- Email: [email protected]
Vaping, Smoking, and the Physical Fitness of Active Young Men
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RESEARCH ARTICLE
Vaping, Smoking, and the Physical Fitness of Active Young Men Eero Dinkeloo, MPH,1,2 Tyson L. Grier, MS,1 Raina D. Brooks, MPH,1 Bruce H. Jones, MD, MPH1
Introduction: Adverse effects of cigarette smoking on physical performance are well studied.
Because of the recent rise in popularity of vaping, it is important to evaluate its effect on fitness both independently and in conjunction with traditional cigarette use.
Methods: This was a secondary analysis performed in 2018 on data collected from U.S. Army Soldiers during 2016. All metrics were self-reported via an electronic questionnaire. Personal characteristics of current ENDS users, smokers, and dual users were compared with a reference group that reported no history of use. Adjusting for age and physical training habits, an ANCOVA was used to compare Army physical fitness test results. A Fisher’s exact test determined specific mean differences between groups.
Results: This study population consisted of 2,854 men aged 24.6 years on average. Differences in
physical training and fitness were shown between the groups. Never users averaged the most total physical training, followed by ENDS users, smokers, and then dual users. Compared with never users on the fitness tests, ENDS users had an adjusted mean difference of +27 seconds on the 2-mile run, 4.56 push-ups, and 2.01 sit-ups; smokers averaged +8 seconds, 2.15 push-ups, and 1.44 sit-ups; and dual users averaged +32 seconds, 5.17 push-ups, and 3.88 sit-ups. Dual users had significantly (p<0.05) lower scores than current smokers and never users on all 3 fitness events.
Conclusions: This study suggests that individuals who use e-cigarettes and tobacco cigarettes average a lower level of fitness than individuals who abstain.
Am J Prev Med 2019;000(000):1−7. © 2019 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
INTRODUCTION
D
evices that use a heating element to aerosolize “e-liquids” into vapor for the user to inhale are known as ENDS. They include products such as e-cigarettes, personal vaporizers, vape pens, and e-hookahs.1,2 Since hitting the market, using ENDS, known as vaping, has grown rapidly, showing significant upward trends in awareness, ever use, and current use.3,4 The percentage of U.S. adults who have ever tried ENDS was estimated at 3.3% in 2010,3 a number that increased to 15.4% in 2016.5 Use of ENDS is even higher in younger populations, to a point where it is now considered a major public health concern.2,6 This is illustrated by the finding that 23.5% of adults aged 18−24 years have ever tried ENDS, whereas 4.2% are current users5 and estimates that school-aged adolescents are vaping at a higher rate than smoking combustible cigarettes.7
Although the toxicants of ENDS vapor are found in lower quantities compared with tobacco cigarette smoke,8,9 it does not mean vaping has been deemed safe.2,10,11 The vapor of ENDS can contain nicotine, volatile organic compounds, tobacco-specific nitrosamines, ultrafine particles, propylene glycol, vegetable glycerin, and metals, such as nickel, tin, and lead.2,6,12−18 These chemicals are reportedly respiratory irritants that can From the 1Injury Prevention Division, Clinical Public Health and Epidemiology Directorate, U.S. Army Public Health Center, Aberdeen Proving Ground, Maryland; and 2Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee Address correspondence to: Eero Dinkeloo, MPH, U.S. Army Public Health Center, Clinical Public Health and Epidemiology Directorate, 8977 Sibert Road, Aberdeen Proving Ground MD 21010. E-mail: [email protected]. 0749-3797/$36.00 https://doi.org/10.1016/j.amepre.2019.08.015
© 2019 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
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cause inflammatory reactions, decreased exhaled nitric oxide levels (a test used to assess pulmonary inflammation), and respiratory flow resistance.10,12,14,19−21 However, the amounts of these toxicants can vary substantially based on the product being used.13−16,18 Despite the emerging emphasis on investigating ENDS, the rapid rise in their popularity has set a fastmoving target. Some studies have found acute respiratory changes similar to those of cigarettes though to a lesser magnitude8,22,23 and symptoms such as sore throat and cough after 10 minutes of use.21 Large cross-sectional surveys of adolescents show a possible association of ENDS use and respiratory symptoms, independent of smoking status or secondhand smoke exposure.20,24 However, no studies have examined the relationship of ENDS use and physical fitness. By contrast, the relationship between tobacco cigarettes and physical performance has been well studied. It has been shown that smoking cigarettes correlates with poorer outcomes on several physical fitness tests,25−28 lower oxygen uptake, impaired heart rate responses to exercise (i.e., ability to increase heart rate commensurate with increased activity), and lower aerobic and muscular endurance compared with nonsmokers.29−34 These findings are present even in younger and trained populations, similar to those being examined in this study,27,35 where they are exaggerated by heavier use36 and reversible by cessation.29,34 Because a sizable measure of a soldier’s effectiveness is dependent on their physical condition, developing and maintaining physical fitness levels within this population is a high priority. Many programs currently exist that are aimed at optimizing health and physical performance, including those aimed at smoking cessation. It is possible that ENDS use deserves to be included with traditional cigarettes in the scope of these programs, but a better understanding of any associated effects is needed. The purpose of this study was to compare the physical fitness levels among male soldiers using ENDS, tobacco cigarettes, or both, and those that have never used either.
METHODS Study Population This was a secondary analysis, performed in 2018, of an electronic survey distributed by the Army Public Health Center to active duty soldiers in a U.S. Army Airborne division between April 2016 and July 2016. Participants were asked about their background, fitness levels, physical training (PT) habits, and injury history. The investigation was approved by the Army Public Health Center Public Health Review Board. Of the initial 6,383 respondents, 3,502 were eligible for this analysis based on if they were men (owing to a limited number of women in the investigation), reported valid Army physical fitness test (APFT) results,
were not on a physical profile that limited their PT or APFT participation, and could be categorized into 1 of the 4 exposure groups. Exclusions were made if responses reported longer weekly unit or personal PT durations than what was considered realistic (n=648): >640 minutes of unit PT or >800 minutes of personal PT.
Measures The exposures of interest in this study were ENDS use and cigarette smoking, which were assessed via self-report from the administered survey. Participants were divided into 4 exposure groups: never users, current ENDS users, current smokers, and current dual users. The never users’ group, used as the reference, consisted of individuals who reported never using tobacco products of any type in their lifetime. Current ENDS users were defined as individuals who reported using ENDS within the last 30 days, reported using ENDS consistently for >30 days, and had no history of using other tobacco products. Current smokers included individuals who reported smoking >100 tobacco cigarettes in their lifetime, smoking in the last 30 days, and had no history of ENDS or other tobacco use. Finally, current dual users consisted of individuals who reported ENDS use and tobacco cigarette use within the last 30 days and smoking ≥100 cigarettes in their lifetime but no history of using other tobacco products. In this study, physical fitness levels were assessed using APFT results. The APFT is designed to test the muscular strength, endurance, and cardiorespiratory fitness of soldiers in the U.S. Army. It consists of 3 events: a timed 2-mile run, 2-minute maximal effort push-ups, and 2-minute maximal effort sit-ups. Active component soldiers are required to complete an official APFT biannually. Soldiers were asked to report their most recent APFT scores on the survey.
Statistical Analysis Following stratification of the population into exposure groups, means and SDs were calculated for personal characteristics, cigarette or ENDS use, and physical activity. Frequencies were displayed for categorical characteristics, and chi-squared tests were used to determine differences across exposure groups. One-way ANOVA was used to compare mean differences in continuous variables across exposure groups, with the exception of cigarette and ENDS use, where independent t-tests were used. To further explore the mean differences in APFT results across exposures, ANCOVA was used to adjust for differences in relevant covariates that differed significantly between groups, which included age and hours of weekly personal PT, and results were reported as the adjusted means for each exposure group. A post-hoc Fisher’s least significant difference test was applied to each significant ANCOVA to determine exposure groups that differed significantly. Statistical significance was defined as p<0.05. SAS version 9.4 was used for all statistical analyses.
RESULTS A total of 2,854 soldiers were included in this study, most of whom (80.5%) had never used tobacco products; 2.2% were classified as current ENDS users, 12.5% were www.ajpmonline.org
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Table 1. Characteristics of Active Component Male Army Soldiers by Level of Exposure (n=2,854) Characteristic
Never users
Smokers
ENDS users
Dual users
p-value
% (n) Age, mean years (§SD) BMI, mean kg/m2 (§SD) Rank, n (%) Enlisted Officers Physical demand of MOS, n (%) Heavy Moderate Light Years smoking, mean (§SD) Cigarettes per day in last month, mean (§SD) Years using ENDS, mean (§SD) Days using ENDS in last month, mean (§SD) Unit PT, mean hours per week (§SD) Personal PT, mean hours per week (§SD)
80.5 (2,298) 24.78 (§5.5) 25.72 (§3.0)
12.5 (355) 24.20 (§4.5) 25.54 (§3.2)
2.2 (63) 21.67 (§3.3) 25.27 (§3.2)
4.8 (138) 24.12 (§4.9) 25.68 (§3.1)
n/a <0.0001a 0.5241a <0.0001b
1,934 (84.2) 364 (15.8)
339 (95.5) 16 (4.5)
57 (90.5) 6 (9.5)
130 (94.2) 8 (5.8) 0.0034b
1,726 (75.1) 370 (16.1) 202 (8.8) n/a n/a n/a n/a 4.42 (§2.3) 3.87 (§3.4)
304 (85.6) 32 (9.0) 19 (5.4) 6.95 (§ 5.4) 8.02 (§6.6) n/a n/a 4.80 (§2.2) 3.40 (§3.3)
50 (79.4) 9 (14.3) 4 (6.3) n/a n/a 1.61 (§1.2) 16.06 (§11.5) 4.33 (§2.0) 3.51 (§2.9)
107 (77.5) 20 (14.5) 11 (8.0) 6.57 (§5.5) 7.52 (§6.6) 1.67 (§1.2) 13.80 (§11.2) 4.44 (§2.2) 3.26 (§3.2)
0.8412c 0.9367c 0.7197c 0.7592c 0.0287a 0.0236a
Note: Boldface indicates statistical significance (p<0.05). a One-way ANOVA. b Chi-square. c Independent t-test. MOS, military occupational specialty; n/a, not applicable; PT, physical training.
classified as current smokers, and 4.8% as dual users. Table 1 displays characteristics of this population by exposure group. ENDS users were significantly younger with a mean age of 21.67 (SD=3.3) years, whereas the other 3 groups ranged from 24.12 (SD=4.9) years to 24.78 (SD=5.5) years. Between groups, BMI did not differ (p=0.52), with group means ranging from 25.27 to 25.72 kg/m2. A majority of the soldiers in this cohort were in military occupational specialties that required heavy physical demands. Current smokers averaged the most weekly unit PT, and current ENDS users averaged the least though the range was only 30 minutes. Personal PT also differed between groups, with a similar variation to what was seen in unit PT. However, unlike unit PT, never users performed the most personal PT and dual users the least. Current smokers’ and dual users’ exposures to tobacco was similar, in that they had both smoked for around 6−7 years and smoked about 8 cigarettes a day. Current ENDS users and dual users both averaged slightly more than 1.5 years of ENDS use and were similar in the number of days vaping in the previous month (16.06 vs 13.80, p=0.76). Table 2 displays the adjusted means of each of the 3 APFT tests. These averages were adjusted for age and hours of weekly personal PT. On average, the group with no tobacco use had the fastest 2-mile run time and performed the most push-ups and sit-ups, whereas the dual users had the slowest run time and least number of & 2019
push-ups and sit-ups. A Fisher’s least significant difference test revealed that dual users differed significantly from both the reference group and current smokers on all 3 events. Current smokers differed significantly from never users on the push-up and sit-up tests, but not the 2-mile run. Current ENDS users averaged poorer performance than never users on all 3 events, but this difference was not significant for the sit-up test. These differences are illustrated in Figure 1, which displays adjusted group means for each APFT event.
DISCUSSION This analysis compared APFT scores among groups of cigarette smokers, ENDS users, dual users, and never users. The primary findings of this study are that dual users of ENDS and cigarettes averaged slower 2-mile run times and fewer push-ups and sit-ups than never users. Furthermore, dual users averaged a significantly poorer performance on all 3 events than did current smokers. Also, current ENDS users had a slower 2-mile run and performed fewer push-ups than never users. Within this study population, 7% reported current ENDS use. Exclusive ENDS users were younger on average than other groups, which is a common finding in the literature.1,3,5,37 It is important to note that this analysis was performed solely on men, which have a reportedly higher usage rate of tobacco products than women.38 Nonetheless, this suggests the rate of ENDS use, similar
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Table 2. Exposure-Specific APFT Performance Means of Active Component Male Army Soldiers, Adjusted for Age and Personal Physical Training Habits (n=2,854) Exposure group No use (n=2,298) APFT component
Smoking (n=355)
ENDS (n=63)
Dual use (n=138) p-value
Adjusted mean (unadjusted mean)
2-mile run (minutes and fractions of a minute)
14.60 (14.60)
14.72 (14.72)
15.03 (14.91)
15.13 (15.13)
Push-up test (reps)
64.97 (65.04)
62.82 (62.58)
60.41 (59.63)
59.86 (59.51)
Sit-up test (reps)
69.81 (69.85)
68.37 (68.21)
67.80 (67.68)
65.92 (65.70)
<0.0001a No use/ENDS, no use/ dual use, dual use/ smokingb <0.0001a No use/smoking, no use/ ENDS, no use/dual use, smoking/dual useb <0.0001a no use/smoking, no use/ dual use, smoking/dual useb
Note: Boldface indicates statistical significance (p<0.05). a Overall ANCOVA p-value. b Statistically significant Fisher’s least significant difference comparisons (p<0.05). APFT, Army physical fitness test; rep, repetition.
Figure 1. Mean Army physical fitness test (APFT) performance by exposure group (n=2,854), adjusted for age and personal physical training habits. www.ajpmonline.org
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to that of cigarettes, could be quite a bit higher than the 4.1% reported in the general adult male population.40 The estimate of overall use in this study is likely underrepresentative of actual rates owing to exclusion criteria of the cohort, which did not measure ever use or include current ENDS users who formerly smoked, who are described as making up a large portion of ENDS users.3,4,37 Rates of current cigarette smoking in this study (17.3%) are comparable with what other surveys have reported in military populations.38,39 This study found that the average time and volume of cigarette smoking was not significantly different between those that exclusively smoked cigarettes and current dual users. The same is true of ENDS use between exclusive ENDS users and dual users, though average length of time using ENDS was substantially less than with cigarettes. This illustrates a concern that smokers may not necessarily reduce conventional cigarette consumption when adding the use of ENDS1; the group of dual users in this study experienced the highest level of exposure. In this analysis, current smokers averaged lower performance on all APFT events than never users though the difference was not statistically significant for the 2-mile run. This finding reaffirms what has been reported by prior studies. Performance on similar fitness tests of muscular endurance have been compared between smokers and nonsmokers within military populations, demonstrating similar findings.25−28 Similarly, muscular strength previously has been found to be lower in smokers, even after adjusting for other factors.30,41 The ENDS users also exhibited lower average performance than never users on all APFT events, but a Fisher’s least significant difference test identified the difference in the 2-mile run and push-ups as statistically significant. It is possible that the shorter amount of exposure to ENDS (1.38 years, SD=1.3) is not enough time to identify the true physical effects that are associated with using ENDS alone. As other studies have noted, looking at smoking histories of up to or even exceeding 10 years, the length of use plays a role in the relationship of cigarette smoking and physical fitness.32,34,36 This has also been observed among smokeless tobacco users, with 1 study reporting that a longer history of use was correlated with worse APFT performance.42 Because average ENDS use among exclusive users was only 1.38 years versus 6.95 years for smokers, it is feasible that the full impact of vaping has yet to be realized. This study found that current dual users of cigarettes and ENDS presented significantly lower mean performances on the 2-mile run, push-ups, and sit-ups tests than did never users. Their performance was also significantly lower than that of current smokers. Therefore, it appears that using both cigarettes and ENDS results in lower & 2019
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fitness levels than smoking alone. However, smoking load did not differ significantly between the smokingonly group and the dual use group. Effects of smoking on the cardiorespiratory system have also been demonstrated in multiple studies, in the form of reduced heart rate response, lower forced expiratory volume, lower maximal oxygen uptake, and slower run times compared with nonsmokers.26,27,29,31−34 A possible reason for this difference in run time may be associated with the added exposure of ENDS use on the respiratory system. Vardavas et al.43 found that among 30 current smokers, acute use of an e-cigarette led to a decrease in exhaled nitric oxide and increases in airway resistance after only 5 minutes of vaping. Other studies have presented similar findings in relation to decreased exhaled nitric oxide23 and peak expiratory flow.22 Admittedly, these effects are not necessarily clinically significant, and other studies have shown no significant changes in forced expiratory volume,8,22 but these do not directly assess acute dual use. These previous findings combined with the results presented here suggest it is possible that using ENDS may have an impact on physical fitness, particularly on cardiorespiratory fitness in those already disadvantaged by smoking cigarettes. Yet, it is important to consider an inherent difference in the behavior of individuals who use tobacco products and those that abstain. This analysis was able to examine some covariates and adjust for age and personal physical activity levels but was not able to measure other characteristics that are found to vary between smokers and nonsmokers such as motivation, diet, alcohol consumption, sleep quality, or risk taking.42,44,45 So far, studies on user profile differences, which include ENDS users, have focused mainly on adolescents and have classified them as “intermediate risk.”46−48 Exclusive ENDS users exhibited behavioral risk factors greater than nonusers but lower than smokers or dual users and protective behaviors lower than nonusers but higher than smokers or dual users.47,48 One such study found no significant difference in overall physical health between the adolescents classified in the same 4 groups used in this analysis but did find variation within ENDS-only users.46 For example, other substance use in the past year was associated with increased ENDS use, whereas a healthier diet was associated with less.46 This shows the variability of other influencing factors across and within these exposure groups that should be accounted for in future research, especially when examining a multifaceted outcome such as physical fitness levels. Although never users had higher performance on the fitness tests, vapers, smokers, and dual users still had relatively high mean fitness scores. This could be attributed to the relatively young population, engaged in a physically demanding occupation, where tobacco use has been found to be associated with lower performance
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than nonsmokers but not necessarily poor performance in this population of active young men. This is shown in other military studies of tobacco use and fitness performance.26−28 However, the importance of maintaining peak fitness within this population, or others like it, should not be understated.
Limitations There are some limitations present in this study. First, all data were collected via self-report surveys, leaving the possibility for reporting or recall bias. However, previous studies looking at the efficacy of self-reported BMI and physical fitness test scores, specifically the APFT, found a high correlation with actual results within this population.49,50 Another main limitation is the quantification of ENDS use. There is not a consensus on how to measure the level of exposure from ENDS using a survey format. Beyond the variability of the number of uses per day or length of inhale between users, the actual concentrations and chemical components can vary between different products.13−16,18 Therefore, it is possible that actual exposure to ENDS-related toxicants could vary within group, independent of the days or years of use. Lastly, former use of tobacco products was not examined by this study. Because the effects from smoking are noted to be reversible after cessation,29,34 it would be worthwhile to examine former ENDS users when an adequate sample size exists. Despite these drawbacks, this was a relatively large sample size of soldiers who do represent a sizable portion of the overall active component of the U.S. Army, which is generally younger (75% aged <35 years), more physically fit, and 85.5% male.38 Consequently, it is also representative of a large portion of adult ENDS users who tend to be young men.37,40
CONCLUSIONS This study examined physical fitness test outcomes and use of ENDS. The primary finding was that current dual users of ENDS and tobacco cigarettes averaged lower performance on the 2-mile run, 2-minute maximal push-up, and 2-minute maximal sit-up tests than never users and significantly slower run times and fewer pushups than current smokers. ENDS-only use was associated with significantly lower performance on the 2-mile run and push-up test than never users. Training and maintaining physical fitness are crucial within this population and among other groups such as emergency personnel, first responders, and athletes, so any exposure detrimental to that goal deserves considerable scrutiny. This is the first study to examine relationships between ENDS and physical fitness performance, making the results novel and useful to inform further examination.
Future research is necessary to build on this relationship and should focus on a more thorough evaluation of both exposure, outcome, and other fitness-related variables.
ACKNOWLEDGMENTS Citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement or approval of the products or services of these organizations. The views expressed in this paper are those of the author(s) and do not necessarily reflect the official policy of the Department of Defense, Department of the Army, U.S. Army Medical Department, or the U.S. Government. This investigation was supported in part by an appointment to the Postgraduate Research Participation Program at the U.S. Army Public Health Center, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and U.S. Army Public Health Center. Author contributions: ED and TG contributed to design of study. RB worked on data collection and managed the database. ED, TG, and BHJ contributed to statistical analysis. ED undertook the first draft, and all authors have contributed to and approved the final manuscript. No financial disclosures were reported by the authors of this paper.
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31. Cooper KH, Gey GO, Bottenberg RA. Effects of cigarette smoking on endurance performance. JAMA. 1968;203(3):189‒192. https://doi.org/ 10.1001/jama.1968.03140030021006. 32. de Borba AT, Jost RT, Gass R, et al. The influence of active and passive smoking on the cardiorespiratory fitness of adults. Multidiscip Respir Med. 2014;9(1):34. https://doi.org/10.1186/2049-6958-9-34. 33. Lauria VT, Sperandio EF, de Sousa TL, et al. Evaluation of dose−response relationship between smoking load and cardiopulmonary fitness in adult smokers: a cross-sectional study. Rev Port Pneumol. 2017;23(2):79–84. https://doi.org/10.1016/j.rppnen.2016.11.007. 34. Sandvik L, Erikssen G, Thaulow E. Long term effects of smoking on physical fitness and lung function: a longitudinal study of 1393 middle aged Norwegian men for seven years. BMJ. 1995;311(7007):715‒718. https://doi.org/10.1136/bmj.311.7007.715. 35. Leyk D, R€ uther T, Witzki A, et al. Physical fitness, weight, smoking, and exercise patterns in young adults. Dtsch Arztebl Int. 2012;109 (44):737‒745. https://doi.org/10.3238/arztebl.2012.0737. 36. Misigoj-Durakovic M, Bok D, Soric M, Dizdar D, Durakovic Z, Jukic I. The effect of cigarette smoking history on muscular and cardiorespiratory endurance. J Addict Dis. 2012;31(4):389‒396. https://doi.org/ 10.1080/10550887.2012.735567. 37. Sussan TE, Shahzad FG, Tabassum E, et al. Electronic cigarette use behaviors and motivations among smokers and non-smokers. BMC Public Health. 2017;17(1):686. https://doi.org/10.1186/s12889-017-4671-3. Tag edP38. U.S. Army Public Health Center. Health of the Force: 2017. https:// phc.amedd.army.mil/Periodical%20Library/2017HealthoftheForceweb.pdf. Published 2017. Accessed 2018. 39. Knapik JJ, Bedno SA. Epidemiological evidence and possible mechanisms for the association between cigarette smoking and injuries (part 1). J Spec Oper Med. 2018;18(1):108‒112. 40. Schoenborn CA, Gindi RM. Electronic cigarette use among adults: United States, 2014. NCHS Data Brief. 2015;217(217):1‒8. 41. Kok MO, Hoekstra T, Twisk JW. The longitudinal relation between smoking and muscle strength in healthy adults. Eur Addict Res. 2012;18(2):70‒75. https://doi.org/10.1159/000333600. 42. Bahrke MS, Baur TS, Poland DF, Connors DF. Tobacco use and performance on the U.S. Army Physical Fitness Test. Mil Med. 1988;153 (5):229‒235. https://doi.org/10.1093/milmed/153.5.229. 43. Vardavas CI, Anagnostopoulos N, Kougias M, Evangelopoulou V, Connolly GN, Behrakis PK. Short-term pulmonary effects of using an electronic cigarette: impact on respiratory flow resistance, impedance, and exhaled nitric oxide. Chest. 2012;141(6):1400‒1406. https://doi. org/10.1378/chest.11-2443. 44. Lynch JP, Hanson K, Kao TC. Health-related behaviors in young military smokers. Mil Med. 2004;169(3):230‒235. https://doi.org/10.7205/ milmed.169.3.230. 45. Scioli ER, Biller H, Rossi J, Riebe D. Personal motivation, exercise, and smoking behaviors among young adults. Behav Med. 2009;35(2):57‒ 64. https://doi.org/10.3200/BMED.35.2.57-66. 46. Dunbar MS, Tucker JS, Ewing BA, et al. Frequency of e-cigarette use, health status, and risk and protective health behaviors in adolescents. J Addict Med. 2017;11(1):55‒62. https://doi.org/10.1097/ADM.0000000000000272. 47. Leventhal AM, Strong DR, Sussman S, et al. Psychiatric comorbidity in adolescent electronic and conventional cigarette use. J Psychiatr Res. 2016;73:71‒78. https://doi.org/10.1016/j.jpsychires.2015.11.008. 48. Wills TA, Knight R, Williams RJ, Pagano I, Sargent JD. Risk factors for exclusive e-cigarette use and dual e-cigarette use and tobacco use in adolescents. Pediatrics. 2015;135(1):e43‒e51. https://doi.org/ 10.1542/peds.2014-0760. 49. Jones SB, Knapik JJ, Sharp MA, Darakjy S, Jones BH. The validity of self-reported physical fitness test scores. Mil Med. 2007;172(2):115‒ 120. https://doi.org/10.7205/milmed.172.2.115. 50. Martin RC, Grier T, Canham-Chervak M, et al. Validity of selfreported physical fitness and body mass index in a military population. J Strength Cond Res. 2016;30(1):26‒32. https://doi.org/10.1519/ JSC.0000000000001026.
RESEARCH ARTICLE
Vaping, Smoking, and the Physical Fitness of Active Young Men Eero Dinkeloo, MPH,1,2 Tyson L. Grier, MS,1 Raina D. Brooks, MPH,1 Bruce H. Jones, MD, MPH1
Introduction: Adverse effects of cigarette smoking on physical performance are well studied.
Because of the recent rise in popularity of vaping, it is important to evaluate its effect on fitness both independently and in conjunction with traditional cigarette use.
Methods: This was a secondary analysis performed in 2018 on data collected from U.S. Army Soldiers during 2016. All metrics were self-reported via an electronic questionnaire. Personal characteristics of current ENDS users, smokers, and dual users were compared with a reference group that reported no history of use. Adjusting for age and physical training habits, an ANCOVA was used to compare Army physical fitness test results. A Fisher’s exact test determined specific mean differences between groups.
Results: This study population consisted of 2,854 men aged 24.6 years on average. Differences in
physical training and fitness were shown between the groups. Never users averaged the most total physical training, followed by ENDS users, smokers, and then dual users. Compared with never users on the fitness tests, ENDS users had an adjusted mean difference of +27 seconds on the 2-mile run, 4.56 push-ups, and 2.01 sit-ups; smokers averaged +8 seconds, 2.15 push-ups, and 1.44 sit-ups; and dual users averaged +32 seconds, 5.17 push-ups, and 3.88 sit-ups. Dual users had significantly (p<0.05) lower scores than current smokers and never users on all 3 fitness events.
Conclusions: This study suggests that individuals who use e-cigarettes and tobacco cigarettes average a lower level of fitness than individuals who abstain.
Am J Prev Med 2019;000(000):1−7. © 2019 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
INTRODUCTION
D
evices that use a heating element to aerosolize “e-liquids” into vapor for the user to inhale are known as ENDS. They include products such as e-cigarettes, personal vaporizers, vape pens, and e-hookahs.1,2 Since hitting the market, using ENDS, known as vaping, has grown rapidly, showing significant upward trends in awareness, ever use, and current use.3,4 The percentage of U.S. adults who have ever tried ENDS was estimated at 3.3% in 2010,3 a number that increased to 15.4% in 2016.5 Use of ENDS is even higher in younger populations, to a point where it is now considered a major public health concern.2,6 This is illustrated by the finding that 23.5% of adults aged 18−24 years have ever tried ENDS, whereas 4.2% are current users5 and estimates that school-aged adolescents are vaping at a higher rate than smoking combustible cigarettes.7
Although the toxicants of ENDS vapor are found in lower quantities compared with tobacco cigarette smoke,8,9 it does not mean vaping has been deemed safe.2,10,11 The vapor of ENDS can contain nicotine, volatile organic compounds, tobacco-specific nitrosamines, ultrafine particles, propylene glycol, vegetable glycerin, and metals, such as nickel, tin, and lead.2,6,12−18 These chemicals are reportedly respiratory irritants that can From the 1Injury Prevention Division, Clinical Public Health and Epidemiology Directorate, U.S. Army Public Health Center, Aberdeen Proving Ground, Maryland; and 2Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee Address correspondence to: Eero Dinkeloo, MPH, U.S. Army Public Health Center, Clinical Public Health and Epidemiology Directorate, 8977 Sibert Road, Aberdeen Proving Ground MD 21010. E-mail: [email protected]. 0749-3797/$36.00 https://doi.org/10.1016/j.amepre.2019.08.015
© 2019 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
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cause inflammatory reactions, decreased exhaled nitric oxide levels (a test used to assess pulmonary inflammation), and respiratory flow resistance.10,12,14,19−21 However, the amounts of these toxicants can vary substantially based on the product being used.13−16,18 Despite the emerging emphasis on investigating ENDS, the rapid rise in their popularity has set a fastmoving target. Some studies have found acute respiratory changes similar to those of cigarettes though to a lesser magnitude8,22,23 and symptoms such as sore throat and cough after 10 minutes of use.21 Large cross-sectional surveys of adolescents show a possible association of ENDS use and respiratory symptoms, independent of smoking status or secondhand smoke exposure.20,24 However, no studies have examined the relationship of ENDS use and physical fitness. By contrast, the relationship between tobacco cigarettes and physical performance has been well studied. It has been shown that smoking cigarettes correlates with poorer outcomes on several physical fitness tests,25−28 lower oxygen uptake, impaired heart rate responses to exercise (i.e., ability to increase heart rate commensurate with increased activity), and lower aerobic and muscular endurance compared with nonsmokers.29−34 These findings are present even in younger and trained populations, similar to those being examined in this study,27,35 where they are exaggerated by heavier use36 and reversible by cessation.29,34 Because a sizable measure of a soldier’s effectiveness is dependent on their physical condition, developing and maintaining physical fitness levels within this population is a high priority. Many programs currently exist that are aimed at optimizing health and physical performance, including those aimed at smoking cessation. It is possible that ENDS use deserves to be included with traditional cigarettes in the scope of these programs, but a better understanding of any associated effects is needed. The purpose of this study was to compare the physical fitness levels among male soldiers using ENDS, tobacco cigarettes, or both, and those that have never used either.
METHODS Study Population This was a secondary analysis, performed in 2018, of an electronic survey distributed by the Army Public Health Center to active duty soldiers in a U.S. Army Airborne division between April 2016 and July 2016. Participants were asked about their background, fitness levels, physical training (PT) habits, and injury history. The investigation was approved by the Army Public Health Center Public Health Review Board. Of the initial 6,383 respondents, 3,502 were eligible for this analysis based on if they were men (owing to a limited number of women in the investigation), reported valid Army physical fitness test (APFT) results,
were not on a physical profile that limited their PT or APFT participation, and could be categorized into 1 of the 4 exposure groups. Exclusions were made if responses reported longer weekly unit or personal PT durations than what was considered realistic (n=648): >640 minutes of unit PT or >800 minutes of personal PT.
Measures The exposures of interest in this study were ENDS use and cigarette smoking, which were assessed via self-report from the administered survey. Participants were divided into 4 exposure groups: never users, current ENDS users, current smokers, and current dual users. The never users’ group, used as the reference, consisted of individuals who reported never using tobacco products of any type in their lifetime. Current ENDS users were defined as individuals who reported using ENDS within the last 30 days, reported using ENDS consistently for >30 days, and had no history of using other tobacco products. Current smokers included individuals who reported smoking >100 tobacco cigarettes in their lifetime, smoking in the last 30 days, and had no history of ENDS or other tobacco use. Finally, current dual users consisted of individuals who reported ENDS use and tobacco cigarette use within the last 30 days and smoking ≥100 cigarettes in their lifetime but no history of using other tobacco products. In this study, physical fitness levels were assessed using APFT results. The APFT is designed to test the muscular strength, endurance, and cardiorespiratory fitness of soldiers in the U.S. Army. It consists of 3 events: a timed 2-mile run, 2-minute maximal effort push-ups, and 2-minute maximal effort sit-ups. Active component soldiers are required to complete an official APFT biannually. Soldiers were asked to report their most recent APFT scores on the survey.
Statistical Analysis Following stratification of the population into exposure groups, means and SDs were calculated for personal characteristics, cigarette or ENDS use, and physical activity. Frequencies were displayed for categorical characteristics, and chi-squared tests were used to determine differences across exposure groups. One-way ANOVA was used to compare mean differences in continuous variables across exposure groups, with the exception of cigarette and ENDS use, where independent t-tests were used. To further explore the mean differences in APFT results across exposures, ANCOVA was used to adjust for differences in relevant covariates that differed significantly between groups, which included age and hours of weekly personal PT, and results were reported as the adjusted means for each exposure group. A post-hoc Fisher’s least significant difference test was applied to each significant ANCOVA to determine exposure groups that differed significantly. Statistical significance was defined as p<0.05. SAS version 9.4 was used for all statistical analyses.
RESULTS A total of 2,854 soldiers were included in this study, most of whom (80.5%) had never used tobacco products; 2.2% were classified as current ENDS users, 12.5% were www.ajpmonline.org
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Table 1. Characteristics of Active Component Male Army Soldiers by Level of Exposure (n=2,854) Characteristic
Never users
Smokers
ENDS users
Dual users
p-value
% (n) Age, mean years (§SD) BMI, mean kg/m2 (§SD) Rank, n (%) Enlisted Officers Physical demand of MOS, n (%) Heavy Moderate Light Years smoking, mean (§SD) Cigarettes per day in last month, mean (§SD) Years using ENDS, mean (§SD) Days using ENDS in last month, mean (§SD) Unit PT, mean hours per week (§SD) Personal PT, mean hours per week (§SD)
80.5 (2,298) 24.78 (§5.5) 25.72 (§3.0)
12.5 (355) 24.20 (§4.5) 25.54 (§3.2)
2.2 (63) 21.67 (§3.3) 25.27 (§3.2)
4.8 (138) 24.12 (§4.9) 25.68 (§3.1)
n/a <0.0001a 0.5241a <0.0001b
1,934 (84.2) 364 (15.8)
339 (95.5) 16 (4.5)
57 (90.5) 6 (9.5)
130 (94.2) 8 (5.8) 0.0034b
1,726 (75.1) 370 (16.1) 202 (8.8) n/a n/a n/a n/a 4.42 (§2.3) 3.87 (§3.4)
304 (85.6) 32 (9.0) 19 (5.4) 6.95 (§ 5.4) 8.02 (§6.6) n/a n/a 4.80 (§2.2) 3.40 (§3.3)
50 (79.4) 9 (14.3) 4 (6.3) n/a n/a 1.61 (§1.2) 16.06 (§11.5) 4.33 (§2.0) 3.51 (§2.9)
107 (77.5) 20 (14.5) 11 (8.0) 6.57 (§5.5) 7.52 (§6.6) 1.67 (§1.2) 13.80 (§11.2) 4.44 (§2.2) 3.26 (§3.2)
0.8412c 0.9367c 0.7197c 0.7592c 0.0287a 0.0236a
Note: Boldface indicates statistical significance (p<0.05). a One-way ANOVA. b Chi-square. c Independent t-test. MOS, military occupational specialty; n/a, not applicable; PT, physical training.
classified as current smokers, and 4.8% as dual users. Table 1 displays characteristics of this population by exposure group. ENDS users were significantly younger with a mean age of 21.67 (SD=3.3) years, whereas the other 3 groups ranged from 24.12 (SD=4.9) years to 24.78 (SD=5.5) years. Between groups, BMI did not differ (p=0.52), with group means ranging from 25.27 to 25.72 kg/m2. A majority of the soldiers in this cohort were in military occupational specialties that required heavy physical demands. Current smokers averaged the most weekly unit PT, and current ENDS users averaged the least though the range was only 30 minutes. Personal PT also differed between groups, with a similar variation to what was seen in unit PT. However, unlike unit PT, never users performed the most personal PT and dual users the least. Current smokers’ and dual users’ exposures to tobacco was similar, in that they had both smoked for around 6−7 years and smoked about 8 cigarettes a day. Current ENDS users and dual users both averaged slightly more than 1.5 years of ENDS use and were similar in the number of days vaping in the previous month (16.06 vs 13.80, p=0.76). Table 2 displays the adjusted means of each of the 3 APFT tests. These averages were adjusted for age and hours of weekly personal PT. On average, the group with no tobacco use had the fastest 2-mile run time and performed the most push-ups and sit-ups, whereas the dual users had the slowest run time and least number of & 2019
push-ups and sit-ups. A Fisher’s least significant difference test revealed that dual users differed significantly from both the reference group and current smokers on all 3 events. Current smokers differed significantly from never users on the push-up and sit-up tests, but not the 2-mile run. Current ENDS users averaged poorer performance than never users on all 3 events, but this difference was not significant for the sit-up test. These differences are illustrated in Figure 1, which displays adjusted group means for each APFT event.
DISCUSSION This analysis compared APFT scores among groups of cigarette smokers, ENDS users, dual users, and never users. The primary findings of this study are that dual users of ENDS and cigarettes averaged slower 2-mile run times and fewer push-ups and sit-ups than never users. Furthermore, dual users averaged a significantly poorer performance on all 3 events than did current smokers. Also, current ENDS users had a slower 2-mile run and performed fewer push-ups than never users. Within this study population, 7% reported current ENDS use. Exclusive ENDS users were younger on average than other groups, which is a common finding in the literature.1,3,5,37 It is important to note that this analysis was performed solely on men, which have a reportedly higher usage rate of tobacco products than women.38 Nonetheless, this suggests the rate of ENDS use, similar
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Table 2. Exposure-Specific APFT Performance Means of Active Component Male Army Soldiers, Adjusted for Age and Personal Physical Training Habits (n=2,854) Exposure group No use (n=2,298) APFT component
Smoking (n=355)
ENDS (n=63)
Dual use (n=138) p-value
Adjusted mean (unadjusted mean)
2-mile run (minutes and fractions of a minute)
14.60 (14.60)
14.72 (14.72)
15.03 (14.91)
15.13 (15.13)
Push-up test (reps)
64.97 (65.04)
62.82 (62.58)
60.41 (59.63)
59.86 (59.51)
Sit-up test (reps)
69.81 (69.85)
68.37 (68.21)
67.80 (67.68)
65.92 (65.70)
<0.0001a No use/ENDS, no use/ dual use, dual use/ smokingb <0.0001a No use/smoking, no use/ ENDS, no use/dual use, smoking/dual useb <0.0001a no use/smoking, no use/ dual use, smoking/dual useb
Note: Boldface indicates statistical significance (p<0.05). a Overall ANCOVA p-value. b Statistically significant Fisher’s least significant difference comparisons (p<0.05). APFT, Army physical fitness test; rep, repetition.
Figure 1. Mean Army physical fitness test (APFT) performance by exposure group (n=2,854), adjusted for age and personal physical training habits. www.ajpmonline.org
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to that of cigarettes, could be quite a bit higher than the 4.1% reported in the general adult male population.40 The estimate of overall use in this study is likely underrepresentative of actual rates owing to exclusion criteria of the cohort, which did not measure ever use or include current ENDS users who formerly smoked, who are described as making up a large portion of ENDS users.3,4,37 Rates of current cigarette smoking in this study (17.3%) are comparable with what other surveys have reported in military populations.38,39 This study found that the average time and volume of cigarette smoking was not significantly different between those that exclusively smoked cigarettes and current dual users. The same is true of ENDS use between exclusive ENDS users and dual users, though average length of time using ENDS was substantially less than with cigarettes. This illustrates a concern that smokers may not necessarily reduce conventional cigarette consumption when adding the use of ENDS1; the group of dual users in this study experienced the highest level of exposure. In this analysis, current smokers averaged lower performance on all APFT events than never users though the difference was not statistically significant for the 2-mile run. This finding reaffirms what has been reported by prior studies. Performance on similar fitness tests of muscular endurance have been compared between smokers and nonsmokers within military populations, demonstrating similar findings.25−28 Similarly, muscular strength previously has been found to be lower in smokers, even after adjusting for other factors.30,41 The ENDS users also exhibited lower average performance than never users on all APFT events, but a Fisher’s least significant difference test identified the difference in the 2-mile run and push-ups as statistically significant. It is possible that the shorter amount of exposure to ENDS (1.38 years, SD=1.3) is not enough time to identify the true physical effects that are associated with using ENDS alone. As other studies have noted, looking at smoking histories of up to or even exceeding 10 years, the length of use plays a role in the relationship of cigarette smoking and physical fitness.32,34,36 This has also been observed among smokeless tobacco users, with 1 study reporting that a longer history of use was correlated with worse APFT performance.42 Because average ENDS use among exclusive users was only 1.38 years versus 6.95 years for smokers, it is feasible that the full impact of vaping has yet to be realized. This study found that current dual users of cigarettes and ENDS presented significantly lower mean performances on the 2-mile run, push-ups, and sit-ups tests than did never users. Their performance was also significantly lower than that of current smokers. Therefore, it appears that using both cigarettes and ENDS results in lower & 2019
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fitness levels than smoking alone. However, smoking load did not differ significantly between the smokingonly group and the dual use group. Effects of smoking on the cardiorespiratory system have also been demonstrated in multiple studies, in the form of reduced heart rate response, lower forced expiratory volume, lower maximal oxygen uptake, and slower run times compared with nonsmokers.26,27,29,31−34 A possible reason for this difference in run time may be associated with the added exposure of ENDS use on the respiratory system. Vardavas et al.43 found that among 30 current smokers, acute use of an e-cigarette led to a decrease in exhaled nitric oxide and increases in airway resistance after only 5 minutes of vaping. Other studies have presented similar findings in relation to decreased exhaled nitric oxide23 and peak expiratory flow.22 Admittedly, these effects are not necessarily clinically significant, and other studies have shown no significant changes in forced expiratory volume,8,22 but these do not directly assess acute dual use. These previous findings combined with the results presented here suggest it is possible that using ENDS may have an impact on physical fitness, particularly on cardiorespiratory fitness in those already disadvantaged by smoking cigarettes. Yet, it is important to consider an inherent difference in the behavior of individuals who use tobacco products and those that abstain. This analysis was able to examine some covariates and adjust for age and personal physical activity levels but was not able to measure other characteristics that are found to vary between smokers and nonsmokers such as motivation, diet, alcohol consumption, sleep quality, or risk taking.42,44,45 So far, studies on user profile differences, which include ENDS users, have focused mainly on adolescents and have classified them as “intermediate risk.”46−48 Exclusive ENDS users exhibited behavioral risk factors greater than nonusers but lower than smokers or dual users and protective behaviors lower than nonusers but higher than smokers or dual users.47,48 One such study found no significant difference in overall physical health between the adolescents classified in the same 4 groups used in this analysis but did find variation within ENDS-only users.46 For example, other substance use in the past year was associated with increased ENDS use, whereas a healthier diet was associated with less.46 This shows the variability of other influencing factors across and within these exposure groups that should be accounted for in future research, especially when examining a multifaceted outcome such as physical fitness levels. Although never users had higher performance on the fitness tests, vapers, smokers, and dual users still had relatively high mean fitness scores. This could be attributed to the relatively young population, engaged in a physically demanding occupation, where tobacco use has been found to be associated with lower performance
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than nonsmokers but not necessarily poor performance in this population of active young men. This is shown in other military studies of tobacco use and fitness performance.26−28 However, the importance of maintaining peak fitness within this population, or others like it, should not be understated.
Limitations There are some limitations present in this study. First, all data were collected via self-report surveys, leaving the possibility for reporting or recall bias. However, previous studies looking at the efficacy of self-reported BMI and physical fitness test scores, specifically the APFT, found a high correlation with actual results within this population.49,50 Another main limitation is the quantification of ENDS use. There is not a consensus on how to measure the level of exposure from ENDS using a survey format. Beyond the variability of the number of uses per day or length of inhale between users, the actual concentrations and chemical components can vary between different products.13−16,18 Therefore, it is possible that actual exposure to ENDS-related toxicants could vary within group, independent of the days or years of use. Lastly, former use of tobacco products was not examined by this study. Because the effects from smoking are noted to be reversible after cessation,29,34 it would be worthwhile to examine former ENDS users when an adequate sample size exists. Despite these drawbacks, this was a relatively large sample size of soldiers who do represent a sizable portion of the overall active component of the U.S. Army, which is generally younger (75% aged <35 years), more physically fit, and 85.5% male.38 Consequently, it is also representative of a large portion of adult ENDS users who tend to be young men.37,40
CONCLUSIONS This study examined physical fitness test outcomes and use of ENDS. The primary finding was that current dual users of ENDS and tobacco cigarettes averaged lower performance on the 2-mile run, 2-minute maximal push-up, and 2-minute maximal sit-up tests than never users and significantly slower run times and fewer pushups than current smokers. ENDS-only use was associated with significantly lower performance on the 2-mile run and push-up test than never users. Training and maintaining physical fitness are crucial within this population and among other groups such as emergency personnel, first responders, and athletes, so any exposure detrimental to that goal deserves considerable scrutiny. This is the first study to examine relationships between ENDS and physical fitness performance, making the results novel and useful to inform further examination.
Future research is necessary to build on this relationship and should focus on a more thorough evaluation of both exposure, outcome, and other fitness-related variables.
ACKNOWLEDGMENTS Citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement or approval of the products or services of these organizations. The views expressed in this paper are those of the author(s) and do not necessarily reflect the official policy of the Department of Defense, Department of the Army, U.S. Army Medical Department, or the U.S. Government. This investigation was supported in part by an appointment to the Postgraduate Research Participation Program at the U.S. Army Public Health Center, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and U.S. Army Public Health Center. Author contributions: ED and TG contributed to design of study. RB worked on data collection and managed the database. ED, TG, and BHJ contributed to statistical analysis. ED undertook the first draft, and all authors have contributed to and approved the final manuscript. No financial disclosures were reported by the authors of this paper.
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