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Biomedical subjects

R Siebers

Publications and source records attributed to R Siebers.

At least 19 recordsLinked to original sources
PubMed1999

Indoor environment, atopy and the risk of the asthma in children in New Zealand.

The objective of this study was to examine the relationship between the indoor environment, atopy and asthma in 7-9-year-old children. Cases and controls were randomly selected from children who participated in the International Study of Asthma and Allergies in Childhood (ISAAC) in Wellington, New Zealand. Cases were children with a previous diagnosis of asthma and current medication use (n = 233) and controls were children with no history of wheezing and no diagnosis of asthma (n = 241). Information was recorded about the indoor environment during the first year of life and currently. Dust was sampled from floors and beds and Der p 1 and Fel d 1 measured using enzyme-linked immunosorbent assays. Skin-prick tests were performed with eight common allergens. Sensitization to Dermatophagoides farinae (OR = 3.19; 95% CI 1.74-5.84), Dermatophagoides pteronyssinus (OR = 2.06; 95% CI 1.16-3.65) and cat (OR = 3.89; 95% CI 1.06-14.30) were independently associated with current asthma. The use of a sheepskin in the first year of life (OR = 1.91; 95% CI 1.11-3.33) was also independently associated with current asthma but current Der p 1 levels showed no association with current asthma. Exposures in early life may be more important than current exposures in determining asthma at age 7-9 years. Prospective studies are needed in New Zealand to determine the relative importance of early life exposures to Der p 1 and other risk factors for asthma.

Air Pollution, Indoor↗
PubMed1999

House dust mite allergen (Der p 1) accumulation on new synthetic and feather pillows.

BACKGROUND: We have previously demonstrated that synthetic pillows contain significantly more Der p 1 than feather pillows. The aim of this study was to compare the accumulation of Der p 1 allergen on new synthetic and new feather pillows. METHODS: Der p 1 was measured in dust samples from pairs of synthetic and feather pillows placed together on 12 beds over a 12-month period. RESULTS: After 12 months synthetic pillows contained higher concentrations of Der p 1 (19.28 microg/g; 95% confidence interval: 9.76-38.07) than feather pillows (6.45 microg/g; 2.96-14.05). There was a significant correlation between Der p 1 concentrations of pillows at 12 months and Der p 1 concentrations of the mattresses at the beginning of the study (r = 0.72; P = 0.008 for both types of pillows). CONCLUSIONS: Synthetic pillows accumulate Der p 1 more rapidly than feather pillows and the accumulation rate of Der p 1 on pillows is governed by the Der p 1 concentration in the immediate environment they are placed in.

Allergens↗
PubMed1998

Biologic pollution in infant bedding in New Zealand: high allergen exposure during a vulnerable period.

BACKGROUND: High exposure to house dust mite and cat allergens in early life predisposes to allergic sensitization and to the development and persistence of asthma. Prevalence and severity of asthma are high in New Zealand. OBJECTIVE: The objective of this study was to determine the concentrations of Der p 1 and Fel d 1 in infant bedding in Wellington, New Zealand. METHODS: Infants were visited at home at a mean age of 11 weeks and again at 15 months. The concentration (microgram/g fine dust) and content (microgram/m2) of Der p 1 (154 infants) and Fel d 1 (75 infants) were measured in dust samples taken from each infant's bed. RESULTS: At 11 weeks, geometric mean (95% confidence intervals) Der p 1 levels were 18.3 micrograms/g (13.8 to 24.1) and 3.51 micrograms/m2 (2.4 to 5.2). By 15 months, Der p 1 had risen significantly to 44.0 micrograms/g (35.0 to 55. 3) and 49.0 micrograms/m2 (36.0 to 66.8). Bedding that included a sheepskin was used by a third of the infants and contained higher concentrations (microgram/g) and content (microgram/m2) of Der p 1 than beds without sheepskins. Cat ownership was the major determinant of Fel d 1 levels, with 48% of infants living with cats. At the first visit, the mean concentration of Fel d 1 in bedding was 44.6 micrograms/g (23.5 to 84.9) for houses with cats and 3.0 micrograms/g (2.1 to 4.3) for those without cats, remaining essentially unchanged at the second visit. When expressed as micrograms per square meter, there was a significant increase between visits, from 8.1 (3.9 to 16. 6) to 39.6 (19.9 to 78.5) in the cat-inclusive households. CONCLUSIONS: Extremely high levels of house dust mite allergen have been found in these infants' environments, which, together with the high levels of cat allergen in almost half who kept cats, are likely to be a major determinant of asthma prevalence and severity in New Zealand.

Allergens↗
PubMed1998

A pilot study of the effect of mechanical ventilation and heat exchange on house-dust mites and Der p 1 in New Zealand homes.

We have examined the effect of reducing relative humidity (RH), with inbuilt mechanical ventilation and heat-exchange (MVHE) units, on house-dust-mite (HDM) counts and allergen levels, in a pilot study of 10 Wellington dwellings. Recent international prevalence studies in adults and children have confirmed a high prevalence of asthma in New Zealand. Sensitivity to HDM is common among the general population, and HDM is the major allergen associated with asthma. Recent studies of allergen levels have confirmed high concentrations of Der p 1 in the domestic environment. While humidity was significantly reduced in those dwellings fitted with ventilation units, no systematic effect on mites or Der p 1 was observed during the study period. When the reductions in humidity were examined in the context of the time spent below the critical equilibrium humidity (CEH), the intervention led to RH values below the CEH for only 39% of the total of 24-h periods for which measurements were made. Reducing RH by means of MVHE in New Zealand domestic dwellings does not lower humidity sufficiently, or long enough, to have any measurable effect on HDM populations.

Allergens↗
PubMed1997

House dust mite allergen levels in public places in New Zealand.

BACKGROUND: House dust mite allergens are a risk factor for asthma in New Zealand, and levels in domestic dwellings have been found to be high compared with levels in most other countries. Studies in other countries have demonstrated lower levels of Dermatophagoides pteronyssinus allergens in public places compared with levels in domestic dwellings. OBJECTIVES: The purpose of this study was to measure reservoir Der p 1 levels in public places in New Zealand and to examine determinants of these levels. METHODS: Reservoir dust was obtained in the two centers (Christchurch and Wellington) from hotels, hospitals, rest homes, churches, primary schools, childcare centers, cinemas, bank head offices, and airplanes; samples were also obtained from ski lodges. Single measurements of temperature and relative humidity were taken with thermohygrometers and an average humidity over 2 weeks was estimated with use of waxed wooden sticks. Information was collected on building construction, type of heating, and frequency of cleaning. Der p 1 levels (micrograms per gram of fine dust) for floor (n = 202), bed (n = 65), and seat (n = 24) samples in public places were expressed as geometric means (95% confidence intervals). RESULTS: Der p 1 levels in public places were significantly lower than domestic levels in both Wellington and Christchurch. Both floor and bed levels were higher in hotels than in other public places. After controlling for potential confounders, floor Der p 1 levels were higher with carpeted floors (p < 0.0001) and lower with recent cleaning (p = 0.02) and bed Der p 1 levels were higher with timber wall construction (p = 0.03). Other building, heating, or cleaning characteristics did not show significant association with allergen levels. CONCLUSION: Der p 1 levels were much lower in public places than in domestic dwellings with floor levels primarily affected by floor covering.

Allergens↗
PubMed1997

Determinants of house dust mite allergen in homes in Wellington, New Zealand.

OBJECTIVES: To measure levels of the major Dermatophagoidespteronyssinus allergen (Der p 1) in homes in Wellington, New Zealand, and to examine factors which affect these levels. METHODS: As part of a study of risk factors for asthma among 474 8-10-year-old children, standard procedures were used to collect reservoir dust and to measure Der p 1 levels on the living room floor and child's bedroom floor and bedding. Der p 1 levels were analysed both as geometric mean microg/g of fine dust and as microg/m2. Questionnaires collected information about factors which might influence these levels, and an average relative humidity in the bed and on the bedroom floor was also measured. RESULTS: Similar geometric mean levels of Der p 1 were found at each floor site - 25.5 microg/g (95% CI: 22.8-28.5) in the living room and 26.4 microg/g (95% CI: 23.7-29.3) on the child's bedroom floor. The geometric mean level of Der p 1 in the child's bed was 46.6 microg/g (95% CI: 42.3-51.3). After controlling for possible confounders, geometric mean living room and bedroom floor Der p 1 levels were significantly higher in households with older carpet than households with no carpets or newer carpets, and higher in the autumn. Households with three or more children had higher levels of Der p 1 than households with fewer children. Bedding levels were significantly higher in beds with kapok or inner sprung mattresses, or wool underlays and at relative humidities above the mean (51%). CONCLUSION: The very high levels of house dust mite allergen (Der p 1) found in Wellington are likely to be due to a variety of life-style and climatic factors. However, the type and age of floor covering appears to be the single most important factor.

Allergens↗
PubMed1996

A pilot study to investigate the pulmonary effects of digoxin in patients with asthma.

AIM: A number of studies have shown that increased salt intake is associated with worsening asthma. The aim of this study was to investigate the respiratory effects of digoxin (a potent inhibitor of Na+K+ATPase) in patients with asthma. METHODS: Eight asthmatic patients were given digoxin (0.5 mg/daily) or matching placebo for 8 days. Treatments were assigned using a randomised double blind, crossover design. Bronchial hyperresponsiveness to methacholine, forced expiratory volume is one second (FEV1, serum potassium (K), urinary sodium and K, heart rate, blood pressure and the QTc interval of the ECG were measured on each treatment. RESULTS: When compared to placebo, digoxin significantly decreased FEV1 (p<0.03); the QTc interval (p<0.05), and increased serum K (p<0.02). There was a tendency for digoxin to increase bronchial hyperresponsiveness. CONCLUSION: In this small study digoxin resulted in a decline in spirometry. Further studies in a larger group of patients should be performed to assess this potentially adverse effect of digoxin.

Adult↗
PubMed1996

Partial vs full beta-receptor agonism. A clinical study of inhaled albuterol and fenoterol.

STUDY OBJECTIVE: To compare the maximal extrapulmonary effects of the beta-agonists albuterol and fenoterol in eight healthy volunteers. SUBJECTS AND METHODS: In this double-blind study, we have examined the maximum cardiac effects (electromechanical systole [QS2I]--a measure of inotropy, heart rate, BP) and metabolic effects (plasma K+ and cyclic adenosine monophosphate [cAMP]) of repeated inhalation of albuternol and fenoterol. In eight healthy volunteers, 400 microg of each drug was administered every 10 min until QS2I and plasma K+ had reached a plateau (+/- 0.1 mmo l/L for K+, and +/- 10 ms for QS2I). The maximum response (Emax) and the dose of albuterol required to produce 50% of the maximum response to fenoterol (ED50F) were calculated. RESULTS: The Emax for fenoterol was significantly greater than albuterol for plasma K+ (-1.4 vs -1.03 mmol/L; p<0.002), QS2I (-71.8 vs 57.5 ms; p=0.047), and cAMP (33.8 vs 18.1 nmol/L; p<0.002). The dose required to produce the ED50f was significantly greater for albuterol than for fenoterol with potency ratios of 1.75, 1.61, and 2.26 for plasma K+, QS2I, and cAMP, respectively. There were no significant differences between fenoterol and albuterol with respect to heart rate (Emax, 44.9 vs 32.5 beats/min; p=0.19; potency ratio, 1.98; p=0.052). CONCLUSIONS: These findings suggest that albuterol behaves as a partial agonist at beta-receptors when compared with fenoterol, and that when inhaled in doses currently recommended for severe asthma, albuterol will result in lesser maximum cardiac and metabolic effects than fenoterol. These findings are consistent with the hypothesis that the property of full receptor agonism may contribute to the increased risk of death associated with fenoterol.

Administration, Inhalation↗