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John Britton

Publications and source records attributed to John Britton.

28 records · Page 2Linked to original sources
PubMed2004

Prospective study of the effect of exposure to other smokers in high school tutor groups on the risk of incident smoking in adolescence.

Adolescent smokers tend to have peers who smoke, but it is unclear whether this arises from self-selection of smoking peers or whether this is a causal effect on the uptake of smoking (incident smoking). The authors used school tutor group current smoking prevalence, an unbiased measure of peer smoking in high schools in the United Kingdom, to estimate the independent effect of peer smoking on incident smoking among high school students. In a prospective cohort study of children aged 13-15 years (grades 9 and 10) in 10 high schools in Nottinghamshire, United Kingdom, smoking behavior was surveyed in 2,881 students in 2000, and the survey was repeated in 2,109 students (73%) in 2001. There were 267 incident smokers (15%) among the 1,766 nonsmokers in 2000. The adjusted odds of incident smoking were significantly higher in girls, in students with parents or siblings who smoke, and in relation to school tutor group current smoking prevalence in 2000 (relative odds for highest relative to the lowest quartile of prevalence = 1.78, 95% confidence interval: 1.20, 2.64). This tutor group effect was independent of having a best friend who smoked in the 2001 study. Incident smoking is therefore increased among students exposed to other students who smoke, and preventing smoking at school may reduce adolescent smoking.

Adolescent↗
PubMed2004

Serum nutrient markers and skin prick testing using data from the Third National Health and Nutrition Examination Survey.

BACKGROUND: Diet nutrients and allergic sensitization both affect the development and severity of asthma, but the interrelationship between oral intake and allergic sensitization is not well characterized, although previous work suggests that a higher vitamin E intake may be protective against allergic sensitization. OBJECTIVE: To determine whether serum levels of dietary antioxidants, lipids, and other nutrients are associated with the presence of allergen skin sensitization. METHODS: Cross-sectional logistic regression analysis of 30 serum nutrient levels in relation to 10 skin test allergens in adults and children in the Third National Health and Nutrition Survey. RESULTS: In adults, allergic skin sensitization was less common in participants with higher serum levels of vitamin E: the adjusted odds ratio (OR) per SD difference in vitamin E level was 0.93 (95% CI, 0.87-0.99). Two of the carotenoids, beta-cryptoxanthin and alpha-carotene, were also inversely associated with allergic skin sensitization (OR, 0.89; 95% CI, 0.83-0.95; and OR, 0.95; 95% CI, 0.91-0.99, respectively). Among adults, serum lycopene had a positive association with allergen sensitization. In youths, however, vitamin A was associated with an increased risk, and high-density lipoprotein cholesterol was associated with a decreased risk of allergic sensitization. The use of vitamin or mineral supplements had little effect on the magnitude of all reported associations. CONCLUSION: Overall, there were no strong or consistent associations between serum levels of potentially antiallergic nutrients, and the occurrence of allergic skin sensitization in these data. However limited, findings suggest that increases in vitamin E, carotenoids, and high-density lipoprotein cholesterol may reduce the risk of allergic skin sensitization.

Adolescent↗
PubMed2003

Control of exposure to mite allergen and allergen-impermeable bed covers for adults with asthma.

BACKGROUND: The effectiveness of avoidance of house-dust-mite allergen (Dermatophagoides pteronyssinus 1 [Der p1]) in the management of asthma is uncertain. METHODS: We conducted a double-blind, randomized, placebo-controlled study of allergen-impermeable bed covers involving 1122 adults with asthma. The primary outcomes were the mean morning peak expiratory flow rate over a four-week period during the run-in phase and at six months and the proportion of patients who discontinued inhaled corticosteroid therapy as part of a phased-reduction program during months 7 through 12. Der p1 was measured in mattress dust in a 10 percent random subsample of homes at entry and at 6 and 12 months. RESULTS: The prevalence of sensitivity to dust-mite allergen was 65.4 percent in the group supplied with allergen-impermeable bed covers (active-intervention group) and 65.1 percent in the control group supplied with non-impermeable bed covers. The concentration of Der p1 in mattress dust was significantly lower in the active-intervention group at 6 months (geometric mean, 0.58 microg per gram vs. 1.71 microg per gram in the control group; P=0.01) but not at 12 months (1.05 microg per gram vs. 1.64 microg per gram; P=0.74). The mean morning peak expiratory flow rate improved significantly in both groups (from 410.7 to 419.1 liters per minute in the active-intervention group, P<0.001 for the change; and from 417.8 to 427.4 liters per minute in the control group, P<0.001 for the change). After adjustment for base-line differences (by analysis of covariance), there was no significant difference between the groups in the peak expiratory flow rate at six months (difference in means, active-intervention group vs. control group, -1.6 liters per minute [95 percent confidence interval, -5.9 to 2.7] among all patients [P=0.46] and -1.5 liters per minute [95 percent confidence interval, -6.9 to 3.9] among mite-sensitive patients [P=0.59]). There was no significant difference between the groups in the proportion in whom complete cessation of inhaled corticosteroid therapy was achieved (17.4 percent in the active-intervention group and 17.1 percent in the control group) or in the mean reduction in steroid dose, either among all patients or among mite-sensitive patients. CONCLUSIONS: Allergen-impermeable covers, as a single intervention for the avoidance of exposure to dust-mite allergen, seem clinically ineffective in adults with asthma.

Adrenal Cortex Hormones↗
PubMed2003

Measuring dietary fatty acid intake:validation of a food-frequency questionnaire against 7 d weighed records.

There are few validated methods of measuring dietary fatty acid intake that are suitable for epidemiological research. The purpose of the present study was to develop and validate a food-frequency questionnaire (FFQ) developed to measure individual dietary fatty acid intakes against 7 d weighed dietary records, in a sample of thirty-one healthy adult volunteers. The FFQ was based on a previously validated questionnaire (DIETQ; Tinuviel Software, Warrington, Ches., UK), adapted to include greater detail on those foods from which the majority of dietary fatty acids are obtained. The FFQ and weighed records were analysed using food nutrient data from McCance and Widdowson's Food Composition Tables, supplemented with a food fatty acid content database (Foodbase, London, UK). Results from the two dietary assessment methods were compared by correlation coefficients and limits of agreement. The mean intake of individual fatty acids tended to be lower when assessed by FFQ. Correlation coefficients comparing unadjusted individual fatty acid intakes assessed by FFQ and weighed records ranged from 0.29 for 18 : 1n-9 to 0.71 for 20 : 4n-6. Adjusting for energy intake tended to increase the correlation coefficients between saturated fatty acids and decrease those between unsaturated fatty acids. In conclusion, this food-frequency method provides reliable estimates of dietary intake of many individual fatty acids for use in epidemiological studies.

Adult↗
PubMed2002

Prospective study of diet and decline in lung function in a general population.

We have investigated the relationship between decline in lung function and dietary intakes of magnesium, vitamin C, and other antioxidant vitamins in a general population cohort in Nottingham, United Kingdom. In 1991, we measured dietary intake by semiquantitative food frequency questionnaire, forced expiratory volume in 1 second (FEV1), and respiratory symptoms in a cross-sectional survey of 2,633 adults aged 18-70. Nine years later we repeated these measures in 1,346 of these individuals. In cross-sectional analyses, after adjustment for smoking and other confounders, higher intakes of vitamin C and magnesium, but not vitamins A or E, were associated with higher levels of FEV1 in both 1991 and 2000. In longitudinal analysis with adjustment for confounders, decline in FEV1 between 1991 and 2000 was lower amongst those with higher average vitamin C intake by 50.8 ml (95% confidence interval, 3.8-97.9) per 100 mg of vitamin C per day, but was unrelated to magnesium intake. There was no relationship between decline in FEV1 and intake of vitamins A or E. This study suggests that a high dietary intake of vitamin C, or of foods rich in this vitamin, may reduce the rate of loss of lung function in adults and thereby help to prevent chronic obstructive pulmonary disease.

Adult↗
PubMed2002

Increase in the prevalence of allergen skin sensitization in successive birth cohorts.

BACKGROUND: Little is known about longitudinal trends in the prevalence of allergen skin sensitization in the general population. OBJECTIVE: We sought to measure the change in prevalence of allergen skin sensitization over a 9-year period in a cohort of adults and hence to determine whether cross-sectional differences in prevalence between age groups are due to an aging or cohort effect. METHODS: In 1991 and 2000, we measured skin sensitization, defined as a wheal diameter of 3 mm or larger than that elicited by a saline control, to Dermatophagoides pteronyssinus, cat fur, mixed grass, Aspergillus fumigatus, and Cladosporium herbarum in a cohort of 1339 adults from Nottingham aged between 18 and 71 years in 1991. Subjects were divided into six 9-year successive birth cohorts, and the effects of birth cohort and the within-subject change from 1991 to 2000 were analyzed in a generalized estimating equation logit model. RESULTS: The unadjusted prevalence of sensitization to any allergen was 30.5% in 1991 and 31.8% in 2000. In cross-sectional analyses the prevalence of sensitization decreased with increasing age at both surveys (risk ratio, 2.15; 95% confidence interval [CI], 1.45-3.17 for 18- to 26-year-old patients relative to 63- to 70-year-old patients in the 1991 survey). In longitudinal analysis there was no within-subject change in sensitization from 1991 to 2000 (adjusted odds ratio, 1.07; 95% CI, 0.97-1.19), but there was a significant cohort effect (adjusted odds ratio per successive 9 year cohort, 1.27; 95% CI, 1.18-1.37). CONCLUSION: The cross-sectional decrease in allergen sensitization with age in the general population arises predominantly from a secular increase in sensitization prevalence with successive birth cohorts and not to a loss of sensitization within subjects over time. As a result of this cohort effect, the prevalence of allergic sensitization has increased in this general adult population sample.

Adolescent↗
PubMedDate not supplied

Occupational exposure to metals and solvents and the risk of motor neuron disease. A case-control study.

Previous studies based on recalled occupational histories have implicated metal and solvent exposure in the etiology of motor neuron disease (MND). We have used death certificates held in pension fund archives and linked unbiased historical occupational records to investigate the effects of occupational exposure to metals or solvents on the risk of death from MND in 22 cases and 206 controls from 22,526 past employees of a major UK engineering company. We found no evidence of increased risk of death from MND in individuals who had worked with either metals (adjusted odds ratio=0.88, 95% CI 0.35-2.22) or solvents (odds ratio=1.12, 95% CI 0.45-2.78), and no relation between disease risk and either duration or intensity of exposure. We conclude that metal and solvent exposures are unlikely to be involved in the etiology of MND.

Aged↗