Biomedical subjects

Heidi J Kalkwarf

Publications and source records attributed to Heidi J Kalkwarf.

14 recordsLinked to original sources

PubMed2006

Measurement error of DXA: interpretation of fat and lean mass changes in obese and non-obese children.

Information on reproducibility of dual-energy X-ray absorptiometry (DXA) measurements is essential because DXA is frequently used by clinicians and researchers to assess body composition changes. We estimated measurement error and absolute and relative smallest detectable differences (SDDs) for fat, lean, and bone mass in children. The SDD is the change necessary to be confident that the change is not a consequence of measurement error. Duplicate whole body DXA (Hologic QDR 4500A, Hologic Inc., Waltham, MA) scans were obtained on 32 obese and 34 non-obese children ages 6-19 yr. Absolute (kg) and relative (coefficient of variation) measurement error and SDD were calculated. Absolute SDDs for fat and lean were higher for obese (1.39 and 1.30 kg, respectively) than for non-obese children (0.42 and 0.47 kg, respectively). The %SDD for fat was lower for obese (3.58%) than non-obese children (5.24%), but for lean the %SDD was higher for obese (2.60%) than non-obese children (1.32%). The SDDs for bone mass were similar for obese and non-obese children. An obese child must lose or gain more absolute fat and lean mass than a non-obese child to be confident that the change is not a reflection of measurement error. Overall, SDD values for fat, lean, and bone mass are low.

Absorptiometry, Photon↗

PubMed2006

A randomized clinical trial of dietary calcium to improve bone accretion in children with juvenile rheumatoid arthritis.

OBJECTIVE: To examine a behavioral intervention (BI) to increase calcium intake in children with juvenile rheumatoid arthritis (JRA) on calcium intake and bone mass 6 and 12 months after treatment. STUDY DESIGN: A randomized trial compared a 6-session BI to a 3-session enhanced standard of care (ESC) with 49 children ages 4 to 10 years with JRA. Calcium intake was assessed via 3-day diet diaries. Total body bone mineral content (BMC), arms and legs BMC, and lumbar spine bone mineral density were assessed by dual energy x-ray absorptiometry. RESULTS: BI maintained an average calcium intake of 1500 mg/d at 6- and 12-month follow-up. This was greater than their baseline level of 972 mg/d, but not greater than the intake of 1300 mg/day maintained by ESC (P=.09). The BI had a 4% and 2.9% greater gain in total body bone mineral content than ESC at 6 and 12 months, respectively (P=.005), and a 7.1% and 5.3% greater gain in arms and legs BMC at 6 and 12 months than ESC (P=.0007). CONCLUSIONS: BI is effective in increasing calcium intake and BMC in children with JRA over a 12-month period.

Adult↗

PubMed2005

Human milk pumping rates of mothers of singletons and mothers of multiples.

Rates of breastfeeding are increasing, but the methods by which human milk is fed to infants is not well described. Using a retrospective survey design, the authors collected information about infant feeding from mothers of term, preterm, singleton, and multiple-gestation infants (n=346). Human milk feeding methods were characterized as solely at the breast, pumped only, or a combination. Sixty-eight percent of mothers in the study fed their infants at least some human milk; 77% of these mothers reported pumping milk. There was no difference in the percentage of pumping based on multiple gestation or length of pregnancy. Feeding human milk solely at the breast at early postpartum time points was associated with longer durations of human milk feeding overall. More research is needed to better understand why mothers choose pumping over direct human milk feedings and to evaluate the health outcomes associated with this practice.

Adult↗

PubMed2005

Effective dose of dual-energy X-ray absorptiometry scans in children as a function of age.

Effective dose, a parameter utilized to assess biological risk related to radiation exposure, may be used to evaluate risk associated with dual-energy X-ray absorptiometry (DXA). We estimated the effective dose from DXA (Hologic QDR 4500A) scans of the lumbar spine (fast array mode), total body, hip (fast array mode), and forearm for children ages 1, 5, 10, and 15 yr and for adults. Entrance dose incorporating backscatter was determined for each scan type. Depth-dose curves were derived using Plexiglas slabs simulating tissue attenuation. Organ depth was estimated using pediatric phantom models. For all scan types, the effective dose decreased as age increased. The effective dose values for a 1-yr-old and an adult, respectively, were 4.7 microSv and 2.2 microSv for a lumbar spine scan performed in fast array mode, 3.4/3.5 microSv and 1.8/2.1 microSv (male/female) for a total body scan, and 0.14 microSv and 0.03 microSv for a forearm scan. There were marked sex differences in the effective dose associated with hip scans (fast array mode) ranging from 15.2 microSv for a 1-yr-old male to 4.6 microSv for an adult female. A comprehensive uncertainty analysis indicated that the effective dose values were reliable within a factor of 3. With the exception of the hip scans in 1- and 5-yr-olds, the effective doses were below the negligible individual dose limit of 10 microSv/yr.

Absorptiometry, Photon↗

PubMed2004

Lactation and maternal bone health.

Women lose bone during lactation, and this is an important mechanism to provide calcium for human milk. Bone loss during lactation occurs even in women with high calcium intakes. Lactation-induced bone loss is transient because bone density increases rapidly after weaning. Bone loss during lactation and recovery after weaning are related to ovarian function and the length of postpartum amenorrhea. The recovery of bone after weaning can occur with shortly spaced pregnancies. Women who have breastfed several infants do not have reduced bone density after menopause. Overall, the transient bone loss during lactation does not seem to increase a woman's risk of osteoporotic fracture in her elder years. Further research is needed on special subgroups of women, such as adolescents, women who are vitamin D deficient or have extremely low calcium intakes, and women who have simultaneously breastfed multiple infants to determine whether these women are able to regain sufficient bone mass after lactation to preserve their bone health.

Adult↗

PubMed2004

Relationships between bone mass and circulating leptin concentrations in Hutterites.

A limited number of previous studies have shown inverse associations between bone mass or density and circulating leptin in humans. Relationships between bone mass and circulating leptin in Hutterites, who have elevated bone density, are unknown. Knowledge gained from studies in mice suggests that Hutterites exhibit traits consistent with a deficiency in circulating leptin or in leptin signaling. We examined relationships between whole body (WB) and regional (lumbar, total hip, femoral neck, trochanter) bone mineral content (BMC) by dual energy X-ray absorptiometry and circulating leptin in 249 Hutterites (137 female) ages 20-55 years and 72 similarly aged non-Hutterites (37 female). We tested the hypothesis that (1) Hutterites will have low circulating leptin concentrations for a given amount of body fat compared to non-Hutterites, and (2) controlling for body fat, there will be an inverse relationship between BMC and circulating leptin among Hutterites. Hutterites had higher BMC than non-Hutterites at all skeletal sites after adjusting for site-specific bone area, age, and sex (P </= 0.02). Hutterite females had higher leptin concentrations than non-Hutterite females [geometric mean and 95% confidence interval (CI): 18.38 (17.18, 19.67) vs. 14.30 (12.55, 16.28), P </= 0.001) after adjusting for WB fat mass. Hutterite males also had higher leptin concentrations than non-Hutterite males [geometric mean and 95% CI: 6.53 (6.11, 6.98) vs. 5.62 (4.98, 6.35), P = 0.03) after adjusting for WB fat mass. We used backward stepwise regression to determine significant (P </= 0.10) covariates to include in models predicting WB and regional BMC among Hutterites (separately by sex). Subsequently, we entered leptin (log-transformed) to models to test for significance (P </= 0.05). After adjusting for covariates, leptin concentration was not a significant predictor of BMC at any site, in either sex, among Hutterites. It is possible that genetic influences that interfere with hypothalamic leptin signaling, in a manner unrelated to adipocyte leptin production, contribute to elevated Hutterite bone density.

Adult↗

PubMed2004

Lactation, weaning, and calcium supplementation: effects on body composition in postpartum women.

BACKGROUND: Concern that long-term weight retention after pregnancy contributes to obesity underscores the need to identify factors that facilitate postpartum weight loss. Lactation is believed to facilitate postpartum weight loss and fat loss. Calcium intake also has been hypothesized to promote weight loss and fat loss. OBJECTIVE: We addressed the following questions: 1) whether lactation enhances loss of fat mass, and 2) whether loss of fat mass during lactation and after weaning is greater in women receiving calcium supplementation than in women receiving placebo. DESIGN: We used data from 87 lactating and 81 nonlactating women enrolled in a randomized, double-blind, calcium supplementation trial from 2 wk to 6 mo postpartum and data from 76 previously lactating and 82 nonlactating women enrolled in a parallel trial from 6 to 12 mo postpartum. Body fat and lean masses were measured by using dual-energy X-ray absorptiometry. RESULTS: Nonlactating women lost whole-body, arm, and leg fat at a faster rate than did lactating women between 2 wk and 6 mo postpartum (lactation group x time effect, P < or = 0.01). Fat mass of the trunk, arms, and legs decreased between 6 and 12 mo postpartum regardless of previous lactation status (time effect, P < or = 0.001). Calcium supplementation did not affect postpartum fat loss. CONCLUSIONS: Body-composition changes occur differently in nonlactating and lactating women during the first 6 mo postpartum and occur at some sites until 12 mo postpartum regardless of previous lactation status. Clinicians should use caution when advising lactating mothers about expected rates of postpartum fat loss. Calcium supplementation (1 g/d) does not promote postpartum weight loss or fat loss.

Adipose Tissue↗

PubMed2004

Vitamin K, bone turnover, and bone mass in girls.

BACKGROUND: Vitamin K has been suggested to have a role in bone metabolism, and low vitamin K intake has been related to low bone density and increased risk of osteoporotic fracture. OBJECTIVE: The objective of this study was to determine whether phylloquinone (vitamin K(1)) intake and biochemical indicators of vitamin K status are related to bone mineral content (BMC) and markers of bone formation and bone resorption in girls. DESIGN: Vitamin K status [plasma phylloquinone concentration and percentage of undercarboxylated osteocalcin (%ucOC)] was measured at baseline in a study of 245 healthy girls aged 3-16 y. Cross-linked N-telopeptide of type 1 collagen (NTx) breakdown, osteocalcin, and bone-specific alkaline phosphatase were measured to reflect bone resorption and formation. BMC of the total body, lumbar spine, and hip and dietary phylloquinone intake were measured annually for 4 y. RESULTS: Phylloquinone intake (median: 45 microg/d) was not consistently associated with bone turnover markers or BMC. Better vitamin K status (high plasma phylloquinone and low %ucOC) was associated with lower bone resorption and formation. Plasma phylloquinone was inversely associated with NTx and osteocalcin concentrations (P < 0.05), and %ucOC was positively associated with NTx and bone-specific alkaline phosphatase concentrations (P < 0.05). Indicators of vitamin K status were not consistently associated with current BMC or gain in BMC over the 4-y study period. CONCLUSIONS: Better vitamin K status was associated with decreased bone turnover in healthy girls consuming a typical US diet. Randomized phylloquinone supplementation trials are needed to further understand the potential benefits of phylloquinone on bone acquisition in growing children.

Adolescent↗

PubMed2004

Comparison of feeding among multiple birth infants.

Mothers of multiples who choose to feed their infants breast milk are faced with a seemingly overwhelming set of circumstances. Since mothers of multiples could potentially feed their infants differing proportions of breast milk, current methods of obtaining breastfeeding data for mothers of singletons may not adequately describe the breastfeeding behaviors of mothers of twins and triplets. The goal of our study was to determine the proportion of breast milk each infant of a multiple set was fed over a six-month period and compare the feeding regimens of sibling infants. Results of this retrospective study based on maternal reports indicated that there was almost complete agreement in the proportion of breast milk fed to siblings born from the same pregnancy, regardless of stratification based on gestational age, plurality, or location of the infants (hospital vs. home). The Pearson correlation coefficient for duration of breast-milk feeding between sibling twins was 0.99 (p < .0001); among sibling triplets the values were .97, .98 and .99 (p < .0001). A better understanding of the process by which twins and triplets are fed breast milk sets the stage for future research and can ultimately lead to the development of strategies to increase breast-milk feeding rates for multiple birth children.

Age Factors↗

PubMed2003

Milk intake during childhood and adolescence, adult bone density, and osteoporotic fractures in US women.

BACKGROUND: Calcium supplements increase bone mass in children, but the effect does not persist once supplementation is discontinued. OBJECTIVE: The objective of this study was to determine whether milk intake during childhood and adolescence, when controlled for current calcium intake, is associated with adult bone mass (ie, bone mineral content), bone mineral density, and the incidence of osteoporotic fracture. DESIGN: We used data from the third National Health and Nutrition Examination Survey of 3251 non-Hispanic, white women age >or=20 y. Bone density was measured at the hip. History of fracture of the hip, spine, or forearm was classified as a lifetime fracture (occurring after age 13 y) or an osteoporotic fracture (occurring after age 50 y). Subjects reported frequency of milk consumption during childhood (aged 5-12 y) and during adolescence (aged 13-17 y). Regression models controlled for weight, height, age, menopause and use of estrogen, physical activity, smoking, and current calcium intake. RESULTS: Among women aged 20-49 y, bone mineral content was 5.6% lower in those who consumed <1 serving of milk/wk (low intake) than in those who consumed >1 serving/d (high intake) during childhood (P < 0.01). Low milk intake during adolescence was associated with a 3% reduction in hip bone mineral content and bone mineral density (P < 0.02). Among women aged >or=50 y, there was a nonlinear association between milk intake during childhood and adolescence and hip bone mineral content and bone mineral density (P < 0.04). Low milk intake during childhood was associated with a 2-fold greater risk of fracture (P < 0.05). CONCLUSION: Women with low milk intake during childhood and adolescence have less bone mass in adulthood and greater risk of fracture.

Absorptiometry, Photon↗

PubMed2003

Vitamin D receptor Fok1 polymorphism and blood lead concentration in children.

Variation in blood lead concentration is caused by a complex interaction of environmental, social, nutritional, and genetic factors. We evaluated the association between blood lead concentration and a vitamin D receptor (VDR) gene polymorphism. Environmental samples and blood were analyzed for lead, nutritional and behavioral factors were assessed, and VDR -Fok1 genotype was determined in 245 children. We found a significant interaction between floor dust lead and genotype on blood lead concentration. For every 1 microg/ft(2) increase in floor dust, children with VDR -FF genotype had a 1.1% increase in blood lead [95% confidence interval (CI), 0.69-1.5], VDR -Ff, 0.53% increase (95% CI, 0.1-0.92), and VDR -ff, 3.8% increase (95% CI, 1.2-6.3); however, at floor dust levels < 10 microg/ft(2), children with VDR -ff had the lowest blood lead concentrations. These data suggest that VDR -Fok1 is an effect modifier of the relationship of floor dust lead exposure and blood lead concentration.

Child, Preschool↗

PubMed2003

Trends in otitis media among children in the United States.

BACKGROUND: The prevalence of repeated otitis media (OM) increased during the 1980s, but it is unknown if the increase has continued. OBJECTIVES: To determine trends in the prevalence of OM, early-onset OM, and repeated OM among US children from 1988 to 1994 and to identify factors that may explain any observed changes. METHODS: The Third National Health and Nutrition Examination Survey was administered in 2 phases: phase I (1988-1991) and phase II (1991-1994), each comprising a national probability sample. OM (ever having had OM), early-onset OM (first episode at <12 months of age), and repeated OM (>or=3 episodes) were assessed for 8261 children <6 years of age. RESULTS: After controlling for risk factors for OM, the prevalence of OM from phase I to phase II increased from 66.7% to 69.7% (odds ratio [OR] = 1.1; 95% confidence interval [CI] =.99, 1.1), early-onset OM increased from 41.1% to 45.8% (OR = 1.1; 95% CI = 1.03, 1.2), and repeated OM increased from 34.8% to 41.1% (OR = 1.2; 95% CI = 1.1, 1.4). This observed increase corresponds to 561,000 and 720,000 more children having early-onset OM and repeated OM, respectively. Child care use, early breastfeeding termination, asthma, and access to health care did not significantly increase from phase I to phase II. The prevalence of early-onset OM and repeated OM was higher for affluent children, but the greatest increase in prevalence was among impoverished children. There was an increase in allergic conditions from phase I to phase II for poor children (22.6% to 30.2%). CONCLUSIONS: The prevalence of early-onset OM and repeated OM continued to increase among preschool children in the United States. Further research to investigate this increasing prevalence should explore changes in management practice and an increase in prevalence of allergic conditions among poor children.

Age of Onset↗

PubMed2002

Bone mineral changes during pregnancy and lactation.

Significant calcium transfer from the mother to the fetus and infant occurs during pregnancy and lactation, theoretically placing the mother at an increased risk for osteoporosis later in life. During pregnancy, intestinal calcium absorption increases to meet much of the fetal calcium needs. Maternal bone loss also may occur in the last months of pregnancy, a time when the fetal skeleton is rapidly mineralizing. The calcium needed for breast milk production is met through renal calcium conservation and, to a greater extent, by mobilization of calcium from the maternal skeleton. Women experience a transient loss of approx 3-7% of their bone density during lactation, which is rapidly regained after weaning. The rate and extent of recovery are influenced by the duration of lactation and postpartum amenorrhea and differ by skeletal site. Additional calcium intake does not prevent bone loss during lactation or enhance the recovery after weaning. The recovery of bone is complete for most women and occurs even with shortly spaced pregnancies. Epidemiologic studies have found that pregnancy and lactation are not associated with an increased risk of osteoporotic fractures.

Adaptation, Physiological↗

PubMedDate not supplied

Breast milk feeding rates of mothers of multiples compared to mothers of singletons.

OBJECTIVE: Over 3% of infants born annually in the United States are from a multiple gestation pregnancy, yet there is little data published about the feeding practices of their mothers. The objectives of this study were to determine and compare the rates of breast milk feeding of mothers of multiples and mothers of singletons. METHODS: Stratified random sampling (n = 686) on the basis of plurality of pregnancy and gestational age at delivery was performed on a 1999 birth certificate database in the greater Cincinnati area. We collected information about infant feeding during the first 6 months of life using a retrospective, self-administered questionnaire and phone interview from mothers of term singletons (TS), preterm singletons (PS), term multiples (TM), and preterm multiples (PM). Data were analyzed using chi-square and logistic or multiple regression. RESULTS: We obtained feeding information from 346 mothers (n = 81 TS, 80 PS, 90 TM, and 95 PM). By 3 days postpartum, PM provided breast milk less often than all other groups: TS = 69%, PS = 66%, TM = 73%, PM = 57% (P =.035). Among mothers who initiated breast milk feeding, the geometric mean duration of at least some breast milk feeding was significantly shorter for PM than for all other groups: TS = 23 weeks, PS = 19 weeks, TM = 24 weeks, and PM = 12 weeks (P =.002). CONCLUSIONS: Further evaluation of the potential causes for the lower breast milk feeding rates among PM is needed to develop effective intervention strategies and increase the number of preterm multiple gestation infants receiving breast milk.

Breast Feeding↗