Health Related Behavior Study 2018 – Health Care and Disease Prevention of the Active Servicemen

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The Health Behavior Survey (HRBS) is a primary survey conducted by the U.S. Department of Defense (DoD) to learn about the health, health-related behaviors, and well-being of service members. The HRBS has been conducted periodically for more than 30 years and covers areas that may affect military readiness or the ability to meet the demands of military life.

The Department of Defense commissioned the RAND Corporation to review and administer the 2018 HRBS to active and reserve military personnel. This summary examines the results of the active component.

This summary examines outcomes for physical activity, body weight, screen time, annual physical assessment, sleep health, and substance use to achieve wakefulness. Some results are also compared to the Healthy People 2020 (HP2020) goals set by the U.S. Department of Health and Human Services for the U.S. population.

Because the military population differs significantly from the general population (e.g., military personnel are more likely to be young and male than the general population), these comparisons are presented only as benchmarks of interest.

Physical Activities

Military personnel have physical fitness requirements designed to promote physical fitness as an essential element of force readiness. Poor physical fitness is associated with injuries and chronic illnesses that can interfere with military readiness.

Physical fitness is also related to mental toughness and physical endurance. HP2020 establishes goals for the U.S. population for moderate physical activity (MPA), vigorous physical activity (VPA), and strength training. These goals include.

  • At least 47.9% participate in at least 150 minutes of physical activity per week or at least 75 minutes of physical activity per week.
  • At least 31.3% participate in physical activity for more than 300 minutes per week or at least 150 minutes per week.
  • At least 24.1% participate in muscle-strengthening activities two or more days per week.


The 2018 HRBS found that members of the active component were favorable on all of these standards. Overall, 71.8% (confidence interval [CI]: 70.8-72.9) of active component members reported doing at least 150 minutes per week or at least 75 minutes per week, and 45.3% (CI: 44.1-46.6) reported doing at least 300 minutes per week or at least 150 minutes per week. The proportion of active members meeting targets exceeded HP2020 targets in each unit.

In addition, 49.6% (CI: 48.4-50.8) of active component members reported exercising with weights at least three days per week. The proportion of active component members who reported exercising at least three days per week exceeded the HP2020 target of exercising twice per week.

Body Weight Status

Nearly 40% of the U.S. population is classified as obese, which increases the risk of premature mortality and several chronic diseases. HP2020 establishes weight goals for adults over age 20 based on the following Centers for Disease Control and Prevention body mass index (BMI) categories.

  • Underweight: less than 18.5 kg/m2 .
  • Normal weight: 18.5-24.0 kg/m2 (HP2020 target: at least 33.9% of the population).
  • Overweight: 25.0-29.9 kg/m2 .
  • Obesity: 30 kg/m2 or more (target HP2020: 30.5% or less of the population).


It is important to keep in mind that BMI is an indirect measure of body fat, and that more muscular limbs may be misclassified as obese or overweight. Overall, the 2018 HRBS survey found that 33.3% (CI: 32.1-34.5) of active component members aged 20 years and older were of normal weight.

This figure is roughly in line with the HP2020 target for those aged 20 years or older. In addition, 15.1% (CI: 14.2-15.9) were obese, with Navy personnel being the most likely to be obese. Although the Army meets the HP2020 obesity target, the high proportion of overweight soldiers may be a cause for concern. However, as we have noted, very obese individuals may be misclassified as overweight or obese based on the conventional body mass index threshold.

Time in front of Screen

Screen time spent in front of a desktop or laptop computer, television, smartphone, tablet or other portable computer, or gaming system is generally sedentary. It is therefore associated with an increased risk of obesity and mortality. Research shows that screen time is a risk factor for many cardiovascular diseases and mortality, regardless of time spent exercising.

The 2018 HRBS survey found that 66.8% (CI: 65.6-68.0) of employees reported spending between one and four hours per day on screen time, and 27.2% (CI: 26.0-28.3) reported spending five or more hours per day. Although there were no significant differences in screen time between service units, younger soldiers were the most likely to report spending five or more hours per day in front of screens.

Annual physical evaluation

Routine physical examinations can detect asymptomatic disease, provide early intervention, and promote healthy behavior. These screenings have been shown to save lives through early detection of cancer and chronic disease, and save money. The military requires all members of the armed forces to undergo an annual medical examination. These exams are called periodic physicals and are also used to assess individual capabilities.

In the 2018 HRBS, respondents were asked if they had undergone a periodic physical exam in the past 12 months. A routine physical exam was defined as a general physical exam rather than an exam for a specific injury, illness, or condition.

Overall, 70.3% (CI 69.1-71.4) reported having had such an exam. Coast Guard members (83.8%, CI: 81.6-86.0) were the most likely to say they had had a routine physical exam in the past 12 months; Air Force members (62.8%, CI: 61.4-64.3) were the least likely to say they had had one.

Sleep Quality

According to HP2020, adequate sleep is at least seven hours per day for U.S. adults aged 22 years and older and eight hours per day for adults aged 18-21 years. Lack of adequate sleep is associated with daytime sleepiness, fatigue, diabetes, cardiovascular disease, obesity, and depression.

In the 2018 HRBS survey, respondents were asked how long they slept on average 24 hours in the past 30 days, how sleep affected their energy levels, and whether they used prescription or over-the-counter medications to fall asleep.

The majority of respondents reported sleeping less than HP2020 recommended, with each service falling below the HP2020 target of 72.8% (Figure 3). In addition, 27.5% (CI: 26.3-28.6) reported moderate to very low energy due to lack of sleep, and 8.2% (CI: 7.5-8.8) reported taking prescription or over-the-counter medications at least three days per week in the past 30 days.

Substance use to stay awake

Energy supplements in the form of caffeinated beverages, over-the-counter and prescription drugs can increase endurance and promote anaerobic activity. They can also have negative consequences, such as sleep disturbances, anxiety, and palpitations.

In the 2018 HRBS survey, respondents were asked how often they used energy drinks, over-the-counter medications, and prescription drugs to stay awake in the past 30 days. Many of the active component members reported using energy drinks to stay awake. For example, 16.5% (CI: 15.5-17.5) reported consuming energy drinks at least three times per week in the past 30 days to stay awake.

Consumption of energy drinks to stay awake was more common in the Navy than in other units. In contrast, few reported resorting to medication to stay awake. For example, 96.4% (CI: 96.0-96.9) of active duty personnel reported never using over-the-counter medication to stay awake in the past 30 days, and 97.5% (CI: 97.2-97.9) reported never using prescription medication to stay awake in the past 30 days.

Conclusions and Implications for Policy

The military will meet the HP2020 targets for normal weight. This may be explained by the prevalence of physical activity among soldiers: most soldiers exceed HP2020 goals for physical activity and strength training.

Although many soldiers are obese by HP2020 standards, the extent to which BMI reflects the physical health and fitness of soldiers is an open question. As part of the review of fitness standards, the Navy and Coast Guard should consider whether BMI is an appropriate measure of soldiers' weight.

Adequate sleep is a constant concern for service members. Lack of sleep and fatigue can have a negative impact on service members' readiness. In addition to short-term effects on performance, poor sleep can have long-term effects on physical and mental health.

This is especially important for tasks that require quick decision-making or constant vigilance, which can be affected by fatigue and insufficient sleep. The military and Coast Guard should strive to raise awareness of the importance of sleep among service personnel.

All recruits are required to undergo an annual medical examination, but many reported that they had not done so in the past year. Focusing on these assessments provides an opportunity to address sleep and weight issues among soldiers and can improve troop health.

Methodology

RAND conducted the 2018 HRBS survey among active and reserve members of the U.S. Air Force, Army, Navy, Marine Corps, and Coast Guard between October 2018 and March 2019. The 2018 HRBS was a confidential online survey that allowed researchers to address reminders to nonrespondents and reduce survey burden by linking responses to administrative data.

The sampling frame used a stratified random sampling method by unit, grade, and sex. The overall weighted response rate for the survey was 9.6%, resulting in a final analytical sample of 17,166 responses.

Missing data were treated by imputation, a statistical procedure in which available data are used to estimate missing values. To represent the workforce, RAND researchers weighted responses to avoid underrepresentation of members serving in certain sections. Point estimates and 95% CIs are presented in this survey summary[3].

RAND researchers tested for differences in each outcome at the level of key factors or subgroups-branch of service, rank, sex, race/ethnicity, and age group-using a two-step procedure based on the Rao-Scott chi-square test for overall differences between individual factor levels, and if the overall test was statistically significant, a two-sample t-test for all possible pairwise comparisons between factor levels (e.g., male and female).

Readers interested in these differences should refer to the full HRBS 2018 Active Component final report. This summary is one of eight summaries of the Active Component; this summary and six of the other seven summaries each correspond to a different chapter of the full report, and the eighth summary provides an overview of all findings and policy implications. A similar set of eight summaries covers the reservist findings.

Restrictions & Limitations

The response rate is considered low for the survey. While a low response rate does not automatically mean that the survey data are biased, it does increase the likelihood that they are. As with any self-report survey, social desirability bias is possible, especially for sensitive questions and topics. For some groups, which represent a small percentage of the total military population, survey estimates may be inaccurate and should be interpreted with caution.

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