Seasonal Fluctuations in Hospitalisation for Pneumonia in Finland

Epidemiological Characterization and the Impact of Healthcare-Associated Pneumonia in Patients Admitted in a Northern Portuguese Hospital

Pneumonia is one of the main causes of hospitalization and mortality. It’s the fourth leading cause of death worldwide. Healthcare-associated infections are the most frequent complication of healthcare and affect hundreds of millions of patients around the world, although the actual number of patients affected is unknown due to the difficulty of reliable data. The main goal of this manuscript is to describe the epidemiological characteristics of patients admitted with pneumonia and the impact of healthcare-associated pneumonia (HCAP) in those patients. It is a quantitative descriptive study with retrospective analysis of the clinical processes of 2436 individuals for 1 year (2018) with the diagnosis of pneumonia. The individuals with ≤5 years old represented 10.4% (n = 253) and ≥65 were 72.6% (n = 1769). 369 cases resulted in death, which gives a sample lethality rate of 15.2%. The severity and mortality index were not sensitive to the death event. We found 30.2% (n = 735) individuals with HCAP and 0.41% (n = 59) with ventilator-associated pneumonia (VAP). In only 59 individuals (2.4%) the agent causing pneumonia was isolated. The high fatality rate obtained shows that pneumonia is a major cause of death in vulnerable populations. Moreover, HCAP is one of the main causes of hospital admissions from pneumonia and death and the most pneumonias are treated empirically. Knowledge of the epidemiology characterization of pneumonia, especially associated with healthcare, is essential to increase the skills of health professionals for the prevention and efficient treatment of pneumonia.

Identification of pediatric respiratory diseases using a fine-grained diagnosis system

Respiratory diseases, including asthma, bronchitis, pneumonia, and upper respiratory tract infection (RTI), are among the most common diseases in clinics. The similarities among the symptoms of these diseases precludes prompt diagnosis upon the patients' arrival. In pediatrics, the patients' limited ability in expressing their situation makes precise diagnosis even harder. This becomes worse in primary hospitals, where the lack of medical imaging devices and the doctors' limited experience further increase the difficulty of distinguishing among similar diseases. In this paper, a pediatric fine-grained diagnosis-assistant system is proposed to provide prompt and precise diagnosis using solely clinical notes upon admission, which would assist clinicians without changing the diagnostic process. The proposed system consists of two stages: a test result structuralization stage and a disease identification stage. The first stage structuralizes test results by extracting relevant numerical values from clinical notes, and the disease identification stage provides a diagnosis based on text-form clinical notes and the structured data obtained from the first stage. A novel deep learning algorithm was developed for the disease identification stage, where techniques including adaptive feature infusion and multi-modal attentive fusion were introduced to fuse structured and text data together. Clinical notes from over 12000 patients with respiratory diseases were used to train a deep learning model, and clinical notes from a non-overlapping set of about 1800 patients were used to evaluate the performance of the trained model. The average precisions (AP) for pneumonia, RTI, bronchitis and asthma are 0.878, 0.857, 0.714, and 0.825, respectively, achieving a mean AP (mAP) of 0.819. These results demonstrate that our proposed fine-grained diagnosis-assistant system provides precise identification of the diseases.

Seasonality and Readmission after Heart Failure, Myocardial Infarction, and Pneumonia

OBJECTIVE

To investigate whether hospital readmission after admission for heart failure (HF), myocardial infarction (MI), and pneumonia varies by season.

DATA SOURCES

All patients in 2005-2009 Healthcare Cost and Utilization Project State Inpatient Databases for New York and California hospitalized for HF, MI, or pneumonia.

STUDY DESIGN

The relationship between discharge season and unplanned readmission within 30 days was evaluated using multivariate modified Poisson regression.

PRINCIPAL FINDINGS

Cohorts included 869,512 patients with HF, 448,945 patients with MI, and 813,593 patients with pneumonia. While admissions varied widely by season, readmission rates only ranged from 25.0 percent (spring) to 25.6 percent (winter) for HF (p > .05), 18.9 percent (summer) to 20.0 percent (winter) for MI (p < .001), and 19.4 percent (spring) to 20.3 percent (summer) for pneumonia (p < .001). In adjusted models, in New York, there was lower readmission in spring and fall (RR: 0.98, 95% CI: 0.96-0.99 for both) after admission for HF and higher readmission in spring (RR: 1.04, 95% CI: 1.01-1.07) after MI. In California, there was lower readmission in spring and winter (RR: 0.95, 95% CI: 0.93-0.96 and RR: 0.96, 95% CI: 0.94-0.98, respectively) after pneumonia.

CONCLUSIONS

Given marked seasonality in incidence and mortality of HF, MI, and pneumonia, the modest seasonality in readmissions suggests that readmissions may be more related to non-seasonally dependent factors than to the seasonal nature of these diseases.

Regional and seasonal variation in Clostridium difficile infections among hospitalized patients in the United States, 2001-2010

BACKGROUND

This study identified national regional and seasonal variations in Clostridium difficile infection (CDI) incidence and mortality among hospitalized patients in the United States over a 10-year period.

METHODS

This was a retrospective cohort study of the U.S. National Hospital Discharge Survey from 2001-2010. Eligible cases had an ICD-9-CM discharge diagnosis code for CDI (008.45). Data weights were used to derive national estimates. CDI incidence and mortality were presented descriptively. Regions were as defined by the U.S. Census Bureau. Seasons included the following: winter (December-February), spring (March-May), summer (June-August), and fall (September-November).

RESULTS

These data represent 2.3 million CDI discharges. Overall, CDI incidence was highest in the Northeast (8.0 CDIs/1,000 discharges) and spring (6.2 CDIs/1,000 discharges). CDI incidence was lowest in the West (4.8 CDIs/1,000 discharges) and fall (5.6 CDIs/1,000 discharges). Peak CDI incidence among children occurred in the West (1.7 CDI/1,000 discharges) and winter (1.5 CDI/1,000 discharges). Mortality among all CDI patients was highest in the Midwest (7.3%) and during the winter (7.9%).

CONCLUSION

The region and season with the highest CDI incidence rates among patients hospitalized in U.S. hospitals were the Northeast and spring, respectively. The highest CDI mortality rates were seen in the Midwest and winter. Children exhibited different regional and seasonal CDI variations compared with adults and older adults.

The co-seasonality of pneumonia and influenza with Clostridium difficile infection in the United States, 1993-2008

Seasonal variations in the incidence of pneumonia and influenza are associated with nosocomial Clostridium difficile infection (CDI) incidence, but the reasons why remain unclear. Our objective was to consider the impact of pneumonia and influenza timing and severity on CDI incidence. We conducted a retrospective cohort study using the US National Hospital Discharge Survey sample. Hospitalized patients with a diagnosis of CDI or pneumonia and influenza between 1993 and 2008 were identified from the National Hospital Discharge Survey data set. Poisson regression models of monthly CDI incidence were used to measure 1) the time lag between the annual pneumonia and influenza prevalence peak and the annual CDI incidence peak and 2) the lagged effect of pneumonia and influenza prevalence on CDI incidence. CDI was identified in 18,465 discharges (8.52 per 1,000 discharges). Peak pneumonia prevalence preceded peak CDI incidence by 9.14 weeks (95% confidence interval: 4.61, 13.67). A 1% increase in pneumonia prevalence was associated with a cumulative effect of 11.3% over a 6-month lag period (relative risk = 1.113, 95% confidence interval: 1.073, 1.153). Future research could seek to understand which mediating pathways, including changes in broad-spectrum antibiotic prescribing and hospital crowding, are most responsible for the associated changes in incidence.

Do seasonal changes and climate influence the etiology of community acquired pneumonia?

INTRODUCTION

Community acquired pneumonia (CAP) is a highly prevalent pathology whose etiology is determined by the characteristics of the geographic region, and the patient. The study of these features is essential for a proper therapeutic approach. Our aim was to study the changes of the causative agent of CAP brought about by the influence of seasonal and climatic changes in our geographic area.

PATIENTS AND METHOD

A prospective and longitudinal study of patients admitted with CAP was done from January 2006 to December 2009. We analyzed demographic data, comorbidities, severity, etiologic agent, complications and mortality. We correlated mean temperature and mean cumulative rainfall for each season with Streptococcus pneumoniae and Legionella pneumophila. Statistical analyses included: Chi squared test, Student's t test for independent samples, variance analysis and Spearman's correlation.

RESULTS

We included 243 patients, 64.6% men and 54.7% over the age of 65. The highest incidence of CAP was in the winter. Streptococcus pneumoniae was the most common causative agent for all seasons except in summer when the main agent was Legionella pneumophila. We observed a significant correlation between the lowest seasonal average temperature and pneumococcal etiology of CAP; inversely, with higher temperatures, Legionella pneumophila was more common. No etiological differences were found by season when related with environmental humidity.

CONCLUSIONS

In our area, Streptococcus pneumoniae was the most common etiological agent in winter with low temperatures; in summer, with high temperatures, the most frequent was Legionella pneumophila.

Intensive care unit admissions for community-acquired pneumonia are seasonal but are not associated with weather or reports of influenza-like illness in the community

PURPOSE

The aims of this study were to determine if there is seasonal variation in the number of intensive care unit (ICU) admissions for community-acquired pneumonia (CAP) and if there is a relationship between these admissions and weather or reports of influenza-like illness in the community.

MATERIALS AND METHODS

In this time series analysis in 3 medical-surgical ICUs (8, 13, and 20 beds) in the Vancouver region, we included patients admitted to adult ICUs for CAP between January 2002 and March 2006. We used Poisson regression to analyze the association between weekly number of ICU admissions for CAP, and average temperature, range in temperature, total precipitation, and cases of influenza-like illness/100 physician visits reported by sentinel physicians in the community.

RESULTS

In 740 patients admitted to ICUs for CAP, admissions peaked each year in the winter-spring months. In multivariate models, a sine function with a single annual peak was independently associated with number of patients admitted to ICU for CAP (rate ratio [95% confidence interval], 1.12 [1.00, 1.26]), but neither the weather measurements nor the weekly rate of reported influenza-like illness was significantly associated.

CONCLUSION

Intensive care unit admissions for CAP are seasonal, but neither weather measurements nor weekly rate of reported influenza-like illness in the community is associated with these admissions.

Seasonality of pneumonia admissions and its association with climate: an eight-year nationwide population-based study

The aim of the study was to examine seasonal variability in monthly admissions for community-acquired pneumonia (CAP) in Taiwan. Our study sample comprised 477,541 pneumonia patients in Taiwan between 1998 and 2005, inclusive. Results showed a fairly consistent seasonal pattern of pneumonia admissions, regardless of sex and age, and for the groups combined. Seasonal trends showed a peak in hospitalizations from January through April, followed by a sharp decrease in May and a trough from August through October. The auto-regressive integrated moving average (ARIMA) test found significant seasonality for all age and sex groups and for the whole sample (all p < 0.001). After adjusting for seasonality, month, and trends, the ARIMA regression models revealed that the monthly pneumonia admissions rate was significantly associated with ambient temperature, for the total sample, for female groups, and for the 65-74 and > or =75 age groups (all p < 0.01). A 1 degrees C decrease in ambient temperature was associated with roughly a 0.03 increase in monthly pneumonia admissions rate (per 10,000 people) for the entire sample. We conclude the monthly pneumonia admissions rate was significantly associated with seasonality, and was higher in periods with low ambient temperatures.

Vitamin D deficiency in young children with severe acute lower respiratory infection

RATIONALE

Acute lower respiratory infection (ALRI) is one of the most common reasons for hospitalization and intensive care unit admission among children. Season related decreases in the immunomodulatory molecule, vitamin D, remain an unexplored factor that might contribute to the increased occurrence of ALRI in children.

OBJECTIVE

To investigate a possible association between vitamin D deficiency and respiratory infection by comparing serum 25 hydroxyvitamin D [25(OH)D] levels in a group of young children with ALRI to an age-matched group without respiratory infection.

PATIENTS AND METHODS

Participants with a diagnosis of bronchiolitis or pneumonia (n = 55 or 50, respectively), as well as control subjects without respiratory symptoms (n = 92), were recruited at the Royal University Hospital, Saskatoon, Saskatchewan, Canada from November 2007 to May 2008. 25(OH)D levels were measured in patient serum using a competitive enzyme linked immunoassay.

RESULTS

The mean vitamin D level for the entire ALRI group was not significantly different from the control group (81 +/- 40 vs. 83 +/- 30 nmol/L, respectively). The mean vitamin D level for the ALRI subjects admitted to the pediatric intensive care unit (49 +/- 24 nmol/L) was significantly lower than that observed for both control (83 +/- 30 nmol/L) and ALRI subjects admitted to the general pediatrics ward (87 +/- 39 nmol/L). Vitamin D deficiency remained statistically related to pediatric intensive care unit admission in the multivariate analysis.

CONCLUSION

No difference was observed in vitamin D levels between the entire ALRI group and control groups; however, significantly more children admitted to the pediatric intensive care unit with ALRI were vitamin D deficient. These findings suggest that the immunomodulatory properties of vitamin D might influence ALRI disease severity.

Epidemiology and impacts of children hospitalized with pneumonia from 1997 to 2004 in Taiwan

BACKGROUND

Few studies have investigated the epidemiology and disease burden of childhood pneumonia in Taiwan, a middle-income country.

METHODS

Using Taiwan's National Health Insurance database, we analyzed the annual population-based incidence and mortality rate of hospitalizations due to pneumonia in children under 18 years old from 1997 to 2004 in Taiwan.

RESULTS

The average annual incidence of hospitalized pneumonia was 1,240 episodes per 100,000 children in those below 18 years old. For children under 5 years old and for infants, the incidence was 3,965 and 4,984 out of 100,000, respectively. Boys were more likely to be affected than girls (male to female risk ratio 1.27, P < 0.001). The disease occurred most frequently in the spring and least frequently in the autumn (P < 0.001). In children below the age of 5 years old, mortality due to pneumonia was 6.7 per 100,000 per year for children and accounted for 4.2% of the total deaths in this population.

CONCLUSIONS

In Taiwan, pneumonia occurs most frequently in the spring, has an annual incidence of hospitalizations of 3,965 episodes per 100,000 children below the age of 5 years old. It accounts for a mortality rate of 6.7 per 100,000 children in that population, four times that of developed countries (1.6-1.8 episodes per 100,000 children-year).

Temporal variation in case fatality of acute myocardial infarction in Finland

BACKGROUND

Previous studies have suggested that seasonal variation and weather conditions have an influence on the incidence and mortality of acute myocardial infarction (AMI). The influence of these factors on AMI: case fatality is less studied. Aims. The aim of this study was to examine the temporal variation of AMI case fatality and the effect of daily weather conditions on it.

METHODS

We analysed death registry and hospital discharge data from all men and women (n=7328) with their first AMI occurrence in the seven largest cities in Finland in the years 1983, 1988, and 1993, aged 25 to 74 years.

RESULTS

The mean annual 28-day case fatality was 44%. We found significant weekly and monthly variation of case fatality (P<0.001). The December holiday season had the highest case fatality throughout the year in women and men aged 65-74 years (P<0.05). The highest weekly case fatality was on Sundays; it differed significantly from the rest of the weekdays only for the oldest age-group (64-74) (P<0.01).

CONCLUSIONS

There is significant weekly and monthly variation in case fatality of AMI. The highest case fatality risk for AMI is during the Christmas season and on Sundays. Weather conditions were not found to have an effect on the case fatality.

Effect of social factors on winter hospital admission for respiratory disease: a case-control study of older people in the UK

BACKGROUND

Every winter, hospitals in the UK and other developed countries experience a surge in respiratory admissions. Ecological studies suggest that social circumstances may be an important determinant.

AIM

To establish the most important factors associated with winter hospital admissions among older people presenting with acute respiratory disease, especially the relative effect of social factors.

DESIGN OF STUDY

case-control study.

SETTING

Seventy-nine general practices in central England.

METHOD

Of a cohort of patients consulting medical services with lower respiratory tract infection or exacerbation of chronic respiratory disease, 157 hospitalised cases were compared to 639 controls. Social, medical, and other factors were examined by interview and GP records.

RESULTS

Measures of material deprivation were not significant risk factors for admission at either individual or area level, although social isolation (odds ratio [OR] 4.5; 95% confidence interval [CI] = 1.3 to 15.8) resulted in an increased risk of admission. The most important independent risk factor was the presence of chronic obstructive pulmonary disease (COPD; OR 4.0; 95% CI = 1.4 to 11.4), other chronic disease (OR 2.9; 95% CI = 1.2 to 7.0), or both (OR 6.7; 95% CI = 2.4 to 18.4). Being housebound was also an independent risk factor (OR 2.2; 95% CI = 1.0 to 4.8).

CONCLUSION

Socioeconomic factors had little relative effect compared with medical and functional factors. The most important was the presence of long-term medical conditions (especially COPD), being housebound, and having received two or more courses of oral steroid treatment in the previous year. This combination of factors could be used by primary medical services to identify older patients most vulnerable to winter admissions. Clinicians should ensure that patients with COPD are better supported to manage their condition.

Seasonal variation in acute hospital admissions and emergency room presentations among children in the Australian Capital Territory

AIM

To examine seasonal variation in hospital use for five paediatric conditions of the Australian Capital Territory residents.

METHODS

Hospital admissions (1993-2004) and emergency room (ER) presentations (1999-2004) for asthma, croup, bronchiolitis, other respiratory conditions and diarrhoea of children aged <5 years were compared by month and season.

RESULTS

The five conditions comprised 14% of admissions and 24% of ER presentations of children aged <5 years. Bronchiolitis (both admissions and ER presentations) were the highest in the 0-1 year age group (>80%) and the other four conditions peaked at 1-2 years. Children aged 0-2 years contributed 66% of diarrhoea, 62% of croup and 44% of other respiratory admissions whereas ER presentations were higher for other respiratory conditions (57%) and lower for croup (47%). Boys showed higher rates of admissions and ER presentations for all conditions except diarrhoea. Strong seasonal associations were apparent. Incident rate ratios of admissions were significantly higher in autumn compared with summer for asthma and croup whereas bronchiolitis and other respiratory conditions admissions were the highest in winter. Diarrhoea admissions were the highest in spring. ER presentations of the five conditions also showed similar associations with season.

CONCLUSION

Hospital admissions and ER presentations of these five conditions showed strong seasonal patterns, knowledge of which could contribute to improved resource planning (staffing) to meet expected increases in demand for services and scheduling of elective admissions. These findings could be extended to develop a model for forecasting hospital use and to explore the causes of these diseases to ameliorate seasonal effects.

A spatial analysis of the determinants of pneumonia and influenza hospitalizations in Ontario (1992-2001)

Previous research on the determinants of pneumonia and influenza has focused primarily on the role of individual level biological and behavioural risk factors resulting in partial explanations and largely curative approaches to reducing the disease burden. This study examines the geographic patterns of pneumonia and influenza hospitalizations and the role that broad ecologic-level factors may have in determining them. We conducted a county level, retrospective, ecologic study of pneumonia and influenza hospitalizations in the province of Ontario, Canada, between 1992 and 2001 (N=241,803), controlling for spatial dependence in the data. Non-spatial and spatial regression models were estimated using a range of environmental, social, economic, behavioural, and health care predictors. Results revealed low education to be positively associated with hospitalization rates over all age groups and both genders. The Aboriginal population variable was also positively associated in most models except for the 65+-year age group. Behavioural factors (daily smoking and heavy drinking), environmental factors (passive smoking, poor housing, temperature), and health care factors (influenza vaccination) were all significantly associated in different age and gender-specific models. The use of spatial error regression models allowed for unbiased estimation of regression parameters and their significance levels. These findings demonstrate the importance of broad age and gender-specific population-level factors in determining pneumonia and influenza hospitalizations, and illustrate the need for place and population-specific policies that take these factors into consideration.

Seasonal variation in orthopedic health services utilization in Switzerland: the impact of winter sport tourism

BACKGROUND

Climate- or holiday-related seasonality in hospital admission rates is well known for many diseases. However, little research has addressed the impact of tourism on seasonality in admission rates. We therefore investigated the influence of tourism on emergency admission rates in Switzerland, where winter and summer leisure sport activities in large mountain regions can generate orthopedic injuries.

METHODS

Using small area analysis, orthopedic hospital service areas (HSAo) were evaluated for seasonality in emergency admission rates. Winter sport areas were defined using guest bed accommodation rate patterns of guest houses and hotels located above 1000 meters altitude that show clear winter and summer peak seasons. Emergency admissions (years 2000-2002, n = 135'460) of local and nonlocal HSAo residents were evaluated. HSAo were grouped according to their area type (regular or winter sport area) and monthly analyses of admission rates were performed.

RESULTS

Of HSAo within the defined winter sport areas 70.8% show a seasonal, summer-winter peak hospital admission rate pattern and only 1 HSAo outside the defined winter sport areas shows such a pattern. Seasonal hospital admission rates in HSAo in winter sport areas can be up to 4 times higher in winter than the intermediate seasons, and they are almost entirely due to admissions of nonlocal residents. These nonlocal residents are in general -and especially in winter- younger than local residents, and nonlocal residents have a shorter length of stay in winter sport than in regular areas. The overall geographic distribution of nonlocal residents admitted for emergencies shows highest rates during the winter as well as the summer in the winter sport areas.

CONCLUSION

Small area analysis using orthopedic hospital service areas is a reliable method for the evaluation of seasonality in hospital admission rates. In Switzerland, HSAo defined as winter sport areas show a clear seasonal fluctuation in admission rates of only nonlocal residents, whereas HSAo defined as regular, non-winter sport areas do not show such seasonality. We conclude that leisure sport, and especially ski/snowboard tourism demands great flexibility in hospital beds, staff and resource planning in these areas.

Seasonal variation in undiagnosed HIV infection on the general medicine and trauma services of two urban hospitals

OBJECTIVE

To examine the seroprevalence of undiagnosed HIV and variation by season among patients admitted to the general internal medicine (GIM) and trauma services of two urban hospitals.

DESIGN

A cross-sectional blinded HIV-1 seroprevalence survey.

SETTING

A 725-bed academic medical center's hospital and an affiliated 324-bed tertiary care hospital.

PARTICIPANTS

Residual serological specimens were obtained for unique patients aged 17 to 65 to study services in summer (June 16 to September 4, 2001) and fall to winter (November 1, 2001 to January 8, 2002).

METHODS

Hospital files provided data on demographics, service type, and discharge clinical categories (fall-winter group only). HIV ELISA (enzyme-linked immunosorbent assay) tests with confirmatory Western blot were linked to subjects' de-identified files. We excluded 34 subjects with known HIV. Of the remaining unique admissions in summer (n=604) and fall-winter (n=978), 60% and 55% were tested, respectively. Predictors of undiagnosed HIV infection were examined using multivariate analysis.

RESULTS

The summer cohort (n=362) had significantly lower unadjusted seroprevalence of undiagnosed HIV infection (1.4%; 95% confidence interval [CI], 0.4% to 3.2%) than the fall-winter cohort (n=539; 3.7%; 95% CI, 2.3% to 5.7%; P=.04). Overall, undiagnosed HIV was somewhat less likely in women (adjusted odds ratio [AOR], 0.45; 95% CI, 0.19 to 1.07) but more likely in black patients (AOR, 3.46; 95% CI, 0.70 to 17.06). In the fall-winter cohort, undiagnosed HIV was more likely for discharges with the following clinical categories versus those with a cardiac condition: dermatologic/breast (AOR, 14.90; 95% CI, 1.20 to 184.77), renal/urological (AOR, 22.43; 95% CI, 2.12 to 236.75), or infectious (AOR, 31.08; 95% CI, 2.40 to 402.98).

CONCLUSIONS

The higher seroprevalence of undiagnosed HIV in the fall-winter admissions to GIM and trauma services supports especially targeting HIV testing in these months.

The seasonality of total hospitalizations in Ontario by age and gender: a time series analysis

BACKGROUND

Consistent and predictable seasonal fluctuations in hospitalizations have been demonstrated for diverse communicable and non-communicable health conditions. The objective of this study was to examine the seasonal patterns of all hospitalizations by age and gender in order to determine whether the hospital system for a large geographical area was subject to consistent, predictable temporal variations.

METHODS

A retrospective population-based study of approximately 14 million residents of Ontario was conducted to assess temporal patterns in all hospitalizations from April 1, 1988 to March 31, 2000. Time series analysis, using spectral analysis, was conducted to assess seasonal variations and trends over time and to account for autocorrelation.

RESULTS

Conspicuous seasonality in hospitalizations was found in every age group for both sexes with the exception of males between the ages of 20 and 39. The average monthly variability ranged from lows of 15% for the age group 20-29 for both sexes, to highs of 34% in males between 5 and 9 years. For the total population, this represents a 12-year average variability of approximately 20% or 20,000 out of 97,000 hospitalizations. For both sexes, peak hospitalizations typically occurred in the spring and autumn for the youngest and oldest age groups, and in January for the middle age groups.

CONCLUSION

Seasonal factors play an important role in the utilization of hospital services in Ontario. The determinants of this seasonality, which include environmental and social/behavioural factors, are not well understood.