Health Publications
Topic: RSS FeedNeurobehavioral performance and work experience in Florida farmworkers - Environmental Medicine
Environmental Health Perspectives, Nov, 2003 by Freya Kamel, Andrew S. Rowland, Lawrence P. Park, W. Kent Anger, Donna D. Baird, Beth C. Gladen, Tirso Moreno, Lillian Stallone, Dale P. Sandler
Table 1. Characteristics of study participants. (a)
All
Controls farmworkers
Characteristics (n=51) (n=288)
Age (years)
28-32 24 24
33-37 22 29
38-43 20 26
44-55 35 21
Mean [ or -] SD 39.9 [ or -] 7.3 38.0 [ or -] 6.7
Sex
Male 41 56
Female 59 44
Ethnicity
Latino 63 89
Non-Latino white 18 3
Other 20 8
Education (years)
0-5 12 39
6-11 24 42
[greater than or equal to] 12 65 19
Mean [ or -] SD 11.9 [ or -] 4.8 6.5 [ or -] 4.2
Acculturation
Not acculturated 22 54
Somewhat acculturated 31 26
Very acculturated 47 20
Language of testing
Spanish 63 89
English 37 11
Lifetime cigarette smoking (pack-years)
Never 57 54
> 0-5 22 29
> 5-15 10 11
> 15 12 6
Alcohol use in previous year (drinks per week)
<1 63 59
1-14 31 26
[greater than or equal to] 15 6 15
Lifetime problems with alcohol use
Never drank 33 30
Drank, no problems 49 47
Drank, had problems 16 23
Usually sleep [greater than or equal to] 7 hrs
Yes 71 81
No 29 19
20:20 vision
Left eye
Yes 65 68
No 35 31
Right eye
Yes 63 69
No 37 31
Ever had severe head injury
No 88 93
Yes 12 7
Ever had any neck or back injury
No 75 78
Yes 25 22
Hand pain
Preferred hand
No 82 83
Yes 18 17
Nonpreferred hand
No 80 88
Yes 20 12
Fern Nursery
Characteristics workers workers
(n=140) (n=147)
Age (years)
28-32 26 24
33-37 27 25
38-43 29 23
44-55 19 28
Mean [ or -] SD 37.8 [ or -] 6.4 38.8 [ or -] 7.3
Sex
Male 56 54
Female 44 46
Ethnicity
Latino 94 82
Non-Latino white 0 6
Other 6 12
Education (years)
0-5 45 35
6-11 41 37
[greater than or equal to] 12 14 27
Mean [ or -] SD 5.8 [ or -] 4.1 7.2 [ or -] 4.5
Acculturation
Not acculturated 66 41
Somewhat acculturated 21 28
Very acculturated 12 31
Language of testing
Spanish 94 81
English 6 19
Lifetime cigarette smoking (pack-years)
Never 60 44
> 0-5 24 37
> 5-15 12 12
> 15 4 7
Alcohol use in previous year (drinks per week)
<1 64 60
1-14 24 27
[greater than or equal to] 15 12 14
Lifetime problems with alcohol use
Never drank 33 27
Drank, no problems 44 47
Drank, had problems 23 26
Usually sleep [greater than or equal to] 7 hrs
Yes 81 80
No 19 20
20:20 vision
Left eye
Yes 69 66
No 31 34
Right eye
Yes 72 68
No 27 32
Ever had severe head injury
No 90 94
Yes 10 6
Ever had any neck or back injury
No 79 78
Yes 21 22
Hand pain
Preferred hand
No 80 85
Yes 20 15
Nonpreferred hand
No 91 86
Yes 9 14
Citrus
workers
Characteristics (n=141)
Age (years)
28-32 21
33-37 28
38-43 26
44-55 26
Mean [ or -] SD 39.0 [ or -] 7.1
Sex
Male 65
Female 35
Ethnicity
Latino 84
Non-Latino white 4
Other 13
Education (years)
0-5 43
6-11 36
[greater than or equal to] 12 21
Mean [ or -] SD 6.4 [ or -] 4.5
Acculturation
Not acculturated 43
Somewhat acculturated 31
Very acculturated 26
Language of testing
Spanish 83
English 17
Lifetime cigarette smoking (pack-years)
Never 46
> 0-5 33
> 5-15 13
> 15 8
Alcohol use in previous year (drinks per week)
<1 52
1-14 32
[greater than or equal to] 15 16
Lifetime problems with alcohol use
Never drank 21
Drank, no problems 50
Drank, had problems 29
Usually sleep [greater than or equal to] 7 hrs
Yes 79
No 21
20:20 vision
Left eye
Yes 70
No 30
Right eye
Yes 67
No 33
Ever had severe head injury
No 93
Yes 7
Ever had any neck or back injury
No 77
Yes 23
Hand pain
Preferred hand
No 82
Yes 18
Nonpreferred hand
No 88
Yes
(a) Table entries are column percentages except where indicated.
Many farmworkers had worked on more than one crop, so the sum of
fern, nursery, and citrus workers is greater than the total number
of farmworkers.
Table 2. Neurobehavioral test measures in controls and farmworkers
Controls
Test measures No. (a) Mean [ or -] SD
Cognitive function
Digit span forward 51 5.63 [ or -] 1.02
Digit span reverse 51 4.12 [ or -] 1.07
Symbol digit latency 49 2,232 [ or -] 774
Sensory function
Vibrotactile threshold PR digit 1 50 0.51 [ or -] 0.19
Vibrotactile threshold PR digit 4 50 0.55 [ or -] 0.23
Vibrotactile threshold NP digit 1 50 0.53 [ or -] 0.26
Vibrotactile threshold NP digit 4 50 0.53 [ or -] 0.28
Contrast sensitivity L eye 1.5 cpd 51 23.1 [ or -] 13.0
Contrast sensitivity L eye 3 cpd 51 35.0 [ or -] 36.4
Contrast sensitivity L eye 6 cpd 51 64.3 [ or -] 56.8
Contrast sensitivity L eye 12 cpd 51 42.5 [ or -] 37.5
Contrast sensitivity L eye 18 cpd 51 16.1 [ or -] 13.4
Contrast sensitivity R eye 1.5 cpd 51 21.1 [ or -] 9.7
Contrast sensitivity R eye 3 cpd 51 37.7 [ or -] 33.0
Contrast sensitivity R eye 6 cpd 51 63.8 [ or -] 53.3
Contrast sensitivity R eye 12 cpd 51 39.9 [ or -] 34.7
Contrast sensitivity R eye 18 cpd 51 13.8 [ or -] 11.0
Psychomotor function
Tapping PR 51 88.3 [ or -] 13.9
Tapping NP 51 80.0 [ or -] 10.9
Tapping alternating 50 46.8 [ or -] 15.1
Santa Ana PR 51 19.9 [ or -] 3.04
Santa Ana NP 51 18.0 [ or -] 2.88
Motor function
Grip strength 51 32.6 [ or -] 9.61
Balance
Postural sway length CON 1 51 37.0 [ or -] 5.66
Postural sway length CON 2 51 48.2 [ or -] 12.3
Postural sway length CON 3 51 48.0 [ or -] 9.17
Postural sway length CON 4 51 75.4 [ or -] 27.1
Postural sway area CON 1 51 2.78 [ or -] 1.70
Postural sway area CON 2 51 3.68 [ or -] 2.48
Postural sway area CON 3 51 4.63 [ or -] 1.99
Postural sway area CON 4 51 10.1 [ or -] 9.54
Farmworkers
Test measures No. (a) Mean [ or -] SD
Cognitive function
Digit span forward 285 4.74 [ or -] 0.99
Digit span reverse 285 3.52 [ or -] 1.00
Symbol digit latency 273 2,680 [ or -] 932
Sensory function
Vibrotactile threshold PR digit 1 281 0.56 [ or -] 0.33
Vibrotactile threshold PR digit 4 281 0.54 [ or -] 0.31
Vibrotactile threshold NP digit 1 279 0.48 [ or -] 0.29
Vibrotactile threshold NP digit 4 280 0.51 [ or -] 0.29
Contrast sensitivity L eye 1.5 cpd 287 21.5 [ or -] 14.3
Contrast sensitivity L eye 3 cpd 287 34.0 [ or -] 24.7
Contrast sensitivity L eye 6 cpd 287 66.4 [ or -] 58.6
Contrast sensitivity L eye 12 cpd 287 45.8 [ or -] 34.9
Contrast sensitivity L eye 18 cpd 287 16.1 [ or -] 12.4
Contrast sensitivity R eye 1.5 cpd 287 23.0 [ or -] 17.7
Contrast sensitivity R eye 3 cpd 287 36.3 [ or -] 24.9
Contrast sensitivity R eye 6 cpd 287 68.2 [ or -] 51.2
Contrast sensitivity R eye 12 cpd 287 50.5 [ or -] 36.0
Contrast sensitivity R eye 18 cpd 287 18.0 [ or -] 13.9
Psychomotor function
Tapping PR 284 79.4 [ or -] 14.7
Tapping NP 284 72.3 [ or -] 12.8
Tapping alternating 284 39.9 [ or -] 15.6
Santa Ana PR 287 18.0 [ or -] 3.49
Santa Ana NP 285 17.4 [ or -] 3.03
Motor function
Grip strength 287 33.8 [ or -] 10.7
Balance
Postural sway length CON 1 285 37.7 [ or -] 6.04
Postural sway length CON 2 285 51.9 [ or -] 13.6
Postural sway length CON 3 285 48.5 [ or -] 9.69
Postural sway length CON 4 285 78.8 [ or -] 23.1
Postural sway area CON 1 285 2.31 [ or -] 1.44
Postural sway area CON 2 285 3.85 [ or -] 2.55
Postural sway area CON 3 285 4.59 [ or -] 2.65
Postural sway area CON 4 285 9.44 [ or -] 4.99
Abbreviations: CON, condition; cpd, cycles per degree; L, left; NP,
nonpreferred hand; PR, preferred hand; Right.
(a) Data for one or more individuals were missing for each test.
Table 3. Base models for neurobehavioral test measures. (a)
Measure, (b) covariate Estimate (95% CI)
Digit span forward
Education, per year 0.78 (0.73 to 0.82)
Acculturation, moderate 0.76 (0.46 to 1.27)
Acculturation, high 0.84 (0.45 to 1.57)
Symbol digit latency
Age, per 10 years 221 (98 to 344)
Education, per year -97 (-119 to -75)
Acculturation, moderate -229 (-434 to -24)
Acculturation, high -323 (-570 to-76)
Usual sleep, [greater than or
equal to] 7 hrs -354 (-565 to -143)
Severe head injury, ever 286 (-26 to 599)
Vibrotactile threshold, PR digit 1
Age, per 10 years 0.05 (0.00 to 0.10)
Sex, female 0.07 (-0.02 to 0.16)
Height, per inch 0.01 (-0.00 to 0.02)
Visual contrast sensitivity, L eye 6 cpd
Age, 33-37 years 6.29 (-10.0 to 22.6)
Age, 38-43 years 14.8 (-1.57 to 31.3)
Age, 44-55 years 22.0 (4.37 to 39.6)
Sex, female 26.4 (14.4 to 38.5)
Visual acuity L eye, not 20/20 24.1 (11.1 to 37.0)
Tapping PR
Sex, female 11.5 (8.77 to 14.3)
Education, per year -1.34 (-1.63 to -1.05)
Santa Ana PR
Age, per 10 years 1.21 (0.71 to 1.72)
Education, per year -0.21 (-0.28 to -0.14)
Severe head injury, ever 1.72 (0.41 to 3.04)
Grip strength
Age, per 10 years 1.48 (0.45 to 2.51)
Sex, female 9.74 (7.90 to 11.6)
Height, per inch -1.15 (-1.42 to -0.88)
Hand pain 2.68 (0.80 to 4.55)
Postural sway, length CON 4
Age, 33-37 years -2.52 (-9.40 to 4.37)
Age, 38-43 years -1.59 (-8.53 to 5.36)
Age, 44-55 years 6.78 (-0.59 to 14.2)
Height, per inch 1.31 (0.50 to 2.13)
Weight, per 10 pounds -1.33 (-2.15 to -0.51)
Alcohol drinks per week, 1-14 -1.55 (-7.38 to 4.29)
Alcohol drinks per week, > 14 10.8 (3.11 to 18.5)
Abbreviations: CON, condition; cpd, cycles per degree; L, left; NP,
nonpreferred hand; PR, preferred hand; R, right.
(a) Results are ORs (95% CIs) for digit span and coefficients (95% CIs)
for other tests; the referent value is 1 for digit span and 0 for other
tests. Models for particular test measures included all variables
listed. In all cases, a higher value indicates worse performance.
(b) The same covariates were included in the base models for each
measure of a test.
Table 4. History of farm work in fern, nursery, and citrus workers. (a)
All Fern
farmworkers workers
Characteristics (n=288) (n=140)
Farm work (years)
1-9 26 15
10-20 50 55
21-41 25 30
Farm work in previous year
No 26 15
Yes 74 85
Farm work before age 14
No 84 86
Yes 16 14
Migrant farm work (years)
0 60 71
1-5 20 17
> 5 20 12
Fern work (months)
No fern work 51 --
[less than or equal to] 100 15 30
100-140 16 34
> 140 18 36
Lifetime bunches of ferns cut
No fern work 51 --
[less than or equal to] 350,000 17 35
350,001-600,000 16 34
> 600,000 15 31
Nursery work (months)
No nursery work 49 75
[less than or equal to] 10 16 9
11-48 16 11
> 48 18 6
Citrus work (months)
No citrus work 51 68
[less than or equal to] 10 17 14
10-42 16 11
> 42 15 8
Nursery Citrus
workers workers
Characteristics (n=147) (n=141)
Farm work (years)
1-9 31 19
10-20 46 43
21-41 22 38
Farm work in previous year
No 35 30
Yes 65 70
Farm work before age 14
No 78 78
Yes 22 22
Migrant farm work (years)
0 53 28
1-5 22 33
> 5 25 39
Fern work (months)
No fern work 76 68
[less than or equal to] 100 16 15
100-140 4 5
> 140 3 12
Lifetime bunches of ferns cut
No fern work 76 68
[less than or equal to] 350,000 15 16
350,001-600,000 5 6
> 600,000 4 11
Nursery work (months)
No nursery work -- 35
[less than or equal to] 10 32 21
11-48 32 23
> 48 36 21
Citrus work (months)
No citrus work 38 --
[less than or equal to] 10 22 35
10-42 23 33
> 42 16 31
(a) Table entries are column percentages. Controls, who had done farm
work for less than 1 month, are not included in the table. Fern,
nursery, and citrus workers were defined as those who had worked more
than 1 month in the specific type of agriculture. Many farmworkers
had worked on more than one crop, so the sum of fern, nursery, and
citrus workers is greater than the total number of farmworkers.
Table 5. Association of neurobehavioral performance with ever
having done farm work. (a)
Test measure Ever farm work
Cognitive function
Digit span forward 1.90 (1.02 to 3.53) **
Digit span reverse 1.28 (0.70 to 2.33)
Symbol digit latency -88.0 (-341 to 165)
Sensory function
Vibrotactile threshold PR digit 1 0.08 (-0.02 to 0.17)
Vibrotactile threshold PR digit 4 0.00 (-0.09 to 0.09)
Vibrotactile threshold NP digit 1 -0.02 (-0.11 to 0.07)
Vibrotactile threshold NP digit 4 0.01 (-0.08 to 0.10)
Contrast sensitivity L eye 1.5 cpd 2.52 (-1.70 to 6.73)
Contrast sensitivity L eye 3 cpd 3.12 (-4.76 to 11.0)
Contrast sensitivity L eye 6 cpd 4.34 (-12.2 to 20.9)
Contrast sensitivity L eye 12 cpd 0.70 (-8.89 to 10.3)
Contrast sensitivity L eye 18 cpd 1.53 (-1.77 to 4.84)
Contrast sensitivity R eye 1.5 cpd -0.94 (-5.92 to 4.05)
Contrast sensitivity R eye 3 cpd 3.87 (-3.76 to 11.5)
Contrast sensitivity R eye 6 cpd 1.16 (-13.1 to 15.4)
Contrast sensitivity R eye 12 cpd -5.97 (-15.3 to 3.36)
Contrast sensitivity R eye 18 cpd -2.72 (-6.25 to 0.80)
Psychomotor function
Tapping PR 4.13 (0.00 to 8.27) *
Tapping NP 3.81 (0.26 to 7.35) **
Tapping alternating 2.34 (-2.49 to 7.17)
Santa Ana PR 1.34 (0.29 to 2.39) **
Santa Ana NP -0.12 (-1.05 to 0.81)
Grip strength -0.46 (-2.49 to 1.57)
Balance
Postural sway length CON 1 0.98 (-0.74 to 2.70)
Postural sway length CON 2 3.86 (-0.15 to 7.88) *
Postural sway length CON 3 1.31 (-1.40 to 4.03)
Postural sway length CON 4 4.74 (-2.20 to 11.7)
Postural sway area CON 1 -0.39 (-0.83 to 0.06) *
Postural sway area CON 2 0.18 (-0.57 to 0.92)
Postural sway area CON 3 0.09 (-0.69 to 0.87)
Postural sway area CON 4 -0.38 (-2.18 to 1.42)
Test measure Ever fern work
Cognitive function
Digit span forward 2.54 (1.29 to 5.03) ***
Digit span reverse 1.45 (0.76 to 2.80)
Symbol digit latency 33.4 (-243 to 309)
Sensory function
Vibrotactile threshold PR digit 1 0.11 (0.00 to 0.21) **
Vibrotactile threshold PR digit 4 0.02 (-0.08 to 0.12)
Vibrotactile threshold NP digit 1 -0.02 (-0.11 to 0.08)
Vibrotactile threshold NP digit 4 0.04 (-0.06 to 0.14)
Contrast sensitivity L eye 1.5 cpd 2.57 (-1.98 to 7.12)
Contrast sensitivity L eye 3 cpd 3.17 (-5.33 to 11.7)
Contrast sensitivity L eye 6 cpd 1.74 (-16.1 to 19.6)
Contrast sensitivity L eye 12 cpd 1.36 (-8.99 to 11.7)
Contrast sensitivity L eye 18 cpd 0.88 (-2.68 to 4.45)
Contrast sensitivity R eye 1.5 cpd -0.16 (-5.54 to 5.21)
Contrast sensitivity R eye 3 cpd 4.66 (-3.58 to 12.9)
Contrast sensitivity R eye 6 cpd 2.03 (-13.4 to 17.4)
Contrast sensitivity R eye 12 cpd -8.01 (-18.1 to 2.05)
Contrast sensitivity R eye 18 cpd -3.24 (-7.05 to 0.56) *
Psychomotor function
Tapping PR 5.38 (0.87 to 9.89) **
Tapping NP 4.85 (0.98 to 8.71) **
Tapping alternating 2.57 (-2.70 to 7.85)
Santa Ana PR 2.29 (1.17 to 3.41) ***
Santa Ana NP 0.69 (-0.31 to 1.68)
Grip strength 0.41 (-1.78 to 2.60)
Balance
Postural sway length CON 1 0.59 (-1.26 to 2.44)
Postural sway length CON 2 5.95 (1.66 to 10.2) ***
Postural sway length CON 3 -0.76 (-3.62 to 2.11)
Postural sway length CON 4 5.94 (-1.53 to 13.4)
Postural sway area CON 1 -0.65 (-1.12 to -0.17) ***
Postural sway area CON 2 0.28 (-0.52 to 1.09)
Postural sway area CON 3 -0.50 (-1.32 to 0.33)
Postural sway area CON 4 -0.26 (-2.20 to 1.68)
Test measure Ever nursery work
Cognitive function
Digit span forward 1.84 (0.9 to 3.51) *
Digit span reverse 1.21 (0.65 to 2.25)
Symbol digit latency -148 (-409 to 112)
Sensory function
Vibrotactile threshold PR digit 1 0.06 (-0.04 to 0.16)
Vibrotactile threshold PR digit 4 0.00 (-0.10 to 0.10)
Vibrotactile threshold NP digit 1 -0.02 (-0.11 to 0.07)
Vibrotactile threshold NP digit 4 0.00 (-0.09 to 0.09)
Contrast sensitivity L eye 1.5 cpd 2.98 (-1.50 to 7.47)
Contrast sensitivity L eye 3 cpd 3.90 (-4.48 to 12.3)
Contrast sensitivity L eye 6 cpd 3.99 (-13.7 to 21.6)
Contrast sensitivity L eye 12 cpd 0.51 (-9.70 to 10.7)
Contrast sensitivity L eye 18 cpd 2.28 (-1.23 to 5.79)
Contrast sensitivity R eye 1.5 cpd -0.91 (-6.21 to 4.39)
Contrast sensitivity R eye 3 cpd 4.07 (-4.06 to 12.2)
Contrast sensitivity R eye 6 cpd 1.52 (-13.7 to 16.7)
Contrast sensitivity R eye 12 cpd -3.34 (-13.2 to 6.56)
Contrast sensitivity R eye 18 cpd -1.55 (-5.28 to 2.19)
Psychomotor function
Tapping PR 3.60 (-0.70 to 7.91)
Tapping NP 3.00 (-0.68 to 6.68)
Tapping alternating 1.59 (-3.44 to 6.61)
Santa Ana PR 0.89 (-0.18 to 1.96)
Santa Ana NP -0.41 (-1.37 to 0.54)
Grip strength -0.81 (-2.95 to 1.34)
Balance
Postural sway length CON 1 1.46 (-0.37 to 3.29)
Postural sway length CON 2 3.56 (-0.72 to 7.84)
Postural sway length CON 3 3.11 (0.28 to 5.95) **
Postural sway length CON 4 6.55 (-0.83 to 13.9) *
Postural sway area CON 1 -0.18 (-0.83 to 13.9) *
Postural sway area CON 2 0.20 (-0.60 to 1.00)
Postural sway area CON 3 0.37 (-0.46 to 1.20)
Postural sway area CON 4 -0.12 (-2.04 to 1.80)
Test measure Ever citrus
Cognitive function
Digit span forward 1.79 (0.92 to 3.46) *
Digit span reverse 1.36 (0.72 to 2.58)
Symbol digit latency -132 (-399 to 135)
Sensory function
Vibrotactile threshold PR digit 1 0.07 (-0.03 to 0.18)
Vibrotactile threshold PR digit 4 -0.01 (-0.11 to 0.09)
Vibrotactile threshold NP digit 1 -0.04 (-0.14 to 0.05)
Vibrotactile threshold NP digit 4 -0.02 (-0.11 to 0.08)
Contrast sensitivity L eye 1.5 cpd 2.93 (-1.62 to 7.48)
Contrast sensitivity L eye 3 cpd 1.76 (-6.75 to 10.3)
Contrast sensitivity L eye 6 cpd 7.00 (-10.9 to 24.9)
Contrast sensitivity L eye 12 cpd 2.39 (-7.97 to 12.7)
Contrast sensitivity L eye 18 cpd 1.87 (-1.70 to 5.44)
Contrast sensitivity R eye 1.5 cpd -1.66 (-7.04 to 3.72)
Contrast sensitivity R eye 3 cpd 3.29 (-4.96 to 11.5)
Contrast sensitivity R eye 6 cpd 1.17 (-14.3 to 16.6)
Contrast sensitivity R eye 12 cpd -6.13 (-16.2 to 3.96)
Contrast sensitivity R eye 18 cpd -1.89 (-5.69 to 1.91)
Psychomotor function
Tapping PR 3.45 (-0.98 to 7.87)
Tapping NP 2.96 (-0.83 to 6.75)
Tapping alternating 1.81 (-3.36 to 6.97)
Santa Ana PR 1.12 (0.00 to 2.23) **
Santa Ana NP -0.62 (-1.59 to 0.36)
Grip strength -0.99 (-3.17 to 1.19)
Balance
Postural sway length CON 1 1.53 (-0.30 to 3.37)
Postural sway length CON 2 4.50 (0.21 to 8.79) **
Postural sway length CON 3 2.80 (-0.07 to 5.67) *
Postural sway length CON 4 7.42 (0.04 to 14.8) *
Postural sway area CON 1 -0.24 (-0.71 to 0.24)
Postural sway area CON 2 0.36 (-0.44 to 1.16)
Postural sway area CON 3 0.42 (-0.41 to 1.25)
Postural sway area CON 4 0.30 (-1.61 to 2.22)
Abbreviations: CON, conditions; cpd, cycles per degree; L, left;
NP, nonpreferred hand; PR, preferred hand; R, right. (a) Results
are ORs (95% CIs) for digit span and coefficients (95% CIs) for
other tests. Farm work exposure variables were added individually
to the models shown in Table 3. Models for fern, nursery, and citrus
work were adjusted for ever having done other types of farm work.
The referenct for all comparisons is the control group; the value
is 1 for digit span and 0 for other tests. In all cases, a higher
value indicates worse performance.
* p < 0.10; ** p < 0.05; *** p < 0.01.
Table 6. Association of quantitative measures of farm work
with neurobehavioral performance. (a)
Digit span
Characteristics forward
Years of farm work
1-9 1.66 (0.83 to 3.34)
10-20 2.01 (1.03 to 3.92) **
21-41 2.31 (1.07 to 4.98) **
Trend p = 0.04
Years of farm work, participants with 6 or more years of education
1-9 1.73 (0.80 to to 3.78)
10-20 2.72 (1.25 to 5.91) **
21-41 4.33 (1.66 to 11.3) **
Trend p = 0.001
Years of farm work, stratified by current or former farm work (b)
Former, 1-9 years 1.74 (0.80 to 3.82)
Former, 10-41 years 2.63 (1.11 to 6.25) **
Current, 1-9 years 1.48 (0.61 to 3.60)
Current, 10-20 years 1.88 (0.93 to 3.79) *
Current, 21-41 years 1.99 (0.91 to 4.36) *
Months of fern work
Other farm work only 1.58 (0.83 to 3.00)
[less than or equal to] 100 3.52 (1.53 to 8.11) ***
101-140 2.62 (1.14 to 6.01) **
> 140 1.80 (0.81 to 4.02)
Bunches of ferns cut
Other farm work only 1.60 (0.84 to 3.04)
[less than or equal to] 350,000 3.56 (1.57 to 8.09) ***
350,001-600,000 2.97 (1.31 to 6.74) ***
> 600,000 1.60 (0.71 to 3.64)
Months of nursery work
Other farm work only 1.98 (1.00 to 3.92) **
[less than or equal to] 10 1.93 (0.86 to 4.3)
11-48 1.10 (0.50 to 2.38)
> 48 2.75 (1.28 to 5.91) ***
Months of citrus work
Other farm work only 2.02 (1.04 to 3.90) **
[less than or equal to] 9 1.81 (0.83 to 3.98)
10-42 1.93 (0.87 to 4.28)
> 42 1.59 (0.70 to 3.60)
Months of fern, nursery, or citrus work
Other farm work only 0.70 (0.24 to 2.43)
Fern [less than or equal to ] 100 2.88 (1.46 to 5.67) ***
Fern 101-140 2.00 (0.99 to 4.02) *
Fern [greater than or equal to ] 140 1.41 (0.72 to 2.76)
Nursery [less than or equal to] 10 1.26 (0.65 to 2.47)
Nursery 11-48 0.63 (0.32 to 1.24)
Nursery [greater than or equal to] 48 1.98 (1.03 to 3.81) **
Citrus [less than or equal to] 9 1.13 (0.59 to 2.13)
Citrus 10-42 1.13 (0.59 to 2.18)
Citrus [greater than or equal to] 42 1.08 (0.55 to 2.12)
Vibrotactile threshold,
Characteristics PR digit 1
Years of farm work
1-9 0.00 (-0.11 to 0.12)
10-20 0.08 (-0.02 to 0.19)
21-41 0.17 (0.05 to 0.28) ***
Trend p = 0.002
Years of farm work, participants with 6 or more years of education
1-9 0.00 (-0.13 to 0.12)
10-20 0.11 (-0.01 to 0.23) *
21-41 0.18 (0.02 to 0.33) ***
Trend p = 0.0007
Years of farm work, stratified by current or former farm work (b)
Former, 1-9 years -0.04 (-0.16 to 0.09)
Former, 10-41 years 0.01 (-0.13 to 0.14)
Current, 1-9 years 0.06 (-0.08 to 0.20)
Current, 10-20 years 0.12 (0.01 to 0.23) **
Current, 21-41 years 0.16 (0.04 to 0.28) ***
Months of fern work
Other farm work only 0.05 (-0.05 to 0.15)
[less than or equal to] 100 0.14 (0.00 to 0.27) **
101-140 0.07 (-0.06 to 0.20)
> 140 0.11 (-0.01 to 0.24) *
Bunches of ferns cut
Other farm work only 0.05 (-0.05 to 0.15)
[less than or equal to] 350,000 0.12 (0.00 to 0.25) *
350,001-600,000 0.09 (-0.04 to 0.22)
> 600,000 0.1 (-0.03 to 0.24)
Months of nursery work
Other farm work only 0.10 (-0.01 to 0.20) *
[less than or equal to] 10 0.07 (-0.05 to 0.20)
11-48 0.07 (-0.06 to 0.20)
> 48 0.04 (-0.09 to 0.16)
Months of citrus work
Other farm work only 0.08 (-0.02 to 0.18)
[less than or equal to] 9 0.07 (-0.06 to 0.19)
10-42 0.10 (-0.03 to 0.23)
> 42 0.05 (-0.08 to 0.18)
Months of fern, nursery, or citrus work
Other farm work only 0.24 (0.05 to 0.43) **
Fern [less than or equal to ] 100 0.11 (0.00 to 0.22) **
Fern 101-140 0.06 (-0.05 to 0.17)
Fern [greater than or equal to ] 140 0.10 (-0.01 to 0.21) *
Nursery [less than or equal to] 10 0.02 (-0.08 to 0.13)
Nursery 11-48 0.01 (-0.10 to 0.12)
Nursery [greater than or equal to] 48 0.01 (-0.11 to 0.11)
Citrus [less than or equal to] 9 0.02 (-0.09 to 0.13)
Citrus 10-42 0.06 (-0.04 to 0.17)
Citrus [greater than or equal to] 42 0.02 (-0.09 to 0.13)
Tapping
Characteristics PR
Years of farm work
1-9 3.01 (-1.64 to 7.66)
10-20 4.26 (-0.18 to 8.71) *
21-41 7.08 (1.86 to 12.3) ***
Trend p = 0.009
Years of farm work, participants with 6 or more years of education
1-9 2.49 (-3.03 to 8.01)
10-20 4.56 (-0.89 to 10.0)
21-41 8.88 (2.13 to 15.6) **
Trend p = 0.02
Years of farm work, stratified by current or former farm work (b)
Former, 1-9 years 1.81 (-3.43 to 7.04)
Former, 10-41 years 3.53 (-2.18 to 9.23)
Current, 1-9 years 4.92 (-0.96 to 10.8)
Current, 10-20 years 5.07 (0.40 to 9.74) **
Current, 21-41 years 6.91 (1.59 to 12.2) **
Months of fern work
Other farm work only 3.42 (-0.86 to 7.71)
[less than or equal to] 100 2.85 (-2.62 to 8.32)
101-140 5.55 (0.06 to 11.0) **
> 140 7.54 (2.26 to 12.8) ***
Bunches of ferns cut
Other farm work only 3.32 (-0.96 to 7.60)
[less than or equal to] 350,000 5.84 (0.46 to 11.2) **
350,001-600,000 2.66 (-2.73 to 8.04)
> 600,000 7.74 (2.29 to 13.2) ***
Months of nursery work
Other farm work only 4.88 (0.37 to 9.40) **
[less than or equal to] 10 3.62 (-1.73 to 8.96)
11-48 1.85 (-3.40 to 7.10)
> 48 5.04 (0.00 to 10.1) *
Months of citrus work
Other farm work only 4.74 (0.36 to 9.12) **
[less than or equal to] 9 4.02 (-1.28 to 9.32)
10-42 2.73 (-2.58 to 8.04)
> 42 3.61 (-1.83 to 9.06)
Months of fern, nursery, or citrus work
Other farm work only 3.72 (-4.01 to 11.4)
Fern [less than or equal to ] 100 0.85 (-3.57 to 5.27)
Fern 101-140 4.18 (-0.48 to 8.85) *
Fern [greater than or equal to ] 140 6.33 (1.91 to 10.8) ***
Nursery [less than or equal to] 10 1.81 (-2.67 to 6.28)
Nursery 11-48 0.38 (-4.18 to 4.93)
Nursery [greater than or equal to] 48 3.94 (-0.38 to 8.27) *
Citrus [less than or equal to] 9 0.60 (-3.73 to 4.93)
Citrus 10-42 -0.46 (-4.82 to 3.90)
Citrus [greater than or equal to] 42 1.44 (-2.99 to 5.88)
Santa Ana
Characteristics PR
Years of farm work
1-9 0.71 (-0.46 to 1.88)
10-20 1.45 (0.32 to 2.58) **
21-41 2.26 (0.98 to 3.53) ***
Trend p = 0.0002
Years of farm work, participants with 6 or more years of education
1-9 0.33 (-0.99 to 1.65)
10-20 1.72 (0.40 to 3.04) **
21-41 2.55 (0.94 to 4.16) ***
Trend p = 0.0002
Years of farm work, stratified by current or former farm work (b)
Former, 1-9 years -0.08 (-1.39 to 1.22)
Former, 10-41 years 1.43 (0.02 to 2.83) **
Current, 1-9 years 1.96 (0.50 to 3.42) ***
Current, 10-20 years 1.71 (0.54 to 2.89) ***
Current, 21-41 years 2.45 (1.16 to 3.73) ***
Months of fern work
Other farm work only 0.76 (-0.31 to 1.82)
[less than or equal to] 100 1.72 (0.38 to 3.07) **
101-140 2.41 (1.04 to 3.77) ***
> 140 2.74 (1.43 to 4.05) ***
Bunches of ferns cut
Other farm work only 0.73 (-0.33 to 1.79)
[less than or equal to] 350,000 1.56 (0.25 to 2.87) **
350,001-600,000 2.89 (1.56 to 4.21) ***
> 600,000 2.48 (1.13 to 3.84) ***
Months of nursery work
Other farm work only 2.07 (0.93 to 3.20) ***
[less than or equal to] 10 0.59 (-0.73 to 1.91)
11-48 0.42 (-0.88 to 1.72)
> 48 1.52 (0.27 to 2.77) **
Months of citrus work
Other farm work only 1.56 (0.45 to 2.68) ***
[less than or equal to] 9 1.31 (0.00 to 2.62) **
10-42 1.4 (0.06 to 2.74) **
> 42 0.57 (-0.79 to 1.93)
Months of fern, nursery, or citrus work
Other farm work only -0.01 (-1.90 to 1.88)
Fern [less than or equal to ] 100 1.28 (0.20 to 2.35) **
Fern 101-140 1.87 (0.72 to 3.01) ***
Fern [greater than or equal to ] 140 2.17 (1.09 to 3.25) ***
Nursery [less than or equal to] 10 -0.44 (-1.52 to 0.64)
Nursery 11-48 -0.73 (-1.83 to 0.36)
Nursery [greater than or equal to] 48 0.62 (-0.43 to 1.67)
Citrus [less than or equal to] 9 0.49 (-0.54 to 1.51)
Citrus 10-42 0.65 (-0.41 to 1.71)
Citrus [greater than or equal to] 42 0.11 (-0.97 to 1.19)
Postural sway,
Characteristics length CON 4
Years of farm work
1-9 3.07 (-0.46 to 1.88)
10-20 4.46 (-3.14 to 12.1)
21-41 6.59 (-1.80 to 15.0)
Trend p = 0.11
Years of farm work, participants with 6 or more years of education
1-9 3.34 (-6.92 to 13.6)
10-20 6.28 (-3.50 to 16.1)
21-41 14.4 (1.94 to 26.8) **
Trend p = 0.06
Years of farm work, stratified by current or former farm work (b)
Former, 1-9 years 1.03 (-8.45 to 10.5)
Former, 10-41 years 10.8 (0.82 to 20.8) **
Current, 1-9 years 5.83 (-4.62 to 16.3)
Current, 10-20 years 3.06 (-4.82 to 10.9)
Current, 21-41 years 5.75 (-2.70 to 14.2)
Months of fern work
Other farm work only 3.57 (-3.83 to 11.0)
[less than or equal to] 100 8.49 (-0.94 to 17.9) *
101-140 8.82 (-0.42 to 18.1) *
> 140 1.02 (-8.04 to 10.1)
Bunches of ferns cut
Other farm work only 3.58 (-3.82 to 11.0)
[less than or equal to] 350,000 9.53 (0.40 to 18.7) **
350,001-600,000 6.91 (-2.35 to 16.2)
> 600,000 0.93 (-8.43 to 10.3)
Months of nursery work
Other farm work only 2.70 (-4.80 to 10.2)
[less than or equal to] 10 6.38 (-2.77 to 15.5)
11-48 2.96 (-6.21 to 12.1)
> 48 9.94 (-0.97 to 18.9) **
Months of citrus work
Other farm work only 1.84 (-5.64 to 9.32)
[less than or equal to] 9 7.94 (-1.00 to 16.9) *
10-42 7.56 (-1.63 to 16.8)
> 42 6.64 (-2.75 to 16.0)
Months of fern, nursery, or citrus work
Other farm work only 5.44 (-8.41 to 19.3)
Fern [less than or equal to ] 100 7.00 (-0.72 to 14.7) *
Fern 101-140 10.4 (2.44 to 18.3) **
Fern [greater than or equal to ] 140 1.85 (-5.92 to 9.61)
Nursery [less than or equal to] 10 3.95 (-3.94 to 11.8)
Nursery 11-48 -0.18 (-8.22 to 7.86)
Nursery [greater than or equal to] 48 8.50 (-0.69 to 16.3) **
Citrus [less than or equal to] 9 6.59 (-0.90 to 14.1) *
Citrus 10-42 6.10 (-1.66 to 13.9)
Citrus [greater than or equal to] 42 6.70 (-1.14 to 14.5) *
Abbreviations: CON, condition; PR, preferred hand.
(a) Results are ORs (95% CIs) for digit span and coefficients (95% CIs)
for other tests. Farm work exposure variables were added to the models
shown in Table 3. The referent for all comparisons is the control
group; the value is 1 for digit span and 0 for other tests. In all
cases, a higher value indicates worse performance.
(b) Current farmworkers had done farm work in the year before testing,
whereas former farmworkers had not.
* p < 0.10; ** p < 0.05; *** p < 0.01.
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