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View the most recent version. Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please " " to request a format other than those available. Iron is essential for biochemical functions in the body at every stage of life. The physiological manifestations of iron-deficiency anemia include reduced immune function and resistance to infection, impaired cognitive performance and behaviour, decreased thermoregulatory performance and energy metabolism, diminished exercise or work capacity, and increased incidence of preterm deliveries and low birthweight infants.
Increased demands for iron because of growth, menstrual losses, or pregnancy may also be factors. These data allow for the examination of associations between selected socio-demographic and health variables and measures of iron status. Body iron is found primarily in hemoglobin, the protein in red blood cells that carries oxygen to tissues. Iron deficiency is typically defined in three stages of increasing severity: iron storage depletion as indicated by low serum ferritin; mild iron deficiency without anemia, based on laboratory evidence of iron-deficient erythropoiesis; and overt iron-deficiency anemia.
Although serum ferritin is a valid measure of total iron storage, 9,10 as a sole indicator of iron deficiency, it must be interpreted cautiously; concentrations could increase as a result of infections and disorders such as chronic inflammation, malignancy and liver disease. During the second stage of iron deficiency, transport iron decreases. A reduction in the size of circulating red blood cells, measured as the mean corpuscular volume, is a reliable indication of reduced hemoglobin synthesis; low values can indicate iron-deficient erythropoiesis. The final stage—iron-deficiency anemia—is often characterized by a reduction in the blood concentration of hemoglobin.
The CHMS covers the population aged 3 to Residents of Indian reserves and Crown lands, institutions and certain remote regions, and full-time members of the Canadian Forces were excluded. Data were collected at 18 sites across Canada from August through November About three-quarters The total sample was comprised of 6, respondents.
The overall response rate was Survey weights produced for the CHMS were used to for the different stages of non-response. Characteristics of the sample can be found in Appendix Table A. Table A Percentage distribution of sample with valid whole blood hemoglobin, mean corpuscular volume and serum ferritin concentrations, by sex, age group, household income and self- perceived health, household population aged 3 to 79, Canada, to Data for from Nutrition Canada 7 , 15 were used as a reference to compare iron status prevalence estimates. Blood was collected by venipuncture. A lavender-top EDTA vacutainer of whole blood specimen was collected for the complete blood count analysis.
The sample size for all hemoglobin, serum ferritin and mean corpuscular volume was 6, respondents. Standardized procedures and quality control monitoring were developed for the collection, processing, aliquoting and analysis of biospecimens and for shipping them to the testing laboratory. Whole blood was analyzed for the complete blood count at the mobile examination centre laboratory using the Beckman Coulter HmX Hematology Analyzer. The laboratory participates in proficiency testing programs and has strict quality control procedures. The complete blood count analysis included determination of hemoglobin and of mean corpuscular volume.
Serum aliquots were frozen at oC and shipped once a week on dry ice to the Health Canada Nutrition Laboratory. Serum was analysed for ferritin by solid phase, two-site chemiluminescent immunometric assay using the Immulite Siemens HealthCare Diagnostics.
Internal quality control and standardized procedures were developed for every assay performed in this laboratory. Vitamin B 12 and folate deficiency were investigated to determine if factors other than iron deficiency contributed to the prevalence of anemia.
Serum vitamin B 12 and red blood cell folate analyses were performed on the Immulite World Health Organization reference values by sex and age group 16 were used to estimate iron sufficiency Appendix Table B. Hemoglobin concentration alone was used as a measure of anemia. Table B World Health Organization hemoglobin, mean corpuscular volume and ferritin reference values for sufficiency, based on criteria, For the most part, the analysis, presents estimates of sufficiency at or above reference values , because this measure yielded larger sample sizes, resulting in a ificant decrease in sampling variability, and thus, more reliable estimates than measures of deficiency below the reference values.
Age, sex, household income and self-perceived health were examined for associations with hemoglobin and serum ferritin levels. Six age groups were specified: 3 to 5, 6 to 11, 12 to 19, 20 to 49, 50 to 64, and 65 to 79 years. Household income during the past 12 months was based on the total income before taxes and deductions of all household members divided by the of people in the household. Respondents reported total household income as a best estimate or within a range, the midpoint of which was used for calculations.
These adjusted household income values were grouped into approximate quartiles. Respondents answered questions about medication use in the past month, including prescriptions, over-the-counter medications, and health products and herbal remedies.
Student's t-test was used to test differences between percentages, arithmetic means, and geometric means. Concentrations were ificantly higher among males than females Table 1. Table 1 Mean hemoglobin, mean corpuscular volume, and ferritin concentrations, by age group and sex, household population aged 3 to 79, Canada, to Table 2 Prevalence of sufficient hemoglobin, by age group and sex, household population aged 3 to 79, Canada, and to A comparison of to CHMS data with of the Nutrition Canada Survey, taking differences in age groups and hemoglobin reference values into , suggests that at most ages, the percentage of people with hemoglobin concentrations above reference values has risen during the past 40 years Table 2.
Concentrations were ificantly higher among males than females. Table 3 Prevalence of sufficient serum ferritin, by age group and sex, household population aged 3 to 79, Canada, to Anemia, however, can be caused not only by low iron, but by other factors. Serum ferritin and mean corpuscular volume concentrations indicate if low hemoglobin is due to iron depletion—very low percentages of sufficiency in these measures would be expected if that was the case.
If the low hemoglobin was primarily a result of low iron, these percentages would be drastically lower. This suggests that the anemia may not have been due to iron deficiency. Similarly, the prevalence of hemoglobin sufficiency was ificantly lower among people in the lowest income quartile, compared with the highest. Mean serum ferritin concentrations did not differ ificantly by household income quartile data not shown. Mean serum ferritin concentrations and the prevalence of hemoglobin and serum ferritin sufficiency did not differ ificantly by self-perceived health data not shown.
No association emerged between mean hemoglobin or serum ferritin concentrations and the consumption of red meat, grains, and fruit and vegetables data not shown. No ificant differences in hemoglobin and serum ferritin sufficiency were apparent between those who took iron-containing multivitamins, compared with those who reported no iron supplementation Table 4.
Table 4 Prevalence of sufficient hemoglobin and serum ferritin, by use of iron supplements, age group and sex, household population aged 3 to 79, Canada, to These are consistent with four small-scale Canadian studies that documented similar or higher percentages of adolescents male and female with low serum ferritin.
Although this analysis focused on iron sufficiency , it is possible to report some estimates of iron deficiency. The comparison with Nutrition Canada data suggests that the prevalence of anemia is currently lower in all age groups younger than But among seniors, the prevalence of anemia is now higher, particularly for women. Therefore, the apparent increase in the prevalence of anemia at ages 65 to 79 may be attributable to factors other than iron deficiency. For example, vitamin B 12 deficiency is a cause of pernicious anemia, with an average age at diagnosis of Red blood cell folate did not appear to contribute to anemia.
As well, blood lead levels are low among Canadians. Socio-economic status may influence determinants of iron status. For instance, higher-income households could have greater access to iron-rich foods. However, this pattern did not persist when serum ferritin was used as a measure of iron stores. Self-perceived health was not associated with hemoglobin or serum ferritin sufficiency. This is consistent with other research findings for young women with depleted iron stores, 30,31 though in contrast to those with anemia. Although diet is related to iron status, no relationship was found with red meat, grain, or fruit and vegetable consumption.
However, CHMS data on dietary iron intake were limited. The questionnaire assessed the frequency, not the amount, of consumption of a partial list of dietary sources of iron. Hence, the variables may not have been specific enough to estimate iron intake and its dietary inhibitors and enhancers. Additionally, information about meat did not include the full scope of meat consumption, thereby potentially underestimating heme iron intake.
A recent study 32 found a weak association between red meat consumption and iron status. As well, other evidence indicates adequate dietary iron intake by much of the population. Use of iron-containing multivitamins was not related to hemoglobin and serum ferritin levels or their adequacy. This may reflect insufficient absorption of the non-heme iron 5 mg to 30 mg per tablet in the supplement as a result of iron inhibitors such as calcium in the diet. Furthermore, absorption of iron from multivitamins may be reduced in iron-replete individuals.
These findings should be interpreted cautiously, as no information was collected about dosage, frequency of use, timing of intake, or reason for taking high-dose supplements. Furthermore, because this is a national sample, regional differences cannot be determinated. Using hemoglobin alone to identify iron deficiency anemia tends to yield overestimates, because anemia due to other causes is included. The CHMS did not include other iron indices such as soluble transferrin receptor, which could have been helpful in distinguishing iron-deficiency anemia from all-cause anemia.
For the first time since the early s, iron indices were measured for the Canadian population. While this study found higher rates of anemia among seniors, factors other than iron deficiency may have contributed to this result. Iron sufficiency of Canadians. Archived Content Information identified as archived is provided for reference, research or recordkeeping purposes.
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