, Hyun-Jin Goo2
, Hyebin Choi3
, Sin Kam4
, Jong-Yeon Kim4
1Daegu Center for Infectious Diseases Control and Prevention, Daegu, Korea
2Department of Medical Administration, Taegu Science University, Daegu, Korea
3Ministry of Health and Welfare Bugok National Hospital, Changnyeong, Korea
4Department of Preventive Medicine, Kyungpook National University School of Medicine, Daegu, Korea
Copyright © 2026 The Korean Society for Preventive Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Conflict of Interest
The authors have no conflicts of interest associated with the material presented in this paper.
Funding
None.
Acknowledgements
None.
Author Contributions
Conceptualization: Hong H, Kim JY. Data curation: Hong H, Goo HJ, Kim JY. Formal analysis: Hong H, Goo HJ, Kim JY. Funding acquisition: None. Methodology: Hong H, Kam S, Kim JY. Writing – original draft: Hong H, Goo HJ, Choi H, Kim JY. Writing – review & editing: Kam S, Kim JY.
| Characteristics | Categories | Total | No screening | Screening | p-value2 |
|---|---|---|---|---|---|
| Age (y) | 58.4±0.3 | 59.0±0.5 | 58.2±0.4 | <0.001 | |
| Sex | Male | 1771 (100) | 558 (52.5) | 1213 (40.1) | <0.001 |
| Female | 2400 (100) | 607 (47.5) | 1793 (59.9) | ||
| Education level | Elementary or less | 864 (100) | 277 (34.6) | 587 (65.4) | <0.001 |
| Middle school | 519 (100) | 155 (29.5) | 364 (70.5) | ||
| High school | 1381 (100) | 412 (30.6) | 969 (69.4) | ||
| College or higher | 1407 (100) | 321 (23.6) | 1085 (76.4) | ||
| Marital status | Married | 3198 (100) | 807 (25.5) | 2391 (74.5) | <0.001 |
| Unmarried | 973 (100) | 358 (38.5) | 615 (61.5) | ||
| Residential area | Urban | 3247 (100) | 868 (27.3) | 2379 (72.7) | 0.012 |
| Rural | 924 (100) | 297 (33.6) | 627 (66.4) | ||
| Economic activity | Employed | 2479 (100) | 682 (57.4) | 1797 (60.3) | 0.012 |
| Unemployed | 1653 (100) | 507 (42.6) | 1185 (39.7) | ||
| Chronic disease | Yes | 2564 (100) | 701 (28.0) | 1863 (72.0) | 0.406 |
| No | 1607 (100) | 464 (29.3) | 1143 (70.7) | ||
| Smoking status | Non-smoker | 2546 (100) | 633 (25.3) | 1913 (74.7) | <0.001 |
| Ex-smoker | 1023 (100) | 278 (26.7) | 745 (73.3) | ||
| Current smoker | 602 (100) | 254 (41.7) | 348 (58.3) | ||
| Physical activity | Practicing | 1716 (100) | 417 (24.6) | 1299 (75.4) | <0.001 |
| Non-practicing | 2455 (100) | 748 (31.4) | 1707 (68.6) | ||
| Self-rated health | Poor | 849 (100) | 272 (32.0) | 577 (68.0) | 0.061 |
| Fair | 2077 (100) | 557 (27.1) | 1520 (72.9) | ||
| Good | 1245 (100) | 336 (28.5) | 909 (71.5) | ||
| Income quintile | Q1 (lowest) | 793 (100) | 292 (40.1) | 501 (59.9) | <0.001 |
| Q2 | 840 (100) | 265 (31.7) | 575 (68.3) | ||
| Q3 | 838 (100) | 227 (27.2) | 611 (72.8) | ||
| Q4 | 853 (100) | 201 (24.1) | 652 (75.9) | ||
| Q5 (highest) | 847 (100) | 180 (20.7) | 667 (79.3) | ||
| Health literacy score3 | 29.4±0.1 | 28.5±0.2 | 29.8±0.1 | <0.001 | |
| Alcohol consumption frequency | No consumption | 1440 (100) | 431 (31.1) | 1009 (66.9) | 0.090 |
| <1 time/mo | 752 (100) | 189 (26.1) | 563 (73.9) | ||
| 1 time/mo | 442 (100) | 118 (27.2) | 324 (72.8) | ||
| 2–4 times/mo | 775 (100) | 205 (27.4) | 570 (72.6) | ||
| ≥2 times/wk | 762 (100) | 222 (28.3) | 540 (71.7) |
Values are presented as number (weighted %) or weighted mean±standard error based on the complex sampling design; Weighted using stratification, clustering, and sampling weights.
1 Cancer screening refers to participation within the previous 2 years.
2 From chi-square tests (categorical variables) and analysis of variance (continuous variables).
3 Health literacy scores range from 10 to 40 (higher=better).
All coefficients are unstandardized; Analyses used complex-sample mediation models with stratification (192 strata), clustering, and sampling weights; All models were adjusted for covariates including sex, education level, residential area, marital status, employment status, chronic disease, self-rated health, smoking status, physical activity, and alcohol frequency; Conditional indirect effects are presented in Table 4 (Johnson-Neyman analysis).
SE, standard error; CI, confidence interval; LL, lower limit; UL, upper limit.
| Age (y) | Effect | SE | 95% CI | p-value | |
|---|---|---|---|---|---|
| LL | UL | ||||
| 40 | −0.076 | 0.152 | −0.375 | 0.222 | 0.616 |
| 50 | 0.092 | 0.096 | −0.096 | 0.281 | 0.338 |
| 54 | 0.160 | 0.083 | −0.003 | 0.323 | 0.055 |
| 54.21 | 0.122 | 0.063 | 0.000 | 0.244 | 0.050 |
| 55 | 0.177 | 0.081 | 0.017 | 0.336 | 0.030 |
| 60 | 0.261 | 0.083 | 0.099 | 0.423 | 0.002 |
| 70 | 0.429 | 0.126 | 0.182 | 0.677 | <0.001 |
| 80 | 0.598 | 0.191 | 0.223 | 0.973 | <0.001 |
Effects represent the conditional effect of income on health literacy at different ages, estimated using complex-sample mediation models with stratification, clustering, and sampling weights; All models were adjusted for sex, education level, residential area, marital status, employment status, chronic disease, self-rated health, smoking status, physical activity, and alcohol frequency.
SE, standard error; CI, confidence interval; LL, lower limit; UL, upper limit.
1 Johnson-Neyman threshold: Age 54.2 years represents a model- and data-dependent approximation; Different populations or model specifications may yield different threshold estimates; For presentation clarity, conditional effects are shown at key ages with the critical threshold explicitly noted; Effects were considered significant when the 95% CIs excluded zero.
| Age (y) | Indirect effect1 | Total effect1 | Indirect NNB (95% CI)2 | Total NNB (95% CI)3 | Proportion mediated (%)4 |
|---|---|---|---|---|---|
| 40–49 | 0.0002 | 0.1513 | 24 139 (778, 82 849) | 33 (23, 56) | 0.1 |
| 50–59 | 0.0046 | 0.1557 | 1084 (523, 16 645) | 32 (23, 53) | 2.9 |
| 60–69 | 0.0090 | 0.1601 | 554 (308, 2734) | 31 (22, 51) | 5.6* |
| ≥70 | 0.0133 | 0.1645 | 372 (204, 2092) | 30 (22, 49) | 8.1** |
All analyses controlled for sex, education level, residential area, marital status, economic activity, chronic disease, self-rated health, smoking status, alcohol consumption, and physical activity, with stratification, clustering, and sampling weights applied.
NNB, number needed to benefit; CI, confidence interval.
1 Effects are in log-odds units per one-quintile increase in household income; Total effect=direct effect of income + indirect effect through the health literacy pathway.
2 Indirect NNB was calculated using the average marginal effect method: NNB=1/[β×p (1–p)], where β is the log-odds coefficient and p is the baseline cancer screening rate (72.5%); The NNB represents the number of individuals requiring income support to yield one additional cancer screening participation through the health literacy mediation pathway; not significant (p>0.05).
3 Total NNB represents the number of individuals requiring income support to produce one additional screening participation through all pathways (direct+indirect).
4 Proportion mediated=(Indirect effect/Total effect)×100, representing the percentage of the total income effect attributable to health literacy mediation; Mediation was statistically significant for age groups [60, 70) and ≥70, accounting for 5.6% and 8.1% of the total effect, respectively.
* p<0.05,
** p<0.01 indicate statistical significance of the mediation pathway based on whether the 95% CI of the indirect effect excludes zero.
| Characteristics | Categories | Total | No screening | Screening | p-value |
|---|---|---|---|---|---|
| Age (y) | 58.4±0.3 | 59.0±0.5 | 58.2±0.4 | <0.001 | |
| Sex | Male | 1771 (100) | 558 (52.5) | 1213 (40.1) | <0.001 |
| Female | 2400 (100) | 607 (47.5) | 1793 (59.9) | ||
| Education level | Elementary or less | 864 (100) | 277 (34.6) | 587 (65.4) | <0.001 |
| Middle school | 519 (100) | 155 (29.5) | 364 (70.5) | ||
| High school | 1381 (100) | 412 (30.6) | 969 (69.4) | ||
| College or higher | 1407 (100) | 321 (23.6) | 1085 (76.4) | ||
| Marital status | Married | 3198 (100) | 807 (25.5) | 2391 (74.5) | <0.001 |
| Unmarried | 973 (100) | 358 (38.5) | 615 (61.5) | ||
| Residential area | Urban | 3247 (100) | 868 (27.3) | 2379 (72.7) | 0.012 |
| Rural | 924 (100) | 297 (33.6) | 627 (66.4) | ||
| Economic activity | Employed | 2479 (100) | 682 (57.4) | 1797 (60.3) | 0.012 |
| Unemployed | 1653 (100) | 507 (42.6) | 1185 (39.7) | ||
| Chronic disease | Yes | 2564 (100) | 701 (28.0) | 1863 (72.0) | 0.406 |
| No | 1607 (100) | 464 (29.3) | 1143 (70.7) | ||
| Smoking status | Non-smoker | 2546 (100) | 633 (25.3) | 1913 (74.7) | <0.001 |
| Ex-smoker | 1023 (100) | 278 (26.7) | 745 (73.3) | ||
| Current smoker | 602 (100) | 254 (41.7) | 348 (58.3) | ||
| Physical activity | Practicing | 1716 (100) | 417 (24.6) | 1299 (75.4) | <0.001 |
| Non-practicing | 2455 (100) | 748 (31.4) | 1707 (68.6) | ||
| Self-rated health | Poor | 849 (100) | 272 (32.0) | 577 (68.0) | 0.061 |
| Fair | 2077 (100) | 557 (27.1) | 1520 (72.9) | ||
| Good | 1245 (100) | 336 (28.5) | 909 (71.5) | ||
| Income quintile | Q1 (lowest) | 793 (100) | 292 (40.1) | 501 (59.9) | <0.001 |
| Q2 | 840 (100) | 265 (31.7) | 575 (68.3) | ||
| Q3 | 838 (100) | 227 (27.2) | 611 (72.8) | ||
| Q4 | 853 (100) | 201 (24.1) | 652 (75.9) | ||
| Q5 (highest) | 847 (100) | 180 (20.7) | 667 (79.3) | ||
| Health literacy score |
29.4±0.1 | 28.5±0.2 | 29.8±0.1 | <0.001 | |
| Alcohol consumption frequency | No consumption | 1440 (100) | 431 (31.1) | 1009 (66.9) | 0.090 |
| <1 time/mo | 752 (100) | 189 (26.1) | 563 (73.9) | ||
| 1 time/mo | 442 (100) | 118 (27.2) | 324 (72.8) | ||
| 2–4 times/mo | 775 (100) | 205 (27.4) | 570 (72.6) | ||
| ≥2 times/wk | 762 (100) | 222 (28.3) | 540 (71.7) |
| Variables | Categories (reference) | B | SE | OR (95% CI) |
|---|---|---|---|---|
| Household income quintile | Continuous (per 1 unit ↑) | 0.148 | 0.032 | 1.16 (1.09, 1.24) |
| Health literacy score | Continuous (per 1 point ↑) | 0.028 | 0.007 | 1.03 (1.01, 1.04) |
| Age | Continuous (per 1 year ↑) | 0.002 | 0.005 | 1.00 (0.99, 1.01) |
| Sex | Female (male) | 0.223 | 0.117 | 1.25 (0.99, 1.57) |
| Education | Middle school (≤elementary) | 0.242 | 0.143 | 1.27 (0.96, 1.69) |
| High school | 0.116 | 0.145 | 1.12 (0.84, 1.50) | |
| ≥College | 0.214 | 0.104 | 1.24 (1.01, 1.52) | |
| Residential area | Urban (rural) | −0.103 | 0.106 | 0.90 (0.73, 1.11) |
| Marital status | Married (unmarried) | 0.396 | 0.097 | 1.49 (1.23, 1.80) |
| Employment status | Employed (unemployed) | 0.165 | 0.086 | 1.18 (0.99, 1.40) |
| Chronic disease | Yes (no) | 0.206 | 0.084 | 1.23 (1.04, 1.45) |
| Self-rated health | Fair (good) | −0.189 | 0.096 | 0.83 (0.69, 1.00) |
| Poor (good) | −0.087 | 0.121 | 0.92 (0.72, 1.16) | |
| Smoking | Former (never) | −0.165 | 0.086 | 0.85 (0.72, 1.01) |
| Current (never) | −0.655 | 0.140 | 0.52 (0.39, 0.69) | |
| Aerobic physical activity | Yes (no) | 0.212 | 0.092 | 1.24 (1.03, 1.48) |
| Alcohol consumption frequency | <1 time/mo (no consumption) | 0.158 | 0.139 | 1.17 (0.89, 1.54) |
| 1 time/mo | 0.196 | 0.153 | 1.22 (0.90, 1.65) | |
| 2–4 times/mo | 0.146 | 0.129 | 1.16 (0.90, 1.49) | |
| ≥2 times/wk | 0.314 | 0.118 | 1.37 (1.09, 1.73) |
| Pathway | B | SE | 95% CI | p-value | |
|---|---|---|---|---|---|
| LL | UL | ||||
| Mediator variable model (Health literacy) | |||||
| Income→Health literacy (a1) | 0.234 | 0.080 | 0.077 | 0.390 | 0.004 |
| Age→Health literacy (a2) | −0.116 | 0.030 | −0.175 | −0.057 | <0.001 |
| Income×Age interaction (a3) | 0.017 | 0.008 | 0.002 | 0.032 | 0.026 |
| Outcome variable model (Cancer screening) | |||||
| Income→Cancer screening (c′) | 0.151 | 0.032 | 0.089 | 0.214 | <0.001 |
| Health literacy→Cancer screening (b) | 0.026 | 0.007 | 0.012 | 0.040 | 0.001 |
| Age→Cancer screening | 0.002 | 0.005 | −0.007 | 0.011 | 0.676 |
| Index of moderated mediation | |||||
| Age moderation index | 0.000438 | 0.000233 | 0.000020 | 0.000896 | 0.048 |
| Age (y) | Effect | SE | 95% CI | p-value | |
|---|---|---|---|---|---|
| LL | UL | ||||
| 40 | −0.076 | 0.152 | −0.375 | 0.222 | 0.616 |
| 50 | 0.092 | 0.096 | −0.096 | 0.281 | 0.338 |
| 54 | 0.160 | 0.083 | −0.003 | 0.323 | 0.055 |
| 54.2 |
0.122 | 0.063 | 0.000 | 0.244 | 0.050 |
| 55 | 0.177 | 0.081 | 0.017 | 0.336 | 0.030 |
| 60 | 0.261 | 0.083 | 0.099 | 0.423 | 0.002 |
| 70 | 0.429 | 0.126 | 0.182 | 0.677 | <0.001 |
| 80 | 0.598 | 0.191 | 0.223 | 0.973 | <0.001 |
| Age (y) | Indirect effect |
Total effect |
Indirect NNB (95% CI) |
Total NNB (95% CI) |
Proportion mediated (%) |
|---|---|---|---|---|---|
| 40–49 | 0.0002 | 0.1513 | 24 139 (778, 82 849) | 33 (23, 56) | 0.1 |
| 50–59 | 0.0046 | 0.1557 | 1084 (523, 16 645) | 32 (23, 53) | 2.9 |
| 60–69 | 0.0090 | 0.1601 | 554 (308, 2734) | 31 (22, 51) | 5.6 |
| ≥70 | 0.0133 | 0.1645 | 372 (204, 2092) | 30 (22, 49) | 8.1 |
Values are presented as number (weighted %) or weighted mean±standard error based on the complex sampling design; Weighted using stratification, clustering, and sampling weights. Cancer screening refers to participation within the previous 2 years. From chi-square tests (categorical variables) and analysis of variance (continuous variables). Health literacy scores range from 10 to 40 (higher=better).
All coefficients are unstandardized; Analyses were conducted using complex-sample logistic regression with stratification, clustering, and sampling weights; Model fit: Nagelkerke R2=0.083.
All coefficients are unstandardized; Analyses used complex-sample mediation models with stratification (192 strata), clustering, and sampling weights; All models were adjusted for covariates including sex, education level, residential area, marital status, employment status, chronic disease, self-rated health, smoking status, physical activity, and alcohol frequency; Conditional indirect effects are presented in SE, standard error; CI, confidence interval; LL, lower limit; UL, upper limit.
Effects represent the conditional effect of income on health literacy at different ages, estimated using complex-sample mediation models with stratification, clustering, and sampling weights; All models were adjusted for sex, education level, residential area, marital status, employment status, chronic disease, self-rated health, smoking status, physical activity, and alcohol frequency. SE, standard error; CI, confidence interval; LL, lower limit; UL, upper limit. Johnson-Neyman threshold: Age 54.2 years represents a model- and data-dependent approximation; Different populations or model specifications may yield different threshold estimates; For presentation clarity, conditional effects are shown at key ages with the critical threshold explicitly noted; Effects were considered significant when the 95% CIs excluded zero.
All analyses controlled for sex, education level, residential area, marital status, economic activity, chronic disease, self-rated health, smoking status, alcohol consumption, and physical activity, with stratification, clustering, and sampling weights applied. NNB, number needed to benefit; CI, confidence interval. Effects are in log-odds units per one-quintile increase in household income; Total effect=direct effect of income + indirect effect through the health literacy pathway. Indirect NNB was calculated using the average marginal effect method: NNB=1/[β× Total NNB represents the number of individuals requiring income support to produce one additional screening participation through all pathways (direct+indirect). Proportion mediated=(Indirect effect/Total effect)×100, representing the percentage of the total income effect attributable to health literacy mediation; Mediation was statistically significant for age groups [60, 70) and ≥70, accounting for 5.6% and 8.1% of the total effect, respectively.