p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 7 9 9 e8 0 3
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
Seatbelt usage: is there an association with obesity? B. Behzad a,*, D.M. King b, S.H. Jacobson c a Department of Information Systems, College of Business Administration, California State University, Long Beach, CA, USA b Department of Industrial and Enterprise Systems Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA c Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL, USA
article info
abstract
Article history:
Wearing a seatbelt can prevent motor vehicle crash deaths. While primary seatbelt laws
Received 20 November 2013
are designed to encourage vehicle passengers to wear seatbelts by allowing law
Received in revised form
enforcement officers to issue tickets when passengers do not wear seatbelts, discomfort
2 June 2014
may discourage obese individuals from wearing a seatbelt. The objective of this study is
Accepted 3 June 2014
to assess the association between state-level obesity and seatbelt usage rates in the US,
Available online 31 August 2014
and to examine the possible role played by seatbelt laws in these associations. The strength of the association between obesity rates, seatbelt usage, and primary seatbelt
Keywords:
laws at the state level is investigated using data from 2006 to 2011. Linear regression
Obesity
analysis is employed. This model estimates that increasing the obesity rate by 1% in a
Seatbelt usage
state where a primary seatbelt law (by which law enforcement officers can issue a
Seatbelt laws
ticket when seatbelts are not worn) is in effect is associated with a 0.06% decrease
Statistics
in seatbelt usage. However the same percentage of increase in the obesity rate in a state
Public health
where no primary seatbelt law is in effect is associated with a 0.55% decrease in seatbelt usage. The magnitude of the statistical association between state obesity rates and statelevel seatbelt usage is related to the existence of a primary seatbelt law, such that obesity has less impact on seatbelt usage in states where primary seatbelt laws are in effect. Published by Elsevier Ltd on behalf of The Royal Society for Public Health.
Introduction In 2011, in the US, 43,945 vehicles were involved in fatal crashes, accounting for 32,367 deaths.1 Studies show that seatbelts may decrease the risk of death for front-seat passengers by 45%, and the risk of mild to dire injury by 50%, with
higher risks for light-truck passengers.2 Moreover, increasing seatbelt usage is considered the most economical means of decreasing death and injuries in a motor vehicle crash, with a 1% increase in seatbelt usage being associated with $800 million in savings to the US economy and 270 fewer deaths reported nationwide.2 Despite this benefit in passenger safety,
* Corresponding author. E-mail addresses: [email protected], [email protected] (B. Behzad). http://dx.doi.org/10.1016/j.puhe.2014.06.003 0033-3506/Published by Elsevier Ltd on behalf of The Royal Society for Public Health.
800
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 7 9 9 e8 0 3
not all vehicle passengers wear seatbelts; seatbelt usage in the US was estimated to be near 84% in 2011.3 However, seatbelt usage rates vary among the states, with rates greater than 90% in 18 states, but less than 80% in 10 states.4 These differences in rates suggest the existence of independent factors influencing seatbelt usage in each state. Two factors that can influence seatbelt usage at the state level are the existence of seatbelt laws and the prevalence of obesity. To encourage seatbelt usage, most states have enacted either a primary seatbelt law where law enforcement officers can issue a ticket for not wearing a seatbelt, or a secondary seatbelt law where law enforcement officers can issue a ticket for not wearing a seatbelt only when another traffic violation has occurred. As of May 2013, 33 states and the District of Columbia had enacted primary seatbelt laws for front seat passengers and 16 states had enacted secondary seatbelt laws; New Hampshire was the only state with neither a primary nor a secondary seatbelt law for adults.5 Obesity can influence seatbelt usage if discomfort discourages obese individuals from wearing a seatbelt. According to Jehle et al. (2012),6 seatbelt usage is 67% more likely among normal weight drivers compared to obese drivers. Exploring the literature shows that obesity is associated with a decrease in seatbelt usage; however, these studies focus on either a limited geographic region in one city or state,6e9 or over a time span of fewer than four years.10e12 These studies suggest that, at the state level, seatbelt usage rates should decrease as obesity increases,6 or increase in the presence of a primary seatbelt law.13 However, the possible interactions between these factors are not clear. For example, it is not clear whether a primary seatbelt law influences the magnitude of the association between obesity and seatbelt usage; if such a law is introduced in a state, should decreasing obesity rates be associated with a larger or smaller increase in seatbelt usage rates? Understanding these potential interactions can help policymakers understand the potential outcomes of integrated policies that intend to simultaneously improve both public health through obesity interventions and public safety by promoting seatbelt usage. The current study examines seatbelt usage rates, obesity rates, and seatbelt laws at the state level with data spanning years 2006e2011, with the goal of quantifying the association between obesity and seatbelt usage rates, and to assess whether seatbelt laws influence this association using linear regression analysis. To control for the influence that other independent factors may exert on seatbelt usage, this study also considers the fraction of drivers who are women, per capita annual personal income, and annual vehicle miles driven per resident as predictors of the seatbelt usage rate in a state. Studies have shown that seatbelt usage rates in a state tend to increase if the percentage of drivers who are women increases,14 or as per capita income increases.15,16
Methods The current study performs regression analysis at the state level, considering obesity rate, existence of a primary seatbelt law, the fraction of drivers who are women, annual vehicle miles travelled per resident, and per capita personal income
as predictors of the seatbelt usage rates in each state. Hence, data measuring these factors at the state level were needed.
Data Data from several government sources were collected for the years 2006e2011. Annual data measuring state-specified seatbelt usage and the existence of a primary seatbelt law for each state were drawn from the US Department of Transportation.17 The Behavioral Risk Factor Surveillance System (BRFSS) reports annual obesity rate estimates for all 50 states and the District of Columbia across 2006e201018 and 2011.19 Following the World Health Organization classifications, an adult's body mass index can classify them as underweight (
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
Seatbelt usage: is there an association with obesity? B. Behzad a,*, D.M. King b, S.H. Jacobson c a Department of Information Systems, College of Business Administration, California State University, Long Beach, CA, USA b Department of Industrial and Enterprise Systems Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA c Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL, USA
article info
abstract
Article history:
Wearing a seatbelt can prevent motor vehicle crash deaths. While primary seatbelt laws
Received 20 November 2013
are designed to encourage vehicle passengers to wear seatbelts by allowing law
Received in revised form
enforcement officers to issue tickets when passengers do not wear seatbelts, discomfort
2 June 2014
may discourage obese individuals from wearing a seatbelt. The objective of this study is
Accepted 3 June 2014
to assess the association between state-level obesity and seatbelt usage rates in the US,
Available online 31 August 2014
and to examine the possible role played by seatbelt laws in these associations. The strength of the association between obesity rates, seatbelt usage, and primary seatbelt
Keywords:
laws at the state level is investigated using data from 2006 to 2011. Linear regression
Obesity
analysis is employed. This model estimates that increasing the obesity rate by 1% in a
Seatbelt usage
state where a primary seatbelt law (by which law enforcement officers can issue a
Seatbelt laws
ticket when seatbelts are not worn) is in effect is associated with a 0.06% decrease
Statistics
in seatbelt usage. However the same percentage of increase in the obesity rate in a state
Public health
where no primary seatbelt law is in effect is associated with a 0.55% decrease in seatbelt usage. The magnitude of the statistical association between state obesity rates and statelevel seatbelt usage is related to the existence of a primary seatbelt law, such that obesity has less impact on seatbelt usage in states where primary seatbelt laws are in effect. Published by Elsevier Ltd on behalf of The Royal Society for Public Health.
Introduction In 2011, in the US, 43,945 vehicles were involved in fatal crashes, accounting for 32,367 deaths.1 Studies show that seatbelts may decrease the risk of death for front-seat passengers by 45%, and the risk of mild to dire injury by 50%, with
higher risks for light-truck passengers.2 Moreover, increasing seatbelt usage is considered the most economical means of decreasing death and injuries in a motor vehicle crash, with a 1% increase in seatbelt usage being associated with $800 million in savings to the US economy and 270 fewer deaths reported nationwide.2 Despite this benefit in passenger safety,
* Corresponding author. E-mail addresses: [email protected], [email protected] (B. Behzad). http://dx.doi.org/10.1016/j.puhe.2014.06.003 0033-3506/Published by Elsevier Ltd on behalf of The Royal Society for Public Health.
800
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 7 9 9 e8 0 3
not all vehicle passengers wear seatbelts; seatbelt usage in the US was estimated to be near 84% in 2011.3 However, seatbelt usage rates vary among the states, with rates greater than 90% in 18 states, but less than 80% in 10 states.4 These differences in rates suggest the existence of independent factors influencing seatbelt usage in each state. Two factors that can influence seatbelt usage at the state level are the existence of seatbelt laws and the prevalence of obesity. To encourage seatbelt usage, most states have enacted either a primary seatbelt law where law enforcement officers can issue a ticket for not wearing a seatbelt, or a secondary seatbelt law where law enforcement officers can issue a ticket for not wearing a seatbelt only when another traffic violation has occurred. As of May 2013, 33 states and the District of Columbia had enacted primary seatbelt laws for front seat passengers and 16 states had enacted secondary seatbelt laws; New Hampshire was the only state with neither a primary nor a secondary seatbelt law for adults.5 Obesity can influence seatbelt usage if discomfort discourages obese individuals from wearing a seatbelt. According to Jehle et al. (2012),6 seatbelt usage is 67% more likely among normal weight drivers compared to obese drivers. Exploring the literature shows that obesity is associated with a decrease in seatbelt usage; however, these studies focus on either a limited geographic region in one city or state,6e9 or over a time span of fewer than four years.10e12 These studies suggest that, at the state level, seatbelt usage rates should decrease as obesity increases,6 or increase in the presence of a primary seatbelt law.13 However, the possible interactions between these factors are not clear. For example, it is not clear whether a primary seatbelt law influences the magnitude of the association between obesity and seatbelt usage; if such a law is introduced in a state, should decreasing obesity rates be associated with a larger or smaller increase in seatbelt usage rates? Understanding these potential interactions can help policymakers understand the potential outcomes of integrated policies that intend to simultaneously improve both public health through obesity interventions and public safety by promoting seatbelt usage. The current study examines seatbelt usage rates, obesity rates, and seatbelt laws at the state level with data spanning years 2006e2011, with the goal of quantifying the association between obesity and seatbelt usage rates, and to assess whether seatbelt laws influence this association using linear regression analysis. To control for the influence that other independent factors may exert on seatbelt usage, this study also considers the fraction of drivers who are women, per capita annual personal income, and annual vehicle miles driven per resident as predictors of the seatbelt usage rate in a state. Studies have shown that seatbelt usage rates in a state tend to increase if the percentage of drivers who are women increases,14 or as per capita income increases.15,16
Methods The current study performs regression analysis at the state level, considering obesity rate, existence of a primary seatbelt law, the fraction of drivers who are women, annual vehicle miles travelled per resident, and per capita personal income
as predictors of the seatbelt usage rates in each state. Hence, data measuring these factors at the state level were needed.
Data Data from several government sources were collected for the years 2006e2011. Annual data measuring state-specified seatbelt usage and the existence of a primary seatbelt law for each state were drawn from the US Department of Transportation.17 The Behavioral Risk Factor Surveillance System (BRFSS) reports annual obesity rate estimates for all 50 states and the District of Columbia across 2006e201018 and 2011.19 Following the World Health Organization classifications, an adult's body mass index can classify them as underweight (
