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Queens College of the City University of New York (A.K.K.), Flushing, New York
National Cancer Institute (A.S.), National Institutes of Health, Bethesda, Maryland
Address correspondence to: Ashima K. Kant, PhD, Dept. of Family, Nutrition, and Exercise Sciences, Remsen Hall, Room 306E, Queens College of the City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367
| ABSTRACT |
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Methods: We used data from the Continuing Survey of Food Intakes by Individuals, 19891991. The analytic sample included subjects aged
25 years with 3 days of dietary data, and medical condition information (n=7,207). A positive response to having been informed by a doctor of having diabetes, heart disease, high blood pressure, cancer, osteoporosis, and stroke indicated the presence of chronic medical condition(s) (n=2,368). Sex-specific linear and logistic regression analyses adjusted for multiple covariates were used to examine the relation of age and morbidity status with nutrient intake.
Results: In men, age was associated with an increased risk of consuming <100% of the Recommended Dietary Allowance (RDA) of vitamin E, vitamin B12, calcium, zinc, and iron (p<0.05), and self-reported morbidity was associated with an increased risk of consuming <100% of the RDA of protein. Relative to men, women were more likely to report less than the RDA of most nutrients examined; however, neither age nor chronic disease status were associated with increased likelihood of reporting <100% of the RDA of any of the nutrients examined. In women, the probability of reporting <100% of the RDA of vitamin A, vitamin B6, folate, vitamin C, and iron, and in men, the probability of reporting <100% of the RDA of vitamin C, declined with age (p<0.05). No adverse effect of age and chronic disease interaction on intake of most nutrients was noted in men or women.
Conclusions: Chronologic age and morbidity were associated with an increased risk of inadequate intake of several nutrients in free-living, independent men but not in women.
Key words: chronic diseases, age, aging, elderly, nutrient intake, CSFII, NFCS, nutrition survey, morbidity, nutritional status, diet quality
| INTRODUCTION |
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The elderly are also at an increased risk of marginal intakes of several nutrients due to a variety of reasons unrelated to the presence of morbidity [4]. Given the high prevalence of morbidity with age and the potential impact of morbidities on nutrient intake, surprisingly little is known about whether morbidity modifies the relation of age with nutrient intake. The issue is important because nutritional adequacy can serve not only as an adjunct to medical management, it may also favorably affect the progression of the disease, improve quality of life, and prolong ability to maintain independent function while contributing to decreased health care expenditure [5,6]. The purpose of this study was to examine the relation of morbidity and age with dietary nutrient intake profiles in a large, nationally representative sample.
| METHODS |
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Analytic Sample
For the purpose of analyses reported here, all respondents aged
25 years, with 3 complete days of dietary information were eligible for inclusion in the analytic sample (n=7394). From this eligible sample, we excluded women who were pregnant (n=68), or lactating (n=48). Also excluded were subjects who did not respond or answered "dont know" to any of the questions about morbidity (n=71). The final analytic sample included 7,207 respondents aged
25 years (3,023 men and 4,184 women), with an analytic response rate of 43.7%.
Information on Chronic Medical Conditions
The CSFII 198991 queried respondents about whether a doctor had ever informed them of having a number of medical conditions. A positive response to questions on having been informed by a doctor about having diabetes, heart disease, high blood pressure, cancer, osteoporosis, and stroke was considered to indicate morbidity. Using these criteria, 2,368 respondents from the analytic sample had at least one morbid condition (unweighted estimate).
Dietary Variables
The dietary variables examined included 3-day average intakes of energy, percent energy from macronutrients, and percent Recommended Dietary Allowances (RDAs) of the vitamins A, E, B6, C, B12, folate, and the minerals calcium, zinc, iron, and potassium [8]. These nutrients were selected because they have been identified as current or potential problems in the US population [9], and from available literature on problem nutrients in the elderly [10]. Because RDA is not available for potassium, we used the estimated minimum requirement of healthy adults, 2000 mg, as the standard [8].
In addition, two nutrient-based measures of overall diet quality were developed. These included: 1) Nutrient Adequacy Score 67 (NAS67), and 2) Nutrient Adequacy Score 100 (NAS100). The NAS67 is a modification of a score reported by Davis et al [11], and is a sum of the number of nutrients (from a total of 11-protein, vitamins A, E, B6, B12, C, folate, and the minerals calcium, zinc, iron, and potassium) reportedly consumed at least at the level of 67% of the age-sex-specific RDA. The NAS100 is similar except using the criterion of 100% of the RDA.
Statistical Analyses
Descriptive statistics for 3-day average dietary intake of energy, percent energy from macronutrients, and selected vitamins and minerals were obtained by categories of chronic medical condition status (none, any), by sex, and by age group (25 to 50, 51 to 64, 65 to 74, and
75 years). The percentage of the population in various categories of socio-demographic and lifestyle variables by morbidity status was also obtained. Nutrient estimates are limited to those reportedly consumed in the diet; nutrients consumed as supplements are not included in these estimates.
Linear regression modeling was used to examine the independent effect of age, morbidity, and age-morbidity interaction on each continuously measured dietary variable. All regression models were stratified by sex. The regression models included each dietary variable as an outcome variable, with age (continuous), chronic medical condition status (none, any), race (white, black, hispanic, other), income as percent of poverty threshold (0 to 130%, 131 to 350%, and
351%), and an age-morbidity status interaction term as predictor variables.
We also determined the percentage of the population consuming <67% and <100% of the sex-age-specific RDA of various nutrients stratified by sex, and morbidity status. It has been suggested that the use of a fixed cutoff of the RDA, e.g., two-third (67%) of the RDA, for determining adequacy may be inappropriate for a variety of reasons [12]. Therefore, the results are presented using 100% of the RDA as cutoff. Because the outcome in these analyses is dichotomous (consuming <100% or
100% of the RDA of each nutrient), we used logistics regression models for examining the relation of age and chronic medical condition status with the risk of consuming <100% or
100% of the RDA of various nutrients. The sex-specific logistic regression models included age, morbidity status, race, income, and an age-morbidity status interaction term as covariates.
Due to the complex multi-stage sampling design of the CSFII survey, standard errors of proportions, means, and regression coefficients were determined using special statistical software, SUDAAN [13]. A two step weighting of the CSFII sample combined sampling weights from the basic and the low-income samples into a single sample [7]. The USDA assigned weighting factors also correct for differential probabilities of selection, non-response, and demographic characteristics [7]. Although we used the USDA assigned sampling weights in all analyses, the possibility of differences in the diets of responders and non-responders to the survey may limit the representativeness of our results.
| RESULTS |
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The mean±SE of age, and the dietary variables, by morbidity status, and by age group, are presented in Tables 1 and 2 for men and women, respectively.
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In women, age was related with an increase in the mean intakes of % RDAs of vitamin A, folate, vitamin C, iron, NAS67, and NAS100 (p<0.05). For all other nutrients (vitamin E, vitamin B6, vitamin B12, calcium, zinc, and potassium), age effect was not significant (p>0.05) in women.
Morbidity Effect
Men without morbidity had higher mean intakes of energy, % energy from fat, and percent RDA of protein, but lower % energy from carbohydrate, relative to men with morbidity (p<0.05). Morbidity was associated with higher % RDA of vitamin C in women (p<0.05).
Age and Morbidity Interaction
No interaction effect of age and chronic medical condition status on nutrient intake was evident in women. In men, the age-morbidity interaction effect was noted for intake of energy, % energy from carbohydrate and fat, and % RDA of protein. Age was associated with lower energy, % energy from fat, % RDA of protein, and higher % energy from carbohydrate in men with and without morbidity; however, the slope was steeper in those with morbidity for each of these nutrients.
Percentage of the Population at Nutritional Risk
Table 3 presents the percentage±SE of the population reporting <100% of the sex-age-specific 1989 RDA of the various nutrients, by morbidity status, by sex, by age group. Irrespective of morbidity status, a large percentage of the population in every agegroup reported consuming less than 100% of the RDA of vitamin A, vitamin E, vitamin B6, and the minerals zinc, and calcium. Likelihood of consuming <100% of all nutrients except vitamin A was higher in women relative to men (p<0.05). Expectedly, a higher proportion was at risk using 100% of the RDA as cutoff compared with the lower cutoff of 67%. (Data using 67% of the RDA as standard are not shown.)
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A slightly higher proportion of men reporting chronic medical condition(s) were at risk of consuming less than the RDA of protein, but the probability of reporting less than the RDA of vitamin E was higher in men without morbidity (p<0.05). Women with morbidity were less likely to report <100% of the RDA of iron. Interaction effect of age and chronic medical condition status on vitamin C intake was evident in men. The age-associated decline in men reporting <100% of the RDA of vitamin C was greater in those with morbidity.
Socio-Demographic and Lifestyle Characteristics of the Analytic Sample
Table 4 presents the percentage of subjects in various categories of socio-demographic and lifestyle variables, by morbidity status. Women made up nearly 57% of those with morbidity. Approximately 70% of those with morbidity were over the age of 51 relative to only 27% for those without morbidity. Those with morbidity were more likely to have <12 years of schooling, and lower income.
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| DISCUSSION |
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Because examining mean nutrient intakes provides little information about the percentage of population at nutritional risk, according to Goodwins suggestion [14], we examined the percentage of men and women consuming less than 100% of the RDA of nutrients according to age and morbidity status (Table 3). In men, increased risk of consuming less than the RDA of several nutrients (protein, vitamin E, vitamin B12, calcium, zinc, and iron) was associated with age, and morbidity (protein). Although relative to men, a higher proportion of women consumed less than the RDA of nearly all nutrients examined, age or morbidity were not associated with an increased risk of consuming less than the RDAs. Conversely, the likelihood of consuming less than the RDA of vitamin A, vitamin C, folate, vitamin B6, and iron declined with age in women. Others have also reported gender differences in nutrient intakes of free living elderly [15,16]. Generally, the age related trends in macro- and micronutrient intake in our study are comparable to estimates from the first phase of the third National Health and Nutrition Examination Survey [17,18]. However, because of the cross-sectional nature of our study, cohort and aging effects can not be differentiated. Notably though, cohort effects were not seen for energy and macronutrient intake in the Baltimore Longitudinal Study of Aging [19].
Limitations of the current RDAs as standards for evaluating age-specific nutrient intake also affect the interpretation of data reported in this study. The 1989 RDAs categorize adults into two categories, 25 to 50 and 51+ years [8]. Due to paucity of data on older adults, past RDAs reflected extrapolation of data from younger adults [20]. With the exception of a lower iron RDA for women in the 51+ category, the RDAs of other nutrients examined in the present study are the same for the two age categories [8]. After reviewing the available evidence, Russel concluded that the 1989 RDAs for vitamin B6, folate, vitamin B12, vitamin D, and calcium may be inadequate for the elderly, where as the RDA for vitamin A may be too high [20]. Future RDAs will likely be different due to the increased availability of evidence on nutrient requirements of older adults, and the evolution in current thinking about the role of nutrients in chronic disease prevention [21].
Our data support the notion of age differences in attention to dietary guidance reported earlier in the nutrition monitoring report [9]. In both men and women, percent energy from fat declined and percent energy from carbohydrate increased with age. These trends may reflect age-associated patterns of food selection. For example, the 60+ year olds were more likely to consume five or more servings of fruits and vegetables, lower fat dairy products, fish and poultry, but were less likely to report beef or salad dressings [9]. In women, these presumed age-associated differences in food selection affected intake of several nutrients favorably. However, in men, the risk of inadequate intake of nutrients contributed by animal foods, and visible or hidden fats (protein, vitamin E, vitamin B12, calcium, zinc, and iron) increased with age. Further investigation of gender and age differences in food selection practices with their potential impact on nutrient intakes of the US population is indicated.
Most available studies of the relation of nutrient intake with morbidity and age have studied elderly subjects (e.g., over 65 years), therefore, the results from these studies are not directly comparable to those reported here. Elderly Finnish men (but not women) with chronic diseases had lower energy intake relative to those without disease [22]. Similar associations were noted in the present study. Free-living elderly with poor physical health status were reported to have lower intakes of vitamins A and C [23,24]. We noted no such associations.
Examination of nutrient intake is only one parameter for assessment of nutritional health. Nutrient absorption, metabolism, utilization, and excretion may be altered by age, pathologic states, or their pharmacologic management [25,26]. Therefore, a comprehensive assessment should include biochemical, and functional measures of nutritional status, which are not available in this study.
It should be noted that the estimates of energy intake for adult participants of CSFII have been reported to be approximately 350 kcals lower than comparable estimates from the first phase of the NHANES III, 198891 [9], suggesting underreporting of food intake in the CSFII sample. Underreporting of food intake has been recognized as a problem in all dietary surveys including the NHANES [27]. Because nutrient intake is strongly correlated with energy intake [28], it is likely that the nutrient intake may be underestimated in our study and the proportion at risk of consuming less than the RDA of various nutrients may be overestimated. However, despite underreporting in both men and women, mean intakes for most nutrients were close to or above the RDAs. Whether a differential in qualitative misreporting due to age or morbidity status exists is not known. To our knowledge the issue of qualitative misreporting has been examined in relation to adiposity only [29,30].
The results of the present study should be interpreted cautiously with the following limitations in mind. First, chronic medical condition status was based on self-report of six medical conditions. No medical record or other health history information was available for this sample to validate the chronic medical condition status measure. However, self-report data for major chronic conditions have been shown to be valid in both young and older subjects [3133]. Also, the association of increased frequency of disability, light level of physical activity, and poor self-described health status in those with self-reported chronic medical condition(s) provides an indirect validation of this measure.
Secondly, the CSFII questionnaire did not include queries on all leading causes of morbidity in the elderly. Especially notable omissions include arthritis, respiratory diseases and cognitive impairments, which may potentially have impact on dietary intake [23,34]. Therefore, it is possible that respondents with medical conditions not included in the CSFII questionnaire or those with undiagnosed disease may be misclassified into the morbidity-free group. Such misclassification may contribute to inability to find a chronic disease effect in regression models. Furthermore, no information was collected on severity of the self-reported medical condition(s), living arrangements, care-giver support, and functional status that might affect nutrient intake. Also, the low response rate to the CSFII survey indicates cautious generalization of the data presented in this study.
In conclusion, neither age nor morbidity were correlates of increased nutritional risk for women in this study. However, in men, an increased risk of consuming <100% of the RDA of dietary protein, vitamin E, vitamin B12, calcium, zinc, and iron was associated with increasing chronologic age, and morbidity (protein only). Thus implying that nutritional interventions for older men require particular attention to these nutrients. Gender differences in food selection patterns should be examined to elucidate gender differences in the relation of age with nutrient intake. More information on age-differences in qualitative and quantitative misreporting is also needed. Lastly, examination of age and morbidity interaction in relation to nutritional health using objective measures of nutritional status presents as an additional area of study.
| ACKNOWLEDGMENTS |
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Received December 1, 1997. Accepted July 1, 1998.
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