Figure 1
Study Flow chart.
Abbreviations: CRC: Colorectal cancer, EA: East Azerbaijan, GP: General practitioner.
Table 1
Baseline characteristic of study population, all variables stated as N(%)1.
| Characteristics2 | Cases (n = 135) | Controls (270) | P-value |
|---|---|---|---|
| Age (years) at index date | 0.21 | ||
| <40 | 9(6.7) | 24(8.9) | |
| 40–49 | 46(34.7) | 71(26.2) | |
| 50–59 | 73(54.1) | 145(53.7) | |
| ≥60 | 7(5.2) | 30(11.1) | |
| BMI | 0.68 | ||
| <25.0 | 39(28.9) | 94(34.8) | |
| 25–29.9 | 47(34.8) | 86(31.9) | |
| ≥30 | 43(31.9) | 65(24.1) | |
| Physical Activity | 0.13 | ||
| Normal | 80(63.5) | 188(70.4) | |
| Medium | 35(27.8) | 66(24.7) | |
| Intensive | 11(8.7) | 13(4.9) | |
| Smoking status | 0.38 | ||
| Never | 120(88.9) | 246(91.1) | |
| Past | 6(4.4) | 13(4.90) | |
| Current | 1(0.7) | 8(3.0) | |
| Alcohol3 | 0.48 | ||
| Never | 94(98.9) | 260(99.6) | |
| Current | 1(1.1) | 1(0.4) | |
| Folic acid supplement intake | 0.52 | ||
| No intake | 101(74.8) | 204(75.5) | |
| In past | 31(23.0) | 65(24.1) | |
| <5 years intake | 21(15.6) | 51(18.8) | |
| ≥5 years intake | 10 (7.4) | 14(5.2) | |
| Family history of cancer | 0.11 | ||
| No | 98(74.8) | 220(81.8) | |
| Yes | 33(25.2) | 49(18.2) | |
| Hypertension | 33(24.4) | 121(44.8) | 0.00 |
| Diabetes | 10(7.4) | 19(7.0) | 0.89 |
| GI discomfort | 29(21.5) | 26(9.6) | 0.00 |
| History of change in weight4 | 0.00 | ||
| Yes | 48(35.5) | 22(10.37) | |
| No | 72(64.4) | 242(89.6) | |
| Vitamin D supplement intake | 0.00 | ||
| No history of intake | 68(51.5) | 46(17.0) | |
| History of intake in past | 64(48.5) | 224(82.9) | |
| <5 years intake | 29(22.0) | 40(14.8) | |
| ≥5 years intake | 35(26.5) | 184(68.1) |
[i] 1 Q square test was applied to obtain the results.
2 Missing values (n, %), BMI (3, 0.1), Physical activity (12, 3.0), Smoking (11, 2.7), Alcohol (11, 2.7), Folic acid supplement intake (4, 1.0), Family history of cancer (5, 1.2), Hypertension (12, 3.0), Vitamin D intake (3, 0.7).
3 Past alcohol intake was not applicable to any of the participants.
4 Defined as >10% change (both increase and decrease) in body weight within study period.
Abbreviations: BMI, body mass index; GI, gastrointestinal.
Table 2
Association between folic acid supplememnt intake and colorectal cancer risk1.
| Folic acid Supplementation | Cases/control (n) | OR (95% CI)2 |
|---|---|---|
| Intake status in past | ||
| No history of intake | 101/204 | ref. |
| History of folic acid intake | 31/65 | 0.95 (0.59 to 1.53) |
| No history of intake | 101/204 | ref. |
| <5 yrs intake | 21/51 | 0.79 (0.45 to 1.39) |
| ≥5 yrs intake | 10/14 | 1.09 (0.52 to 2.26) |
| Classification by tumour site | ||
| No history of intake | 101/204 | ref. |
| Colon (with history of folate intake) | 23/65 | 1.28 (0.70 to 2.14) |
| Rectum (with history of folate intake) | 8/65 | 0.71 (0.33 to1.53) |
[i] 1 Adjusted for matching variables including age and villages.
2 Overall P-Value >0.05.
Table 3
Multivariate analyses comparing relative risks for colorectal cancer in relation to folic acid supplement intake, using varying criteria for definition of exposure and inclusion of adjustment variables.
| Sensitivity analysis | Exposed cases/control (n) | OR (95% CI)1 history of folic acid intake vs no intake | OR (95% CI)1 ≥5 yrs folic acid intake vs no intake |
|---|---|---|---|
| All exposures recorded at least 36 months since diagnosis | 27/61 | 0.81 (0.46 to 1.42) | 1.00 (0.3.7 to 2.65) |
| Restricted analysis to those with full information on adjusting variables | 22/62 | 0.95 (0.51 to 1.79) | 0.81 (0.32 to 2.05) |
[i] 1 Adjusted for smoking, body mass index, hypertension, diabetes, GI disorders, Overall P-value >0.05.
Abbreviations: CI, Confidence interval.
Figure 2
Odds ratio of colorectal cancer in cases with history of folic acid intake, compared with those with no history of intake, categorized by various factors.1
1 Results are from multivariate conditional logistic regression for study population stratified by corresponding variables. Results for current smoking subgroups were not present due to small numbers.