Daylight Savings Time: Spring Forward to more Pediatric Fractures ?
1Department of Orthopedic Surgery, 500 University Dr. Hershey PA 17033, USA
Corresponding author: Carissa Sawyer, Department of Orthopedic Surgery, Pennsylvania State University College of Medicine, 1632 N 5th St Harrisburg, PA 17102, Tel: 651-492-0345; Email: firstname.lastname@example.org
Orthopedic injuries in children account for a considerable proportion of pediatric emergency room visits each year. Many of these injuries stem from a fall at play . The incidence of these injuries may be associated with environmental and temporal factors such as changes in the weather, time of day or amount of sunlight, as these conditions often promote more outdoor play, risky physical
activity, falls and injuries.
Previous authors have reported that the incidence of fractures and emergency room admissions increases during warmer fair-weather days [2-8]. However, many of the previous studies were not specific to children or orthopedic injuries. One study by Kennedy reported that the volume of pediatric fractures increased with warmer weather – the highest number of injuries occurred in May and in the temperature range of 70o to 79o. However, Kennedy did not address factors such as hour of injury, amount of rain or snow on the ground, or the effect of gaining an extra hour of sunlight during daylight savings time (DST).
This study will examine the effect of DST (and other environmental factors) on the incidence of pediatric fractures. We hypothesize that once DST occurs in the spring (the second Sunday in March), there will be an increase in the amount of fractures due to the extra hour of sunlight and increasingly warmer weather allowing more outdoor, active play [9-11]. The outcome of this study may help predict days in which there will be a high volume of pediatric orthopedic complaints, thus resulting in better allocation of orthopedic and emergency room personnel and equipment.
Materials and Methods
The study was approved by the College of Medicine Institutional Review Board. A retrospective chart review was performed between December 2014 and May 2015 on 69 patients from the College of Medicine under the age of 18 years who had sustained at least one displaced fracture requiring reduction in the emergency room with a mini-C arm. The mini-C arm is a portable fluoroscope that delivers minimal radiation to the patient and simplifies pediatric facture care [12,13]. Three of the patients in the study initially had a closed reduction using the mini-C arm, which then failed and required an open reduction in the operating room, these patients were still included in the current study. The current study collected fracture data in children from December 1st 2014 through March 7th 2015 (pre-daylight savings time) and March 8th 2015 through May 31st 2015 (post-daylight savings time).
Data obtained from these charts included gender, age, date and time of injury, bones fractured, mechanism of injury, and type of reduction needed. In 19 patients, no injury time was listed in the chart, so these patients were not included in the time of day analysis. Weather data from the day of the injury was extracted from the archives available at the National Climatic Data Center’s Quality Controlled Local Climatological Database . The primary weather observation post was the Harrisburg International Airport station, located approximately nine miles from the Medical Center. The weather data obtained included: average temperature, hours of sunlight, and “significant weather” conditions such as snow, rain, freezing rain, and thunderstorms. Significant weather was recorded every 30 minutes by the NCDC, and each type of significant weather that occurred at all during that day appeared in the daily summary.
Two groups of patients were compared: those with injuries occurring before DST and those with injuries occurring after DST. These groups were analyzed based on the factors listed above. Weather data was analyzed based on days on which a pediatric fracture occurred that required a reduction versus days without a pediatric fracture. While analyzing the effect of temperature and sunlight hours, only outdoor injuries were considered because indoor injuries presumably occur
independently of temperature and sunlight. Statistical analyses included basic descriptive statistics for pediatric fractures and each of the variables. Chi-square analysis and two-tailed t-tests were used to determine which variable demonstrated a statistical difference with regard to incidence of pediatric fractures before vs after DST.
During the 182 days in the study period, 69 pediatric fractures requiring reduction with the mini-C arm were treated, for an average of 1 per 2.64 days. There were 25 (36%) fractures that occurred before DST and 44 (64%) that occurred after DST (Figure 1). Demographic information of the patients included in the study is outlined in Table 1. Gender and age of the children injured was analyzed using a chi-square analysis and a two tail t-test, respectively. There was no statistically significant difference between the gender or age of children that obtained orthopedic injuries before vs after DST (p=0.153 and p=0.183 respectively). The average age at the time of injury was 10.08 years.
Number of Pediatric Orthopedic Injuries before vs after Daylight Savings Time
Figure 1. Relationship between number of pediatric orthopedic injuries before versus after DST.
Table 1. Demographic information for patients involved in study.
A chi square analysis comparing the 6 months in the study demonstrated that the rate of pediatric orthopedic fractures varied for all 6 months (p<0.005). For example, the spring months of April and May had a higher number of fractures than the winter months (Figure 2). Days of the week were also examined. The chi-square test demonstrated that there was no statistically significant difference between the days
of the week on which pediatric orthopedic injuries occurred before vs after daylight savings (p=0.686). Although not statistically significant, more fractures occurred on Saturday (p=.071). In fact, the rate of fractures on Saturday doubled after daylight savings time from 6 to 12.
Month vs Number of Injuries
Number of Pediatric Fractures
Dec Jan Feb Mar April May Month of the Year
Figure 2. Relationship between number of pediatric orthopedic injuries and month of the year.
The time of day at which the pediatric orthopedic injury occurred was separated into two categories: 3PM-8PM and 8PM-3PM, with the thought that there would likely be more injuries occurring during the “after school” hours of 3-8PM. A chi-square analysis (which was weighted accordingly for the uneven number of hours in each group) supported our hypothesis in that there were significantly more injuries that occurred between 3PM-8PM than from 8PM-3PM(p<0.0001). Additionally, the peak time of injury for this study was 5:37 PM. Neither the child’s gender nor age significantly affected the time of injury.
When comparing whether the children’s orthopedic injury occurred outdoors vs indoors, a chi-square test indicated that there was a significant difference between indoor and outdoor location of fracture before DST vs after DST (p<0.05). Significantly more children injured themselves outdoors after DST (74%) than before (26%). Furthermore, a two tailed t-test revealed that on days with at least one pediatric fracture which occurred outdoors, the temperature was significantly warmer than days without injuries (p<0.005) (Figure 3).
Temperature vs Number of Outdoor Injuries
0-10 ℉ 11-20℉ 21-30℉ 31-40℉ 41-50℉ 51-60℉ 61-70℉ 71-80℉
Number of Outdoor Injuries
Figure 3. Relationship between number of outdoor pediatric orthopedic injuries and average daily temperature.
Sunlight hours were analyzed using a chi-squared analysis. This revealed that days with pediatric orthopedic injuries occurring outdoors had significantly more sunlight hours than on days without injuries (p<0.005) (Figure 4). The final environmental factor that was studied was the weather classification for type of day. The weather was separated into 5 categories: sunny, cloudy, rain, freezing rain and snow based on the significant weather recorded on that day from the National Climatic Data Center as well as the description of the type of day in Harrisburg, PA (sunny, partly cloudy, cloudy, etc) from the Weather Channel. A chi-squared test comparing fracture rates during all 5 weather categories compared to pre vs post DST revealed a statistically significant difference (p<0.01). More fractures occurred on sunny days after DST (74%) than before (26%).
Sunlight Hours vs Number of Outdoor Injuries
Number of Outdoor Fractures
10-10.99 11-11.99 12-12.99 13-13.99 14-14.99
Figure 4. Relationship between number of pediatric orthopedic injuries and daily hours of sunlight.
The mechanism of injury and type of reduction needed were the last two variables studied. Mechanism of injury was broken down into 6 categories: fall on outstretched hand (FOOSH) from a stable object, FOOSH from wheels (bicycle, skateboard, scooter), FOOSH from snow (skiing, snowboarding), FOOSH from standing, sports injury and trampoline injury. An “other” category was created for injuries that did not fit into any of these categories, and those 4 injuries were not included in the final analysis. The number of fractures occurring from the various mechanisms of injury was significantly different before vs after DST (p<0.05). The type of reduction needed was separated into 4 categories: cast only, cast + closed reduction, subcutaneous pin, and open reduction. A chi-squared test showed no significant difference among these reduction categories before vs after DST (p=0.297).
This purpose of this study was to examine the effect of DST and other related environmental factors such as sunlight hours and warm weather, on the incidence of pediatric fractures. We hypothesized that once DST occurs in the spring, there would be an increase in the amount of fractures due to the extra hour of sunlight and increasingly warmer weather allowing more outdoor, active play [9-11].
Although the association between emergency room visits and warm weather has been recognized [1-7], few of these papers focused on children. Two authors found that for both pediatric and total emergency room admissions, temperatures, hours of sunshine, day of the week and month of the year affected the number of admissions, with a direct association between trauma attendance and pleasant weather [2,4]. These studies however, did not focus on orthopedic injuries. Two studies investigated the relationship between pediatric orthopedic injuries and environmental factors, both illustrating that pediatric fractures increased during warmer months of May-August. Specifically, pediatric fractures increased with more sunlight hours, and decreased with precipitation [5,15].
Loder found a significant increase in the number of fractures during the warmer months and that weekdays demonstrated a higher proportion of fractures occurring in the morning and at school. Overall Loder reported that the peak time of injury was 6:00PM . Only one study has reported that with longer evening daylight there was an increase in daily physical activity . To our knowledge, no study to date has examined how DST affects the pediatric orthopedic fracture rate.
This current study of 69 pediatric fractures demonstrated a number of temporal and environmental factors related to the frequency of pediatric fractures. For example, injuries occurred significantly more frequently in the warmer months (April and May), with warmer temperatures, and with more daily hours of sunlight (13-13.99 hours). In addition, the time of day played a role in pediatric orthopedic injuries in that significantly more children were injured in the 3PM- 8PM “after school” time range compared to 8PM-3PM, with the peak time occurring at 5:37PM. This finding supports Loder’s analysis and our hypothesis.
In regards to DST, there were more outdoor injuries and injuries that occurred on “sunny” days that occurred post- DST as compared to pre-DST. The mechanism of injury differed significantly pre vs post DST, with more outdoor- type mechanisms (ie, fall from wheels, sports-related injury, trampoline) occurring after DST occurred. Factors that did not appear to have an effect on the frequency of pediatric orthopedic injuries included gender and age of the child.
DST was first introduced in the US in 1918 during World War I. It was repealed seven months later, until President Roosevelt instituted year round DST in 1942. The original reason why daylight savings time was started was to gain an extra hour of sunlight for “after work activities” during the summer while sacrificing that same hour during the colder winter months . DST became widely adopted in throughout the world as a result of the 1970’s energy crisis, as proponents argued it would cut down on energy consumption and reduce the need for lighting and heating. Today, all states in the United States except Arizona and Hawaii participate in DST. Arizona and Hawaii claim that
this schedule was unnecessary for their hot climate because it is easier to participate in outdoor activities when the temperature was cooler in the evening.
The findings of the current study performed in the state of Pennsylvania support the original hypothesis that after DST with the added hour of sunlight, children will be more likely to play outdoors and sustain injuries. This increased rate of pediatric fractures, combined with the fact DST may not reduce energy costs as much as it was once thought to, questions its usefulness. In fact, multiple authors suggest that daylight savings time actually increases energy costs [17,18]. The current study demonstrates more musculoskeletal injuries require reduction after the onset of DST – therefore, costs associated with such injuries in children could potentially be reduced substantially if DST was abandoned.
The results of the current study demonstrate helpful information for emergency room personnel planning and resource distribution related to pediatric orthopedic care. Resource needs can be anticipated to be higher after DST, in the warmer months, during the “after school rush” of 3PM- 8PM and on days with higher average temperatures.
One limitation to our study is the small sample size, as well as the fact that only one subset of fractures was collected
– ones that came through the Emergency Department and needed reduction with the mini-C arm. Although it would strengthen the study to include non-reduced fractures, during this time period it was not possible. The only fracture data that could accurately be collected were the ones from the mini-C arm, in which the timestamp was on. Additionally, the true overall effect of DST on pediatric injuries would require a careful analysis of other injury types – such as traumatic brain injury, blunt abdominal, lacerations, etc. Without this information, it is difficult to know whether the results are simply due to background noise of an increase in all traumatic pediatric injuries during summer months vs a real increase in incidence of fractures. Although collecting all types of pediatric injuries was not practical with our study, it could act as a pilot study leading to a larger, multi- center prospective study examining the full effect of DST on pediatric injuries. Additionally, the current study analyzed only 1 season of DST. A supplementary analysis of several (5- 10 years) DST seasons would strengthen the hypothesis that the current study examines. An additional limitation is that the geographical region studied experiences all four seasons and the results may only apply to the weather patterns of central Pennsylvania and similar climates. Finally, not all of the variability in pediatric orthopedic injuries can be attributed to temporal and environmental factors. For example, other outside factors such as vacation, sports competitions on game day cannot be ruled out as potential causes of increased amount of injuries.
In conclusion, significantly more pediatric orthopedic injuries occurred after Daylight Savings Time than before, a finding further supported by the environmental factors explored in this study: there was an increase in pediatric
orthopedic injuries in warmer temperatures and with more hours of sunlight. Additionally, more fractures occurred outdoors after DST than before DST, indicating that the extra hour of sunlight may have promoted more outdoor play and thus more injuries. Finally, the time of day was an important factor in when children injured themselves – more pediatric fractures occurred during the after-school range of 3PM- 8PM, with a peak time of 5:37PM.
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