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

EffectsVerbal memory testDigit Symbol Coding testTapping testMini-Mental State Examination
WomenMenWomenMenWomenMenWomenMen
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 SDNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo 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 SDNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo significant interaction with ageNo 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 mediationMediationMediationMediationMediationMediationNo mediationNo mediation
 Previous0.005 (−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)
 Occasional0.22 (−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)MediationNo mediationNo mediationNo mediationMediationNo mediationMediationNo 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 age0.15 (−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 age0.13 (−0.17 to 0.44)
  +1 SD−0.26 (−0.72 to 0.20)
 5 or more0.16 (−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 SD0.60 (−0.57 to 1.76)
  Mean age0.20 (−0.52 to 0.93)
  +1 SD−0.19 (−0.81 to 0.43)
Snuff (ref: never)No mediationNo mediationNo mediationNo mediationNo mediationNo mediationNo mediationNo 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)
 Current0.11 (−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)MediationMediationNo mediationMediationMediationMediationNo mediationNo 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.