Body Mass Index, Playing Position, Race, and the Cardiovascular Mortality of Retired Professional Football Players
2012; Elsevier BV; Volume: 109; Issue: 6 Linguagem: Inglês
10.1016/j.amjcard.2011.10.050
ISSN1879-1913
AutoresSherry Baron, Misty J. Hein, Everett J. Lehman, Christine M. Gersic,
Tópico(s)Sports Performance and Training
ResumoConcern exists about cardiovascular disease (CVD) in professional football players. We examined whether playing position and size influence CVD mortality in 3,439 National Football League players with ≥5 pension-credited playing seasons from 1959 to 1988. Standardized mortality ratios (SMRs) compared player mortality through 2007 to the United States population of men stratified by age, race, and calendar year. Cox proportional hazards models evaluated associations of playing-time body mass index (BMI), race, and position with CVD mortality. Overall player mortality was significantly decreased (SMR 0.53, 95% confidence interval [CI] 0.48 to 0.59) as was mortality from cancer (SMR 0.58, 95% CI 0.46 to 0.72), and CVD (SMR 0.68, 95% CI 0.56 to 0.81). CVD mortality was increased for defensive linemen (SMR 1.42, 95% CI 1.02 to 1.92) but not for offensive linemen (SMR 0.70, 95% CI 0.45 to 1.05). Defensive linemen's cardiomyopathy mortality was also increased (SMR 5.34, 95% CI 2.30 to 10.5). Internal analyses found that CVD mortality was increased for players of nonwhite race (hazard ratio 1.69, 95% CI 1.13 to 2.51). After adjusting for age, race, and calendar year, CVD mortality was increased for those with a playing-time BMI ≥30 kg/m2 (hazard ratio 2.02, 95% CI 1.06 to 3.85) and for defensive linemen compared to offensive linemen (hazard ratio 2.07, 95% CI 1.24 to 3.46). In conclusion, National Football League players from the 1959 through 1988 seasons had decreased overall mortality but those with a playing-time BMI ≥30 kg/m2 had 2 times the risk of CVD mortality compared to other players and African-American players and defensive linemen had higher CVD mortality compared to other players even after adjusting for playing-time BMI. Concern exists about cardiovascular disease (CVD) in professional football players. We examined whether playing position and size influence CVD mortality in 3,439 National Football League players with ≥5 pension-credited playing seasons from 1959 to 1988. Standardized mortality ratios (SMRs) compared player mortality through 2007 to the United States population of men stratified by age, race, and calendar year. Cox proportional hazards models evaluated associations of playing-time body mass index (BMI), race, and position with CVD mortality. Overall player mortality was significantly decreased (SMR 0.53, 95% confidence interval [CI] 0.48 to 0.59) as was mortality from cancer (SMR 0.58, 95% CI 0.46 to 0.72), and CVD (SMR 0.68, 95% CI 0.56 to 0.81). CVD mortality was increased for defensive linemen (SMR 1.42, 95% CI 1.02 to 1.92) but not for offensive linemen (SMR 0.70, 95% CI 0.45 to 1.05). Defensive linemen's cardiomyopathy mortality was also increased (SMR 5.34, 95% CI 2.30 to 10.5). Internal analyses found that CVD mortality was increased for players of nonwhite race (hazard ratio 1.69, 95% CI 1.13 to 2.51). After adjusting for age, race, and calendar year, CVD mortality was increased for those with a playing-time BMI ≥30 kg/m2 (hazard ratio 2.02, 95% CI 1.06 to 3.85) and for defensive linemen compared to offensive linemen (hazard ratio 2.07, 95% CI 1.24 to 3.46). In conclusion, National Football League players from the 1959 through 1988 seasons had decreased overall mortality but those with a playing-time BMI ≥30 kg/m2 had 2 times the risk of CVD mortality compared to other players and African-American players and defensive linemen had higher CVD mortality compared to other players even after adjusting for playing-time BMI. In 1990 the National Football League (NFL) Players Association requested that the National Institute for Occupational Safety and Health (NIOSH) investigate the rate and causes of death of NFL players because of concerns about player longevity and excess cardiovascular disease (CVD) mortality. In 1994 the NIOSH1Baron S. Rinsky R. Health Hazard Evaluation Report, National Football League Players Mortality Study Report No. HETA 88-085. Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Atlanta, GA1994Google Scholar reported that players from the 1959 through 1988 seasons experienced decreased overall mortality, but CVD mortality was higher in linemen compared to nonlinemen and in players with an increased playing-time body mass index (BMI) compared to other players. Subsequent studies of retired and active professional players have documented higher rates of CVD risk factors—including hypertension, increased left atrial size, and metabolic syndrome—in relation to player position and size.2Miller M.A. Croft L.B. Belanger A.R. Romero-Corral A. Somers V.K. Roberts A.J. Goldman M.E. Prevalence of metabolic syndrome in retired National Football League players.Am J Cardiol. 2008; 101: 1281-1284Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar, 3Croft L.B. Belanger A. Miller M.A. Roberts A. Goldman M.E. Comparison of National Football League linemen versus nonlinemen of left ventricular mass and left atrial size.Am J Cardiol. 2008; 102: 343-347Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar, 4Tucker A.M. Vogel R.A. Lincoln A.E. Dunn R.E. Ahrensfield D.C. Allen T.W. Castle L.W. Heyer R.A. Pellman E.J. Strollo Jr, P.J. Wilson P.W. Yates A.P. Prevalence of cardiovascular disease risk factors among National Football League players.JAMA. 2009; 301: 2111-2119Crossref PubMed Scopus (111) Google Scholar, 5Hurst R.T. Burke R.F. Wissner E. Roberts A. Kendall C.B. Lester S.J. Somers V. Goldman M.E. Wu Q. Khandheria B. Incidence of subclinical atherosclerosis as a marker of cardiovascular risk in retired professional football players.Am J Cardiol. 2010; 105: 1107-1111Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 6Rice T.B. Dunn R.E. Lincoln A.E. Heyer R.A. Yates A.P. Wilson P.W. Pellmen E.J. Allen T.W. Newman A.B. Strollo Jr, P.J. National Football League Subcommittee on Cardiovascular HealthSleep-disordered breathing in the National Football League.Sleep. 2010; 33: 819-824PubMed Google Scholar The 1994 report on NFL mortality was based on a small number of cardiovascular deaths (38) owing to the relatively short vital status follow-up period. We report on 16 additional years of follow-up, expanding our understanding of players' mortality as they age beyond their status as elite athletes.MethodsA cohort of 3,439 NFL players was constructed from a 1990 NFL pension fund database and included all pension-vested players (≥5 pension-credited playing seasons) from the 1959 through 1988 seasons. The pension fund database includes each player's name, Social Security number, date of birth, and year of each credited season. Player race was collected because of known racial differences in United States mortality. Race was determined based on players' self-identification using standard racial categories on a response form accompanying a letter introducing the study sent to players' last known address. For nonrespondents (48%) race was assigned using available pictures in yearly media guides.1Baron S. Rinsky R. Health Hazard Evaluation Report, National Football League Players Mortality Study Report No. HETA 88-085. Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Atlanta, GA1994Google Scholar Position played and height and weight during the last season played were assigned using data reported annually by the NFL teams and compiled in a commercial publication.7Neft D. Cohen R. Korch R. The Sports Encyclopedia: Pro Football. St. Martin's Press, New York1992Google Scholar BMI (weight in kilograms divided by height in meters squared) was categorized using standard cutpoints: normal (18.5 to <25 kg/m2), overweight (25 to 10. SMRs were also calculated by position category and for the offensive and defensive linemen subgroups.Internal analyses compared mortality across player position categories. Because stratified SMRs are generally not comparable, directly standardized rate ratios and 95% CIs for each position category relative to category I were obtained using the life-table analysis system.11Schubauer-Berigan M.K. Hein M.J. Raudabaugh W.M. Ruder A.M. Silver S.R. Spaeth S. Steenland K. Petersen M.R. Waters K.M. Update of the NIOSH life table analysis system: a person-years analysis program for the windows computing environment.Am J Ind Med. 2011; 54: 915-924Crossref PubMed Scopus (63) Google Scholar We also used Cox proportional hazards regression models to evaluate the association of position category and BMI with CVD mortality (International Classification of Diseases, Tenth Revision codes I00 through I78). Attained age was used as the time scale; consequently, age was controlled for in the models. BMI was treated as a categorical variable using standard cutpoints but additional models treating BMI as a continuous variable were evaluated. In addition to position category and BMI, other covariates included race (white/Hispanic, African-American/all other races), era of play (play ended before vs in 1980 [median] or later), and time since last played (<10 vs ≥10 years). We also controlled for the calendar year of follow up (by decades) because recent studies have found that age-adjusted CVD mortality has been decreasing over time.12Ford E.S. Ajani U.A. Croft J.B. Critchley J.A. Labarthe D.R. Kottke T.E. Giles W.H. Capewell S. Explaining the decrease in U.S. deaths from coronary disease, 1980–2000.N Engl J Med. 2007; 356: 2388-2398Crossref PubMed Scopus (2132) Google Scholar Because BMI and position category are strongly associated, in our models we first examined the independent effect of BMI on CVD mortality. Additional models examined the added effect of position category on CVD mortality while adjusting for the role of BMI.The proportional hazards assumption for BMI was tested using a time-dependent interaction term between age (<55 vs ≥55 years) and BMI category. To examine the impact of possible racial misclassification we conducted additional stratified analyses comparing findings for players with self-reported versus observationally assigned race. All regression modeling used the SAS 9.2 procedure PHREG (SAS Institute, Cary, North Carolina). A 2-sided p value <0.05 was considered statistically significant. The study protocol was approved by the NIOSH institutional review board.ResultsThe initial cohort included 3,732 NFL players but 292 players with unknown race and 1 "player" who was actually a trainer were excluded. By the end of follow-up in 2007, the final cohort of 3,439 players contributed 104,776 person-years at risk and 334 deaths. On average the cohort was followed for 26.8 ± 8.7 years (mean ± SD) after retirement from the NFL. For players still alive, the median age at the study end date was 57 years; 60% of the players were white (including 15 Hispanics) and 39% were African-American (Table 1). Players were evenly distributed among the 3 position categories and 10% of the cohort had a BMI <25 kg/m2 and 34% had a BMI ≥30 kg/m2. BMI varied across position categories with <1% of category I, 18% of category II, and 82% of category III players having a BMI ≥30 kg/m2. Demographically, the players were similar across the position categories except a larger proportion of category III players were of white race. Within category III offensive and defensive linemen were similar except offensive linemen were more likely to be of white race and to have a BMI ≥30 kg/m2.Table 1Characteristics of National Football League players cohort, overall and by position category (1960 to 2007)VariableOverall (n = 3,439)Position Category⁎Player position was categorized into 3 broad position categories: category I (defensive back, n = 549; punter/kicker, n = 79; punter, n = 49; quarterback, n = 192; and wide receiver, n = 311), category II (fullback, n = 89; halfback, n = 55; linebacker, n = 513; offensive end, n = 4; running back, n = 252; and tight end, n = 184), and category III (defensive positions: defensive end, n = 238; defensive lineman, n = 41; defensive tackle, n = 174; nose guard, n = 7; and nose tackle, n = 38; offensive positions: center, n = 126; offensive guard, n = 234; offensive lineman, n = 62; and offensive tackle, n = 242).IIIIII—DefensiveIII—Offensive(n = 1,180)(n = 1,097)(n = 498)(n = 664)Race White2,070 (60%)631 (53%)606 (55%)291 (58%)542 (82%) African-American1,355 (39%)548 (46%)486 (44%)203 (41%)118 (18%) Other14 (<1%)1 (<1%)5 (<1%)4 (1%)4 (1%)Vital status as of December 31, 2007 Alive3,105 (90%)1,095 (93%)998 (91%)422 (85%)590 (89%) Dead334 (10%)85 (7%)99 (9%)76 (15%)74 (11%)First credited season Median (range)1973 (1950–1984)1973 (1950–1984)1974 (1950–1984)1972 (1950–1984)1972 (1950–1984) Before 19802,685 (78%)912 (77%)847 (77%)398 (80%)528 (80%) 1980 and after754 (22%)268 (23%)250 (23%)100 (20%)136 (20%)Age (years) at first credited season†Age at first credited season is age on July 1 of the year of the first credited season of play. Median (range)22 (19–34)22 (19–34)22 (21–28)23 (21–28)22 (21–28) ≤21789 (23%)248 (21%)258 (24%)112 (22%)171 (26%) 221,614 (47%)572 (48%)532 (48%)214 (43%)296 (45%) 23701 (20%)245 (21%)215 (20%)106 (21%)135 (20%) ≥24335 (10%)115 (10%)92 (8%)66 (13%)62 (9%)Number of credited seasons‡Number of credited seasons does not necessarily equal the number of seasons played. Median (range)8 (5–25)8 (5–25)7 (5–17)8 (5–20)8 (5–17)Age (years) at death Median (range)54 (27–81)54 (27–80)53 (28–78)53 (31–81)55 (29–76)Age (years) at date last observed—nondeceased Median (range)57 (45–88)57 (45–88)56 (45–82)58 (45–84)57 (45–83) <50633 (20%)218 (20%)212 (21%)84 (20%)119 (20%) 50–54738 (24%)267 (24%)263 (26%)82 (19%)126 (21%) 55–59565 (18%)197 (18%)162 (16%)90 (21%)116 (20%) 60–69890 (29%)309 (28%)282 (28%)120 (28%)179 (30%) ≥70279 (9%)104 (9%)79 (8%)46 (11%)50 (8%)Body mass index (kg/m2) Median (range)29 (22–39)26 (22–34)29 (24–34)31 (24–37)31 (25–39) 18.5–<25342 (10%)337 (29%)4 (<1%)1 (<1%)0 (0%) 25–<301,944 (57%)841 (71%)897 (82%)114 (23%)92 (14%) 30–<351,125 (33%)2 ( 0.05) and did not confound the relation between cardiovascular disease mortality and body mass index.Model 3‡Model 3 hazard ratios for player position are adjusted for age, body mass index, race, and calendar year.Model 4§In Model 4, position category III was further divided into offensive and defensive positions; hazard ratios for player position are adjusted for age, body mass index, race, and calendar year.Body mass index (kg/m2) 18.5–<25111 (reference)1 (reference)1 (reference)1 (reference) 25–<30530.82 (0.43–1.58)0.85 (0.45–1.64)0.80 (0.39–1.65)0.80 (0.39–1.65) ≥30621.85 (0.98–3.52)2.02 (1.06–3.85)1.54 (0.64–3.71)1.58 (0.66–3.78)Race White841 (reference)1 (reference)1 (reference) Nonwhite421.69 (1.13–2.51)1.71 (1.15–2.55)1.57 (1.05–2.36)Calendar year Before 198091 (reference)1 (reference)1 (reference) 1980–1989240.76 (0.33–1.72)0.77 (0.34–1.74)0.78 (0.35–1.78) 1990–1999420.43 (0.18–1.01)0.44 (0.19–1.03)0.45 (0.19–1.07) 2000 and after510.26 (0.10–0.64)0.27 (0.11–0.66)0.28 (0.12–0.71)Player position□Player position was categorized into 3 broad position categories: category I (defensive back, punter/kicker, punter, quarterback, and wide receiver), category II (fullback, halfback, linebacker, offensive end, running back, and tight end), and category III (defensive positions: defensive end, defensive lineman, defensive tackle, nose guard, and nose tackle; offensive positions: center, offensive guard, offensive lineman, and offensive tackle). Category I321 (reference)1 (reference) Category II291.02 (0.58–1.81)1.01 (0.57–1.78) Category III1.38 (0.72–2.64) Defensive411.86 (0.96–3.62)¶Adjusting for age, body mass index, race, and calendar year; the hazard ratio for defensive versus offensive linemen is 2.07 (95% confidence interval 1.24 to 3.46) and the hazard ratio for defensive linemen versus all other positions is 1.97 (95% confidence interval 1.29 to 3.00). Offensive240.90 (0.43–1.86)Model fit −2 log likelihood1,792.111,775.011,773.601,765.48 Akaike information criterion1,796.111,787.011,789.601,783.48 Schwarz Bayesian criterion1,801.781,804.021,812.301,809.00Likelihood-ratio testvs null modelvs model 1vs model 2vs model 2 Chi-square (degrees of freedom)18.86 (2)17.10 (4)1.40 (2)9.53 (3) p Value 0.05) and did not confound the relation between cardiovascular disease mortality and body mass index.‡ Model 3 hazard ratios for player position are adjusted for age, body mass index, race, and calendar year.§ In Model 4, position category III was further divided into offensive and defensive positions; hazard ratios for player position are adjusted for age, body mass index, race, and calendar year.□ Player position was categorized into 3 broad position categories: category I (defensive back, punter/kicker, punter, quarterback, and wide receiver), category II (fullback, halfback, linebacker, offensive end, running back, and tight end), and category III (defensive positions: defensive end, defensive lineman, defensive tackle, nose guard, and nose tackle; offensive positions: center, offensive guard, offensive lineman, and offensive tackle).¶ Adjusting for age, body mass index, race, and calendar year; the hazard ratio for defensive versus offensive linemen is 2.07 (95% confidence interval 1.24 to 3.46) and the hazard ratio for defensive linemen versus all other positions is 1.97 (95% confidence interval 1.29 to 3.00). Open table in a new tab In our subgroup analysis of category III offensive and defensive linemen (model 4; Table 4) CVD mortality for defensive linemen, adjusting for BMI, age, race, and calendar year, was increased compared to offensive linemen (hazard ratio 2.07, 95% CI 1.24 to 3.46) and to all other positions combined (hazard ratio 1.97, 95% CI 1.29 to 3.00). Also, we found a statistically significant interaction between decade of follow-up and defensive linemen position (likelihood ratio, chi-square 8.1, 3 degrees of freedom, p = 0.04). Adjusting for age, race, and BMI, the increased CVD mortality in defensive linemen compared to other players was observed only for follow-up years before 2000 (Figure 1) . This
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