Background

Cross-sectional studies have linked greater polychlorinated biphenyl (PCB) exposure to adverse neuropsychological effects in older adults, including learning, memory, and depressive symptoms. However, no studies among older adults have evaluated the association over time.

Objectives

To assess the effect of serum PCB levels on neuropsychological function over a 14-year period in a cohort of older men and women from a PCB-contaminated area of New York State.

Methods

In 2000–2002, we assessed serum PCB levels and neuropsychological function (including the California Verbal Learning Test Trial 1 (CVLTT1) for verbal memory and learning, and the Beck Depression Index (BDI) for depressive symptoms) in 253 men and women, ages 55–74 years. A total of 116 (46%) persons repeated the PCB and neuropsychological assessment 14 years later. To assess the association over time, we used generalized estimating equations with clustering variables time, total PCB (∑PCB), and ∑PCB × time, and adjusted for baseline age, sex, smoking, and total serum-lipids. For statistically significant ∑PCB × time interactions, we evaluated the association between PCBs and either verbal memory and learning or depressive symptoms while holding ∑PCB constant at the 10th and 90th percentiles to clarify the direction of the interaction.

Results

Over the study period, serum ∑PCB levels (wet-weight) declined by 22%, and were associated with different patterns of change over time for memory (∑PCB × Time β = 0.08 p = 0.009) and depressive symptoms (∑PCB × Time β = -0.16 p = 0.013). Specifically, verbal memory and learning decreased (β = -0.08 p = 0.008) and depressive symptoms increased (β = 0.17 p = 0.008) among persons with low exposure (∑PCB levels at the 10th percentile), while persons with high exposure (90th percentile) showed non-significant improvements.

Discussion

In this cohort, declining ∑PCB levels were likely due at least in part to low rates of local fish consumption in recent decades, given the ban since 1976. The decreased verbal memory and learning and increased depressive symptoms over time among persons with low serum ∑PCB levels is consistent with studies of normative aging. However, the small improvements in those outcomes among those with high serum ∑PCB levels was unexpected. Healthy survivor selection bias or uncontrolled confounding may explain this result. It may also indicate that the neurotoxic impacts of PCBs in older adults are not permanent, but future studies are needed to confirm this possibility.

中文翻译：

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纽约州老年人中多氯联苯和神经心理功能的纵向研究

背景

横断面研究已将更多的多氯联苯（PCB）暴露与老年人的不良神经心理影响联系在一起，包括学习，记忆和抑郁症状。但是，没有关于老年人的研究随时间推移评估这种关联。

目标

为了评估纽约州PCB污染地区的一组年龄较大的男性和女性在14年内血清PCB水平对神经心理功能的影响。

方法

在2000–2002年，我们评估了253个年龄段的男性和女性的血清PCB水平和神经心理功能（包括用于言语记忆和学习的加利福尼亚语言学习测试试验1（CVLTT1），以及用于抑郁症状的贝克抑郁指数（BDI））。 55-74年。14年后，共有116人（46％）重复了PCB和神经心理学评估。为了评估随时间变化的关联性，我们使用了带有聚类变量时间，总PCB（∑PCB）和∑PCB×时间的广义估计方程，并针对基线年龄，性别，吸烟和总血脂进行了调整。对于具有统计学意义的∑PCB×时间交互作用，我们评估了PCB与言语记忆和学习或抑郁症状之间的关联，同时将∑PCB保持在第10个百分位和第90个百分位，以阐明交互作用的方向。

结果

在研究期间，血清∑PCB水平（湿重）下降了22％，并与记忆力随时间变化的不同模式（∑PCB×时间β= 0.08 p = 0.009）和抑郁症状（∑PCB×时间β= -0.16 p = 0.013）。具体而言，在低暴露水平（∑PCB处于第10个百分位）的人中，语言记忆和学习能力下降（β= -0.08 p = 0.008），抑郁症状增加（β= 0.17 p = 0.008），而高暴露人群（第90位）百分位数）显示出不显着的改善。

讨论

在这个队列中，∑PCB水平下降可能至少部分是由于自1976年以来的该禁令，最近几十年来当地鱼类消费量较低。随着时间的推移，血清∑低的人的言语记忆和学习能力下降，抑郁症状增加PCB水平与规范老化研究一致。但是，在血清∑PCB水平较高的人群中，这些结局的改善很小，这是出乎意料的。健康的幸存者选择偏见或不受控制的混杂可能解释了这一结果。这也可能表明多氯联苯对老年人的神经毒性影响不是永久性的，但是需要进一步的研究来确认这种可能性。