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Table 3 Naïve and corrected odds ratios for each fatty acid group/ratio and decline in Word Fluency Test (WFT)3 using two approaches and RCAL/SIMEX methods: Change in estimate (Δbias) and precision (Δprecision) compared to the naïve estimates; ARIC (1987–1998)1

From: Measurement error adjustment in essential fatty acid intake from a food frequency questionnaire: alternative approaches and methods

  Odds Ratios (95% Confidence Intervals)
Fatty acid groups and ratios j 2 Naïve (Q1 = T) External validation with biomarkers (M/N) (Approach A) Internal repeat measurements (Q2/Q3) (Approach B)
    RCAL SIMEX RCAL SIMEX
6p 1.03 (0.93, 1.14) 0.98 (0.76, 1.25) 0.98 (0.83, 1.16) 1.04 (0.75, 1.21) 0.97 (0.80,1.18)
   Δbias4 __ __ 0.05 c 0.05 c -0.01 a 0.06 c
   Δprecision5 __ __ 1.34   1.14   1.32   1.33  
3p 1.01 (0.92, 1.12) 1.02 (0.77, 1.36) 1.01 (0.86, 1.17) 1.22 (0.90, 1.64) 1.15 (0.96,1.39)
   Δbias __ __ -0.01 a 0.00   -0.21 a -0.14 a
   Δprecision __ __ 1.45   1.12   1.50   1.19  
6H 1.18 (1.06, 1.31)* 1.63 (1.26, 2.14)* 1.34 (1.14, 1.56)* 1.19 (0.48, 2.91) 1.20 (0.56,2.56)
   Δbias __ __ -0.45 a -0.16 a -0.01 a -0.02 a
   Δprecision __ __ 1.37   1.11   4.91   3.70  
3H 0.85 (0.75, 0.96)* 0.73 (0.58, 0.90)* 0.80 (0.66, 0.96)* 0.80 (0.62, 1.04) 0.83 (0.68,1.02)
   Δbias __ __ 0.12 a 0.05 a 0.05 a 0.02 a
   Δprecision __ __ 1.21   1.14   1.31   1.17  
6 1.03 (0.97, 1.14) 1.08 (0.82, 1.41) 1.04 (0.89, 1.22) 0.96 (0.76, 1.21) 0.96 (0.81,1.15)
   Δbias __ __ -0.05 a -0.01 a 0.07 c 0.07 c
   Δprecision __ __ 1.46   1.17   1.35   1.21  
3 0.94 (0.85, 1.05) 0.71 (0.56, 0.90)* 0.80 (0.65, 0.97)* 0.85 (0.62, 1.17) 0.90 (0.73,1.11)
   Δbias __ __ 0.23 a 0.14 a 0.09 a 0.04 a
   Δprecision __ __ 1.30   1.21   1.53   1.23  
3p/6p 1.01 (0.91, 1.11) 1.03 (0.81, 1.30) 1.03 (0.88, 1.21) 1.21 (0.95, 1.53) 1.14 (0.95,1.36)
   Δbias __ __ -0.02 a -0.02 a -0.20 a -0.13 a
   Δprecision __ __ 1.32   1.13   1.32   1.17  
3H/6H 0.86 (0.76, 0.97)* 0.77 (0.64, 0.93)* 0.79 (0.65, 0.96)* 0.84 (0.65, 1.10) 0.87 (0.70,1.08)
   Δbias __ __ 0.09 a 0.07 a 0.02 a -0.01 b
   Δprecision __ __ 1.14   1.16   1.33   1.21  
3/6 0.95 (0.85, 1.06) 0.91 (0.76, 1.10) 0.92 (0.78, 1.08) 1.04 (0.85, 1.27) 1.04 (0.87,1.23)
   Δbias __ __ 0.04 a 0.03 a -0.09 c -0.09 c
   Δprecision __ __ 1.16   1.11   1.20   1.13  
  1. 1 Q1: Food frequency questionnaire measurement at visit 1 of fatty acid group intake as % of energy intake or ratio of n-3 to n-6 groups. M: biomarker of fatty acid intake in cholesteryl ester fraction of plasma; N: biomarker of fatty acid intake in phospholipid fraction of plasma; Q2: Repeat of Q1 measured at visit 2 among a subset of the cohort; Q3: Repeat of Q1 measured at visit 3 among the surviving baseline cohort; WFT: Word Fluency Test; RCAL: Regression Calibration; SIMEX: Simulation Extrapolation.
  2. 2 See table 3.
  3. 3 Each exposure is entered into the logistic regression model as a z-score and the outcome is binary with 1: decline and 0: no decline based on the reliable change index (RCI) criterion. RCI < -1.645 constitutes clinically significant decline between the two ARIC visits 2 and 4, which were separated by 6 years. The odds ratio is interpreted as increase in risk of cognitive decline with each 1 SD increase in the fatty acid exposure.
  4. 4 Δbias = ORnaive - ORcorrected. a: naïve estimate is biased towards the null; b: naïve estimate is biased away from the null; c: naïve estimate is biased through the null. The null value for an odds ratio is 1.00.
  5. 5 Δprecision = CLRcorrected/CLRnaive. CLR or Confidence Limit Ratio is the ratio of the upper 95% confidence limit over the lower one.