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RESULTS

During 1992–1996, there were a total of 68,770 drivers in the medical conditions program excluding drivers in functional ability level 1 (commercial drivers) and level 2 (drivers whose medical condition has resolved). The majority of drivers (54,825, 79.7%) were licensed in a single functional ability category (one medical condition). The remaining drivers (13,832, 20.1%) were licensed in two or more functional ability categories (that is, reported 2 or more medical conditions) during the study period. Most of the drivers reporting multiple conditions were licensed in two functional ability categories; however, the number per licensed driver ranged from one to seven categories during the study period. This is shown in Table 3.

Table 3.
Number of Functional Ability Categories Reported by Drivers with Medical Conditions in Utah, 1992 – 1995

 
Number of Categories Count Percent
1 54,825 79.9%
2 10,595 15.4%
3 2,403 3.5%
4 653 0.9%
5 146 0.2%
6 28 0.0%
7 7 0.0%
Total 68,770 100.0%
Table 4 shows the two way categorical combinations for drivers who were licensed in multiple functional ability categories. Note that drivers may appear more than one time, depending upon the number of functional ability categories reported. The most common 2-way combinations of functional ability categories were "cardiovascular and diabetes," "cardiovascular and vision," and "cardiovascular and pulmonary." As noted, only 2-way combinations were considered.

Table 4.
Two Way Combinations of Drivers Licensed in Multiple Functional Ability Categories, Utah Driver License Division, 1992- 1995

 
  Diabetes Cardiovascular Pulmonary Neurological Epilepsy Learning Psychiatric Alcohol Vision musculoskeletal
Cardiovascular 5,436                  
Pulmonary 717 1,796                
Neurological 614 941 223              
Epilepsy 173 280 89 369            
Learning 102 197 48 380 117          
Psychiatric 497 853 299 243 168 228        
Alcohol 81 98 57 61 52 38 269      
Vision 1,359 1,933 372 315 100 92 176 25    
musculoskeletal 401 574 205 547 80 127 194 53 180  
Functional 
Motor		 241 330 94 637 72 150 118 38 140 780
Figure 2 shows the percentages of drivers who were licensed in multiple functional ability categories, by each functional ability category. Over half of these drivers with multiple conditions were in the respective "cardiovascular" and "diabetes and other metabolic conditions" functional ability categories.

Figure 2 -- Drivers Licensed in Multiple Functional Ability Categories, Percentage by Category

Analyses performed for drivers who reported single medical conditions are presented in Tables 5-7. For each functional ability category, rates of citations, crashes, and at-fault crashes are presented, broken out for each functional ability level. Rates are compared to age- and location- matched controls, and odds ratios generated. Analyses are omitted for subgroups that contained too few subjects or events to allow for meaningful analysis.

Table 5.
Relative Risk for Citations, Single Functional Ability Category and Corresponding Comparison Groups, by Functional Ability Level

 
Condition Level Medical Conditions Control Group Rate Ratio
Drivers Citations # Days Rate Drivers Citations # Days Rate Ratio L 95% U 95% Significance
Diabetes 3 5,121 501 3,246,531 1.543 9,956 3,003 16,002,739 1.877 0.822 0.75 0.90 **
  4 6,924 1,959 6,388,418 3.067 13,576 5,941 20,812,910 2.854 1.074 1.02 1.13  
  5 801 140 316,278 4.427 1,588 719 2,400,555 2.995 1.478 1.23 1.77 *
  6 192 12 25,235 4.755 379 174 549,517 3.166 1.502 0.84 2.68  
  7 144 4 11,916 3.357 287 134 434,634 3.083 1.089 0.40 2.94  
  8 11 1 847 11.806 22 14 36,551 3.830 3.082 0.45 21.14  
  9 6 1 455 21.978 12 4 15,397 2.598 8.460 1.36 52.44 *
  10 18 0 6,627 0.000 36 17 50,640 3.357 Zero Rate      
  11 33 6 9,119 6.580 66 32 93,870 3.409 1.930 0.82 4.55  
Cardiovascular 3 16,192 1,175 9,342,197 1.258 29,918 8,212 50,582,274 1.623 0.775 0.73 0.82 **
  4 4,271 217 2,021,556 1.073 8,201 1,963 13,126,357 1.495 0.718 0.62 0.83 **
  5 982 36 255,469 1.409 1,926 445 2,991,355 1.488 0.947 0.67 1.33  
  6 138 0 14,079 0.000 270 81 414,798 1.953 0.000      
  7 10 0 878 0.000 20 15 29,323 5.115 Zero Rate      
  8 6 0 1,253 0.000 12 1 18,385 0.544 Zero Rate      
  9 1 0 128 0.000 2 0 2,997 0.000 Zero Rate      
  10 3 0 1,222 0.000 6 4 8,418 4.752 Zero Rate      
  11 11 8 5,369 14.900 22 11 35,036 3.140 4.746 2.08 10.83 *
Pulmonary 3 2,055 338 1,283,858 2.633 4,058 1,706 6,083,179 2.804 0.939 0.84 1.05  
  4 760 63 363,022 1.735 1,498 488 2,336,598 2.089 0.831 0.64 1.08  
  5 612 37 306,710 1.206 1,212 295 1,883,754 1.566 0.770 0.55 1.08  
  7 217 3 50,490 0.594 428 87 664,096 1.310 0.454 0.15 1.39  
  9 20 0 3,850 0.000 40 10 67,371 1.484 Zero Rate      
  10 14 0 2,691 0.000 28 6 47,373 1.267 Zero Rate      
  11 8 1 733 13.643 16 5 25,487 1.962 6.954 1.10 43.97 *
Neurological 3 510 57 281,984 2.021 1,010 355 1,556,600 2.281 0.886 0.67 1.17  
  4 402 45 206,311 2.181 797 287 1,241,932 2.311 0.944 0.69 1.29  
  5 318 36 165,579 2.174 627 211 963,848 2.189 0.993 0.70 1.41  
  6 136 7 58,892 1.189 270 98 415,232 2.360 0.504 0.24 1.07  
  7 60 3 21,018 1.427 119 26 190,673 1.364 1.047 0.32 3.45  
  9 3 0 374 0.000 6 0 8,375 0.000 Zero Rate      
  10 11 4 5,803 6.893 22 16 33,885 4.722 1.460 0.49 4.34  
  11 9 1 5,595 1.787 18 5 24,214 2.065 0.866 0.10 7.40  
Condition Level Medical Conditions Control Group Rate Ratio
Drivers Citations # Days Rate Drivers Citations # Days Rate Ratio L 95% U 95% Significance
Epilepsy 3 564 138 322,206 4.283 1,111 689 1,677,433 4.107 1.043 0.87 1.25  
  4 2,307 829 2,103,023 3.942 4,562 2,674 6,763,679 3.953 0.997 0.92 1.08  
  5 917 101 202,135 4.997 1,815 1,101 2,606,464 4.224 1.183 0.97 1.45  
  6 281 13 21,759 5.975 557 345 794,758 4.341 1.376 0.79 2.39  
  7 317 11 26,087 4.217 626 388 899,850 4.312 0.978 0.54 1.78  
  8 465 21 51,332 4.091 919 544 1,320,262 4.120 0.993 0.64 1.54  
  10 91 8 23,457 3.411 178 108 255,716 4.223 0.808 0.39 1.65  
  11 98 9 27,345 3.291 193 85 295,129 2.880 1.143 0.58 2.27  
Psychiatric 3 6,219 1,648 4,528,381 3.639 12,205 5,877 18,678,295 3.146 1.157 1.10 1.22 *
  4 1,730 370 668,171 5.538 3,424 1,680 5,080,122 3.307 1.674 1.50 1.87 *
  5 508 63 90,773 6.940 1,004 531 1,511,605 3.513 1.976 1.53 2.55 *
  6 207 14 31,172 4.491 409 241 623,137 3.868 1.161 0.68 1.99  
  9 91 2 14,817 1.350 182 119 277,611 4.287 0.315 0.08 1.18  
  10 17 3 4,507 6.656 34 24 52,107 4.606 1.445 0.44 4.77  
  11 20 0 7,951 0.000 40 15 63,855 2.349 Zero Rate      
Vision 3 6,657 709 2,264,533 3.131 12,814 4,397 19,078,918 2.305 1.359 1.26 1.47 *
  4 2,120 202 742,145 2.722 4,145 1,203 6,215,686 1.935 1.406 1.21 1.63 *
  5 1,854 359 1,286,255 2.791 3,622 1,064 5,495,635 1.936 1.442 1.28 1.62 *
  6 1,240 119 700,795 1.698 2,372 468 3,504,635 1.335 1.272 1.04 1.55 *
  7 146 5 46,826 1.068 289 39 438,558 0.889 1.201 0.47 3.04  
  8 141 20 53,346 3.749 278 59 395,674 1.491 2.514 1.54 4.10 *
  9 32 0 5,704 0.000 63 9 91,639 0.982 Zero Rate      
  10 59 9 39,825 2.260 118 20 170,892 1.170 1.931 0.89 4.18  
  11 44 4 26,004 1.538 87 18 120,303 1.496 1.028 0.35 3.04  
Rates are expressed as citations per 10,000 license days.
* The confidence interval does not include 1.0. Therefore, the higher rate of the medical conditions group is statistically significant.
** indicates that the medical conditions group has a statistically significant lower rate.
Table 6.
Relative Risk for All Crashes, Single Functional Ability Category and Corresponding Comparison Groups, by Functional Ability Level
 
Condition Level Medical Conditions Control Group Rate Ratio
Drivers Crashes # Days Rate Drivers Crashes # Days Rate Ratio L 95% U 95% Significance
Diabetes 3 5,121 422 3,246,531 1.300 9,956 1,770 16,002,739 1.106 1.175 1.06 1.31 *
  4 6,924 1,263 6,388,418 1.977 13,576 2,837 20,812,910 1.363 1.450 1.36 1.55 *
  5 801 58 316,278 1.834 1,588 335 2,400,555 1.396 1.314 1.00 1.73  
  6 192 6 25,235 2.378 379 76 549,517 1.383 1.719 0.76 3.91  
  7 144 3 11,916 2.518 287 69 434,634 1.588 1.586 0.50 4.99  
  8 11 0 847 0.000 22 4 36,551 1.094 Zero Rate      
  9 6 0 455 0.000 12 0 15,397 0.000 Zero Rate      
  10 18 0 6,627 0.000 36 8 50,640 1.580 Zero Rate      
  11 33 2 9,119 2.193 66 17 93,870 1.811 1.211 0.28 5.23  
Cardiovascular 3 16,192 983 9,342,197 1.052 29,918 5,142 50,582,274 1.017 1.035 0.97 1.11  
  4 4,271 183 2,021,556 0.905 8,201 1,297 13,126,357 0.988 0.916 0.78 1.07  
  5 982 43 255,469 1.683 1,926 308 2,991,355 1.030 1.635 1.19 2.24 *
  6 138 0 14,079 0.000 270 39 414,798 0.940 Zero Rate      
  7 10 0 878 0.000 20 5 29,323 1.705 Zero Rate      
  8 6 0 1,253 0.000 12 3 18,385 1.632 Zero Rate      
  9 1 0 128 0.000 2 0 2,997 0.000 Zero Rate      
  10 3 0 1,222 0.000 6 1 8,418 1.188 Zero Rate      
  11 11 3 5,369 5.588 22 2 35,036 0.571 9.788 2.29 41.86 *
Pulmonary 3 2,055 213 1,283,858 1.659 4,058 798 6,083,179 1.312 1.265 1.09 1.47 *
  4 760 51 363,022 1.405 1,498 283 2,336,598 1.211 1.160 0.86 1.56  
  5 612 33 306,710 1.076 1,212 205 1,883,754 1.088 0.989 0.68 1.43  
  7 217 5 50,490 0.990 428 73 664,096 1.099 0.901 0.36 2.23  
  9 20 0 3,850 0.000 40 5 67,371 0.742 Zero Rate      
  10 14 0 2,691 0.000 28 6 47,373 1.267 Zero Rate      
  11 8 1 733 13.643 16 4 25,487 1.569 8.693 1.41 53.45 *
Neuralgic 3 510 50 281,984 1.773 1,010 169 1,556,600 1.086 1.633 1.20 2.23 *
  4 402 42 206,311 2.036 797 133 1,241,932 1.071 1.901 1.35 2.67 *
  5 318 32 165,579 1.933 627 110 963,848 1.141 1.693 1.15 2.50 *
  6 136 9 58,892 1.528 270 57 415,232 1.373 1.113 0.55 2.25  
  7 60 4 21,018 1.903 119 23 190,673 1.206 1.578 0.55 4.52  
  9 3 0 374 0.000 6 0 8,375 0.000 Zero Rate      
  10 11 2 5,803 3.447 22 6 33,885 1.771 1.946 0.40 9.37  
  11 9 1 5,595 1.787 18 2 24,214 0.826 2.164 0.21 22.51  
Condition Level Medical Conditions Control Group Rate Ratio
Drivers Crashes # Days Rate Drivers Crashes # Days Rate Ratio L 95% U 95% Significance
Epilepsy 3 564 86 322,206 2.669 1,111 262 1,677,433 1.562 1.709 1.34 2.17 *
  4 2,307 563 2,103,023 2.677 4,562 1,047 6,763,679 1.548 1.729 1.56 1.91 *
  5 917 59 202,135 2.919 1,815 451 2,606,464 1.730 1.687 1.29 2.21 *
  6 281 8 21,759 3.677 557 141 794,758 1.774 2.072 1.03 4.16 *
  7 317 5 26,087 1.917 626 184 899,850 2.045 0.937 0.39 2.28  
  8 465 15 51,332 2.922 919 240 1,320,262 1.818 1.608 0.96 2.70  
  10 91 8 23,457 3.411 178 45 255,716 1.760 1.938 0.93 4.06  
  11 98 4 27,345 1.463