Lead exposure and rate of change in cognitive function in older women

Abstract

Background Higher long-term cumulative lead exposure predicts faster cognitive decline in older men, but evidence of an association in women is lacking. Objective To determine if there is an association between lead exposure and cognitive decline in women. Methods This study considers a sample of 584 women from the Nurses’ Health Study who live in or near Boston, Massachusetts. We quantified lead exposure using biomarkers of lead exposure assessed in 1993–2004 and evaluated cognitive decline by repeated performance on a telephone battery of cognitive tests primarily assessing learning, memory, executive function, and attention completed in 1995–2008. All cognitive test scores were z-transformed for use in analyses. We used linear mixed models with random effects to quantify the association between each lead biomarker and change in cognition overall and on each individual test. Results Consideration of individual tests showed greater cognitive decline with increased tibia lead concentrations, a measure of long-term cumulative exposure, for story memory and category fluency. The estimated excess annual decline in overall cognitive test z-score per SD increase in tibia bone lead concentration was suggestive, although the confidence intervals included the null (0.024 standard units, 95% confidence interval: −0.053 , 0.004 – an additional decline in function equivalent to being 0.33 years older). We found little support for associations between cognitive decline and patella or blood lead, which provide integrated measures of exposure over shorter timeframes. Conclusions Long-term cumulative lead exposure may be weakly associated with faster cognitive decline in community-dwelling women, at least in some cognitive domains.

Associations of cumulative Pb exposure and longitudinal changes in Mini-Mental Status Exam scores, global cognition and domains of cognition: The VA Normative Aging Study

“…Other studies of longitudinal change in cognition have noted similar trends as well. 11,30,37 Clinical treatment for pre-clinical declines in cognition would be strengthened by effective biomarkers of dementia; this expanding area of research could also lead to longitudinal testing improvements in epidemiologic risk factor identification. 38–40 …”

“…29 Basic Model $$\text{italicCognitive test}=B_0+B_1\times Pb+B_2\times {\mathit{\text{Time}}}_{\text{italicfromVisit}1}+B_{3}false({\mathit{\text{Time}}}_{\text{italicfromVisit}1}\times Pbfalse)+B_4\times {\mathit{\text{Age}}}_{\mathit{\text{FirstCognitiveTest}}}+B_5\times \text{italicEducation}+B_6\times \text{italicSmokingStatus}+B_7\times \text{italicAlcohol}$$ First-test Indicator model: $$\text{italicCognitive test}=B_0+B_1\times Pb+B_2\times {\mathit{\text{Time}}}_{\text{italicfromVisit}1}+B_3\times false({\mathit{\text{Time}}}_{\text{italicfromVisit}1}\times Pbfalse)+B_4\times {\mathit{\text{Age}}}_{\mathit{\text{FirstCognitiveTest}}}+B_5\times \text{italicEducation}+B_6\times \text{italicSmokingStatus}+B_7\times \text{italicAlcohol}+B_8\times \text{italicFirstTestIndicator}$$ This model, similar to one employed in prior studies 30 can partially account for the learning effect by separating the change from visit 1 to visit 2, and regressing based on longitudinal changes from subsequent visits. Because MMSE is susceptible to a learning effect, as we observed in our study, we chose to report analyses based on the first-test indicator model.…”

Association of lead and cadmium exposure with frailty in US older adults

“…Second, exposure to lead and cadmium has been related to a higher risk of several pathologic conditions that are also linked to frailty. Environmental exposure to lead in the elderly has been associated with cognitive decline (Bandeen-Roche et al 2009;Grashow et al 2013;Nordberg et al 2000;Power et al 2014;Shih et al 2006;van Wijngaarden et al 2011), impaired motor skills (Grashow et al 2013), increased blood pressure (Perlstein et al 2007), ischemic heart disease (Jain et al 2007), decreased renal function (Tsaih et al 2004), falls and fractures in women (Khalil et al 2008), hearing loss (Park et al 2010) and vision problems (Schaumberg et al 2004;Wu et al 2014). Cadmium, for which fewer studies have been conducted in the elderly, has also been associated with an increased risk of atherosclerotic plaques (Fagerberg et al 2012), peripheral artery disease (Tellez-Plaza et al 2013a), osteoporosis (Engstrom et al 2011;Gallagher et al 2008) and macular degeneration (Shiue 2013;Wu et al 2014).…”

APOE ε4 allele modifies the association of lead exposure with age-related cognitive decline in older individuals

“…For cognitive performance, we evaluated “total” cognitive function integrating multiple cognitive tests (Table 1) (Power et al, 2014; 2013). Cognitive data were collected at multiple visits approximately 3.6 years apart, with nearly 2.7 visits (min=1, max=7) per subject and 3,566 visits in total were included, from 1993 to 2004.…”