Impairments of Memory and Learning in Older Adults Exposed to Polychlorinated Biphenyls via Consumption of Great Lakes Fish

Environmental Health Perspectives, June, 2001 by Susan L. Schantz, Donna M. Gasior, Elena Polverejan, Robert J. McCaffrey, Anne M. Sweeney, Harold E.B. Humphrey, Joseph C. Gardiner

Confounding Variables

Through a careful review of the literature, we identified a large number of demographic, lifestyle, psychological, and health-related variables as potential confounders. These are listed in Table 2 and were described in detail in a previous publication (13). A comparison of the demographic, lifestyle, and psychological characteristics of the fish eaters and non-fish eaters has also been published previously (12). Fish eaters and non-fish eaters had very similar demographic characteristics, reported similar patterns of smoking and alcohol consumption, and had comparable scores on measures of intellectual functioning and affect. The only medical condition that differed between fish eaters and non-fish eaters was arthritis, which was reported more frequently in male fish eaters. Although PCB and DDE levels are correlated with fish-eating status, we hypothesized that any effects observed on the outcome measures would be due to contaminant exposure rather than fish consumption per se. Therefore, fish eaters and non-fish eaters were combined and analyses were performed using regression procedures.

Table 2. Summary of covariates by category.(a)

                                    Psychological
Demographic      Lifestyle          functioning         Health

Age              Activity level     Overall             Self-rating of
Sex                Leisure/sports       intellectual      overall
Education          Occupational         function          health
Income             Household          WAIS-R            General health
Employment         Stair climbing       Vocabulary        (e.g., body
  status         Tobacco use            subtest           mass index,
Marital status   Alcohol            Emotion/stress        hearing loss,
Social support       consumption      Beck Depression     visual
Household size   Caffeine               Inventory         impairment)
Dominant hand        consumption      State-Trait       Physical
                                        Anxiety           symptoms
                                        Inventory         (e.g.,
                                                          fatigue,
                                                          dizziness,
                                                          minor colds)
                                                        Medical
                                                          conditions
                                                          (e.g.,
                                                          arthritis,
                                                          thyroid
                                                          disease,
                                                          hypertension)
                                                        Prescription
                                                          and nonpre-
                                                          scription
                                                          drug use,
                                                          categorized
                                                          by class
                                                          (e.g.
                                                          antibiotics,
                                                          diuretics,
                                                          acetami-
                                                          nophen)
                                                        History of
                                                          psychiatric
                                                          illness,
                                                          head injury,
                                                          stroke

(a) For a complete list, see Schantz et al. (13).