The Association of Lead with Cataracts and Vision-Related

Problems inPerimenopausal Women

Imogene A. Drakes, PhD, MS. MBA, FACHE

Statement of the Problem

• Cataracts are the major cause of blindness in the world (World Health

Organization [WHO], 2006); the leading cause of vision loss in the United States (Centers for Disease Control and Prevention, 2013b).

• Cataracts and other vision-related issues appear earlier in women; women have a higher risk for vision-related problems (Congdon et al.,

2004, WHO, 2013).

• Literature review did not reveal any specific causative factor.

• Women will continue to have longer lifespans than men (WHO, 2013).

• Women’s vision impairment problems should be addressed (WHO, 2013).

Purpose

The purpose of this research was to determine if there is any association between the release of lead during perimenopausal bone demineralization and the incidence of cataracts and other vision-related issues in women.

• Cataracts can interfere with daily activities and if left untreated may lead to blindness (American Optometric Association, 2004; World Health Organization, 2006).

• The only treatment for cataracts is to have surgery. (Taylor, 2002).

• Not everyone has access to cataract surgery (West et al., 1998)

• Cataract surgeries are not without risk (CDC, 2007).

• The majority of people will develop cataracts if they live long enough (Taylor, 2002).

Impact of Cataracts on Individuals

• In 1966, Dr. Claire Patterson testified to Congress on the harmful effects of lead (Needleman, 2000; Tepper & Levin, 1975).

• Efforts were made to reduce lead and other toxic burden in the environment (Needleman, 2000; Tepper & Levin, 1975).

• Lead air emissions decreased and so did blood lead levels (Environmental Protection Agency, 1995; Pirkle et al., 1994).

• The Environmental Protection Agency (EPA) reported that lead levels in the soil were still very high (EPA, 2001).

• However the U.S. population is not exposed to lead in a ubiquitous manner (EPA, 2001).

Lead and the General Population

• Median age range for menopause for U.S. women is 51.2 years (Reynolds & Obermeyer, 2005).

• Bone loss begins to occur in the menopausal years (Harmon & Talbert, 1985; Weyermann & Brenner (1998).

• Depending on heredity and estrogen status, bone demineralization may begin in the premenopausal years (Armamento-Villareal et al., 1992).

• Postmenopausal women and smokers had higher levels of blood lead than any other group (Silbergeld et al., 1988).

• High postmenopausal and post osteoporosis blood lead levels were negatively associated with degree of parity (Silbergeld et al., 1988).

• Inverse association correlated with reports that lead is leached from bone during pregnancy, lactation, and osteoporosis (Silbergeld et al., 1988).

Lead and Perimenopausal Women

• Postmenopausal bone demineralization is a complex process (Weitzmann & Pacifici, 2006).

• Possible causes include

• Decrease in release of parathyroid hormone

• Decreased absorption of calcium from the intestine

• Impaired activation to precursors of vitamin D (Cummings et al., 1985; Riggs & Melton, 1984).

• Significant bone mineral depletion occurs during the first two to four years after the menses cease (Ruegsegger et al., 1984).

Postulated Mechanism for Mobilization of Lead Post Menopause

• Lead is a possible causative factor for age-related diseases such as hypertension and renal dysfunction (Hu et al., 1996).

• Lead could also be implicated in other age-related diseases (Hu et al., 1996).

• Women are at risk for bone demineralization during the perimenopausal period (Harmon & Talbert, 1985).

• Risk for damage by lead to internal organs increases as a result of this phenomenon (Gulson et al., 1995; Hu & Hernandez-Avila, 2002; Jain et al., 2007; Korrick et al., 1999; Nash et al., 2003; Nash et al., 2004; Rothenberg et al., 2002).

• Lead mobilized during bone demineralization is associated with deleterious effects such as hypertension (Nash et el. 2003).

Deleterious Effects of Endogenous Lead

• Results of study on cataracts in twins revealed environment plays a role in cataractogenesis (Hammond et al., 2000).

• In 2004 Schaumberg et al. (2004) reported an association between endogenous lead and cataracts.

• In 2005 Neal et al. (2005) verified lead can cause cataracts.

• Theories for mechanism of damage to the lens by lead include:

• Glutathione metabolism

• Changes in redox status

• Imbalance in calcium homeostasis

• Modification of lens protein (Park et al., unpublished).

Lead as Possible Cause for Cataractogenesis

• Hypothesis is that endogenous lead damages eye lenses of postmenopausal or perimenopausal women by lead through a linear mechanism.

• As hormones decrease, bone demineralizes (Ruegsegger et al., 1984).

• Demineralized bone releases lead to blood (Rabinowitz et al., 1976).

• Blood carries the lead to various parts of the body (Rabinowitz et al., 1976).

• Endogenous lead can cause opacities (Neal et al. 2005).

Main Hypothesis for Study

• There were no issues of privacy or personal harm which needed to be addressed by informed consent.

• The datasets used for this study had already been de-identified and can be downloaded from http://www.cdc.gov/nchs/nhanes.htm.

• The research proposal was approved by the University Institutional Review Board (IRB) prior to data analysis.

Ethical Procedures

Research Design

• Study was quantitative; design was case control.

• Design mirrors that of landmark study on lead and cataracts performed by Schaumberg et al. (2004).

• Study population: Women, aged 40 - 55 years, who participated in the 2005-2006, and 2007 -2008 National Health and Nutrition Examination Surveys (NHANES).

• Data is publicly available on the Centers for Disease Control and Prevention’s website (at http://www.cdc.gov/nchs/nhanes.htm).

• Women who showed signs of mobilized lead were the cases; women who did not were the controls.

Importance and Health Relevance of Study

• Women live longer than men; needs of many aging women not satisfactorily addressed and in a timely manner (Laskar, 2011).

• Economic burden could be very significant (Laskar, 2011).

• Results of study could close gap on important eye health issues for women.

• There is growing need to decrease cataracts and other vision-related issues in U.S. population that is aging and increasing.

• U.S. States Census Bureau (2013) estimated that percent of population >65 years of age will increase from 12% (2000 census) to about 20% in the year 2050; working population relative to those > 65 years will shrink.