Examining the relationship between pubertal stage, adolescent health behaviours and stress

Background. This paper examines the associations between puberty and three important health behavlours (smoking, food intake and exercise) and explores whether these associations are mediated by puberty's relationship to stress and psychological difficulties.Method. Data were taken from the first year of the ongoing, 5-year, Health and Behaviours in Teenagers Study (HABITS). This is a school-based study set in 36 schools in London. In the first year of the study, 4320 students (2578 boys, 1742 girls) in their first year of secondary education took part.Results. Among girls, being more pubertally advanced was associated with a greater likelihood of having tried smoking. Among boys, being more pubertally advanced was associated with a greater likelihood of having tried smoking, a higher intake of high-fat food and higher levels of exercise. More pubertally advanced girls experienced more stress but not more psychological difficulties. There were no associations between puberty and either stress or psychological difficulties in boys. Stress and psychological difficulties were associated with health behaviours in girls and boys, but neither of these factors mediated the relationship between pubertal stage and health behaviours found in girls.Conclusions. These results suggest that the onset of puberty has a marked effect on the development of health behaviours. Puberty was related to an acceleration of the development of unhealthy behaviours, except for exercise behaviour in boys, where advanced puberty was associated with more exercise. These changes were unrelated to adolescent issues of stress and a causal explanation for these associations must be sought elsewhere

Assessing smoking status in children, adolescents and adults: cotinine cut-points revisited

Aims To reassess saliva cotinine cut-points to discriminate smoking status. Cotinine cut-points that are in use were derived from relatively small samples of smokers and non-smokers 20 or more years ago. It is possible that optimal cut-points may have changed as prevalence and exposure to passive smoking have declined. Design Cross-sectional survey of the general population, with assessment of self-reported smoking and saliva cotinine. Participants A total of 58 791 respondents aged 4 years and older in the Health Survey for England for the years 1996-2004 who provided valid saliva cotinine specimens. Measures Saliva cotinine concentrations, demographic variables, self-reported smoking, presence or absence of smoking in the home, a composite index of social disadvantage derived from occupation, housing tenure and access to a car. Findigns A cut-point of 12 ng/ml performed best overall, with specificity of 96.9% and sensitivity of 96.7% in discriminating confirmed cigarette smokers from never regular smokers. This cut-point also identified correctly 95.8% of children aged 8-15 years smoking six or more cigarettes a week. There was evidence of substantial misreport in claimed ex-smokers, especially adolescents (specificity 72.3%) and young adults aged 16-24 years (77.5%). Optimal cut-points varied by presence (18 ng/ml) or absence (5 ng/ml) of smoking in the home, and there was a gradient from 8 ng/ml to 18 ng/ml with increasing social disadvantage. Conclusions The extent of non-smokers' exposure to other people's tobacco smoke is the principal factor driving optimal cotinine cut-points. A cut-point of 12 ng/ml can be recommended for general use across the whole age range, although different cut-points may be appropriate for population subgroups and in societies with differing levels of exposure to secondhand smoke

Children's exposure to second-hand smoke 10 years on from smoke-free legislation in England: Cotinine data from the Health Survey for England 1998-2018

BACKGROUND: We aimed to investigate trends in children's exposure to second-hand tobacco smoke in England from 1998 to 2018. METHODS: We used twenty-one years of data from the Health Survey for England, a yearly repeated cross-sectional population study. A total of 49,460 children participated between 1998 and 2018, of whom 17,463 were biochemically confirmed non-smokers aged 4-15. We examined changes in (i) the proportion of children living in reported smoke-free homes and (ii) second-hand smoke uptake, measured quantitatively using saliva cotinine concentration. FINDINGS: The percentage of children living in a home reported to be smoke-free increased from 63.0% (95% CI 60.5%-65.2%) in 1998 to 93.3% (91.8%-94.6%) in 2018. This increase was most pronounced among children with a smoker parent, rising from 17.1% (14.7%-19.8%) to 75.9% (70.8%-80.4%). Segmented regression showed that the rate of adoption of smoke-free homes accelerated leading up to the 2007 ban on smoking in public places, growing most rapidly in the four years after its entry into law. Between 1998 and 2018, there was a ten-fold decline in geometric mean cotinine among non-smoking children, from 0.50 ng/ml (0.46-0.56) to 0.05 ng/ml (0.04-0.06). A total of 65.0% (61.2%-68.6%) of children had undetectable cotinine in 2018, up from 14.3% (12.7%-16.0%) in 1998. Children living in rented accommodation were more exposed than those from owner-occupied households, but they experienced similar relative declines across years. INTERPRETATION: Cotinine data show that children's exposure to second-hand smoke has fallen by some 90% since 1998, with an apparent acceleration in adoption of smoke-free homes since the 2007 ban on smoking in public places. A norm has emerged that sees smoking in the home as inappropriate, almost universally where parents are non-smokers, but also increasingly among smoking parents

The Performance of Photometric Reverberation Mapping at High Redshift and the Reliability of Damped Random Walk Models

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Accurate methods for reverberation mapping using photometry are highly sought after since they are inherently less resource intensive than spectroscopic techniques. However, the effectiveness of photometric reverberation mapping for estimating black hole masses is sparsely investigated at redshifts higher than $z\approx0.04$. Furthermore, photometric methods frequently assume a Damped Random Walk (DRW) model, which may not be universally applicable. We perform photometric reverberation mapping using the Javelin photometric DRW model for the QSO SDSSJ144645.44+625304.0 at z=0.351 and estimate the H$\beta$ lag of $65^{+6}_{-1}$ days and black-hole mass of $10^{8.22^{+0.13}_{-0.15}}M_{\odot}$. An analysis of the reliability of photometric reverberation mapping, conducted using many thousands of simulated CARMA process light-curves, shows that we can recover the input lag to within 6 per cent on average given our target's observed signal-to-noise of > 20 and an average cadence of 14 days (even when DRW is not applicable). Furthermore, we use our suite of simulated light curves to deconvolve aliases and artefacts from our QSO's posterior probability distribution, increasing the signal-to-noise on the lag by a factor of $\sim2.2$. We exceed the signal-to-noise of the Sloan Digital Sky Survey Reverberation Mapping Project (SDSS-RM) campaign with a quarter of the observing time per object, resulting in a $\sim200$ per cent increase in SNR efficiency over SDSS-RM.Peer reviewedFinal Accepted Versio

GMRT 610-MHz observations of the faint radio source population – and what these tell us about the higher radio-frequency sky

We present 610-MHz Giant Metrewave Radio Telescope observations of 0.84 deg$^{2}$ of the AMI001 field (centred on 00$^{h}$23$^{m}$10$^{s}$, +31°53′) with an rms noise of 18 μJy beam$^{-1}$ in the centre of the field. A total of 955 sources are detected, and 814 are included in the source count analysis. The source counts from these observations are consistent with previous work. We have used these data to study the spectral index distribution of a sample of sources selected at 15.7 GHz from the recent deep extension to the Tenth Cambridge (10C) survey. The median spectral index, α, (where S ∝ ν$^{−α}$) between 0.08<$\textit{S}$$_{15.7GHz}$/mJy<0.2 is 0.32 ± 0.14, showing that star-forming galaxies, which have much steeper spectra, are not contributing significantly to this population. This is in contrast to several models, but in agreement with the results from the 10C ultradeep source counts; the high-frequency sky therefore continues to be dominated by radio galaxies down to S$_{15.7GHz}$ = 0.1 mJy.The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. IHW thanks the Science and Technologies Facilities Council for a studentship. IHW and MJJ acknowledge support from the Square Kilometre Array South Africa. IHW thanks the South African Astronomical Observatory, where some of this work was carried out

The faint radio source population at 15.7 GHz-IV. The dominance of core emission in faint radio galaxies

We present 15-GHz Karl G. Jansky Very Large Array observations of a complete sample of radio galaxies selected at 15.7 GHz from the Tenth Cambridge (10C) survey. 67 out of the 95 sources (71 per cent) are unresolved in the new observations and lower-frequency radio observations, placing an upper limit on their angular size of ~2 arcsec. Thus compact radio galaxies, or radio galaxies with very faint jets, are the dominant population in the 10C survey. This provides support for the suggestion in our previous work that low-luminosity ($L<10^{25} \, \textrm{W Hz}^{-1}$) radio galaxies are core-dominated, although higher-resolution observations are required to confirm this directly. The 10C sample of compact, high-frequency selected radio galaxies is a mixture of high-excitation and low-excitation radio galaxies and displays a range of radio spectral shapes, demonstrating that they are a mixed population of objects

The faint radio source population at 15.7 GHz - II. Multi-wavelength properties

A complete, flux density limited sample of 96 faint ($> 0.5$ mJy) radio sources is selected from the 10C survey at 15.7 GHz in the Lockman Hole. We have matched this sample to a range of multi-wavelength catalogues, including SERVS, SWIRE, UKIDSS and optical data; multi-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts are available for 24 sources. Photometric reshifts are estimated for the sources with multi-wavelength data available; the median redshift of the sample is 0.91 with an interquartile range of 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud, indicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples selected at lower frequencies, where radio-quiet AGN and starforming galaxies are present in significant numbers at these flux density levels. All six radio-quiet sources have rising radio spectra, suggesting that they are dominated by AGN emission. These results confirm the conclusions of Paper I that the faint, flat-spectrum sources which are found to dominate the 10C sample below $\sim 1$ mJy are the cores of radio galaxies. The properties of the 10C sample are compared to the SKADS Simulated Skies; a population of low-redshift starforming galaxies predicted by the simulation is not found in the observed sample.IHW acknowledges a Science and Technology Facilities Council studentship. IHW, MJ, MV acknowledge support from the Square Kilometre Array South Africa project and the South African National Research Foundation. MV is supported by the European Commission Research Executive Agency FP7-SPACE- 2013-1 Scheme (Grant Agreement 607254 - Herschel Extragalactic Legacy Project - HELP). This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Opinions expressed and conclusions arrived at are those of the authors and not necessarily attributed to the SKA SA. We thank the anonymous referee for their helpful comments.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stv190