CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION Computerized neurobehavioral testing was administered to a random half-sample of examinees aged 20-59 years by a trained examiner in a soundproof room in the mobile examination center (MEC). A screening questionnaire was administered to assess factors that might have affected test performance. There were no medical or safety exclusions for this component. Because this examination was administered on a selected subsample in the examination center, the central nervous system (CNS) sample weight (WTPFCNS6) should be used for data analysis. For more information on the use of sample weights in NHANES III data analysis, refer to the NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996b). Three computerized tests were used to evaluate central nervous system function. They were: (1) a simple reaction time test (SRTT), a basic measure of motor response speed to a visual stimulus; (2) a symbol-digit substitution test (SDST), a test of coding ability; and (3) a serial-digit learning test (SDLT), a short-term memory test. These tests are components of the Neurobehavioral Evaluation System 2 (NES2) developed by Baker and Letz (1985; Letz, 1990). NES2 is a system of computerized tests designed to assess neurobehavioral function in epidemiological studies of populations with occupational or environmental exposure to chemicals. The tests were administered on a Compaq 286 DeskPro(TM) personal computer (12.5 MHz, 80286 CPU chip) configured with 640K RAM, one 1.2MB floppy disk drive, one parallel port, two serial ports, a standard game joystick controller board, and an Ethernet interface board. The system used the standard, detachable keyboard with a custom-made wooden keyboard overlay that left only the top row of digit keys exposed to prevent inadvertent contact with keys not needed in the testing; it also used a standard, monochrome (green) Compaq monitor. In September 1991, between the conclusion of Phase 1 and the initiation of Phase 2 data collection, the monitors were replaced with comparable, new amber monitors due to a deterioration in display performance. A push-button, computer-game joystick (NES2 Joystick by Neurobehavioral Systems, Inc., Winchester, MA) was used to record the SRTT responses. The tests were administered by health technicians, MEC interviewers, and translators who were trained to perform the testing. Before examinations began, special training sessions were held at NCHS or at the offices of the contractor responsible for survey operations. Training sessions also occurred at MEC sites during the survey, and retraining was done approximately twice per year. The test was conducted in English or Spanish, and examinees who could not speak English or Spanish were not tested. English or Spanish language instructions appeared on the computer screen for each test, and the examiner also gave the instructions verbally. Translators were trained to administer the testing independently or with a health technician. The training was conducted in the MEC by a Spanish-speaking health technician, Spanish-speaking NCHS staff member, or Spanish-speaking MEC interviewer trained to administer the CNS test. Training for translators included reviewing the manual with the trainer, performing the tests as an examinee, and administering the examination in Spanish. Physical comfort may have affected examinees' test results. The air conditioning in the soundproof room used for testing sometimes failed to maintain an optimally comfortable room temperature. Because of this, room temperature (CNPTEMP) was recorded for use as a covariate; however, this practice did not begin until the second year of the survey. The location of the thermometer within the room and the time that temperature was recorded were not consistent throughout the survey. For instance, some examiners entered the temperature at the beginning of the testing session, and others recorded it at the end of the session. This source of error is likely to be small. Initially, some trials of the SRTT were performed with both the non-preferred hand and the preferred hand. Early in the survey, the procedure was changed to perform all trials only with the preferred hand. As a result, analysts may want to exclude SRTT data from those examinees who used both hands for the test. The affected data have a value of "2 Non-preferred hand used on trials 31-50" for the variable CNPNBPH (LOG: Number of trials with preferred hand). During Phase 2 of the survey, reading glasses were available for examinees who forgot to bring their own reading glasses to the MEC. Examinees could select from four pairs of glasses of different diopters or magnifying powers (+1.0 diopter, +1.5 diopters, +2.0 diopters, and +2.5 diopters). Although all examiners were well-trained in standardized procedures for these tests, performance on neurobehavioral tests may have been subject to an examiner effect. This would have been particularly likely when the examiner encouraged the examinee during the exam, as was the case in NHANES III. Therefore, analysts should consider using the examiner number (CNPTECH) as a covariate in analyses of data from these tests. For details of the examination protocol, see the Neurobehavioral Testing Procedures Manual (U.S. DHHS, 1996b). Data processing and editing were performed to ensure internal data consistency. Notes have been provided for variables requiring additional explanation. NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ CONDITIONS AFFECTING TEST RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5502 How much sleep did you get last night? CNPQ01 Would you say about the usual amount, less than usual, or more than usual? 3131 1 About usual amount 1552 2 Less than usual 461 3 More than usual 518 8 Blank but applicable 25649 Blank 5503 Right now would you say you are feeling CNPQ02 energetic, fresh, average, tired, or exhausted? 280 1 Energetic 668 2 Fresh 2815 3 Average 1229 4 Tired 152 5 Exhausted 518 8 Blank but applicable 25649 Blank 5504 How much familiarity do you have with CNPQ03 computers or video games? Would you say none, some, or a lot? 2167 0 None 2268 1 Some 709 2 A lot 518 8 Blank but applicable 25649 Blank 5505 Not counting decaffeinated products, how CNPQ04 many cups of coffee, tea, or cola have you had in the past 3 hours? 4912 0 None 164 1 One 68 2 2 or more 518 8 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ CONDITIONS AFFECTING TEST RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5506 How many drinks of alcohol have you had CNPQ05 in the past 3 hours? Include any alcoholic drinks such as wine, beer, or hard liquor. 5080 0 None 47 1 One 17 2 2 or more 518 8 Blank but applicable 25649 Blank 5507 Which hand do you prefer to use for this CNPQ06 test? 4720 1 Right 424 2 Left 518 8 Blank but applicable 25649 Blank 5508 Simple Reaction Time Test (SRTT) CNPQ07 completed 5138 1 Yes 63 2 No 461 8 Blank but applicable 25649 Blank 5509 Symbol Digit Substitution Test (SDST) CNPQ08 completed 5092 1 Yes 109 2 No 461 8 Blank but applicable 25649 Blank 5510 Serial Digit Learning Test (SDLT) CNPQ09 completed 4962 1 Yes 236 2 No 464 8 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ CONDITIONS AFFECTING TEST RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5511 How hard did you try to perform this CNPQ10 computer test? 135 0 None/not at all 1268 1 Some 1137 2 A lot 2596 3 As hard as I could 526 8 Blank but applicable 25649 Blank 5512 Language used for test administration CNPLANG 4460 1 English 685 2 Spanish 517 8 Blank but applicable 25649 Blank 5513-5515 Room temperature (degrees Fahrenheit) CNPTEMP 4013 060-092 1649 888 Blank but applicable 25649 Blank 5516-5520 Examiner number CNPTECH 5207 01001-09018 455 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5521 LOG: Number of trials with preferred CNPNBPH hand 4896 1 Preferred hand used on all 50 trials 242 2 Non-preferred hand used on trials 31-50 524 8 Blank but applicable 25649 Blank 5522-5525 SRTT: Trial 01 reaction time (msec) CNPRT01 5138 0064-3866 524 8888 Blank but applicable 25649 Blank 5526-5529 SRTT: Trial 02 reaction time (msec) CNPRT02 5138 0071-3533 524 8888 Blank but applicable 25649 Blank 5530-5533 SRTT: Trial 03 reaction time (msec) CNPRT03 5138 0050-3509 524 8888 Blank but applicable 25649 Blank 5534-5537 SRTT: Trial 04 reaction time (msec) CNPRT04 5138 0060-3538 524 8888 Blank but applicable 25649 Blank 5538-5541 SRTT: Trial 05 reaction time (msec) CNPRT05 5138 0103-3993 524 8888 Blank but applicable 25649 Blank 5542-5545 SRTT: Trial 06 reaction time (msec) CNPRT06 5138 0059-1831 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5546-5549 SRTT: Trial 07 reaction time (msec) CNPRT07 5138 0081-2778 524 8888 Blank but applicable 25649 Blank 5550-5553 SRTT: Trial 08 reaction time (msec) CNPRT08 5138 0122-3486 524 8888 Blank but applicable 25649 Blank 5554-5557 SRTT: Trial 09 reaction time (msec) CNPRT09 5138 0054-1764 524 8888 Blank but applicable 25649 Blank 5558-5561 SRTT: Trial 10 reaction time (msec) CNPRT10 5138 0088-1965 524 8888 Blank but applicable 25649 Blank 5562-5565 SRTT: Trial 11 reaction time (msec) CNPRT11 5138 0056-1004 524 8888 Blank but applicable 25649 Blank 5566-5569 SRTT: Trial 12 reaction time (msec) CNPRT12 5138 0055-1708 524 8888 Blank but applicable 25649 Blank 5570-5573 SRTT: Trial 13 reaction time (msec) CNPRT13 5138 0059-3607 524 8888 Blank but applicable 25649 Blank 5574-5577 SRTT: Trial 14 reaction time (msec) CNPRT14 5138 0083-2524 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5578-5581 SRTT: Trial 15 reaction time (msec) CNPRT15 5138 0137-1204 524 8888 Blank but applicable 25649 Blank 5582-5585 SRTT: Trial 16 reaction time (msec) CNPRT16 5138 0135-1205 524 8888 Blank but applicable 25649 Blank 5586-5589 SRTT: Trial 17 reaction time (msec) CNPRT17 5138 0106-3234 524 8888 Blank but applicable 25649 Blank 5590-5593 SRTT: Trial 18 reaction time (msec) CNPRT18 5138 0068-1210 524 8888 Blank but applicable 25649 Blank 5594-5597 SRTT: Trial 19 reaction time (msec) CNPRT19 5138 0068-1457 524 8888 Blank but applicable 25649 Blank 5598-5601 SRTT: Trial 20 reaction time (msec) CNPRT20 5138 0060-2470 524 8888 Blank but applicable 25649 Blank 5602-5605 SRTT: Trial 21 reaction time (msec) CNPRT21 5138 0072-1457 524 8888 Blank but applicable 25649 Blank 5606-5609 SRTT: Trial 22 reaction time (msec) CNPRT22 5138 0085-1203 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5610-5613 SRTT: Trial 23 reaction time (msec) CNPRT23 5138 0118-1202 524 8888 Blank but applicable 25649 Blank 5614-5617 SRTT: Trial 24 reaction time (msec) CNPRT24 5138 0071-2480 524 8888 Blank but applicable 25649 Blank 5618-5621 SRTT: Trial 25 reaction time (msec) CNPRT25 5138 0051-1202 524 8888 Blank but applicable 25649 Blank 5622-5625 SRTT: Trial 26 reaction time (msec) CNPRT26 5138 0145-2521 524 8888 Blank but applicable 25649 Blank 5626-5629 SRTT: Trial 27 reaction time (msec) CNPRT27 5138 0061-2896 524 8888 Blank but applicable 25649 Blank 5630-5633 SRTT: Trial 28 reaction time (msec) CNPRT28 5138 0068-3230 524 8888 Blank but applicable 25649 Blank 5634-5637 SRTT: Trial 29 reaction time (msec) CNPRT29 5138 0098-1962 524 8888 Blank but applicable 25649 Blank 5638-5641 SRTT: Trial 30 reaction time (msec) CNPRT30 5138 0120-3991 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5642-5645 SRTT: Trial 31 reaction time (msec) CNPRT31 5138 0062-1202 524 8888 Blank but applicable 25649 Blank 5646-5649 SRTT: Trial 32 reaction time (msec) CNPRT32 5138 0121-1204 524 8888 Blank but applicable 25649 Blank 5650-5653 SRTT: Trial 33 reaction time (msec) CNPRT33 5138 0092-3995 524 8888 Blank but applicable 25649 Blank 5654-5657 SRTT: Trial 34 reaction time (msec) CNPRT34 5138 0130-3589 524 8888 Blank but applicable 25649 Blank 5658-5661 SRTT: Trial 35 reaction time (msec) CNPRT35 5138 0130-3535 524 8888 Blank but applicable 25649 Blank 5662-5665 SRTT: Trial 36 reaction time (msec) CNPRT36 5138 0057-1344 524 8888 Blank but applicable 25649 Blank 5666-5669 SRTT: Trial 37 reaction time (msec) CNPRT37 5138 0052-1202 524 8888 Blank but applicable 25649 Blank 5670-5673 SRTT: Trial 38 reaction time (msec) CNPRT38 5138 0092-1513 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5674-5677 SRTT: Trial 39 reaction time (msec) CNPRT39 5138 0120-2975 524 8888 Blank but applicable 25649 Blank 5678-5681 SRTT: Trial 40 reaction time (msec) CNPRT40 5138 0139-2272 524 8888 Blank but applicable 25649 Blank 5682-5685 SRTT: Trial 41 reaction time (msec) CNPRT41 5138 0076-1200 524 8888 Blank but applicable 25649 Blank 5686-5689 SRTT: Trial 42 reaction time (msec) CNPRT42 5138 0139-3534 524 8888 Blank but applicable 25649 Blank 5690-5693 SRTT: Trial 43 reaction time (msec) CNPRT43 5138 0063-1055 524 8888 Blank but applicable 25649 Blank 5694-5697 SRTT: Trial 44 reaction time (msec) CNPRT44 5138 0052-1062 524 8888 Blank but applicable 25649 Blank 5698-5701 SRTT: Trial 45 reaction time (msec) CNPRT45 5138 0125-0999 524 8888 Blank but applicable 25649 Blank 5702-5705 SRTT: Trial 46 reaction time (msec) CNPRT46 5138 0081-1209 524 8888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SIMPLE REACTION TIME TEST (SRTT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5706-5709 SRTT: Trial 47 reaction time (msec) CNPRT47 5138 0120-3338 524 8888 Blank but applicable 25649 Blank 5710-5713 SRTT: Trial 48 reaction time (msec) CNPRT48 5138 0121-2727 524 8888 Blank but applicable 25649 Blank 5714-5717 SRTT: Trial 49 reaction time (msec) CNPRT49 5138 0085-2013 524 8888 Blank but applicable 25649 Blank 5718-5721 SRTT: Trial 50 reaction time (msec) CNPRT50 5138 0069-1006 524 8888 Blank but applicable 25649 Blank 5722-5729 SRTT summary: Mean reaction time (msec) See note CNPMENRT 5138 00000154-660.0606 524 88888888 Blank but applicable 25649 Blank 5730-5737 SRTT summary: Standard deviation of the See note CNPSDRT reaction times (msec) 5138 010.8057-176.2465 524 88888888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5738-5739 SDST: Number of errors, trial 1 CNP1ERR 3514 00 None 821 01 1 error 330 02 2 errors 178 03 3 errors 106 04 4 errors 65 05 5 errors 29 06 6 errors 12 07 7 errors 29 08 8 errors 8 09 9 errors 570 88 Blank but applicable 25649 Blank 5740-5744 SDST: Latency 1, trial 1 (sec) See note CNP1LAT1 5092 -54.3-043.1 570 88888 Blank but applicable 25649 Blank 5745-5749 SDST: Latency 2, trial 1 (sec) See note CNP1LAT2 5092 -34.5-061.8 570 88888 Blank but applicable 25649 Blank 5750-5754 SDST: Latency 3, trial 1 (sec) See note CNP1LAT3 5092 -43.4-038.3 570 88888 Blank but applicable 25649 Blank 5755-5759 SDST: Latency 4, trial 1 (sec) See note CNP1LAT4 5092 -42.6-059.4 570 88888 Blank but applicable 25649 Blank 5760-5764 SDST: Latency 5, trial 1 (sec) See note CNP1LAT5 5092 -41.7-00026 570 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5765-5769 SDST: Latency 6, trial 1 (sec) See note CNP1LAT6 5092 -34.9-061.5 570 88888 Blank but applicable 25649 Blank 5770-5774 SDST: Latency 7, trial 1 (sec) See note CNP1LAT7 5092 -21.2-080.9 570 88888 Blank but applicable 25649 Blank 5775-5779 SDST: Latency 8, trial 1 (sec) See note CNP1LAT8 5092 -59.2-062.9 570 88888 Blank but applicable 25649 Blank 5780-5784 SDST: Latency 9, trial 1 (sec) See note CNP1LAT9 5092 -41.1-039.2 570 88888 Blank but applicable 25649 Blank 5785-5790 SDST: Total latency, trial 1 (sec) See note CNP1TOTL 5092 011.07-212.98 570 888888 Blank but applicable 25649 Blank 5791-5792 SDST summary: Number of correct CNPCORR1 responses for latencies 2 through 9, trial 1 8 00 32 01 24 02 65 03 106 04 159 05 316 06 755 07 3627 08 570 88 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5793-5798 SDST summary: Error-corrected latency See note CNPCLAT1 for trial 1 - total latency/number of correct responses (sec) 5084 001.38-095.68 570 888888 Blank but applicable 25657 Blank 5799-5800 SDST: Number of errors, trial 2 CNP2ERR 4117 00 None 616 01 1 error 170 02 2 errors 90 03 3 errors 47 04 4 errors 27 05 5 errors 13 06 6 errors 4 07 7 errors 4 08 8 errors 4 09 9 errors 570 88 Blank but applicable 25649 Blank 5801-5805 SDST: Latency 1, trial 2 (sec) See note CNP2LAT1 5092 -36.8-037.9 570 88888 Blank but applicable 25649 Blank 5806-5810 SDST: Latency 2, trial 2 (sec) See note CNP2LAT2 5092 -48.5-057.3 570 88888 Blank but applicable 25649 Blank 5811-5815 SDST: Latency 3, trial 2 (sec) See note CNP2LAT3 5092 -0028-00055 570 88888 Blank but applicable 25649 Blank 5816-5820 SDST: Latency 4, trial 2 (sec) See note CNP2LAT4 5092 -18.1-099.9 570 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5821-5825 SDST: Latency 5, trial 2 (sec) See note CNP2LAT5 5092 -27.3-00048 570 88888 Blank but applicable 25649 Blank 5826-5830 SDST: Latency 6, trial 2 (sec) See note CNP2LAT6 5092 -22.1-032.8 570 88888 Blank but applicable 25649 Blank 5831-5835 SDST: Latency 7, trial 2 (sec) See note CNP2LAT7 5092 -54.9-038.3 570 88888 Blank but applicable 25649 Blank 5836-5840 SDST: Latency 8, trial 2 (sec) See note CNP2LAT8 5092 -20.6-025.5 570 88888 Blank but applicable 25649 Blank 5841-5845 SDST: Latency 9, trial 2 (sec) See note CNP2LAT9 5092 -86.9-052.1 570 88888 Blank but applicable 25649 Blank 5846-5851 SDST: Total latency, trial 2 (sec) See note CNP2TOTL 5092 003.79-467.95 570 888888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5852-5853 SDST summary: Number of correct CNPCORR2 responses for latencies 2 through 9, trial 2 4 00 7 01 10 02 26 03 34 04 75 05 158 06 539 07 4239 08 570 88 Blank but applicable 25649 Blank 5854-5859 SDST summary: Error-corrected latency See note CNPCLAT2 for trial 2 - total latency/number of correct responses (sec) 5088 001.51-104.18 570 888888 Blank but applicable 25653 Blank 5860-5861 SDST: Number of errors, trial 3 CNP3ERR 4103 00 None 658 01 1 error 179 02 2 errors 63 03 3 errors 46 04 4 errors 16 05 5 errors 12 06 6 errors 4 07 7 errors 7 08 8 errors 4 09 9 errors 570 88 Blank but applicable 25649 Blank 5862-5866 SDST: Latency 1, trial 3 (sec) See note CNP3LAT1 5092 -24.4-040.1 570 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5867-5871 SDST: Latency 2, trial 3 (sec) See note CNP3LAT2 5092 -24.8-032.4 570 88888 Blank but applicable 25649 Blank 5872-5876 SDST: Latency 3, trial 3 (sec) See note CNP3LAT3 5092 -23.6-042.5 570 88888 Blank but applicable 25649 Blank 5877-5881 SDST: Latency 4, trial 3 (sec) See note CNP3LAT4 5092 -0038-041.7 570 88888 Blank but applicable 25649 Blank 5882-5886 SDST: Latency 5, trial 3 (sec) See note CNP3LAT5 5092 -31.8-029.2 570 88888 Blank but applicable 25649 Blank 5887-5891 SDST: Latency 6, trial 3 (sec) See note CNP3LAT6 5092 -32.2-034.6 570 88888 Blank but applicable 25649 Blank 5892-5896 SDST: Latency 7, trial 3 (sec) See note CNP3LAT7 5092 -23.8-034.9 570 88888 Blank but applicable 25649 Blank 5897-5901 SDST: Latency 8, trial 3 (sec) See note CNP3LAT8 5092 -25.4-037.7 570 88888 Blank but applicable 25649 Blank 5902-5906 SDST: Latency 9, trial 3 (sec) See note CNP3LAT9 5092 -15.4-00027 570 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5907-5912 SDST: Total latency, trial 3 (sec) See note CNP3TOTL 5092 008.49-145.23 570 888888 Blank but applicable 25649 Blank 5913-5914 SDST summary: Number of correct CNPCORR3 responses for latencies 2 through 9, trial 3 5 00 7 01 11 02 17 03 39 04 63 05 154 06 600 07 4196 08 570 88 Blank but applicable 25649 Blank 5915-5920 SDST summary: Error-corrected latency See note CNPCLAT3 for trial 3 - total latency/number of correct responses (sec) 5087 001.21-105.03 570 888888 Blank but applicable 25654 Blank 5921-5922 SDST: Number of errors, trial 4 CNP4ERR 3971 00 None 708 01 1 error 229 02 2 errors 108 03 3 errors 46 04 4 errors 22 05 5 errors 3 06 6 errors 2 07 7 errors 2 08 8 errors 1 09 9 errors 570 88 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5923-5927 SDST: Latency 1, trial 4 (sec) See note CNP4LAT1 5092 -25.8-099.9 570 88888 Blank but applicable 25649 Blank 5928-5932 SDST: Latency 2, trial 4 (sec) See note CNP4LAT2 5092 -88.2-087.2 570 88888 Blank but applicable 25649 Blank 5933-5937 SDST: Latency 3, trial 4 (sec) See note CNP4LAT3 5092 -26.4-076.6 570 88888 Blank but applicable 25649 Blank 5938-5942 SDST: Latency 4, trial 4 (sec) See note CNP4LAT4 5092 -15.7-024.8 570 88888 Blank but applicable 25649 Blank 5943-5947 SDST: Latency 5, trial 4 (sec) See note CNP4LAT5 5092 -22.2-035.8 570 88888 Blank but applicable 25649 Blank 5948-5952 SDST: Latency 6, trial 4 (sec) See note CNP4LAT6 5092 -32.9-030.8 570 88888 Blank but applicable 25649 Blank 5953-5957 SDST: Latency 7, trial 4 (sec) See note CNP4LAT7 5092 -17.2-024.5 570 88888 Blank but applicable 25649 Blank 5958-5962 SDST: Latency 8, trial 4 (sec) See note CNP4LAT8 5092 -28.3-034.8 570 88888 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SYMBOL DIGIT SUBSTITUTION TEST (SDST) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5963-5967 SDST: Latency 9, trial 4 (sec) See note CNP4LAT9 5092 -18.3-034.2 570 88888 Blank but applicable 25649 Blank 5968-5973 SDST: Total latency, trial 4 (sec) See note CNP4TOTL 5092 010.29-178.86 570 888888 Blank but applicable 25649 Blank 5974-5975 SDST summary: Number of correct CNPCORR4 responses for latencies 2 through 9, trial 4 1 00 3 01 2 02 19 03 39 04 103 05 199 06 678 07 4048 08 570 88 Blank but applicable 25649 Blank 5976-5981 SDST summary: Error-corrected latency See note CNPCLAT4 for trial 4 - total latency/number of correct responses (sec) 5091 001.36-138.71 570 888888 Blank but applicable 25650 Blank 5982-5986 SDST summary: Mean of the two See note CNPCBEST lowest error-corrected latencies (sec/correct digit) 5077 01.38-022.2 570 88888 Blank but applicable 25664 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SERIAL DIGIT LEARNING TEST (SDLT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5987 SDLT: Total 0 trials CNPT0TRA 4388 1 1 trial 0 510 2 2 trial 0 52 3 3 trial 0 11 4 4 trial 0 1 5 5 trial 0 700 8 Blank but applicable 25649 Blank 5988 SDLT: Score, trial 1 See note CNP1SCOR 608 0 Correct 976 1 2/3 correct 3378 2 Incorrect 700 8 Blank but applicable 25649 Blank 5989 SDLT: Score, trial 2 See note CNP2SCOR 1518 0 Correct 1098 1 2/3 correct 2346 2 Incorrect 700 8 Blank but applicable 25649 Blank 5990 SDLT: Score, trial 3 See note CNP3SCOR 1783 0 Correct 929 1 2/3 correct 1748 2 Incorrect 700 8 Blank but applicable 26151 Blank 5991 SDLT: Score, trial 4 See note CNP4SCOR 1465 0 Correct 795 1 2/3 correct 1325 2 Incorrect 700 8 Blank but applicable 27026 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SERIAL DIGIT LEARNING TEST (SDLT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5992 SDLT: Score, trial 5 See note CNP5SCOR 1103 0 Correct 620 1 2/3 correct 1100 2 Incorrect 700 8 Blank but applicable 27788 Blank 5993 SDLT: Score, trial 6 See note CNP6SCOR 790 0 Correct 552 1 2/3 correct 893 2 Incorrect 700 8 Blank but applicable 28376 Blank 5994 SDLT: Score, trial 7 See note CNP7SCOR 658 0 Correct 450 1 2/3 correct 731 2 Incorrect 700 8 Blank but applicable 28772 Blank 5995 SDLT: Score, trial 8 See note CNP8SCOR 518 0 Correct 396 1 2/3 correct 618 2 Incorrect 700 8 Blank but applicable 29079 Blank 5996-5997 SDLT summary: Trials to criterion CNPTSTOC 502 02 875 03 762 04 588 05 396 06 307 07 1463 08 69 09 700 88 Blank but applicable 25649 Blank NHANES III Examination Data File ------------------------------------------------------------------------ CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION ------------------------------------------------------------------------ SERIAL DIGIT LEARNING TEST (SDLT) ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5998-5999 SDLT summary: Total score CNPTTSCR 4962 00-16 700 88 Blank but applicable 25649 Blank NOTES CNP1LAT1-CNP1LAT9, CNP2LAT1-CNP2LAT9, CNP3LAT1-CNP3LAT9, CNP4LAT1-CNP4LAT9: Latencies for trials 1-4 A total of five trials were conducted in the Symbol Digit Substitution Test (SDST), a practice trial (not included in these data) and four actual trials (trials 1-4). The practice trial was primarily for training the examinee in the test procedure. It did not accept incorrect responses, and data from the practice trial are not included in this file. If the examinee entered an incorrect digit, a short beep sounded, and no digit was entered on the screen; to proceed, a correct digit had to be entered. If the examinee made more than four errors during the practice trial, the trial was repeated. If the examinee made more than four errors on the second attempt of the practice trial, the test was discontinued, and the next test was initiated automatically. Symbols and digits were paired differently on each trial. Although incorrect responses were allowed on the four actual trials, more than four errors resulted in a message emphasizing the need to avoid errors. These variables represent the latency to enter each of the nine digits of each trial. Incorrect responses were reported as negative values. CNP1SCOR-CNP8SCOR: Serial Digit Learning Test (SDLT) score Note that to allow comparison with NES2 results from other settings the scoring convention for this variable differs from that usually applied to the NHANES III data, where 0 indicates none or never. Examinees received a score of 0 if all eight digits were entered correctly, 1 if six or seven digits were entered correctly, and 2 if fewer than six digits were entered correctly. CNP1TOTL, CNP2TOTL, CNP3TOTL, CNP4TOTL: Total latency, trials 1-4 CNP1TOTL represents the time elapsed on trial 1 from the time the first item was answered to the time the ninth item was answered. Therefore, it does not include the latency to respond to the first symbol. CNP2LAT1-CNP2LAT9: Latencies for trial 2 See note for CNP1LAT1-CNP1LAT9. CNP2TOTL: Total latency, trial 2 See note for CNP1TOTL. CNP3LAT1-CNP3LAT9: Latencies for trial 3 See note for CNP1LAT1-CNP1LAT9. CNP3TOTL: Total latency, trial 3 See note for CNP1TOTL. CNP4LAT1-CNP4LAT9: Latencies for trial 4 See note for CNP1LAT1-CNP1LAT9. CNP4TOTL: Total latency, trial 4 See note for CNP1TOTL. CNPCBEST: Mean of two lowest error-corrected latencies This single summary measure for the SDST is the mean of the error-corrected latencies (CNPCLAT1-CNPCLAT4) on the two best (lowest latency) of the four trials. The units for this summary measure are "sec/correct digit." CNPCLAT1, CNPCLAT2, CNPCLAT3, CNPCLAT4: Error-corrected latency for trials 1-4 The error-corrected latency was calculated for each of the four actual trials. It is the mean number of seconds per correct digit for each trial, excluding the first item in the trial. If the number of correct responses for latencies 2 through 9 was 0, CNPCLAT1 was set to missing (blank). Otherwise, CNPCLAT1=CNP1TOTL/CNPCORR1. CNPCLAT2: Error-corrected latency for trial 2 See note for CNPCLAT1. CNPCLAT3: Error-corrected latency for trial 3 See note for CNPCLAT1. CNPCLAT4: Error-corrected latency for trial 4 See note for CNPCLAT1. CNPMENRT: Mean reaction time To calculate the mean reaction time, values from the first ten trials (CNPRT01-CNPRT10) were excluded as well as values from other trials that were greater than or equal to 750 msec or less than or equal to 50 msec. This mean may not be valid if the number of trials included in the average was less than 20. CNPSDRT: Standard deviation of the reaction time To calculate the standard deviation of the reaction time, values from the first ten trials (CNPRT01-CNPRT10) were excluded as well as values from other trials that were greater than or equal to 750 msec or less than or equal to 50 msec. This statistic may not be valid if the number of trials included in the calculation was less than 20.