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Original Research Communications |
| ABSTRACT |
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Objective: This study was designed to explore the applicability of published regression equations to estimate stature of Puerto Rican and other Hispanic elderly persons living in the northeastern United States and to formulate ethnicity-specific equations for these persons.
Design: The study subjects (6092 y of age) included 569 Hispanics and a comparison group of 153 non-Hispanic whites. Equations to estimate stature of Hispanics and Puerto Ricans living in the northeastern United States were developed with regression models in a randomly selected subgroup of the Hispanics. These equations were tested with the remaining Hispanic subgroup.
Results: The published equations significantly overestimated stature of our Hispanic subjects. Equations developed for Massachusetts Hispanics and Puerto Ricans provided estimates of stature that did not differ significantly from measured stature. We found further that equations for non-Hispanic whites published in 1985 predicted statures of our relatively low-income, non-Hispanic white subjects better than did newer 1998 equations developed from a national sample.
Conclusions: The stature of elderly Hispanics from the northeastern United States can be estimated by using equations derived from the same population. These, or similar equations, should be used to estimate stature of frail elderly persons for whom standing height cannot be taken accurately. Socioeconomic status as well as ethnicity may affect results when knee height equations are used.
Key Words: Anthropometry knee height stature elderly Hispanics Puerto Ricans northeastern United States HHANES Hispanic Health and Nutrition Examination Survey third National Health and Nutrition Examination Survey NHANES III Mexicans Massachusetts Hispanic Elders Study
| INTRODUCTION |
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Knee height has been proposed to estimate the stature of elderly (810) and disabled (11, 12) subjects. The aging process does not affect the length of long bones, such as those in arms and legs, as it does vertebral height (1315). Furthermore, predicted stature is considered a valid surrogate to be used in the construction of anthropometric indexes (10) and adjusting and interpreting of body-composition measurements (14, 16, 17).
Chumlea et al (8) developed equations to estimate the stature of elderly subjects using knee height. More recently, these authors proposed new equations to estimate stature from knee height using the nationally representative sample from the third National Health and Nutrition Examination Survey (NHANES III; 10). These new equations are specific for the 3 ethnic groups studied in NHANES III: non-Hispanic whites, non-Hispanic blacks, and Mexican Americans.
Because of the recency of publication of these 1998 ethnicity-specific equations, there is no information available about the application of such equations to other elderly populations. However, the ability of such equations to successfully predict stature in other ethnic groups seems questionable. Myers et al (18) showed that the 1985 Chumlea et al (8) equations led to systematic errors when applied to elderly Japanese Americans. Prothro and Rosenbloom (19) showed that ethnicity-specific equations were needed to predict the stature of elderly African Americans.
The study reported here originated from an epidemiologic survey, the Massachusetts Hispanic Elders Study (MAHES), which included primarily Puerto Ricans. The purpose of this analysis was to explore the applicability of recommended regression equations (8, 10, 20) to estimate the stature of an elderly Hispanic group residing in Massachusetts and, if necessary, to formulate ethnicity-specific equations that will allow valid estimations of the stature of those subjects who are difficult to measure because of postural problems.
| SUBJECTS AND METHODS |
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Information on posture was collected during the anthropometric survey, which was approved by the Human Investigation Review Committee of Tufts/New England Medical Center. Subjects with kyphosis or other physical problems that prevented them from standing fully straight for their stature measurements (n = 207) or with leg amputations (n = 8) were excluded from analysis, as were 88 for whom there were incomplete anthropometric data. In addition, the ratio of knee height to total height was estimated. Those subjects outside the mean ± 3 SDs were considered outliers and were also excluded from this study (n = 5). In total, 308 subjects (210 Hispanics and 98 non-Hispanic whites) were excluded, leaving a working sample of 569 Hispanics and 153 non-Hispanic whites. The Hispanic subjects selected for this study were further randomly divided into 2 groups: a development group (n = 294), in whom regression equations were developed to estimate stature, and a validation group (n = 275), in whom the equations were tested.
Measurements
The anthropometric measures used in this study were stature (cm) and knee height (cm). Information about whether the subject had straight or stooped posture or other problems affecting posture was also recorded. Measures were taken in duplicate at the subjects' homes. A Harpenden pocket stadiometer (Holtain Ltd, Crosswell, United Kingdom) that included a base plate with an attached steel tape centimeter ruler was used to measure stature and sitting knee height. Measurements were recorded to the nearest 0.1 cm. Knee height was defined as the distance from the anterior surface of the thigh, just proximal to the patella, to the sole of the foot when the knee and ankle were flexed at a 90° angle (8).
Statistical methods
Descriptive analyses of the characteristics of the sample and cross-group comparisons were conducted by using the general linear models (GLM) procedure and 2 independent sample t tests. Pearson correlations were used to measure associations between stature, knee height, and age within each of the ethnic and sex groups. SPSS for WINDOWS (version 7.5; SPSS Inc, Chicago) was used for all analyses.
Previously specified equations are presented in Table 1
. They include those developed in a group of 269 non-Hispanic whites (6590 y of age) and originally recommended for elderly Americans by Chumlea et al (8), and the newly published equations for elderly non-Hispanic whites and Mexican Americans. These new equations were developed with 1369 non-Hispanic white men (aged 60102.8 y), 1472 non-Hispanic white women (aged 6098.5 y), 497 Mexican American men (aged 6096.7 y), and 457 Mexican American women (aged 6098.5 y) (10). The equations in Table 1
were tested for applicability to our study group. The differences between the measured stature of the study subjects and stature estimated with those equations were assessed by using paired t tests to evaluate the applicability of these formulas to estimate stature of MAHES subjects.
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| (1) |
The regression equations were used to predict stature of MAHES subjects in the validation group. Paired t tests were performed to determine the magnitude and significance of the differences between measured stature and estimated stature produced with each of the Hispanic and Puerto Rican regression equations.
| RESULTS |
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0.001). No significant sex differences in age were detected. The means and SDs for age, stature, and knee height, by sex and ethnic group from MAHES are shown in Table 2
0.001) and knee height (P
0.001) remained significant after GLM adjustment for age in both sexes. Puerto Ricans also differed from other Hispanics in age, stature, and knee height; these differences in stature (P
0.001) and knee height (men: P
0.001; women: P
0.01) remained significant after adjustment for age.
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60 y) to have about the same stature as HHANES Puerto Ricans but to be shorter than the HHANES Mexican Americans in both sexes. Both male and female MAHES Puerto Ricans were
1.0 cm shorter in stature than their HHANES counterparts. Likewise, when compared with NHANES III Mexican Americans, our northeastern Hispanic subjects of both sexes also had shorter statures but larger knee heights. Women from both ethnic groups had similar mean ages, but Puerto Rican men were a little younger than were NHANES Mexican American men. There were no age differences between MAHES and NHANES non-Hispanic whites but our non-Hispanic white subjects were shorter in stature and had shorter knee heights than their NHANES III counterparts.
Pearson correlations between stature and knee height (Table 3
) were strong and positive for each of the ethnic and sex subgroups of the study sample. Age was significantly and negatively associated with stature in each group of women and for non-Hispanic white men. Age was not significantly associated with stature in Hispanic men in total or for the Puerto Rican or other Hispanic subgroups. Knee height and age correlations were also negative but were only significant for non-Hispanic white and Puerto Rican women.
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5.0 cm (P < 0.001) and the Mexican American equations overestimated stature by 2.4 cm (P < 0.001) for these other Hispanic men and by 1.8 cm (P < 0.001) for women.
We also estimated non-Hispanic white stature using the 1985 and 1998 Chumlea et al equations (8, 10) (Table 4
). The 1985 equation estimated stature of non-Hispanic white men accurately, with only 0.1 cm of difference between measured and estimated stature. In the case of the non-Hispanic white women, the 1985 equation overestimated stature significantly by
1.7 cm (P < 0.001). The newer 1998 non-Hispanic white equations (10) predicted stature of MAHES non-Hispanic white men with less accuracy, overestimating stature by
2.8 cm (P < 0.001). For women, the 1998 equation overestimated stature by >2.1 cm (P < 0.001), slightly more than did the 1985 equation.
Clearly, more specific predictors of stature for northeastern Hispanic elderly persons are needed. Therefore, we used the data from the development subset of the study group to formulate regression models to estimate stature from knee height and age of elderly MAHES Hispanics (Table 5
). Knee height and age resulted in strong models for the explanation of the variance in stature of Hispanic women (R2 = 0.73) and Puerto Rican women (R2 = 0.70). Knee height alone made up the final model for stature of men in the Hispanic (R2 = 0.72) and Puerto Rican (R2 = 0.77) groups. The addition of age did not improve the regression models in either group of men.
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| DISCUSSION |
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After adjustment for age, elderly Hispanic men and women were shorter and had shorter knee heights than their respective non-Hispanic white comparison group. Racial and ethnic differences in stature of elderly subjects have also been reported in the literature (4, 5, 10). Ethnic differences in length of body segments have also been documented. For example, Chumlea et al (10), working with the NHANES III data reported that non-Hispanic whites had significantly larger knee height and sitting height than did their Mexican American counterparts.
When compared with the HHANES elderly Puerto Rican subjects, our MAHES Puerto Rican subjects were shorter, which may be due to differences in age ranges in the 2 samples. On the other hand, NHANES Mexican Americans, with a larger age range, were taller but had smaller knee heights than the MAHES Hispanics. Differences in stature between MAHES Hispanics and the nationally representative samples from HHANES and NHANES reinforce previous reports indicating differences among Hispanic subgroups (21).
Changes in stature have been estimated at 3.65.6 cm between the ages of 25 and 74 y by using the samples from the National Health Examination Survey (NHES, 19601962), NHANES II (19761980), and HHANES (19821984) (4). These were cross-sectional samples, in which changes in stature with age or with secular trends cannot be separated. Declines in stature with age, estimated with longitudinal studies, have been documented (2225). For example, in the SENECA Study, a longitudinal study of elderly Europeans, there was a decrease of
12 cm in stature over 4 y from 7075 to 7479 y of age (22). Differences in stature between the youngest and oldest groups (2270 y of age) in a longitudinal study of non-Hispanic white men, the Normative Aging Study, was estimated at 7.3 cm (24). The investigators in this study were able to estimate, over a 10-y follow-up period, the amount of the difference in height due to aging (4.3 cm) and to secular trends (3.00 cm) (24).
The significant, positive correlation between stature and recumbent knee height reported previously by other researchers (8, 18, 19) for elderly non-Hispanic whites was also observed in the elderly Hispanic and non-Hispanic white subjects studied here using sitting knee height. Analysis of reliability, when using recumbent or sitting position to measure knee height, has produced high reliability coefficients (8). Knee height is considered a reliable measure because it is easy to measure in either a sitting or a recumbent position, regardless of the individual's mobility (10).
Both Hispanic and non-Hispanic white MAHES women had significantly smaller knee heights with increasing age, a finding that has also been reported by others (8, 11). This could be explained by cohort differences; however, the cross-sectional sample used here does not allow further exploration of this issue. Age was not significantly associated with knee height for the Hispanic men included in the study sample. Similar results were reported for men in some previous studies (8, 18), although significant differences in knee height with age have been reported in other groups of men (10, 24).
The recently published equations for Mexican Americans (10) did not to predict accurately the stature of the MAHES subjects. This clearly shows that these equations should not be used for non-Mexican American Hispanic groups in the northeastern United States. The elderly Hispanics in this study were from different ethnic backgroundsPuerto Rican, Dominican, Cuban, and Central and South Americanand included only a few Mexican Americans. These MAHES Hispanics had shorter stature and larger knee height than the NHANES Mexican Americans, indicating a different proportional distribution of body segments. Further testing of these equations for Mexican Americans is needed in the southwestern United States, where they may be more appropriately used.
With the MAHES sample of northeastern non-Hispanic whites, the 1985 non-Hispanic white equations (8) predicted stature of men more accurately than did the new 1998 equations developed by Chumlea et al (10). The differences between measured and predicted stature of MAHES non-Hispanic white women were significantly different when using the 1985 and 1998 non-Hispanic white equations, although the difference obtained with the 1985 equation (1.7 cm) was slightly lower than the one obtained with the 1998 equation (2.1 cm). These findings, particularly the lack of precision of the 1998 equations, were unanticipated. The 1985 study was based on a small convenience sample of non-Hispanic whites who were free of postural problems, whereas the 1998 equations were based on the total sample from NHANES III without restrictions based on posture (10). The MAHES non-Hispanic whites included in the study reported here were also free of obvious postural problems, which may make them more similar to the 1985 group.
Cohort differences among the MAHES and the other non-Hispanic white groups could also be due to socioeconomic and ecologic conditions. The non-Hispanic white group of the MAHES study is a comparison group obtained from the same neighborhood in which the Hispanic subjects resided. In general, this sample had a lower-than-average socioeconomic level, making them different from the national population. A significant association between socioeconomic status and loss of stature has been reported, with a slower rate of decline for women in the high socioeconomic status categories compared with those in the lower category (7). Despite the inclusion of subjects with postural problems, the NHANES non-Hispanic whites were taller than the MAHES subjects, with mean stature of 174 cm compared with 170 cm for men and 159 cm compared with 157 cm for women, respectively. Mean ages were similar between the 2 groups at
71 y for men and women.
Puerto Ricans are the largest Hispanic subgroup living in the northeastern United States and they made up >50% of the MAHES sample of Hispanics. Therefore, we conducted specific analyses for this group and compared them with the rest of the elderly Hispanics living in Massachusetts. The differences observed between the Puerto Ricanspecific and the more general Hispanic equations were not large. We therefore concluded that the use of only one set of equations for this group of Hispanics, including Puerto Ricans, was acceptable. For more specific work with Puerto Ricans or other Hispanic groups it is possible that more accurate results may be obtained with the use of subgroup-specific equations.
In conclusion, equations were developed to estimate the stature of elderly Hispanics residing in the northeastern United States. These equations will be used to estimate stature in subjects for whom standing height was not measured or in whom postural problems were indicative of unreliable measures of stature. Existing equations for elderly Mexican Americans are not appropriate for use with Puerto Ricans or for other heterogeneous groups of elderly Hispanics. The equations developed here for northeastern Hispanics and Puerto Ricans require further testing to determine their applicability in independent samples.
| FOOTNOTES |
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2 The contents of this publication do not necessarily reflect the views or policies of the US Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the US government.
3 Supported in part by NIA grant AG10425-05 and US Department of Agriculture contract 53-3K06-01.
4 Address reprint requests to OI Bermúdez, Dietary Assessment Research Program, US Department of Agriculture/HNRCA, 711 Washington Street, Boston, MA 02111. E-mail: Bermudez_he{at}hnrc.tufts.edu.
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