Table 4.
Results of mediation analysis for the total sample, women (n=3890) and men (n=3321): total, direct and indirect effects of area-level socioeconomic status on cognitive function (outcomes): the Tromsø Study 2015–2016
| Effects | Verbal memory test | Digit Symbol Coding test | Tapping test | Mini-Mental State Examination | ||||
| Women | Men | Women | Men | Women | Men | Women | Men | |
| B (95% CI) | B (95% CI) | B (95% CI) | B (95% CI) | B (95% CI) | B (95% CI) | B (95% CI) | B (95% CI) | |
| Total effect* | 0.28 (0.19 to 0.38) | 0.32 (0.23 to 0.41) | 1.81 (1.32 to 2.33) | 2.22 (1.77 to 2.70) | 1.06 (0.69 to 1.41) | 1.23 (0.89 to 1.57) | 0.28 (0.18 to 0.37) | |
| Association at:† | ||||||||
| −1 SD | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | 0.40 (0.26 to 0.55) | No significant interaction with age |
| Mean age | 0.28 (0.17 to 0.39) | |||||||
| +1 SD | 0.16 (0.02 to 0.31) | |||||||
| Direct effect‡ | 0.27 (0.17 to 0.36) | 0.29 (0.20 to 0.39) | 1.74 (1.15 to 2.28) | 2.01 (1.58 to 2.53) | 0.89 (0.50 to 1.22) | 1.11 (0.76 to 1.46) | 0.27 (0.16 to 0.36) | |
| Association at:† | ||||||||
| −1 SD | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | No significant interaction with age | 0.38 (0.24 to 0.53) | No significant interaction with age |
| Mean age | 0.27 (0.16 to 0.38) | |||||||
| +1 SD | 0.15 (0.004 to 0.30) | |||||||
| Indirect effect, combined§ | 0.009 (−0.01 to 0.05) | 0.03 (−0.001 to 0.05) | 0.08 (−0.06 to 0.29) | 0.21 (0.02 to 0.33) | 0.16 (0.07 to 0.31) | 0.12 (0.01 to 0.23) | 0.01 (−0.01 to 0.04) | 0.02 (−0.01 to 0.04) |
| PME¶ | 0.03 (−0.08 to 0.15) | 0.09 (0.01 to 0.18) | 0.04 (−0.05 to 0.16) | 0.09 (0.03 to 0.17) | 0.15 (0.04 to 0.29) | 0.10 (0.01 to 0.20) | 0.05 (−0.05 to 0.17) | 0.06 (−0.03 to 0.17) |
| Exposure-adjusted effects of mediators: | ||||||||
| Smoking (ref: never) | No mediation | Mediation | Mediation | Mediation | Mediation | Mediation | No mediation | No mediation |
| Previous | 0.005 (−0.12 to 0.13) | −0.12 (−0.26 to 0.02) | −0.01 (−0.76 to 0.74) | −1.03 (−1.81 to to 0.25) | 0.15 (−0.36 to 0.66) | −0.34 (−0.87 to 0.19) | 0.03 (−0.11 to 0.17) | −0.06 (−0.21 to 0.08) |
| Occasional | 0.22 (−0.14 to 0.59) | 0.11 (−0.20 to 0.43) | −1.92 (−4.03 to 0.21) | −0.61 (−2.40 to 1.18) | −1.69 (−3.11 to to 0.24) | −0.86 (−2.09 to 0.38) | 0.10 (−0.34 to 0.53) | −0.09 (−0.43 to 0.25) |
| Current | −0.04 (−0.24 to 0.15) | −0.35 (−0.56 to to 0.14) | −2.11 (−3.26 to to 0.96) | −2.33 (−3.54 to to 1.12) | −2.08 (−2.86 to to 1.29) | −2.15 (−2.98 to to 1.32) | −0.09 (−0.31 to 0.13) | −0.07 (−0.30 to 0.15) |
| Alcohol (ref: 0 units) | Mediation | No mediation | No mediation | No mediation | Mediation | No mediation | Mediation | No mediation |
| 1–2 units | 0.37 (0.15 to 0.59) | 0.07 (−0.24 to 0.38) | 0.87 (−0.44 to 2.19) | 1.44 (−0.34 to 3.24) | 1.16 (0.26 to 2.07) | 0.49 (−0.72 to 1.71) | 0.18 (−0.14 to 0.51) | |
| Association at:† | ||||||||
| −1 SD | 0.50 (0.21 to 0.76) | |||||||
| Mean age | 0.15 (−0.12 to 0.42) | |||||||
| +1 SD | −0.19 (−0.63 to 0.25) | |||||||
| 3–4 units | 0.35 (0.09 to 0.61) | 0.09 (−0.23 to 0.41) | 0.77 (−0.72 to 2.29) | 1.19 (−0.65 to 3.05) | 1.39 (0.36 to 2.43) | 0.21 (−1.04 to 1.48) | 0.22 (−0.120 to 0.56) | |
| Association at:† | ||||||||
| −1 SD | 0.53 (0.15 to 0.91) | |||||||
| Mean age | 0.13 (−0.17 to 0.44) | |||||||
| +1 SD | −0.26 (−0.72 to 0.20) | |||||||
| 5 or more | 0.16 (−0.31 to 0.64) | 0.02 (−0.35 to 0.38) | 0.49 (−2.24 to 3.26) | 0.25 (−1.83 to 2.33) | 0.28 (−1.58 to 2.17) | 0.16 (−1.25 to 1.58) | 0.09 (−0.29 to 0.48) | |
| Association at:† | ||||||||
| −1 SD | 0.60 (−0.57 to 1.76) | |||||||
| Mean age | 0.20 (−0.52 to 0.93) | |||||||
| +1 SD | −0.19 (−0.81 to 0.43) | |||||||
| Snuff (ref: never) | No mediation | No mediation | No mediation | No mediation | No mediation | No mediation | No mediation | No mediation |
| Previous | −0.17 (−0.60 to 0.27) | 0.12 (−0.10 to 0.35) | −0.80 (−3.33 to 1.70) | −0.69 (−2.00 to 0.62) | −0.08 (−1.81 to 1.64) | −0.14 (−1.04 to 0.77) | 0.53 (−0.01 to 1.08) | 0.20 (−0.04 to 0.45) |
| Current | 0.11 (−0.32 to 0.55) | 0.15 (−0.08 to 0.39) | −2.14 (−4.66 to 0.37) | −1.85 (−3.21 to to 0.50) | −1.09 (−2.81 to 0.63) | −0.70 (−1.62 to 0.22) | −0.08 (−1.04 to 0.88) | 0.08 (−0.17 to 0.34) |
| Physical activity (ref: sedentary) | Mediation | Mediation | No mediation | Mediation | Mediation | Mediation | No mediation | No mediation |
| Light activity | 0.20 (0.02 to 0.39) | 0.16 (−0.02 to 0.35) | 1.05 (−0.02 to 2.13) | 1.52 (0.47 to 2.56) | 1.04 (0.32 to 1.78) | 1.41 (0.70 to 2.12) | 0.11 (−0.09 to 0.31) | 0.29 (0.09 to 0.48) |
| Moderate-to-vigorous activity | 0.23 (0.01 to 0.45) | 0.22 (0.03 to 0.42) | 0.64 (−0.61 to 1.91) | 1.49 (0.36 to 2.61) | 1.90 (1.04 to 2.76) | 1.37 (0.60 to 2.13) | 0.04 (−0.19 to 0.28) | 0.23 (0.02 to 0.44) |
All models were adjusted for age and individual-level SES and accounted for area-level clustering.
Bold typeface indicates significance.
*Association between exposure and outcome: main effect presented when age is not a significant moderator; age-specific associations presented when age was a significant moderator.
†If significant interaction with moderator (age).
‡Association between exposure and outcome not explained by mediators.
§Association between exposure and outcome through mediators (dietary variables not included).
¶The proportion of the total effect mediated by mediator(s).
B, regression coefficient; CI, confidence interval; PME, proportion of mediated effect; SD, Standard deviation; SES, socioeconomic status.