Association between heavy metal exposure and poor working memory and possible mediation effect of antioxidant defenses during aging.
BACKGROUND
Inverse associations have been observed between memory performance and blood concentrations of cadmium (Cd) and lead (Pb). Low antioxidant cell activity has also been linked to decline in memory due to aging. However, it has not yet been established whether the heavy metal-memory relationship is mediated by differences in antioxidant activity.


METHODS
We examined Cd and Pb levels, as well as oxidative stress parameters, in blood samples from 125 older adults (age range 50-82years). The Counting Span Test (CST) was used to evaluate working memory capacity (WMC). The Monte Carlo Method for Assessing Mediation (MCMAM) was used to analyze the mediation role of antioxidant activity in the heavy metals-memory association.


RESULTS
High blood Cd (BCd) concentration alone, and in combination with elevated blood Pb (BPb) concentration, was associated with poor WMC (p≤0.001) and low enzymatic antioxidant defenses (p≥0.006). The variance in WMC accounted for by BCd or by BCd combine with BPb was 20.6% and 18.6%, respectively. The MCMAM revealed that the influence of BCd and BPb concentrations on WMC was mediated by low antioxidant capacity (confidence interval - CI: 0.072 to -0.064 for BCd; CI: -0.062 to -0.045 for BPb).


CONCLUSIONS
These findings showed Pb and Cd blood concentration in older adults, even at levels below the current recommended threshold, was negatively associated with WMC and that this relationship may be partly mediated by low antioxidant defenses. Knowledge on the environmental factors that negatively influence brain and cognition during aging can help inform public policy strategies to prevent and control the adverse effects of environmental contaminant exposure during aging.
Department of Medical-Surgical Nursing, School of Nursing, University of São Paulo, Av. Dr. Enéas de Carvalho Aguiar, 419, São Paulo, SP 05403000, Brazil. Electronic address: junery@usp.br.
Juliana Nery
JN
Souza-Talarico
Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 580, São Paulo, SP 05434070, Brazil. Electronic address: tmarcour@usp.br.
Tania
T
Marcourakis
Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Av. do Café, s/n, Ribeirão Preto, SP 14040903, Brazil. Electronic address: fbarbosa@fcfrp.usp.br.
Fernando
F
Barbosa
Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 580, São Paulo, SP 05434070, Brazil. Electronic address: silviaberlanga@gmail.com.
Silvia Berlanga
SB
Moraes Barros
Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 580, São Paulo, SP 05434070, Brazil. Electronic address: diogopineda@gmail.com.
Diogo Pineda
DP
Rivelli
Department of Psychobiology, Federal University of São Paulo, Rua Botucatu, 862, São Paulo, SP 04023-062, Brazil. Electronic address: spompeia@gmail.com.
Sabine
S
Pompéia
Behavioral and Cognitive Neurology Unit, Department of Internal Medicine, Faculty of Medicine, Federal University of Minas Gerais, Av. Prof. Alfredo Balena, 190, Belo Horizonte, MG 30130100, Brazil. Electronic address: caramel@ufmg.br.
Paulo
P
Caramelli
Centre for Studies on Human Stress, Mental Health Research Centre Fernand Seguin, Hospital Louis H. Lafontaine, Université de Montréal, 7401, rue Hochelaga, Montréal, Québec H1N 3M5, Canada. Electronic address: pierrich.plusquellec@umontreal.ca.
Pierrich
P
Plusquellec
Centre for Studies on Human Stress, Mental Health Research Centre Fernand Seguin, Hospital Louis H. Lafontaine, Université de Montréal, 7401, rue Hochelaga, Montréal, Québec H1N 3M5, Canada. Electronic address: sonia.lupien@umontreal.ca.
Sonia J
SJ
Lupien
Department of Clinical Chemistry and Toxicology, School of Pharmaceutical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 580, São Paulo, SP 05434070, Brazil.
Raphael Fernandes
RF
Catucci
Department of Medical-Surgical Nursing, School of Nursing, University of São Paulo, Av. Dr. Enéas de Carvalho Aguiar, 419, São Paulo, SP 05403000, Brazil. Electronic address: aregiani@usp.br.
Andrea Regiani
AR
Alves
Department of Psychobiology, Federal University of São Paulo, Rua Botucatu, 862, São Paulo, SP 04023-062, Brazil. Electronic address: deborah.suchecki@gmail.com.
Deborah
D
Suchecki
D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000502:physiology*; D002104:Cadmium / Q000009:adverse effects / Q000097:blood*; D004781:Environmental Exposure / Q000009:adverse effects*; D006801:Humans; D007854:Lead / Q000009:adverse effects / Q000097:blood*; D008570:Memory, Short-Term / Q000187:drug effects*; D019216:Metals, Heavy / Q000009:adverse effects / Q000097:blood; D008875:Middle Aged
D000975:Antioxidants; D019216:Metals, Heavy; D002104:Cadmium; D007854:Lead
Cadmium; Emerging country economy; Lead; Oxidative stress; Working memory capacity