PubMed Health⌕ Search

Biomedical subjects

A C Looker

Publications and source records attributed to A C Looker.

At least 19 recordsLinked to original sources
PubMed2006

Impact of increased overweight on the projected prevalence of osteoporosis in older women.

INTRODUCTION: Overweight is increasing worldwide, but particularly in the United States of America. Higher body weight is associated with higher bone density, so our goal was to estimate whether the higher prevalence of overweight is likely to reduce osteoporosis among older women. METHODS: We calculated the prevalence of osteoporosis by weight status in older women using data from the third National Health and Nutrition Examination Survey (NHANES III, 1988-94). We defined overweight as a body mass index (BMI) >or=25 and osteoporosis as a femur neck bone mineral density (BMD) value 2.5 standard deviations or more below the mean of that of young women. To estimate the expected prevalence of osteoporosis, we applied the prevalence of osteoporosis by weight status from NHANES III to the corresponding weight status prevalence from NHANES 1999-2002. RESULTS: Of older women in NHANES 1999-2002, 68% were overweight compared to 62% in NHANES III. Overweight status was significantly related to osteoporosis prevalence (P < 0.001). However, the expected prevalence of osteoporosis in NHANES 1999-2002 was only slightly lower than that seen in NHANES III (16.8% vs 18.1%, respectively). CONCLUSIONS: The increasing prevalence of overweight among older US women appears unlikely to be accompanied by a significant reduction in osteoporosis.

Aged↗
PubMed2004

Maternal history of osteoporosis and femur geometry.

Most studies that have examined the role of skeletal factors in the relationship between an individual's family history of fracture or osteoporosis and their fracture risk have focused on bone density. In this study, we expanded the scope of skeletal factors to include geometric properties (subperiosteal width, section modulus, cortical thickness, and buckling ratio) in addition to areal bone mineral density (BMD). We compared these skeletal factors at the femur neck and shaft by self-reported maternal history of osteoporosis (OP HX) from 5334 non-Hispanic whites, ages > or =20 years in the Third National Health and Nutrition Examination Survey (NHANES III, 1988-94). A total of 213 men and 315 women reported a positive OP HX (e.g., their biological mother had sustained a hip fracture after age 50 years or had a physician's diagnosis of osteoporosis). Differences in bone density and geometry by OP HX were examined after adjusting for potential confounding variables. Several bone parameters differed significantly by OP HX in both sexes at the femur neck, but none differed at the femur shaft. At the neck, those with a positive OP HX had values that differed by approximately 3% to 4% (lower for BMD, bone mineral content (BMC), cross-sectional area, and cortical thickness; higher for buckling ratios) from those with a negative OP HX (P < 0.05). The magnitude of these relationships was similar in both sexes, but differences were greater in younger versus older adults. In conclusion, both men and women with a positive maternal history of osteoporosis may be at greater risk of femur neck fracture owing to thinner cortices and lower BMC, which in turn results in potentially greater cortical instability (buckling ratio) at this skeletal site.

Absorptiometry, Photon↗
PubMed2002

Patterns of osteocalcin and bone specific alkaline phosphatase by age, gender, and race or ethnicity.

A variety of biochemical markers of bone turnover that assess bone formation or resorption are now available for research and clinical application. However, our understanding of the usual pattern of these measures over age in the general population is limited. Therefore, values of two bone formation markers, serum osteocalcin (Oc) and bone specific alkaline phosphatase (bone ALP), were compared by age, gender, and race or ethnicity using serum obtained from a subsample of blacks, whites, and Mexican Americans from the third National Health and Nutrition Examination Survey (NHANES). In all racial and ethnic groups, mean values of both serum Oc and bone ALP were lower in women than in men <50 years old. In individuals > or =50 years of age, Oc was significantly higher in women than in men. When analyzed in these two broad age groups, Oc was lower in older black men than in white or Mexican American men, but bone ALP was not different among the groups. In women, Oc levels tended to be lower in the black women than in white or Mexican American women. In contrast, bone ALP tended to be lower in white women than in black or Mexican American women. On the other hand, when analyzed by decade, patterns differed between the two markers in both men and women. In women, both Oc and bone ALP rose postmenopausally. However, bone ALP plateaued in the sixth through eighth decades, whereas Oc levels tended to increase further. In men, Oc was highest in the 20-29 year age group, declined and stabilized, then increased again in the seventh decade. In contrast, mean bone ALP did not differ by decade in men. Our data document differences in levels of circulating Oc and bone ALP by age, gender, and race/ethnicity. The age patterns reflected by the two markers are not concordant and distinctions are most evident in the latter decades. Our findings suggest that the specific osteoblast activity reflected by these markers responds differently to the physiologic changes that occur later in life.

Adult↗
PubMed2001

Weight loss from maximum body weight among middle-aged and older white women and the risk of hip fracture: the NHANES I epidemiologic follow-up study.

Although weight loss increases bone loss and hip fracture risk in older women, little is known about the relation between weight loss in middle-aged women and subsequent hip fracture risk. The objective of this study was to determine the association between weight loss from reported maximum body weight in middle-aged and older women and the risk of hip fracture. Data were from a nationally representative sample of 2180 community-dwelling white women aged 50-74 years from the Epidemiologic Follow-up Study of the first National Health and Nutrition Examination Survey (NHEFS). In this prospective cohort study, incident hip fracture was ascertained during 22 years of follow-up. The adjusted relative risks associated with weight loss of 10% or more from maximum body weight were elevated for both middle-aged (RR 2.54; 95% CI 1.10-5.86) and older women (RR 2.04; 95% CI 1.37-3.04). For both ages combined, women in the lowest tertile of body mass index at maximum who lost 10% or more of weight had the highest risk of hip fracture (RR 2.37; 95% CI 1.32-4.27). Weight loss from maximum reported body weight in women aged 50-64 years and 65-74 years increased their risk of hip fracture, especially among those who were relatively thin. Weight loss of 10% or more from maximum weight among both middle-aged and older women is an important indicator of hip fracture risk.

Aged↗
PubMed2001

Does body size account for gender differences in femur bone density and geometry?

The extent to which greater bone strength in men is caused by proportionately greater bone mass versus bigger bone size is not clear, primarily because the larger overall body size of men has made direct comparisons of skeletal measures difficult. We examined gender differences in femur neck (FN) areal bone mineral density (BMD) values collected from 5,623 non-Hispanic whites aged 20+ years in the third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) before and after correction for measured height and weight. We supplemented the conventional areal BMD data (Hologic QDR 1000) with measurements of areal BMD and geometric properties (subperiosteal width, section modulus, and cortical thickness) made at narrow "cross-sectional" regions traversing the FN and the proximal shaft using a structural analysis program. Before body size adjustment, men had significantly higher values than women for all variables at the three measurement sites (p < 0.0001). Adjustment for body size reduced the differences between the sexes for all variables but had a greater effect on BMD (1-8% higher in men) than on geometry (5-17% higher in men). When examined by age, the sex discrepancy was significantly greater in the older group for all variables except subperiosteal widths. We conclude that although body size difference may account for most of the areal BMD difference between men and women, male bones are still bigger in ways that suggest greater bone strength. These differences may contribute importantly to lower fracture risk in men.

Absorptiometry, Photon↗
PubMed2001

Jogging and bone mineral density in men: results from NHANES III.

OBJECTIVES: This cross-sectional population-based study assessed the association of jogging with femoral bone mineral density (BMD) in men. METHODS: Data are from a nationally representative sample of 4254 men aged 20 to 59 years from the Third National Health and Nutrition Examination Survey (NHANES III). Total femoral BMD was measured by dual energy x-ray absorptiometry. Jogging was self-reported. RESULTS: Jogging (any vs none) was strongly associated with higher BMD in multivariate models (P < .01) for both young and middle-aged men. Men who jogged 9 or more times per month had higher BMD levels than those who jogged only 1 to 8 times per month (P = .01). CONCLUSIONS: Jogging is associated with higher femoral neck BMD in men. Additional large-scale studies that measure all aspects of jogging are warranted.

Absorptiometry, Photon↗
PubMed2000

Clinical use of biochemical markers of bone remodeling: current status and future directions.

Biochemical markers of bone turnover provide a means of evaluating skeletal dynamics that complements static measurements of bone mineral density (BMD). This review evaluates the use of commercially available bone turnover markers as aids in diagnosis and monitoring response to treatment in patients with osteoporosis. High within-person variability complicates but does not preclude their use. Elevated bone resorption markers appear to be associated with increased fracture risk in elderly women, but there is less evidence of a relationship between bone formation markers and fracture risk. The critical question of predicting fracture efficacy with treatment has not been answered. Changes in bone markers as currently determined do not predict BMD response to either bisphosphonates or hormone replacement therapy. Single measurements of markers do not predict BMD cross-sectionally (except possibly in the very elderly), or change in BMD in individual patients, either treated or untreated. On the other hand, research applications of bone turnover markers are of value in investigating the pathogenesis and treatment of bone diseases. Markers have potential in the clinical management of osteoporosis, but their use in this regard is not established. Additional studies with fracture endpoints and information on negative and positive predictive value are needed to evaluate fully the utility of bone turnover markers in individual patients.

Biomarkers↗
PubMed2000

Serum ferritin and death from all causes and cardiovascular disease: the NHANES II Mortality Study. National Health and Nutrition Examination Study.

PURPOSE: The purpose of this study was to assess the association between serum ferritin and death from all causes, cardiovascular diseases (CVD), CHD and myocardial infarction (MI). Positive body iron stores have been proposed as a risk factor for coronary heart disease (CHD). While most epidemiologic studies using serum ferritin and other measures of body iron stores have not found an association between iron and heart disease risk, the hypothesis remains controversial. As a result, we examined the relationship of serum ferritin, the principle blood measure of body iron stores, to risk of death in a cohort with a standardized exam and long follow-up. METHODS: The baseline data for this prospective cohort study were collected in 1976-1980 as part of the second National Health and Nutrition Examination Study (NHANES II) with mortality follow-up using the National Death Index (NDI) through December 31, 1992. The analytic sample (n = 1604) consisted of 128 black men, 658 white men, 100 black women and 718 white women 45-74 years of age at baseline who, based on self-reported data, were free of coronary heart disease at baseline and had no missing data. The main outcome measures were the relative risk of death for persons with serum ferritin levels: <50 microg/L; or 100-199 microg/L; or > or =200 microg/L was compared to persons with serum ferritin levels of 50-99 microg/L adjusted for possible confounding using the Cox proportional hazards model. RESULTS: Most of the deaths were among white men (n = 254) and women (n = 168). There were relatively few deaths among black men (n = 50) and too few in women (n = 23) to reliably model. The largest number of CVD (n = 119), CHD (n = 82), and MI (n = 49) deaths were in white men while there were 69 CVD, 45 CHD and 13 MI deaths in white women. Black men with a serum ferritin level of <50 microg/L had a significantly higher adjusted risk of death from all causes (RR = 3.1 with 95% confidence limits of 1.5-6.5). There were no other statistically significant associations for all causes mortality for the other three race/sex groups. Additionally, there were no statistically significant associations between serum ferritin and any of the cardiovascular endpoints for any of the groups. There was an apparent but nonsignificant u-shaped association between serum ferritin and all causes mortality in black men and between serum ferritin and CVD death in white women. However, in both cases very wide confidence limits preclude further interpretation. CONCLUSIONS: Overall, the results do not support the hypothesis that positive body iron stores, as measured by serum ferritin, are associated with an increased risk of CVD, CHD or MI death or between serum ferritin and all causes mortality. Most of the research to date with serum ferritin has been conducted in European men or in European American men. Our results are consistent with the primarily negative results for that race/sex group. More research is needed in women and minority groups, including an explanation of why such an association would exist in these groups but not in white men before an association can be established in them.

Black or African American↗
PubMed2000

Structural trends in the aging femoral neck and proximal shaft: analysis of the Third National Health and Nutrition Examination Survey dual-energy X-ray absorptiometry data.

Hip scans of U.S. adults aged 20-99 years acquired in the Third National Health and Nutrition Examination Survey (NHANES III) using dual-energy X-ray absorptiometry (DXA) were analyzed with a structural analysis program. The program analyzes narrow (3 mm wide) regions at specific locations across the proximal femur to measure bone mineral density (BMD) as well as cross-sectional areas (CSAs), cross-sectional moments of inertia (CSMI), section moduli, subperiosteal widths, and estimated mean cortical thickness. Measurements are reported here on a non-Hispanic white subgroup of 2,719 men and 2,904 women for a cortical region across the proximal shaft 2 cm distal to the lesser trochanter and a mixed cortical/trabecular region across the narrowest point of the femoral neck. Apparent age trends in BMD and section modulus were studied for both regions by sex after correction for body weight. The BMD decline with age in the narrow neck was similar to that seen in the Hologic neck region; BMD in the shaft also declined, although at a slower rate. A different pattern was seen for section modulus; furthermore, this pattern depended on sex. Specifically, the section modulus at both the narrow neck and the shaft regions remains nearly constant until the fifth decade in females and then declined at a slower rate than BMD. In males, the narrow neck section modulus declined modestly until the fifth decade and then remained nearly constant whereas the shaft section modulus was static until the fifth decade and then increased steadily. The apparent mechanism for the discord between BMD and section modulus is a linear expansion in subperiosteal diameter in both sexes and in both regions, which tends to mechanically offset net loss of medullary bone mass. These results suggest that aging loss of bone mass in the hip does not necessarily mean reduced mechanical strength. Femoral neck section moduli in the elderly are on the average within 14% of young values in females and within 6% in males.

Absorptiometry, Photon↗
PubMed1999

Increased serum transferrin saturation is associated with lower serum transferrin receptor concentration.

BACKGROUND: Serum transferrin receptor (sTfR) concentrations are increased in iron deficiency. We wished to examine whether they are decreased in the presence of potential iron-loading conditions, as reflected by increased transferrin saturation (TS) on a single occasion. METHODS: We compared sTfR concentrations between 570 controls with normal iron status and 189 cases with increased serum TS on a single occasion; these latter individuals may be potential cases of iron overload. Cases and controls were selected from adults who had been examined in the third National Health and Nutrition Examination Survey (1988-1994) and for whom excess sera were available to perform sTfR measurements after the survey's completion. Increased TS was defined as >60% for men and >55% for women; normal iron status was defined as having no evidence of iron deficiency, iron overload, or inflammation indicated by serum ferritin, TS, erythrocyte protoporphyrin, and C-reactive protein. RESULTS: Mean sTfR and mean log sTfR:ferritin were approximately 10% and 24% lower, respectively, in cases than in controls (P <0.002). Cases were significantly more likely to have an sTfR value <2.9 mg/L, the lower limit of the reference interval, than were controls (odds ratio = 1.8; 95% confidence interval, 1.04-2.37). CONCLUSION: Our results support previous studies that suggested that sTfR may be useful for assessing high iron status in populations.

Adult↗
PubMed1998

Prevalence of elevated serum transferrin saturation in adults in the United States.

BACKGROUND: A population-based hemochromatosis screening program that uses serum transferrin saturation has been proposed, but few data exist on the number of U.S. adults that such a program would identify for further testing. OBJECTIVE: To determine the prevalence of an initially elevated serum transferrin saturation and the prevalence of concurrently elevated serum transferrin saturation and serum ferritin levels in the adult population of the United States. DESIGN: Nationally representative cross-sectional survey of the noninstitutionalized U.S. civilian population. PARTICIPANTS: 15 839 men and nonpregnant women 20 years of age and older who were examined in the third National Health and Nutrition Examination Survey (1988-1994). MEASUREMENTS: Single measurements of serum transferrin saturations and serum ferritin levels. Cut-off values used to define elevated serum transferrin saturation ranged from greater than 45% to greater than 62%. RESULTS: The prevalence of initially elevated serum transferrin saturation ranged from 1% to 6%. Approximately 11% to 22% of those with elevated serum transferrin saturation had concurrently elevated serum ferritin levels. The prevalence of elevated serum transferrin saturation was lower in women than in men when the same cut-off value was used to define elevated serum transferrin saturation. The prevalence of elevated serum transferrin saturation in non-Hispanic black persons and Mexican-Americans was similar to or slightly less than that in non-Hispanic white persons. The prevalence of elevated serum transferrin saturation in persons 20 to 49 years of age was as high as or higher than that in older adults. CONCLUSIONS: A hemochromatosis screening program that uses a cut-off value of greater than 60% to define elevated serum transferrin saturation would identify an estimated 1.4 to 2.5 million U.S. adults for further testing.

Adult↗
PubMed1998

Distribution of transferrin saturations in the African-American population.

To determine if transferrin saturations in African Americans may reflect the presence of a gene that influences iron metabolism, we analyzed the distribution of these values in 808 African Americans from the second National Health and Nutrition Survey. We tested for a mixture of three normal distributions consistent with population genetics for a major locus effect in which the proportion of normal homozygotes is p2; of heterozygotes, 2pq; of affected homozygotes, q2; and in which p+q = 1. Three subpopulations based on transferrin saturation were present (P < .0001) and the fit to a mixture of three normal distributions was good (P = .2). A proportion of .009 was included in a subpopulation with a mean +/- standard deviation transferrin saturation of 63.4% +/- 5.7% (postulated homozygotes for a gene that influences iron metabolism), while a proportion of .136 had an intermediate saturation of 38.0% +/- 5.7% (postulated heterozygotes) and .856 a saturation of 24.6% +/- 5.7% (postulated normal homozygotes). These proportions were consistent with population genetics because the sum of the square roots of the proportions with the lowest mean transferrin saturation (P = .925) and the highest (q = 0.093) was approximately 1 (1.018). The results are consistent with the presence in African Americans of a common locus that influences iron metabolism.

Adult↗
PubMed1998

Updated data on proximal femur bone mineral levels of US adults.

This paper describes data on bone mineral levels in the proximal femur of US adults based on the nationally representative sample examined during both phases of the third National Health and Nutrition Examination Survey (NHANES III, 1988-94), and updates data previously presented from phase 1 only. The data were collected from 14,646 men and women aged 20 years and older using dual-energy X-ray absorptiometry, and included bone mineral density (BMD), bone mineral content (BMC) and area of bone scanned in four selected regions of interest (ROI) in the proximal femur: femur neck, trochanter, intertrochanter and total. These variables are provided separately by age and sex for non-Hispanic whites (NHW), non-Hispanic blacks (NHB) and Mexican Americans (MA). NHW in the southern United States had slightly lower BMD levels than NHW in other US regions, but these differences were not sufficiently large to prevent pooling of the data. The updated data provide valuable reference data on femur bone mineral levels of noninstitutionalized adults. The updated data on BMD for the total femur ROI of NHW have been selected as the reference database for femur standardization efforts by the International Committee on Standards in Bone Measurements.

Absorptiometry, Photon↗
PubMed1998

Risk factors for hip fracture in white men: the NHANES I Epidemiologic Follow-up Study.

This prospective population-based study assessed predictors of hip fracture risk in white men. Participants were members of the Epidemiologic Follow-up Study cohort of the First National Health and Nutrition Examination Survey, a nationally representative sample of noninstitutionalized civilians who were followed for a maximum of 22 years. A cohort of 2879 white men (2249 in the nutrition and weight-loss subsample, 1437 in the bone density subsample) aged 45-74 years at baseline (1971-1975) were observed through 1992. Ninety-four percent of the original cohort were successfully traced. Hospital records and death certificates were used to identify a total of 71 hip fracture cases (61 in the nutrition and weight-loss subsample, 26 in the bone-density subsample). Among the factors evaluated were age at baseline, previous fractures other than hip, body mass index, smoking status, alcohol consumption, nonrecreational physical activity, weight loss from maximum, calcium intake, number of calories, protein consumption, chronic disease prevalence, and phalangeal bone density. The risk adjusted relative risk (RR) of hip fracture was significantly associated with presence of one or more chronic conditions (RR = 1.91, 95% confidence interval [CI] = 1.19-3.06), weight loss from maximum > or = 10% (RR = 2.27, 95% CI 1.13-4.59), and 1 SD change in phalangeal bone density (RR = 1.73, 95% CI 1.11-2.68). No other variables were significantly related to hip fracture risk. Although based on a small number of cases, this is one of the first prospective studies to relate weight loss and bone density to hip fracture risk in men.

Age Factors↗
PubMed1997

Pervasive occult gastrointestinal bleeding in an Alaska native population with prevalent iron deficiency. Role of Helicobacter pylori gastritis.

OBJECTIVE: To confirm prevalent iron deficiency among Yupik Eskimos living in Alaska and to explore the frequency of and potential lesions accounting for occult gastrointestinal bleeding. DESIGN: Descriptive survey. SETTING: Rural Arctic community. SUBJECTS: A total of 140 adult volunteers from 3 villages in the Yukon-Kuskokwim Delta region of western Alaska. MAIN OUTCOME MEASURES: Daily iron intake, hematologic and biochemical indexes of iron status, fecal hemoglobin levels, stool parasites, and endoscopic findings. RESULTS: While dietary iron intake by Yupiks was similar to that of a reference population, iron deficiency prevalence was increased 13-fold in Yupik men and 4-fold in Yupik women. Fecal hemoglobin levels were elevated in 90% of subjects contrasted with only 4% of a reference group; median levels were 5.9 and 0.5 mg of hemoglobin per gram of stool, respectively. Among 70 Yupik subjects with elevated fecal hemoglobin levels who had endoscopy performed, 68 (97%) had an abnormal gastric appearance consisting of erythema, mucosal thickening, diffuse mucosal hemorrhages, erosions, or ulcerations. Gastric biopsies revealed chronic active gastritis with associated Helicobacter pylori in 68 (99%) of 69. No other hemorrhagic gastrointestinal disease was detected. CONCLUSIONS: Based on this study sample, occult gastrointestinal bleeding appears to be pervasive in the Yupik population and likely underlies the prevalent iron deficiency. An atypical hemorrhagic gastritis associated with H pylori infection is present almost universally and may represent the bleeding source.

Adult↗