Table 1: Sample characteristics

From: Age of first exposure to American football and long-term neuropsychiatric and cognitive outcomes

 Total sample (N=214)AFE <12 (n=101)AFE12 (n=113)P
Age, mean (s.d.) years50.68 (13.33)48.22 (10.87)52.87 (14.91)0.009
Race, n (%) white192 (89.7)92 (91.1)100 (88.5)0.53
Education, mean (s.d.) years17.07 (2.27)17.09 (2.38)17.04 (2.19)0.89
Learning disability (N=206 due to missing data), n (%) yes19 (9.2)10 (10.6)9 (8.0)0.52
Reported psychotropic medication, n (%) yes77 (36.0)39 (38.6)38 (33.6)0.45
Reported psychiatric diagnosis, n (%) yes (N=167 due to missing data)a100 (59.9)52 (65.8)48 (54.5)0.14
Seasons of football play, median (IQR)12.25 (9)14.00 (10)10.00 (8)<0.001
AFE to football, mean (s.d.)11.12 (2.47)8.98 (1.65)13.04 (1.14)<0.001
Total number of concussions (N=210 due to missing data), median (IQR)b17.75 (37)25.00 (88)15.00 (23)<0.001
Total number of concussions outside of sport/military (N=208 due to missing data), median (IQR)c1.00 (2)1.00 (2)1.00 (2)0.17
     
Highest level of football play, n (%)   0.54
 High school43 (20.1)20 (19.8)23 (20.4) 
 College103 (48.1)51 (50.5)52 (46.0) 
 Professional68 (31.8)30 (29.7)38 (33.6) 
     
Primary position, n (%)d   
 Offensive linemen69 (32.7)26 (26.3)43 (38.4) 
 Running back64 (30.3)35 (35.4)29 (25.9) 
 Tight end27 (12.8)15 (15.2)12 (10.7) 
 Offensive skill51 (24.2)23 (23.2)28 (25.0) 
 Defensive line72 (34.8)30 (30.3)42 (38.9) 
 Linebacker58 (28.0)31 (31.3)27 (25.0) 
 Defensive back77 (37.2)38 (38.4)39 (36.1) 
  1. Abbreviations: AFE, age of first exposure; IQR, interquartile range.
  2. Independent sample t-tests and χ2-analyses were used to compare differences between the AFE groups, except for seasons of football play, total number of concussions and total number of concussions outside of sport/military for which Mann–Whitney U-test was conducted due to a non-normal distribution. Proportion of white versus other was tested and the highest level of football play was transformed to amateur versus professional.
  3. aIncludes reported history of depression, anxiety, bipolar disorder, schizophrenia and/or other psychiatric difficulties.
  4. bSelf-reported number of concussions after being provided with a modern definition of concussion.62
  5. cOnly 39 (18.2%) subjects reported a military history, and the median number of head injuries experienced during the military was 0 (IQR=1).
  6. dPlayers could indicate both a primary offensive and defensive position and therefore could be represented more than once. The bold is used for those P values that are significant.