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Biomedical subjects

Alan Lucas

Publications and source records attributed to Alan Lucas.

At least 19 recordsLinked to original sources
PubMed2007

Infant nutrition and stereoacuity at age 4-6 y.

BACKGROUND: Breastfeeding has been reported to benefit visual development in children. A higher concentration of docosahexaneoic acid (DHA) in breast milk than in formula has been proposed as one explanation for this association and as a rationale for adding DHA to infant formula, but few long-term data support this possibility. OBJECTIVE: The objectives of the study were, first, to test the hypothesis that breastfeeding benefits stereoscopic visual maturation and, second, if that benefit is shown, to ascertain whether it is mediated by the dietary intake of DHA. DESIGN: Stereoacuity was measured by using the random dot E test (primary outcome), and visual acuity was measured by using the Sonksen-Silver acuity system (secondary outcome) in previously breastfed (n = 78) or formula-fed (n = 184) children aged 4-6 y who had been followed prospectively from birth. In the formula-fed group, children were randomly assigned to receive formula with either DHA or arachidonic acid (n = 94) or a control formula (n = 90) for the first 6 mo. RESULTS: Breastfed children had a significantly (P = 0.001) greater likelihood of foveal stereoacuity (high-grade or < 100 s/arc) than did formula-fed children (odds ratio: 2.5; 95% CI: 1.4, 4.5) independent of potential confounding (P = 0.005). Stereoacuity did not differ significantly between children randomly assigned to DHA-supplemented or control formula. None of the groups differed in Sonksen-Silver visual acuity. CONCLUSIONS: These findings support the hypothesis that breastfeeding benefits long-term stereoscopic development. An effect of DHA cannot be excluded, but the lack of difference in stereoacuity between infants randomly assigned to DHA-containing and those assigned to control formula raises the hypothesis that factors in breast milk other than DHA account for the observed benefits.

Breast Feeding↗
PubMed2006

Promotion of faster weight gain in infants born small for gestational age: is there an adverse effect on later blood pressure?

BACKGROUND: Being born small for gestational age is associated with later risk factors for cardiovascular disease, such as high blood pressure. Promotion of postnatal growth has been proposed to ameliorate these effects. There is evidence in animals and infants born prematurely, however, that promotion of growth by increased postnatal nutrition increases rather than decreases later cardiovascular risk. We report the long-term impact of growth promotion in term infants born small for gestational age (birth weight <10th percentile). METHODS AND RESULTS: Blood pressure was measured at 6 to 8 years in 153 of 299 (51%) of a cohort of children born small for gestational age and randomly assigned at birth to receive either a standard or a nutrient-enriched formula. The enriched formula contained 28% more protein than standard formula and promoted weight gain. Diastolic and mean (but not systolic) blood pressure was significantly lower in children assigned to standard compared with nutrient-enriched formula (unadjusted mean difference for diastolic blood pressure, -3.2 mm Hg; 95% CI, -5.8 to -0.5; P=0.02) independent of potential confounding factors (adjusted difference, -3.5 mm Hg; P=0.01). In observational analyses, faster weight gain in infancy was associated with higher later blood pressure. CONCLUSIONS: In the present randomized study targeted to investigate the effect of early nutrition on long-term cardiovascular health, we found that a nutrient-enriched diet increased later blood pressure. These findings support an adverse effect of relative "overnutrition" in infancy on long-term cardiovascular disease risk, have implications for the early origins of cardiovascular disease hypothesis, and do not support the promotion of faster weight gain in infants born small for gestational age.

Adult↗
PubMed2006

Evaluation of Lunar Prodigy dual-energy X-ray absorptiometry for assessing body composition in healthy persons and patients by comparison with the criterion 4-component model.

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) is widely used to assess body composition in research and clinical practice. Several studies have evaluated its accuracy in healthy persons; however, little attention has been directed to the same issue in patients. OBJECTIVE: The objective was to compare the accuracy of the Lunar Prodigy DXA for body-composition analysis with that of the reference 4-component (4C) model in healthy subjects and in patients with 1 of 3 disease states. DESIGN: A total of 215 subjects aged 5.0-21.3 y (n = 122 healthy nonobese subjects, n = 55 obese patients, n = 26 cystic fibrosis patients, and n = 12 patients with glycogen storage disease). Fat mass (FM), fat-free mass (FFM), and weight were measured by DXA and the 4C model. RESULTS: The accuracy of DXA-measured body-composition outcomes differed significantly between groups. Factors independently predicting bias in weight, FM, FFM, and percentage body fat in multivariate models included age, sex, size, and disease state. Biases in FFM were not mirrored by equivalent opposite biases in FM because of confounding biases in weight. CONCLUSIONS: The bias of DXA varies according to the sex, size, fatness, and disease state of the subjects, which indicates that DXA is unreliable for patient case-control studies and for longitudinal studies of persons who undergo significant changes in nutritional status between measurements. A single correction factor cannot adjust for inconsistent biases.

Absorptiometry, Photon↗
PubMed2006

Assessing occupational mercury exposures during the on-site processing of spent fluorescent lamps.

On-site processing of spent fluorescent lamps reduces storage space requirements and prevents mercury-containing lamp contents from entering the municipal waste stream, but such processing activities are typically not carried out in facilities specifically designed for the operation. This circumstance is of particular concern because lamp-handling and -crushing operations can release mercury vapors and aerosols that constitute an occupational exposure risk. In the study reported here, sampling for airborne mercury was performed during the processing of fluorescent lamps in an enclosed work area and in an open, outdoor work environment. In both enclosed and open work environments, exposures in excess of the established mercury exposure limit were detected. Simple interventions to prevent this possible unanticipated source of mercury exposure are described.

Conservation of Natural Resources↗
PubMed2005

Adiponectin predicts insulin resistance but not endothelial function in young, healthy adolescents.

BACKGROUND: Adiponectin, an adipocyte-derived hormone found in lower concentration with greater adiposity, is suggested to reduce the risk of insulin resistance, atherosclerosis, and cardiovascular disease. We tested this hypothesis in a healthy, nonobese population. METHODS AND RESULTS: Brachial artery flow-mediated endothelial-dependent vasodilation and distensibility, measures of vascular function relevant to the early atherosclerotic process, were determined in 294 adolescents (aged 13-16 yr) using high-resolution vascular ultrasound. Fasting insulin concentration and the homeostasis model assessment of insulin resistance were used to estimate insulin resistance. Fat mass was measured by bioelectric impedance analysis; fasting serum adiponectin concentration by RIA; and lipid profile, fasting insulin, glucose, and C-reactive protein concentrations using standard laboratory techniques. Adiponectin concentration was associated with insulin resistance independent of potential confounding factors (e.g. -1.3% change in fasting insulin concentration per 10% increase in adiponectin concentration; 95% confidence interval, -2.4% to -0.1%; P = 0.03), but not with flow-mediated endothelial-dependent vasodilation or arterial distensibility. CONCLUSIONS: Lower adiponectin concentration was associated with lower insulin sensitivity in a healthy, nonobese population. Our study supports the hypothesis that adiponectin benefits insulin sensitivity from a young age but, in contrast to experimental models and data from older subjects, does not affect vascular changes associated with early atherosclerosis.

Adiponectin↗
PubMed2005

Long-term programming effects of early nutrition -- implications for the preterm infant.

The current focus of nutritional science has shifted from meeting needs to determining the biological effects that nutrition has on immediate and lifetime health. Of particular interest is the concept of programming, the idea that "a stimulus or insult during a critical or sensitive period of development can have long-term or lifetime effects on an organism." Evidence that early nutrition has such "programming" effects in animals is overwhelming. In humans, retrospective observations show a relationship between adult disease and size in early life, though it is difficult to prove nutritional cause from observational associations and therefore difficult to use such data to underpin health policy. However, the results of randomized intervention trials of early nutrition with long-term follow-up are emerging. These experimental studies show that nutrition in early life has a major impact on health into early adulthood, notably on cardiovascular disease risk, bone health and cognitive function. These new findings have major biological, social and medical implications and should increasingly underpin health practices.

Animals↗
PubMed2004

Breastmilk feeding and lipoprotein profile in adolescents born preterm: follow-up of a prospective randomised study.

BACKGROUND: Breastfeeding is associated with reduced cholesterol concentration later in life, but previous studies have not used random assignment of infant diet with prospective follow-up. We tested the hypothesis that breastmilk feeding benefits the lipoprotein profile in adolescents born preterm, in whom randomisation to different diets at birth is feasible. METHODS: 926 infants born preterm were randomly assigned in two parallel trials to receive (trial 1) donated banked breastmilk or preterm formula, or (trial 2) standard term formula or preterm formula, as sole diet or as supplements to mother's milk in both trials. We followed up 216 participants at age 13-16 years and measured ratio of low-density to high-density lipoprotein cholesterol (LDL to HDL), ratio of apolipoprotein B to apolipoprotein A-1 (apoB to apoA-1), and concentration of C-reactive protein (CRP; a measure of the inflammatory process associated with atherosclerosis). RESULTS: Adolescents who had been randomised to banked breastmilk had a lower CRP concentration (p=0.006) and LDL to HDL ratio (mean difference 0.34 [14% lower], 95% CI -0.67 to -0.01; p=0.04) than those given preterm formula. A greater proportion of human milk intake in infancy was associated with lower ratios of LDL to HDL (p=0.03) and apoB to apoA-1 (p=0.004)--independent of gestation and potential confounding factors--and with lower CRP concentration (p=0.03). CRP concentration correlated with the two lipoprotein ratios (p<0.0001 and p=0.003, respectively). INTERPRETATION: Our data provide experimental evidence for the long-term benefits of breastmilk feeding on the risk of atherosclerosis.

Adolescent↗
PubMed2004

Is slower early growth beneficial for long-term cardiovascular health?

BACKGROUND: Accelerated neonatal growth increases the later propensity to cardiovascular disease (CVD) in animals, whereas slower growth is thought to have a beneficial effect. To test this hypothesis in humans, we measured flow-mediated endothelium-dependent dilation (FMD) in a population subject to slower early growth and in healthy controls. METHODS AND RESULTS: High-resolution vascular ultrasound was used to measure the change in brachial artery diameter in response to reactive hyperemia in adolescents age 13 to 16 years who were either part of a cohort born preterm and followed up prospectively (n=216) or controls born at term (n=61). Greater weight gain or linear growth in the first 2 weeks postnatally was associated with lower FMD at adolescence (regression coefficient, -0.026-mm change in mean arterial diameter per 100-g increase in weight; 95% CI, -0.040 to -0.012 mm; P=0.0003) independent of birthweight and potential confounding factors. Mean FMD in the half of the preterm population with the lowest rates of early growth was higher than in both the half with the greatest growth (P=0.001) and subjects born at term (P=0.03). CONCLUSIONS: FMD was 4% lower in adolescents with the highest compared with the lowest rate of weight gain in the first 2 weeks after birth, a substantial negative effect similar to that for insulin-dependent diabetes mellitus or smoking in adults. Our findings are consistent with the adverse effects of accelerated neonatal growth on long-term cardiovascular health and suggest that postnatal growth patterns could explain the previously reported association between birthweight and later CVD.

Birth Weight↗
PubMed2004

Randomized, double-blind trial of long-chain polyunsaturated fatty acid supplementation with fish oil and borage oil in preterm infants.

OBJECTIVE: To test the efficacy and safety of long-chain polyunsaturated fatty acid (LCPUFA) supplementation with gamma-linolenic acid, a precursor of arachidonic acid, and docosahexaenoic acid in preterm infants. STUDY DESIGN: Preterm (<35 weeks, < or =2000 g birth weight) infants (n=238) randomly assigned to unsupplemented or LCPUFA-supplemented formula to 9 months after term. The main outcome measure was the Bayley Mental and Psychomotor Indexes (MDI, PDI) at 18 months after term. Safety outcome measures were anthropometry (9 and 18 months), feed tolerance, infection, and clinical complications. RESULTS: There were no significant differences in neurodevelopment between groups overall. In preplanned subgroup analyses, LCPUFA-supplemented boys had significantly higher Bayley MDI than did control boys (difference, 5.7 points; 95% CI, 0.3 to 11.1; P=.04). LCPUFA-supplemented infants showed significantly greater weight gain (difference, 310 g; 95% CI, 30 to 590 g; P=.03) and length gain (difference, 1.0 cm; 95% CI, 0.02 to 1.9; P=.05) between birth and 9 months, with greater effect in boys (weight difference at 9 months, 510 g; 95% CI, 80 to 930 g; P=.02; length difference at 18 months, 1.8 cm; 95% CI, 0.1 to 1.8; P=.03). CONCLUSIONS: This trial, using the strategy of providing gamma-linolenic acid as a source of arachidonic acid, showed efficacy for growth and for neurodevelopment in boys, with no adverse effects. These data have important implications for LCPUFA-supplementation strategy in preterm infants.

Body Height↗
PubMed2004

Prematurity and reduced body fatness at 8-12 y of age.

BACKGROUND: Increasing evidence suggests that body composition, an important factor influencing morbidity and mortality in adult life, might be programmed by early growth and nutrition. Children born preterm remain shorter and lighter than their term-born peers during childhood, but it is unclear whether the size difference is associated with altered body composition. OBJECTIVE: We tested the hypothesis that both fat mass (FM) and fat-free mass (FFM) are proportionately lower in children born preterm than in children born at term. DESIGN: A total of 497 children born preterm and 95 children born at term were studied at 8-12 y of age. Body composition was determined with the use of skinfold thicknesses and dual-energy X-ray absorptiometry (in 200 preterm and 95 term children). FM and FFM were normalized for height to give fat mass index (FMI) and fat-free mass index (FFMI), respectively. RESULTS: Children born preterm were significantly lighter than those born at term and had lower FM and FFM. However, FMI was significantly lower in preterm children, whereas FFMI was not. FMI was also significantly lower in boys than in girls and in children with higher activity levels. Additional data available for the preterm group showed no association between birth weight, gestational age, or neonatal diet and later FMI or FFMI. CONCLUSIONS: The smaller size of children born preterm than of children born at term is associated with lower FM but not FFM when normalized for height. We hypothesize that this could result in a reduction in the risk of obesity and related diseases during adult life.

Absorptiometry, Photon↗
PubMed2004

Neurodevelopment in children born small for gestational age: a randomized trial of nutrient-enriched versus standard formula and comparison with a reference breastfed group.

OBJECTIVE: Many studies have shown that children born small for gestational age (SGA) are at a neurodevelopmental disadvantage. We have shown that nutrient enrichment of formula fed to term SGA infants improves their growth and hypothesized that it also would improve their neurodevelopmental outcome. DESIGN: A randomized, controlled trial of standard term-infant (n = 147) or nutrient-enriched (n = 152) formula for the first 9 months. A reference group of 175 breastfed SGA infants was also recruited. SETTING: Subjects were recruited in 5 maternity hospitals in Cambridge, Nottingham, and Leicester, all in the United Kingdom. PARTICIPANTS: Healthy, term infants (gestation: > or =37 weeks) with birth weight <10th centile. OUTCOME MEASURES: Bayley mental and psychomotor scores at 18 months (primary) and developmental scores from Knobloch, Pasamanick, and Sherrard's developmental screening inventory at 9 months (secondary). RESULTS: There was no significant intergroup difference in Bayley Mental Development Index (MDI) or Psychomotor Development Index (PDI) scores at 18 months. However, at 9 months, children fed the enriched formula had a significantly lower developmental quotient (99.5 vs 102.0; 95% confidence interval [CI] for difference: -4.6, -0.4). A significant disadvantage was seen in girls (-5.1; 95% CI: -7.8, -2.4) but not in boys (0.9; 95% CI: -2.4, 4.2). Breastfed infants had significantly higher MDI and PDI scores at 18 months than formula-fed infants. Confounding factors accounted for approximately 34% of the observed association between breastfeeding and MDI score and none of the association between breastfeeding and PDI score. CONCLUSIONS: The previously reported enhanced linear growth in SGA children fed enriched formula was not matched by a neurodevelopmental advantage. At 9 months, girls fed the enriched formula had a significant developmental disadvantage, although this was not seen at 18 months. Later follow-up will determine any long-term effects on health or development. Meanwhile, use of enriched formula for term SGA children should not be promoted. It seems that breastfeeding may be especially beneficial for neurodevelopment in children born SGA.

Breast Feeding↗
PubMed2003

Low nutrient intake and early growth for later insulin resistance in adolescents born preterm.

BACKGROUND: In animals, acceleration of neonatal growth is thought to increase the later propensity to insulin resistance and non-insulin-dependent diabetes, whereas slow growth as a consequence of undernutrition is thought to have a beneficial effect. To test this hypothesis in people, we measured fasting concentrations of 32-33 split proinsulin, a marker of insulin resistance, in adolescents born preterm who had participated in randomised intervention trials of neonatal nutrition, and in adolescents born at term. METHODS: We determined fasting 32-33 split proinsulin concentration in participants aged 13-16 years born preterm and randomised to receive a nutrient-enriched or lower-nutrient diet (n=216) or in a reference group born at term (n=61). FINDINGS: Fasting 32-33 split proinsulin concentration was greater in children given a nutrient-enriched diet (geometric mean 7.2 pmol/L, 95% CI 6.4-8.1) than in those given the lower-nutrient diet (5.9 pmol/L [5.2-6.4]; mean difference 20.6% [5.0-36.3]; p=0.01). Healthy babies born at term had similar fasting 32-33 split proinsulin concentrations (6.9 pmol/L; 6.0-8.2) to the nutrient-enriched group. In non-randomised analyses, fasting 32-33 split proinsulin concentration was associated with greater weight gain the first 2 weeks of life (13.2% [5.4-20.9] change per 100 g weight increase; p=0.001) independent of birthweight, gestation, neonatal morbidity, and demographic, anthropometric, and socioeconomic factors. INTERPRETATION: Our results suggest that relative undernutrition early in life in children born preterm may have beneficial effects on insulin resistance.

Adolescent↗
PubMed2003

Cortical anomalies associated with visuospatial processing deficits.

Children born preterm provide a fruitful population for studying structure-function relationships because they often have specific functional deficits in the context of normal neurological status. We selected a group of preterm adolescents with deficits in judgment of line orientation. Despite their very low birth weight, all were neurologically normal with no consistent abnormalities on conventional magnetic resonance imaging. However, voxel-based morphometric analysis of their magnetic resonance imaging scans showed areas of decreased gray matter and increased white matter most prominently in right ventral extrastriate cortex, close to an area previously implicated in the line orientation task. We suggest that these anomalies of cortical architecture relate to impaired performance on the line orientation task.

Adolescent↗
PubMed2003

Programming of lean body mass: a link between birth weight, obesity, and cardiovascular disease?

BACKGROUND: A high birth weight has been suggested to increase the later risk of obesity, as measured by body mass index, but, paradoxically, to decrease the later propensity to cardiovascular disease. Programming of more lean tissue rather than fat mass by a high birth weight might explain this paradox and also explain the association of birth weight with later body mass index. This concept has been inadequately tested. OBJECTIVE: The objective was to test the hypothesis that a high birth weight programs a greater proportion of lean mass in children and adolescents. DESIGN: Body fat mass and fat-free mass were assessed by both skinfold-thickness measurement and bioelectrical impedance analysis in adolescents aged 13-16 y (n = 78) who were part of a study that investigated the early origins of cardiovascular disease. Body composition was assessed by dual-energy X-ray absorptiometry in a separate group of younger children. RESULTS: An increase in birth weight of 1 SD was significantly associated with a 0.9-1.4-kg (2-3%) increase in fat-free mass in adolescents but not with an increase in fat mass. This association was independent of age, sex, height, pubertal stage, socioeconomic status, and physical activity. Similar observations were made in younger children. CONCLUSIONS: Our data support the hypothesis that fetal growth, measured by birth weight, programs lean mass later in life. Our observations may therefore explain the association of birth weight with body mass index and have implications for the early origins of both obesity and cardiovascular disease.

Absorptiometry, Photon↗
PubMed2003

Growth and development of premature infants fed predominantly human milk, predominantly premature infant formula, or a combination of human milk and premature formula.

BACKGROUND: In a recent meta-analysis, human milk feeding of low birth-weight (LBW) infants was associated with a 5.2 point improvement in IQ tests. However, in the studies in this meta-analysis, feeding regimens were used (unfortified human milk, term formula) that no longer represent recommended practice. OBJECTIVE: To compare the growth, in-hospital feeding tolerance, morbidity, and development (cognitive, motor, visual, and language) of LBW infants fed different amounts of human milk until term chronologic age (CA) with those of LBW infants fed nutrient-enriched formulas from first enteral feeding. METHODS: The data in this study were collected in a previous randomized controlled trial assessing the benefit of supplementing nutrient-enriched formulas for LBW infants with arachidonic acid and docosahexaenoic acid. Infants (n = 463, birth weight, 750-1,800 g) were enrolled from nurseries located in Chile, the United Kingdom, and the United States. If human milk was fed before hospital discharge, it was fortified (3,050-3,300 kJ/L, 22-24 kcal/oz). As infants were weaned from human milk, they were fed nutrient-enriched formula with or without arachidonic and docosahexaenoic acids (3,300 kJ/L before term, 3,050 kJ/L thereafter) until 12 months CA. Formula fed infants were given nutrient-enriched formula with or without added arachidonic and docosahexaenoic acids (3,300 kJ/L to term, 3,050 kJ/L thereafter) until 12 months CA. For the purposes of this evaluation, infants were categorized into four mutually exclusive feeding groups: 1) predominantly human milk fed until term CA (PHM-T, n = 43); 2) >/= 50% energy from human milk before hospital discharge (>/= 50% HM, n = 98); 3) < 50% of energy from human milk before hospital discharge (< 50% HM, n = 203); or 4) predominantly formula fed until term CA (PFF-T, n = 119). RESULTS: PFF-T infants weighed approximately 500 g more at term CA than did PHM-T infants. This absolute difference persisted until 6 months CA. PFF-T infants were also longer (1.0-1.5 cm) and had larger head circumferences (0.3-1.1 cm) than both PHM-T and >/= 50% HM infants at term CA. There was a positive association between duration of human milk feeding and the Bayley Mental Index at 12 months CA (P = 0.032 full and P = 0.073 reduced, statistical models) after controlling for the confounding variables of home environment and maternal intelligence. Infants with chronic lung disease fed >/= 50% HM until term CA (n = 22) had a mean Bayley Motor Index about 11 points higher at 12 months CA compared with infants PFF-T (n = 24, P = 0.033 full model). CONCLUSION: Our data suggest that, despite a slower early growth rate, human milk fed LBW infants have development at least comparable to that of infants fed nutrient-enriched formula. Exploratory analysis suggests that some subgroups of human milk fed LBW infants may have enhanced development, although this needs to be confirmed in future studies.

Adult↗