods are straightforward and presented with detail to provide accessible and replicable implementation for researchers and practitioners.

Description of Trends over the Week in Alcohol-Related Ambulance Attendance Data

Alcohol harms are often determined using a proxy measure based on temporal patterns during the week when harms are most likely to occur. This study utilised coded Australian ambulance data from the Victorian arm of the National Ambulance Surveillance System (NASS) to investigate temporal patterns across the week for alcohol-related ambulance attendances in 2019. These patterns were examined by season, regionality, gender, and age group. We found clear temporal peaks: from Friday 6:00 p.m. to Saturday 3:59 a.m. for both alcohol-involved and alcohol-intoxication-related attendance, from Saturday 6:00 p.m. to Sunday 4:59 a.m. for alcohol-involved attendances, and from Saturday 5:00 p.m. to Sunday 4:49 a.m. for alcohol-intoxication-related attendances. However, these temporal trends varied across age groups. Additionally, hours during Thursday and Sunday evenings also demonstrated peaks in attendances. There were no substantive differences between genders. Younger age groups (18-24 and 25-29 years) had a peak of alcohol-related attendances from 7:00 p.m. to 7:59 a.m. on Friday and Saturday nights, whereas the peak in attendances for 50-59 and 60+ years was from 5:00 p.m. to 2:59 a.m. on Friday and Saturday nights. These findings further the understanding of the impacts of alcohol during different times throughout the week, which can guide targeted policy responses regarding alcohol use and health service capacity planning.

Is the time of calling helpful for differentiating transient ischaemic attack and stroke from mimics in primary care out-of-hours services? A cross-sectional study

OBJECTIVES

Telephone triage of patients suspected of transient ischaemic attack (TIA) or stroke is challenging. Both TIA and stroke more likely occur during daytime, with a peak in the morning hours. Thus, the time of calling might be a helpful determinant during telephone triage. We assessed the time of calling in patients with stroke-like symptoms who called the out-of-hours services in primary care (OHS-PC), and evaluated whether the time of calling differed between patients with TIA or stroke compared with those with mimics.

DESIGN

Cross-sectional study.

SETTING

Six OHS-PC locations in the Netherlands.

PARTICIPANTS

1269 telephone triage recordings of patients calling the OHS-PC because of stroke-like symptoms. We collected information on patient characteristics, symptoms, time of calling and urgency allocation. The final diagnosis related to each triage call was based on letters from the neurologist (retrieved from the patient's general practitioner).

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measures were the time of calling hourly and 4 hourly, and the risk of TIA or stroke/hour. The secondary outcome measure was the risk ratio of TIA or stroke in the morning (08:00-12:00h) versus other hours.

RESULTS

Mean age was 68.6 (SD±18.5) years, 56.9% were women and 50.0% had a TIA or stroke. The risk ratio of TIA or stroke among people calling with stroke-like symptoms between 08:00-12:00h versus other hours was 1.13 (95% CI 1.00 to 1.28, p=0.070). After correction for age and sex, the adjusted risk ratio was 0.94 (95% CI 0.80 to 1.10, p=0.434).

CONCLUSION

In patients who called the OHS-PC because of stroke-like symptoms, the time of calling did not differ between patients with TIA or stroke and patients with mimics.

TRIAL REGISTRATION NUMBER

The Netherlands National Trial Registry (NTR7331).

Only a Minority of Thrombectomy Candidates Are Admitted During Night Shift: A Rationale for Diurnal Stroke Care Planning

Background: Widespread quick access to mechanical thrombectomy (MT) for acute ischemic stroke (AIS) is one of the main challenges in stroke care. It is unclear if newly established MT units are required 24 h/7 d. We explored the diurnal admission rate of patients with AIS potentially eligible for MT to provide a basis for discussion of daytime-adapted stroke care concepts. Methods: Data collected from the Baden-Württemberg Stroke Registry in Germany were assessed (2008-2012). We analyzed the admission rate of patients with AIS stratified by the National Institutes of Health Stroke Scale (NIHSS) score at admission in 3-h intervals. An NIHSS score ≥10 was considered a predictor of large vessel occlusion. The average annual admission number of patients with severe AIS were stratified by stroke service level and calculated for a three-shift model and working/non-working hours. Results: Of 91,864, 22,527 (21%) presented with an NIHSS score ≥10. The average admission rates per year for a hospital without Stroke Unit (SU), with a local SU, with a regional SU and a stroke center were 8, 52, 90 and 178, respectively. Approximately 61% were admitted during working hours, 54% in the early shift, 36% in the late shift and 10% in the night shift. Conclusions: A two-shift model, excluding the night shift, would cover 90% of the patients with severe AIS. A model with coverage during working hours would miss ~40% of the patients with severe AIS. To achieve a quick and area-wide MT, it seems preferable for newly implemented MT-units to offer MT in a two-shift model at a minimum.

Self-reported sleep disturbance in ambulance attendances for suicidal ideation and attempted suicide between 2012 and 2017

BACKGROUND

Sleep disturbances are among the top-ten warning signs for suicide, however there has been limited investigation of the relationship between these variables in acute presentations, particularly community settings. We examined ambulance attendances for suicide ideation and attempt to explore the role of sleep and co-morbid factors (mental health symptoms, attendance time, and alcohol and benzodiazepine use).

METHODS

Coded clinical records from Ambulance Victoria for the period 1 January 2012 to 30 June 2017 were analysed.

RESULTS

Paramedics attended 97,198 cases of suicidal ideation or suicide attempt during the study period. Just over half (56.4%) of these were for suicidal ideation, and 43.6% were for attempted suicide. Depression symptomology-related attendances were more common than those for anxiety and despite a lower proportion of both sleep and current anxiety-related symptoms, benzodiazepine use was significantly more common in attendances for suicide attempts (25.9%) than for ideation (2.2%). Co-morbid benzodiazepine use was associated with attempted suicide (OR: 10.37 (10.04-10.72), in a hierarchical regression model.

LIMITATIONS

Data represent self-report/paramedic observation only, and do include validated measures of sleep or drug use. Sleep disturbance is likely under recorded in ambulance attendances given the primary role of paramedics is to stabilise patients, and minimise risk of harm during transport.

CONCLUSION

This study reports internationally unique data, and provides the first examination of ambulance coded clinical records for suicide ideation and attempt. Sleep disturbances had a unique role in these attendances, over and above common co-occurring factors including drug use and mental health diagnoses.

Diurnal, weekly and seasonal variations of chest pain in patients transported by emergency medical services

OBJECTIVES

Chest pain is among the leading causes for emergency medical services (EMS) activation. Acute myocardial infarction (MI) is not only one of the most critical aetiologies of chest pain, but also one of few conditions encountered by EMS that has been shown to follow a circadian pattern. Understanding the diurnal relationship between the inflow of chest pain patients and the likelihood of acute MI may inform prehospital and emergency department (ED) healthcare providers regarding the prediction, and hence prevention, of dire outcomes.

METHODS

This was a secondary analysis of previously collected data from an observational prospective study that enrolled consecutive chest pain patients transported by a large metropolitan EMS system in the USA. We used the time of EMS call to determine the time-of-day of the indexed encounter. Two independent reviewers examined available medical data to determine our primary outcome, the presence of MI, and our secondary outcomes, infarct size and 30-day major adverse cardiac events (MACE). We estimated infarct size using peak troponin level.

RESULTS

We enrolled 2065 patients (age 56±17, 53% males, 7.5% with MI). Chest pain encounters increased from 9:00 AM to 2:00 PM, with a peak at 1:00 PM and a nadir at 6:00 AM. Acute MI had a bimodal distribution with two peaks: 10 AM in ST-elevation MI, and 10 PM in non-ST-elevation MI. ST-elevation MI with afternoon onset was an independent predictor of infarct size. Acute MI with winter and early spring presentation was an independent predictor of 30-day MACE.

CONCLUSIONS

EMS-attended chest pain calls follow a diurnal pattern, with the most vulnerable patients encountered during afternoons and winter/spring seasons. These data can inform prehospital and ED healthcare providers regarding the time of presentation where patients are more likely to have an underlying MI and subsequently worse outcomes.

Mathematical modeling of circadian rhythms

Circadian rhythms are endogenous ~24-hr oscillations usually entrained to daily environmental cycles of light/dark. Many biological processes and physiological functions including mammalian body temperature, the cell cycle, sleep/wake cycles, neurobehavioral performance, and a wide range of diseases including metabolic, cardiovascular, and psychiatric disorders are impacted by these rhythms. Circadian clocks are present within individual cells and at tissue and organismal levels as emergent properties from the interaction of cellular oscillators. Mathematical models of circadian rhythms have been proposed to provide a better understanding of and to predict aspects of this complex physiological system. These models can be used to: (a) manipulate the system in silico with specificity that cannot be easily achieved using in vivo and in vitro experimental methods and at lower cost, (b) resolve apparently contradictory empirical results, (c) generate hypotheses, (d) design new experiments, and (e) to design interventions for altering circadian rhythms. Mathematical models differ in structure, the underlying assumptions, the number of parameters and variables, and constraints on variables. Models representing circadian rhythms at different physiologic scales and in different species are reviewed to promote understanding of these models and facilitate their use. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Models of Systems Properties and Processes > Organ, Tissue, and Physiological Models.

Meta-analysis of day-of-week variation of acute aortic rupture or dissection

INTRODUCTION

We performed a meta-analysis to assess the presence of a day-of-week rhythmic variability of acute aortic rupture or dissection (AARD) onset.

EVIDENCE ACQUISITION

Eligible studies were observational studies enrolling patients with AARD and reporting day-of-week variation of AARD. Study-specific estimates, i.e. day-of-week incidence of AARD, were combined using the random-effects model. Chronobiological analysis was performed by applying a partial Fourier series to pooled day-of-week incidence by using the inverse-variance weighted least-squares method.

EVIDENCE SYNTHESIS

We identified 9 eligible studies enrolling a total of 28,036 patients with AARD. Pooled incidence of AARD was 12.8% on Sunday, 15.9% on Monday, 14.8% on Tuesday, 15.1% on Wednesday, 14.7% on Thursday, 14.1% on Friday, and 12.1% on Saturday. Chronobiological analysis identified a significant (P=0.0098) day-of-week pattern in the occurrence of AARD with a peak on Monday and a nadir on Saturday. Pooled analysis demonstrated significantly more incidence on Monday than on Saturday (relative risk: 1.247; 95% CI: 1.131 to 1.374; P=0.012).

CONCLUSIONS

Incidence of AARD was 12.8%, 15.9%, 14.8%, 15.1%, 14.7%, 14.1%, and 12.1%, on Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday, respectively. A significant day-of-week pattern in the occurrence of AARD with a peak on Monday and a nadir on Saturday was identified with significantly more incidence on Monday than on Saturday.

Clinical Aspects of Human Circadian Rhythms

Circadian rhythmicity can be important in the pathophysiology, diagnosis, and treatment of clinical disease. Due to the difficulties in conducting the necessary experimental work, it remains unknown whether ~24-h changes in pathophysiology or symptoms of many diseases are causally linked to endogenous circadian rhythms or to other diurnal factors that change across the day, such as changes in posture, activity, sleep or wake state, or metabolic changes associated with feeding or fasting. Until the physiology is accurately known, appropriate treatment cannot be designed. This review includes an overview of clinical disorders that are caused or affected by circadian or diurnal rhythms. The clinical side effects of disruption of circadian rhythmicity, such as in shiftwork, including the public health implications of the disrupted alertness and performance, are also discussed.

"Timing" of arrival and in-hospital mortality in a cohort of patients under anticoagulant therapy presenting to the emergency departments with cerebral hemorrhage: A multicenter chronobiological study in Italy

Therapy with oral anticoagulants (OACs) is a risk factor for cerebral hemorrhage (CH). Although different studies have been undertaken to investigate the timing of the onset of major cardiovascular events, no data exist on temporal patterns of the onset of CH in subjects treated with OACs. The aim of this study is to evaluate the timing of CH in patients treated with OACs. All patients who developed CH under OACs therapy and admitted to 28 Italian Emergency Departments (EDs) between September 2011 and July 2013 were enrolled. Age, sex, time and location of the hemorrhagic lesion, type of the bleeding events (idiopathic or post-traumatic), anticoagulant therapy (warfarin or new oral anticoagulants - NOAs) and time of ED admission (i.e., hour, day, month and season) were recorded. Five hundred and seventeen patients (63.2% male aged 80 ± 7.9 yrs) with CH were involved. Warfarin was taken by 494 patients (95.6%), and NOAs by 23 (4.4%). In-hospital mortality (IHM) was recorded in 208 cases (40.2%). Cosinor analysis showed a peak of CH arrival between 12:00 and 14:00 h both in the whole population (PR 73.9%, p = 0.002) and the male subgroup (PR 65.2%, p = 0.009), whereas females showed an anticipated morning peak between 08:00 and 10:00 h (PR 65.7%, p = 0.008). A further analysis between idiopathic and post-traumatic CH confirmed the presence of a 24 h pattern with a peak between 12:00 and 14:00 h (PR 58.5%, p = 0.019) and between 08:00 and 10:00 h (PR80.1%, p < 0.001) for idiopathic events and post-traumatic hemorrhages, respectively. Moreover, a seasonal winter peak was identified for idiopathic forms (PR 74%, p = 0.035), and a summer peak for post-traumatic forms (PR 77%, p = 0.025). The present study suggests the presence of a temporal pattern of ED arrivals in CH patients treated with OACs.

Why and when citizens call for emergency help: an observational study of 211,193 medical emergency calls

BACKGROUND

A medical emergency call is citizens' access to pre-hospital emergency care and ambulance services. Emergency medical dispatchers are gatekeepers to provision of pre-hospital resources and possibly hospital admissions. We explored causes for access, emergency priority levels, and temporal variation within seasons, weekdays, and time of day for emergency calls to the emergency medical dispatch center in Copenhagen in a two-year study period (December 1(st), 2011 to November 30(th), 2013).

METHODS

Descriptive analysis was performed for causes for access and emergency priority levels. A Poisson regression model was used to calculate adjusted ratio estimates for the association between seasons, weekdays, and time of day overall and stratified by emergency priority levels.

RESULTS

We analyzed 211,193 emergency calls for temporal variation. Of those, 167,635 calls were eligible for analysis of causes and emergency priority level. "Unclear problem" was the most frequent category (19%). The five most common causes with known origin were categorized as "Wounds, fractures, minor injuries" (13%), "Chest pain/heart disease" (11%), "Accidents" (9%), "Intoxication, poisoning, drug overdose" (8%), and "Breathing difficulties" (7%). The highest emergency priority levels (Emergency priority level A and B) were assigned in 81% of calls. In the analysis of temporal variation, the total number of calls peaked at wintertime (26%), Saturdays (16%), and during daytime (39%).

CONCLUSION

The pattern of citizens' contact causes fell into four overall categories: unclear problems, medical problems, intoxication and accidents. The majority of calls were urgent. The magnitude of unclear problems represents a modifiable factor and highlights the potential for further improvement of supportive dispatch priority tools or educational interventions at dispatch centers. Temporal variation was identified within seasons, weekdays and time of day and reflects both system load and disease occurrence. Data on contact patterns could be utilized in a public health perspective, benchmarking of EMS systems, and ultimately development of best practice in the area of emergency medicine.

Chronobiology of acute aortic rupture or dissection: a systematic review and a meta-analysis of the literature

OBJECTIVES

Identification and quantification higher risk incidence of aortic rupture or dissection (AARD) could be of clinical interest and improve preventive strategies.

BACKGROUND

Several studies and subsequent meta-analyses have shown chronobiologic variations in the timing of occurrence of myocardial infarction, stroke, and pulmonary embolism. Conversely, such evidences are currently lacking for AARD despite a number of studies available dealing with periodicity.

METHODS

MEDLINE, EMBASE, and Google Scholar databases were searched up to July 2013. Temporal variation in the incidence of AARD was analyzed including all studies analyzing seasonal, monthly, weekly, and circadian aggregations. Two authors independently reviewed and extracted data.

RESULTS

Forty-two studies for a total of more than 80 000 patients were included. Our results showed a significantly increased incidence of AARD in Winter (Chi-square 854.92, p < 0.001), with a relative risk (RR) of 1.171 (99% CI 1.169, 1.172), in December (Chi-square 361.03, p < 0.001), RR of 1.142 (99% CI 1.141, 1.143), on Monday (Chi-square 428.09, p < 0.001), RR of 1.214 (99% CI 1.211, 1.216), and in the hours between 6 am and 12 pm (Chi-square 212.02, p < 0.001), RR of 1.585 (99% CI 1.562, 1.609). Subgroup and sensitivity analyses confirmed the results of principal analyses.

CONCLUSIONS

Our data strongly support the presence of evident rhythmic patterns in the incidence of acute aortic events, characterized by significantly higher risk in Winter, in December, on Monday and between 6 am and 12 pm. Future studies are needed to better clarify the underlying mechanisms and clinical implications.

Age and admission times as predictive factors for failure of admissions to discharge-stream short-stay units

OBJECTIVE

Discharge-stream emergency short-stay units (ESSU) improve ED and hospital efficiency. Age of patients and time of hospital presentations have been shown to correlate with increasing complexity of care. We aim to determine whether an age and time cut-off could be derived to subsequently improve short-stay unit success rates.

METHODS

We conducted a retrospective audit on 6703 (5522 inclusions) patients admitted to our discharge-stream short-stay unit. Patients were classified as appropriate or inappropriate admissions, and deemed successful if discharged out of the unit within 24 h; and failures if they needed inpatient admission into the hospital. We calculated short-stay unit length of stay for patients in each of these groups. A 15% failure rate was deemed as acceptable key performance indicator (KPI) for our unit.

RESULTS

There were 197 out of 4621 (4.3%, 95% CI 3.7-4.9%) patients up to the age of 70 who failed admission to ESSU compared with 67 out of 901 (7.4%, 95% CI 5.9-9.3%, P < 0.01) of patients over the age of 70, reflecting an increased failure rate in geriatric population. When grouped according to times of admission to the ESSU (in-office 06.00-22.00 hours vs out-of-office 22.00-06.00 hours) no significant difference rates in discharge failure (4.7% vs 5.2%, P = 0.46) were noted.

CONCLUSION

Patients >70 years of age have higher rates of failure after admission to discharge-stream ESSU. Although in appropriately selected discharge-stream patients, no age group or time-band of presentation was associated with increased failure rate beyond the stipulated KPI.

Improving the coding and classification of ambulance data through the application of International Classification of Disease 10th revision

Objectives This paper aims to examine whether an adaptation of the International Classification of Disease (ICD) coding system can be applied retrospectively to final paramedic assessment data in an ambulance dataset with a view to developing more fine-grained, clinically relevant case definitions than are available through point-of-call data. Methods Over 1.2 million case records were extracted from the Ambulance Victoria data warehouse. Data fields included dispatch code, cause (CN) and final primary assessment (FPA). Each FPA was converted to an ICD-10-AM code using word matching or best fit. ICD-10-AM codes were then converted into Major Diagnostic Categories (MDC). CN was aligned with the ICD-10-AM codes for external cause of morbidity and mortality. Results The most accurate results were obtained when ICD-10-AM codes were assigned using information from both FPA and CN. Comparison of cases coded as unconscious at point-of-call with the associated paramedic assessment highlighted the extra clinical detail obtained when paramedic assessment data are used. Conclusions Ambulance paramedic assessment data can be aligned with ICD-10-AM and MDC with relative ease, allowing retrospective coding of large datasets. Coding of ambulance data using ICD-10-AM allows for comparison of not only ambulance service users but also with other population groups. What is known about the topic? There is no reliable and standard coding and categorising system for paramedic assessment data contained in ambulance service databases. What does this paper add? This study demonstrates that ambulance paramedic assessment data can be aligned with ICD-10-AM and MDC with relative ease, allowing retrospective coding of large datasets. Representation of ambulance case types using ICD-10-AM-coded information obtained after paramedic assessment is more fine grained and clinically relevant than point-of-call data, which uses caller information before ambulance attendance. What are the implications for practitioners? This paper describes a model of coding using an internationally recognised standard coding and categorising system to support analysis of paramedic assessment. Ambulance data coded using ICD-10-AM allows for reliable reporting and comparison within the prehospital setting and across the healthcare industry.

Breaking heart: chronobiologic insights into takotsubo cardiomyopathy

A considerable amount of evidence has shown that the major acute cardiovascular diseases, ie, myocardial infarction, sudden cardiac death, stroke, pulmonary embolism, and rupture or dissection of aortic aneurysms do not occur randomly in time, but exhibit specific temporal patterns in their onset, according to time of day, month or season, and day of the week. This contributes to the definition of "chronorisk", where several factors, not harmful if taken alone, are capable of triggering unfavorable events when presenting all together within the same temporal window. This article reviews the actual knowledge about time of onset of takotsubo cardiomyopathy.

Urban morbidity in summer: ambulance dispatch data, periodicity and weather

Over recent years the impact of weather on human health has become more severe, especially for people living in urban areas. Even though many studies have analysed the impact of weather on human mortality, few have quantified the impact of heat on morbidity, including ambulance response calls. In this study, 13,354 calls collected in the city of Florence (Italy) during summer were analyzed by month, day of the week, hour, and time slot of the day. An objective air mass classification was used to classify days and time slots with similar weather characteristics and a multiple variable analysis was applied to evaluate the relationship between emergency calls and weather. A positive trend was observed in the morning and a negative one during the night for all emergency calls, but only for food poisoning and alcoholic diseases. Calls for cardiovascular events increased in the morning and on hot days. Calls for psychiatric disorders rose significantly with temperature during the afternoon. The total number of calls and those for alcoholic diseases rose during the hottest nights. Our results, which show a clear relationship between ambulance response calls, periodicity, and weather, could contribute to an understanding the impact of weather on morbidity.

Ambulance demand: random events or predicable patterns?

BACKGROUND

Occupational, social and recreational routines follow temporal patterns, as does the onset of certain acute medical diseases and injuries. It is not known if the temporal nature of injury and disease transfers into patterns that can be observed in ambulance demand. This review examines eligible study findings that reported temporal (time of day, day of week and seasonal) patterns in ambulance demand.

METHODS

Electronic searches of Medline and Cumulative Index of Nursing and Allied Health Literature were conducted for papers published between 1980 and 2011. In addition, hand searching was conducted for unpublished government and ambulance service documents and reports for the same period.

RESULTS

38 studies examined temporal patterns in ambulance demand. Six studies reported trends in overall workload and 32 studies reported trends in a subset of ambulance demand, either as a specific case type or demographic group. Temporal patterns in overall demand were consistent between jurisdictions for time of day but varied for day of week and season. When analysed by case type, all jurisdictions reported similar time of day patterns, most jurisdictions had similar day of week patterns except for out-of-hospital cardiac arrest and similar seasonal patterns, except for trauma. Temporal patterns in case types were influenced by age and gender.

CONCLUSIONS

Temporal patterns are present in ambulance demand and importantly these populations are distinct from those found in hospital datasets suggesting that variation in ambulance demand should not be inferred from hospital data alone. Case types seem to have similar temporal patterns across jurisdictions; thus, research where demand is broken down into case types would be generalisable to many ambulance services. This type of research can lead to improvements in ambulance service deliverables.

Seasonal and weekly patterns of hospital admissions for nonfatal and fatal myocardial infarction

OBJECTIVE

This retrospective study, based on the database of hospital admissions of the region Emilia-Romagna [RER], Italy, was aimed to confirm the existence of a seasonal or weekly pattern of hospital admission of acute myocardial infarction (AMI) and to verify possible differences between nonfatal or fatal cases.

METHODS

The study included all cases of patients with AMI hospitalized between 1998 and 2006. Day of admission was categorized, respectively, into four 3-month intervals, into twelve 1-month intervals, and into seven 1-day intervals for statistical analysis, performed by chi(2) test goodness of fit and partial Fourier series on total cases, males, females, and nonfatal and fatal cases.

RESULTS

The database included 64 191 cases of AMI (62.9% males, 12.3% fatal). Acute myocardial infarction was most frequent in winter and least in summer (P < .0001). The highest number of cases was recorded in January and the lowest in July (P < .0001). Chronobiologic analysis showed winter peaks for total cases (January, P = .035), females (December, P = .009), and fatal cases (January, P < .001). Acute myocardial infarction was most frequent on Monday and least on Sunday (P < .0001). Comparing observed vs expected events, there was a significantly higher frequency of cases on weekdays and reduced on weekends, for total (P < .0001), nonfatal (P < .0001), and fatal cases (P = .0001).

CONCLUSIONS

This study confirms a significantly higher frequency of AMI admissions in winter and on a Monday. No difference in the frequency of nonfatal vs fatal events, depending of patients' admissions on weekdays or weekends, was found.

Circadian Variation in Stroke Onset: Identical Temporal Pattern in Ischemic and Hemorrhagic Events

Stroke is the culmination of a heterogeneous group of cerebrovascular diseases that is manifested as ischemia or hemorrhage of one or more blood vessels of the brain. The occurrence of many acute cardiovascular events--such as myocardial infarction, sudden cardiac death, pulmonary embolism, critical limb ischemia, and aortic aneurysm rupture--exhibits prominent 24 h patterning, with a major morning peak and secondary early evening peak. The incidence of stroke exhibits the same 24 h pattern. Although ischemic and hemorrhagic strokes are different entities and are characterized by different pathophysiological mechanisms, they share an identical double-peak 24 h pattern. A constellation of endogenous circadian rhythms and exogenous cyclic factors are involved. The staging of the circadian rhythms in vascular tone, coagulative balance, and blood pressure plus temporal patterns in posture, physical activity, emotional stress, and medication effects play central and/or triggering roles. Features of the circadian rhythm of blood pressure, in terms of their chronic and acute effects on cerebral vessels, and of coagulation are especially important. Clinical medicine has been most concerned with the prevention of stroke in the morning, when population-based studies show it is of greatest risk during the 24 h; however, improved protection of at-risk patients against stroke in the early evening, the second most vulnerable time of cerebrovascular accidents, has received relatively little attention thus far.

Pattern of poisoning in the elderly: an experience from Tehran

INTRODUCTION

Poisoning is considered a significant health problem in the elderly. This study aimed to portray the pattern of poisoning in the elderly population of Tehran.

METHODS

This cross-sectional study included all patients aged 60 years and older with acute poisoning who attended the emergency department of the Loghman-Hakim hospital over a six-month period (n=299).

RESULTS

Episodes of poisoning were more common in men (70.9%) and the majority of incidents took place in the patient's own home (84.3%). Most episodes were accidental (53.2%) followed by attempted suicide (32.4%). Opioids and opiate products accounted for 54.02% of the non-pharmaceutical substances that were involved in episodes of poisoning. Overdose with opioids and opiate products, was higher in male patients than in female patients. The most frequently involved drug groups were benzodiazepines, antidepressants, and analgesics. The most common cause of accidental poisoning was overdose by drug abusers. The Poisoning Severity Score was minor in 25.4%, moderate in 52.2%, and severe in 17.1% of patients. Asymptomatic patients accounted for 5.4% of the total. Unfortunately, 11.7% of patients died. The main agents involved in the fatal cases were opioids and opiate products.

CONCLUSION

The commonest method of accidental poisoning was overdose in opioid and opiate abusers. Attempted suicide was also very common comprising about one third of all cases. The high mortality observed in this study warrants attention to the risk factors and prognostic factors of poisoning in elderly.

Influence of circadian rhythm on mortality after myocardial infarction: Data from a prospective cohort of emergency calls

Myocardial infarction (MI) occurs more frequently in the morning as a result of the concomitant unfavorable timing of several physiological parameters and/or biochemical conditions. However, little is known about the possible influence of this circadian pattern on prognosis. To evaluate whether the time of symptom onset could potentially influence mortality from acute MI, this prospective study considered all consecutive MIs admitted to the ED of Ferrara, Italy, after a call to the Emergency Coordinating Unit from January 1, 1998, to December 31, 2001. The total sample consisted of 442 MIs (mean age, 68.7 years; males, 72%). Eighty patients (males, 82.5%) died in the ED; the remaining 362 were admitted to the hospital. Of these, 50 (males, 60%) died during their hospital stay. Based on the timing of their symptom onset, cases were categorized both into 24 1-hour intervals and four 6-hour intervals (midnight to 5:59 am, 6:00 am to 11:59 am, noon to 5:59 pm, and 6:00 pm to 11:59 pm), and the circadian distributions of fatal versus nonfatal MIs were compared. The circadian variation of MI peaked between 6:00 am and noon (P < .001), and in this period, there was a trend toward a higher frequency of fatal cases (41.5% vs. 35.2%; chi(2) = 1.911, P = .167). To verify whether this higher frequency of fatal events in the morning hours could be related to possible higher severity of cases observed in that hours, a further separate analysis considering age, infarct site, and peak levels of MB was made. Again, no significant temporal differences among the four 6-hour intervals were found between fatal and nonfatal Mis, although a trend toward older age was observed in morning MIs. Not only the frequency, but also the mortality, of acute MI could be increased in the morning hours. This could be of practical interest for emergency doctors and could have significant implications for acute treatment, because several studies have reported a lowered efficacy of thrombolytic drugs in the morning hours.