Total plasma homocysteine values among elderly subjects: Findings from the Maracaibo Aging Study

Abstract

Objectives:

The present study generated baseline data for total homocysteine (tHcy) in elderly Caribbeans of Hispanic ancestry, residing in Venezuela, their country of origin.

Design and methods:

2106 participants in the Maracaibo Aging Study (MAS), older than 55 years, underwent standardized clinical and laboratory assessments, including measurement of plasma tHcy levels, folate, and vitamin B12 in fasting samples.

Results:

tHcy concentration in the healthy, normative group ranged from 4.1 to 31.8 μmol/L, with a median of 11.5 ± 4.7 μmol/L. tHcy level increased with age, was significantly higher in men than in women, and exhibited inverse correlations with folate and vitamin B12.

Conclusions:

tHcy levels of the MAS participants were generally higher than levels previously reported for community-dwelling elderly populations from other countries. The normative centile curves for tHcy can be used in disease risk analysis for this population, and possibly for other Hispanic populations residing in the Caribbean.

Introduction

Homocysteine (Hcy) is an amino acid derived from methionine demethylation. To reconstitute methionine, Hcy can acquire a methyl group from methyltetrahydrofolate in a reaction catalyzed by vitamin B12-dependent methyltransferase [1]. Age and gender affect the plasma levels of Hcy and previous studies have shown that values of plasma total Hcy (tHcy) increase throughout life, and that men exhibit higher values than women [2], [3]. Diet, micronutrient supplementation, smoking, and alcohol consumption may further influence tHcy levels [4], [5], [6], [7]. Although it has been suggested that the Hispanic populations exhibit lower tHcy levels than non-Hispanic populations [8], [9], [10], [11], there is insufficient information on tHcy from different ethnic groups, particularly elderly Hispanics, to test this hypothesis. To date, no tHcy values have been published for elderly Hispanics residing in a developing country. Given differences in nutrition and other lifestyle factors, Hcy levels for these individuals are likely to differ from levels of elderly Hispanics living in developed countries.

High plasma tHcy level constitutes a risk factor for several unfavorable conditions common among elderly people, including cardiovascular diseases [12], [13], [14], [15], [16], [17], Alzheimer's disease [18], and colon cancer [19]. To classify an individual as at risk for a specific disease using a laboratory parameter, it is necessary to determine the physiological range of that parameter, and the range for individuals with the disease [20].

Availability of appropriate normative data for elderly populations is critical to overcoming the current uncertainty in using tHcy levels to classify an older individual as at risk, and for treatment planning and outcome measurement. Although previous studies measured tHcy levels among elderly free of disease [21], [22], [23], [24], no study has provided baseline information about tHcy levels in a Caribbean population of Hispanic descent, residing in their country of origin.

The present work took advantage of an ongoing study of elderly people living in an urban community in Maracaibo, Venezuela, to determine the distribution of tHcy values among subjects older than 55 years. Healthy individuals in this population were used to generate normative tHcy values. The distribution of tHcy values was also determined for a reference sample that exhibited optimal levels of folate and vitamin B12.