Background
Methods
Parent study population
Ancillary study population
Data and measurement
Ancillary survey administration
Analysis
Results
Sample characteristics
Characteristics | $2 incentive %(n) | $5 incentive %(n) | p-value |
---|---|---|---|
Age* | |||
< 50 | 34.29 (228) | 30.32 (201) | 0.1924 |
50-75 | 33.53 (223) | 33.18 (220) | 0.8867 |
> 75 | 32.18 (214) | 36.50 (242) | 0.1898 |
Race*
| |||
Caucasian | 68.57 (456) | 68.78 (456) | 1.000 |
African American | 15.79 (105) | 17.65 (117) | 0.4206 |
Other | 15.64 (104) | 13.57 (90) | 0.3148 |
Sex*
| |||
Female | 18.95 (126) | 13.88 (92) | 0.0213 |
Male | 81.05 (539) | 86.12 (571) | 0.3368 |
Education**
| |||
Grade 11 or less | 15.96 (64) | 21.32 (87) | 0.0612 |
High school grad | 30.42 (122) | 33.58 (137) | 0.8687 |
Some college/tech deg | 33.92 (136) | 27.21 (111) | 0.1117 |
College grad | 14.21 (57) | 13.24 (54) | 0.7758 |
Post grad (MS, PhD) | 5.49 (22) | 4.66 (19) | 0.6394 |
Income***
| |||
Under $20,000 | 50.76 (201) | 50.00 (192) | 0.6498 |
$20,000-40,000 | 31.31 (124) | 31.25 (244) | 0.7979 |
$40,000-$60,000 | 10.86 (43) | 11.98 (46) | 0.7505 |
Over $60,000 | 7.07 (28) | 6.77 (26) | 0.7855 |
Marital Status*
| |||
Married/Living with Someone | 54.44 (362) | 54.75 (363) | 0.9704 |
Not Married | 45.56 (303) | 45.25 (300) | 0.9028 |
Charlson comorbidity score*
| |||
0 | 46.17 (307) | 42.23 (280) | 0.2651 |
1 | 20.30 (135) | 22.47 (284) | 0.4061 |
2+ | 33.53 (223) | 35.29 (234) | 0.6069 |
Mental health diagnoses*
| |||
No mental health diagnosis | 46.32 (308) | 47.66 (316) | 0.7488 |
Substance abuse only | 8.72 (58) | 8.75 (58) | 1.000 |
Psychiatric only | 28.27 (188) | 26.85 (178) | 0.6012 |
Dual diagnosis | 16.69 (111) | 16.74 (111) | 1.000 |
Rural/Urban Status*
| |||
Urban | 94.89 (631) | 90.80 (602) | 0.4089 |
Rural | 5.11 (34) | 9.20 (61) | 0.0056 |
Response rates
First Mailing/Reminder postcard | Final Response | |||||||
---|---|---|---|---|---|---|---|---|
$2 | $5 | Unadjusted p-value* | Adjusted odds of responding with $5 incentive vs. $2 incentive ** | $2 | $5 | p-value* | Adjusted odds of responding with $5 incentive vs. $2 incentive** | |
Overall Response Rate (Cumulative) | 47.67% N = 317 | 57.77% N = 383 | 0.0002 |
1.50 (1.21-1.86)
| 65.41% N = 435 | 67.27% N = 446 | 0.4741 | 1.09 (0.87-1.36) |
Age
| 0.0007 | 0.7525 | ||||||
< 50 | 32.02% | 41.29% |
1.49 (1.01-2.22)
| 49.56% | 50.25% | 1.03 (0.70-1.50) | ||
50-75 | 54.71% | 62.73% | 1.39 (0.95-2.04) | 71.30% | 72.73% | 1.07 (0.71-1.63) | ||
> 75 | 57.01% | 66.94% |
1.53 (1.04-2.23)
| 76.17% | 76.45% | 1.02 (0.66-1.57) | ||
Race
| 0.0002 | 0.6142 | ||||||
Caucasian | 58.33% | 68.42% |
1.55 (1.18-2.03)
| 78.07% | 78.07% | 1.00 (0.73-1.37) | ||
African American | 30.48% | 44.44% |
1.83 (1.05-3.17)
| 52.38% | 56.41% | 1.77 (0.69-2.00) | ||
Other | 18.27% | 21.11% | 1.20 (0.59-2.43) | 23.08% | 26.67% | 1.21 (0.63-2.33) | ||
Sex
| 0.0008 | 0.6642 | ||||||
Female | 31.75% | 41.30% | 1.51 (0.86-2.65) | 56.35% | 51.09% | .081 (0.47-1.39) | ||
Male | 51.39% | 60.42% |
1.44 (1.14-1.83)
| 67.53% | 69.88% | 1.12 (0.87-1.44) | ||
Marital Status
| 0.0002 | 0.4799 | ||||||
Married/Living with someone | 53.04% | 69.70% |
2.04 (1.50-2.76)
| 72.38% | 76.58% | 1.25 (0.89-1.74) | ||
Not Married | 41.25% | 43.33% | 1.09 (0.79-1.50) | 57.10% | 56.00% | 0.96 (0.69-1.32) | ||
Charlson Comorbidity Score
| 0.0003 | 0.5408 | ||||||
0 | 43.97% | 52.86% |
1.43 (1.03-1.98)
| 60.26% | 63.21% | 1.13 (0.81-1.58) | ||
1 | 44.44% | 29.23% | 1.57 (0.98-2.51) | 64.44% | 34.86% | 1.09 (0.67-1.78) | ||
2+ | 54.71% | 64.96% |
1.53 (1.05-2.24)
| 73.09% | 72.65% | 0.98 (0.65-1.48) | ||
Mental health diagnoses
| 0.0003 | 0.4929 | ||||||
No Mental Health Diagnosis | 54.55% | 62.66% |
1.40 (1.02-1.92)
| 70.78% | 72.47% | 1.09 (0.77-1.54) | ||
Substance abuse only | 41.38% | 58.62% | 2.01 (0.96-4.20) | 60.34% | 68.97% | 1.46 (0.68-3.14) | ||
Psychiatric only | 43.09% | 55.62% |
1.66 (1.10-2.50)
| 64.89% | 64.04% | 0.96 (0.63-1.48) | ||
Dual diagnosis | 39.64% | 46.85% | 1.34 (0.79-2.29) | 54.05% | 56.76% | 1.12 (0.66-1.89) | ||
Rural/Urban Status
| 0.0007 | 0.6519 | ||||||
Urban | 46.43% | 55.98% |
1.47 (1.17-1.84)
| 64.82% | 65.45% | 1.03 (0.81-1.30) | ||
Rural | 70.59% | 75.41% | 1.28 (0.50-3.27) | 76.47% | 85.25% | 1.78 (0.61-5.14) |
$2 condition | $5 condition | |
---|---|---|
First Mailing-total cost per participant*
| $5.25 | $8.25 |
First mailing response rate | 47.67% | 57.77% |
Total cost/returned survey ($) | $11.01 | $14.28 |
Second Mailing-total cost per participant**
| $2.40 | $2.40 |
Second mailing response rate | 33.91% | 22.50% |
Total cost/returned survey ($) | $7.08 | $10.67 |
Final Response
| ||
Cumulative response rate | 65.41% | 67.27% |
Total cost/returned survey ($) | $9.95 | $13.77 |
$2 incentive | $5 Incentive | ||||||
---|---|---|---|---|---|---|---|
Characteristics | Ancillary study population | $2 incentive population | 1st Mailing | 2ndMailing | $5 incentive population | 1stMailing | 2ndMailing |
(N = 1328) | (N = 665) | (N = 317) | (N = 435) | (N = 663) | (N = 383) | (N = 446) | |
Age
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< 50 | 32.30 (429) | 34.29 (228) | 23.03 (73) | 25.98 (113) | 30.32 (201) | 21.67 (83) | 22.65 (101) |
50-75 | 33.36 (443) | 33.53 (223) | 38.49 (122) | 36.55 (159) | 33.18 (220) | 36.03 (138) | 35.87 (160) |
> 75 | 34.34 (456) | 32.18 (214) | 38.49 (122) | 37.47 (163) | 36.50 (242) | 42.30 (162) | 41.48 (185) |
Race
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Caucasian | 68.67 (912) | 68.57 (456) | 83.91 (266) | 81.84 (356) | 68.78 (456) | 81.46 (312) | 79.82 (356) |
African American | 16.72 (222) | 15.79 (105) | 10.09 (32) | 12.64 (55) | 17.65 (117) | 13.58 (52) | 14.80 (66) |
Other | 14.61 (194) | 15.64 (104) | 5.99 (19) | 5.52 (24) | 13.57 (90) | 4.96 (19) | 5.38 (24) |
Sex
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Female | 16.42 (218) | 18.95 (126) | 12.62 (40) | 16.32 (71) | 13.88 (92) | 9.92 (38) | 10.54 (47) |
Male | 83.58 (1110) | 81.05 (539) | 87.38 (277) | 83.68 (364) | 86.12 (571) | 90.08 (345) | 89.46 (399) |
Marital Status
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x
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Married/Living with Someone | 54.59 (725) | 54.44 (362) | 60.57 (192) | 60.23 (262) | 54.75 (363) | 66.06 (253) | 62.33 (278) |
Not Married | 45.41 (603) | 45.56 (303) | 39.43 (125) | 39.77 (173) | 45.25 (300) | 33.94 (130) | 37.67 (168) |
Charlson comorbidity score
| |||||||
0 | 44.20 (587) | 46.17 (307) | 42.59 (135) | 42.53 (185) | 42.23 (280) | 38.64 (148) | 39.69 (177) |
1 | 21.39 (284) | 20.30 (135) | 18.93 (60) | 20.00 (87) | 22.47 (284) | 21.67 (83) | 22.20 (99) |
2+ | 34.41 (457) | 33.53 (223) | 38.49 (122) | 37.47 (163) | 35.29 (234) | 39.69 (152) | 38.12 (170) |
Mental health diagnoses
| |||||||
No mental health diagnosis | 46.99 (624) | 46.32 (308) | 53.00 (168) | 50.11 (218) | 47.66 (316) | 51.70 (198) | 51.35 (229) |
Substance abuse only | 8.73 (116) | 8.72 (58) | 7.57 (24) | 8.05 (35) | 8.75 (58) | 8.88 (34) | 8.97 (40) |
Psychiatric only | 27.56 (366) | 28.27 (188) | 25.55 (81) | 28.05 (122) | 26.85 (178) | 25.85 (99) | 25.56 (114) |
Dual diagnosis | 16.72 (222) | 16.69 (111) | 13.88 (44) | 13.79 (60) | 16.74 (111) | 13.58 (52) | 14.13 (63) |
Rural/Urban Status
|
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Urban | 92.85 (1233) | 94.89 (631) | 92.43 (293) | 94.02 (409) | 90.80 (602) | 87.99 (337) | 88.34 (394) |
Rural | 7.15 (95) | 5.11 (34) | 7.57 (24) | 5.98 (26) | 9.20 (61) | 12.01 (46) | 11.66 (52) |