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PubMed1999

The effects of demonstrator social status and prior foraging success on social learning in laying hens.

Opportunities for social learning within a group of animals are likely to be influenced by the social dynamics of that group. Some individuals may be more influential demonstrators than others even when there are no differences in their skill level or performance. In this study of domestic hens, Gallus gallus domesticus, differences in demonstrator salience were examined. From 24 separate flocks we selected as demonstrators a dominant cockerel, a dominant hen, a mid-ranking hen or a subordinate hen. Demonstrators were pretrained to perform an operant discrimination task to obtain food. Six observers from each flock individually watched the demonstrator perform the task for four 5-min sessions held on consecutive days. On the fifth day observers were tested individually in the operant chamber. We analysed data from 19 flocks, where there were no quantitative differences in demonstrator performance. Observer hens of relatively high social status performed more correct operant pecks than observer hens of relatively low social status. Demonstrator category also had a significant effect on subsequent observer behaviour. Hens that had observed cockerels performed very few general pecks or operant pecks. Hens that had observed dominant hens performed more operant pecks, but hens that had observed sub-ordinate hens performed more general pecks in the chamber. The results suggested either that there was an interaction between dominance and gender in demonstrator salience or that dominant hens might have been influential because of some factor imperfectly associated with their dominance status. A possible candidate was the foraging ability of the dominant hens. In a second experiment using the same protocol, we manipulated the prior foraging success of dominant hens from four additional flocks but this had no significant effect on their subsequent influence as demonstrators. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMedDate not supplied

Dietary adaptations of Plio-Pleistocene Bovidae: implications for hominid habitat use.

Detailed reconstructions of vegetation structure are critical to understanding morphological and behavioral adaptations of Plio-Pleistocene African hominids, Savanna grassland habitats are often postulated as being influential in the evolution of many hominid adaptations (e.g., bipedality, foraging behaviors), yet the existence of this habitat type throughout the African Plio-Pleistocene has not been clearly established. Broad-scale reconstructions of hominid habitats as "savanna-mosaic" do not account for the fact that African grasslands may be classified into at least two different types: edaphic grasslands, which include seasonally flooded valley grasslands; and secondary grasslands, which include vast, relatively dry savanna grasslands. Though edaphic grasslands have existed for millions of years, it is unknown when secondary grasslands became widespread. The presence of specific microhabitats, including secondary grasslands, at a number of hominid sites was investigated in this study through reconstruction of diet and habitat preference in five extinct bovid taxa that were contemporaneous with early hominids. To reconstruct diet in extinct taxa, morphological correlates of dietary preferences were identified through a comparative study of cranial form in extant bovids. Metric data from cranial material of the five African Plio-Pleistocene bovid taxa were compared with extant bovid results, which yielded information of specific feeding behaviors of the extinct taxa. Reconstructed diets suggest that the earliest taxa to inhabit secondary grasslands in East Africa were Connochaetes gentryi and Parmularius altidens at around 2 m.y.a. It may therefore be inferred that secondary grasslands became prevalent at this time. This inference of secondary grassland development suggests that adaptations to this habitat type were not related to the origin of the Hominidae or to the evolution of bipedality in hominids. However, evidence suggests that this habitat type was influential in the evolution of Homo erectus sensu lato just after 2 m.y.a. in East Africa.

Adaptation, Physiological↗

PubMed1987

The relationship between nurse characteristics and perceptions of psychotropic medications in residential facilities for the retarded.

A total of 227 nurses were surveyed regarding their attitudes, perceptions, and knowledge about the use of psychotropic drugs. In general, greater age, male sex, status, and higher qualifications tended to covary and were associated with perception of greater involvement by senior nurses in drug-related decisions, more satisfaction with the level of in-service training, awareness of certain side effects, perception of interdisciplinary decision making as a clinical reality, and the view that psychologists were not influential in medication-related decisions. Those without these characteristics (e.g., females, younger nurses) more often advocated greater use of medical and laboratory tests, ongoing training, and alternatives to drugs. Nurses working in nonambulatory units more often saw senior nursing staff as influential in decisions to stop drug treatment and more often recommended that alternatives to pharmacology be employed. Some tentative conclusions about the dynamics surrounding medication use in these facilities were offered to account for these patterns.

Adolescent↗

PubMed1998

[Late outcome of severed extensor tendons in the area of the hand and fingers].

In the care and further treatment of patients with hand injuries, a necessary requirement of the hand surgeon is that he be able to cope with the interlocking factors that are no longer influential, for example, the type and extent of the trauma or the age of the patient; the influential factors are a thought-out care plan, atraumatic action with regard to optimal restoration of the hand. This also showed a retrospective analysis of results and post-examination from flexor tendon injuries in the hand of 298 patients, who were surgically cared for from 1984 to 1994 at the surgical clinic of the University of Jena. Of the 298 patients 119 patients with 198 flexor tendon injuries (165 fingers and 33 thumbs) were followed up. For objective assessment of the treatment results, the assessment scheme Buck-Gramcko was used.

Adolescent↗

PubMed2007

Reliability and uncertainty in the estimation of pKa by least squares nonlinear regression analysis of multiwavelength spectrophotometric pH titration data.

When drugs are poorly soluble then, instead of the potentiometric determination of dissociation constants, pH-spectrophotometric titration can be used along with nonlinear regression of the absorbance response surface data. Generally, regression models are extremely useful for extracting the essential features from a multiwavelength set of data. Regression diagnostics represent procedures for examining the regression triplet (data, model, method) in order to check (a) the data quality for a proposed model; (b) the model quality for a given set of data; and (c) that all of the assumptions used for least squares hold. In the interactive, PC-assisted diagnosis of data, models and estimation methods, the examination of data quality involves the detection of influential points, outliers and high leverages, that cause many problems when regression fitting the absorbance response hyperplane. All graphically oriented techniques are suitable for the rapid estimation of influential points. The reliability of the dissociation constants for the acid drug silybin may be proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data. The uncertainty in the measurement of the pK (a) of a weak acid obtained by the least squares nonlinear regression analysis of absorption spectra is calculated. The procedure takes into account the drift in pH measurement, the drift in spectral measurement, and all of the drifts in analytical operations, as well as the relative importance of each source of uncertainty. The most important source of uncertainty in the experimental set-up for the example is the uncertainty in the pH measurement. The influences of various sources of uncertainty on the accuracy and precision are discussed using the example of the mixed dissociation constants of silybin, obtained using the SQUAD(84) and SPECFIT/32 regression programs.

Antioxidants↗

PubMed2003

Water characterization and seasonal heavy metal distribution in the Odiel River (Huelva, Spain) by means of principal component analysis.

The Iberian Pyrite Belt is the largest mass of sulfide and manganese ores in Western Europe. Its sulfide oxidation is the origin of a heavily acidic drainage that affects the Odiel River in southwestern Huelva (Spain). To assess physicochemical, contamination parameters, heavy metal distribution and its seasonal variation in the upper Odiel River and in El Lomero mines, three water samplings were undertaken and analyzed between July 1998 and November 1999. Water from the Odiel River in the polluted zone showed low pH values (2.76-3.51), high heavy metal content, and high values of conductivity (1410-3648 microS/cm) and dissolved solids (1484-5602 mg/L). Principal Component Analysis (PCA) showed that variables related with the products of the pyrite oxidation and the salts that are solubilized by the high acidity generated in the oxidation of sulfides, grouped in the first component, accounted for 40.88% of total variance, and were the main influential factor in physicochemical water sample properties. The second influential factor was minority metals (nickel, cobalt, cadmium). Heavy metals showed three different seasonal patterns, closely related with saline efflorescences formed next to the river bed: majority metals (iron, copper, manganese, zinc); minority metals (lead, nickel, cobalt, cadmium); and chromium, which had a distinctive behavior.

Environmental Monitoring↗

PubMed2000

Experimental kinetic rates of food-chain and waterborne radionuclide transfer to freshwater fish: a basis for the construction of fish contamination charts.

A standardized procedure is proposed to obtain from laboratory experiments the kinetic accumulation and release rates necessary to calibrate dynamic models to quantify radionuclide direct and trophic transfer in fish. The model takes into account the food-chain effect, the feeding rate, and the growth of organisms. It takes as examples (54)Mn, (60)Co, and (137)Cs transfer dynamics through a simple pelagic food-chain (phytoplankton, zooplankton, prey fish, and predator fish). The estimated kinetic rates used in quantifying all the transfers of the three radioactive pollutants through the pelagic food chain are compared from the radioecological point of view. For fish, comparison was based on the calculation of concentration factors referring to direct transfer from water and trophic transfer factors. For the prey fish and the predator fish, direct transfer gave the following order for accumulation (60)Co < (137)Cs < (54)Mn. Values reached at equilibrium in L/kg WW were respectively for the prey fish and the predator fish: 8.7 < 27.4 < 107 and 4.14 < 6.59 < 13.4. For the trophic route, (137)Cs is the most accumulated (TTF(eq) = 0.485 in 291 days for the prey fish and TTF(eq) = 1.45 in 17 years for the predator fish). A sensitivity analysis adapted to the case of a chronic contamination scenario of a watercourse was run. It showed that the phytoplankton biomass, the contact time of these drifting particles from a release point to the station where they are ingested and the feeding rates of the fish are the most influential parameter with regard to the concentration in fish, whatever the trophic level. Contamination charts are constructed for the predator fish to illustrate the relationship between the most influential ecological parameters and the radionuclide concentration in fish for simple contamination scenarios. They are shown to be effective tools for helping in the choice of the most relevant value of aggregated concentration factors (ACFs: radionuclide concentration ratio between the organism and the water, referred to steady-state and to all possible transfer pathways) for a given key ecological situation in a given ecosystem. An example is given of a simple chronic release scenario of 1 Bq/L and a phytoplanktonic bloom period. For (137)Cs, the ACF increases with increasing contact time and increasing feeding rate, to nearly 550 L/kg WW at equilibrium. For (54)Mn, ACF reaches 65 L/kg WW. For (60)Co, the general pattern of the relationship is due to the rapid kinetic rates governing the distribution of the radionuclide between dissolved and solid (phytoplankton) phases with a maximum value for ACF of 7.2 L/kg WW for the case study. Analysis of these charts provides a basis for overall guidelines for chronic releases in a given watercourse.

Animals↗

PubMed2005

A comparative study of voice complaints and risk factors for voice complaints in female student teachers and practicing teachers early in their career.

A cross-sectional questionnaire survey was performed to compare female student teachers (454 subjects; 1st to 4th year of training) and practicing teachers (82 female teachers; 1st to 4th year of teaching career) of primary education early in their career, with regard to risk factors perceived to be a negative influence on the voice, and the relative risk of the given risk factors for voice complaints. This enables the observation of whether there is a sudden increase or difference in the perceived risk factors after starting a professional teaching career. Additionally, the existence of a history of voice problems during training was questioned among the teachers. Teachers with voice complaints compared to teachers without voice complaints reported a history of voice complaints during their training (P =0.013). Teachers compared to student teachers reported more voice complaints at the moment and/or during the past year (P =0.002). The following data were obtained from student teachers and teachers reporting voice complaints. Only around a third of the subjects of both groups sought voice care (P =0.286-0.893). Risk factors were estimated in relation to voice complaints. Student teachers reported less frequently than teachers that stress (P =0.014), work pressure (P =0.003) and the composition of the class (P =0.013) have a negative influence on their voice. Student teachers reported less frequently than teachers that the number of people they communicate with (P <0.001) and the deterioration of their general physical condition (P =0.010) have a negative influence on their voice. Student teachers reported more frequently than teachers that environmental irritants (P <0.001) and humidity (P =0.020) of the classroom have a negative influence on their voice. Student teachers more than teachers were of the opinion that the attention paid to the voice during their training was sufficient (P <0.001). To test whether professional status (student teacher versus teacher) is an effect modifier for the risk factors, odds ratios (OR) were compared between the group of teachers and of student teachers (total group with and without voice complaints) to search for interactions between the risk factors and professional status. There is a significant difference in the pattern of risk factors for student teachers and teachers (P =0.010). There is an indication that vocal loading factors and environmental factors are more influential in student teachers and that there is a tendency for psycho-emotional factors to be more influential for teachers early in their career.

Adolescent↗

PubMed2006

Changes in tubular dysfunction marker levels in parallel with the levels of copper, rather than cadmium, in urine of middle-aged women in non-polluted areas.

OBJECTIVE: This study was initiated to investigate if and to what extent the elevations in urinary alpha(1)- and beta(2)-microglobulins (alpha(1)-MG and beta(2)-MG, respectively) are specific to Cd nephro-toxicity. METHODS: Stored urine samples, collected from 1,000 adult women in 11 prefectures all over Japan, were analysed for eight elements (Ca, Cd, Co, Cu, Mg, Mn, Ni and Zn), alpha(1)-MG, beta(2)-MG, creatinine (CR) and specific gravity (SG); the data were cited from previous publications. The levels of eight elements and two MGs were expressed as observed and after correction for CR or SG (1.016). Age, CR and SG distributed normally, whereas two MGs and eight elements distributed log-normally. The 1,000 cases were classified into quartiles (i.e., 250 cases/group) of the lowest to the highest values (Groups A to D) for each element. RESULTS: alpha(1)-MG and beta(2)-MG increased as a function of Ca, Cd and Cu when corrected for CR, and the two MGs increased in parallel only with Cd and Cu after SG correction. Prevalence of alpha(1)-MG-uria (cut-off values; 5.3 and 6.5 mg/g cr or l) and beta(2)-MG-uria (cut-off values; 300 and 400 microg/g cr or l) was elevated with increasing Ca, Cd and Cu when corrected for CR, but only with Cd and Cu when corrected for SG. Multiple regression analysis of 353 cases of 50-59 year-old women with the eight element levels as independent variables and one of the two MGs as a dependent variable showed that Cu was the most influential element, and both Cd and Zn were less influential. CONCLUSIONS: Urinary levels of alpha(1)-MG and beta(2)-MG among women with no environmental Cd exposure correlated more closely with Cu levels than Cd levels in urine. The observation suggests that sub-clinical elevation in alpha(1)-MG and beta(2)-MG is not always attributable to nephro-toxicity of Cd, and that consideration on possible effects of other elements such as Cu is necessary.

Adult↗

PubMed2006

Research in medical education: balancing service and science.

Since the latter part of the 1990's, the English-speaking medical education community has been engaged in a debate concerning the types of research that should have priority. To shed light on this debate and to better understand its implications for the practice of research, 23 semi-structured interviews were conducted with "influential figures" from the community. The results were analyzed using the concept of "field" developed by the sociologist Pierre Bourdieu. The results reveal that a large majority of these influential figures believe that research in medical education continues to be of insufficient quality despite the progress that has taken place over the past 2 decades. According to this group, studies tend to be both redundant and opportunistic, and researchers tend to have limited understanding of both theory and methodological practice from the social sciences. Three factors were identified by the participants to explain the current problems in research: the working conditions of researchers, budgetary restraints in financing research in medical education, and the conception of research in the medical environment. Two principal means for improving research are presented: intensifying collaboration between PhD's and clinicians, and encouraging the diversification of perspectives brought to bear on research in medical education.

Curriculum↗

PubMed2007

An agenda for future debate on concepts of health and disease.

The traditional contrast between naturalist and normativist disease concepts fails to capture the most salient features of the health concepts debate. By using health concepts as a window on background notions of medical science and ethics, I show how Christopher Boorse (an influential naturalist) and Lennart Nordenfelt (an influential normativist) actually share deep assumptions about the character of medicine. Their disease concepts attempt, in different ways, to shore up the same medical model. For both, health concepts function like demarcation criteria in the philosophy of science: they mark off the jurisdiction of medical science, and protect it from an inappropriate intrusion of socioeconomic factors, which threaten the integrity of modern medicine. These views are challenged by new developments in healthcare such as managed care and total quality review. To frame the health concepts debate in a way that better captures the issues integral to these new developments, I advance a new way of reading the distinction between weak and strong normativists. Strong normativists are skeptical of the demarcation project, think facts and values cannot be disentangled, and hold that socioeconomic conditions unavoidably influence how pathology is understood. The new health concepts debate should be framed as one between weak and strong normativists, and it concerns how we should respond to the current developments in health care.

Attitude to Health↗

PubMed2005

Factors that influence prescribers in their selection and use of COX-2 selective inhibitors as opposed to non-selective NSAIDs.

OBJECTIVE: To identify factors that influence prescribers in their selection and use of cyclo-oxygenase-2 (COX-2) selective inhibitors as opposed to non-selective non-steroidal anti-inflammatory drugs (NSAIDs) and report the tendency to co-prescribe gastro-protection with these agents. SETTING: All 579 general practitioners (GPs) in one geographical area, Lothian, Scotland, UK. METHOD: Postal questionnaires; simple and factorial designed case series questionnaire. MAIN OUTCOME MEASURES: Categorisation of responses to clinical and non-clinical factors into highly, partially or not influential. The quantitative influence of the most prominent clinical factors on prescribing choice and the tendency of co-prescription of gastro-protection with these agents. RESULTS: Responses from 229 (40%) GPs suggested the following as most influential: Drug Evaluation Panel recommendations, Lothian Joint Formulary, local practice formulary, history of peptic ulcer disease (PUD), history of gastro-intestinal (GI) adverse effects with NSAIDs and advanced age. Advice from other physicians, patient demand, history of alcohol gastritis, history of gastro-oesophageal reflux disease, history of functional dyspepsia, concomitant use of low dose aspirin and concomitant use of gastro-protective agents were regarded to have moderate influence. Information directly from pharmaceutical industry and regular smoking were regarded as having weak influence. An 18% response to the factorial designed questionnaire using the most prominent clinical factors suggested that history of either GI adverse effects associated with non-selective NSAIDs or PUD resulted in more pronounced increase in the frequency (15%) of decision to prescribe COX-2 selective inhibitors than advanced age (10%). Concomitant use of low dose aspirin had little effect on GPs' decisions. The mean percentage of GPs choosing to co-prescribe gastro-protection was higher with non-selective NSAIDs (64%) than with COX-2 selective inhibitors (22%). CONCLUSION: Local authoritative guidance and history of GI complications highly influenced the GPs in their use and choice of either COX-2 selective inhibitors or non-selective NSAIDs. As expected the use of gastro-protection was more frequently chosen with non-selective NSAIDs than COX-2 selective inhibitors.

Age Factors↗

PubMedDate not supplied

How individual clinicians make admission decisions in psychiatric emergency rooms.

The goal of this study was to understand how individual clinicians make admission decisions in the psychiatric emergency room. Clinical and demographic data were collected on 7485 consecutive visits to four psychiatric hospitals in Israel during 1991 and 1992. This was about one-third of visits to psychiatric emergency rooms in Israel during this time. Twenty-one decision makers who made at least 50 decisions and admitted more than 15 and less than 85% of patients were included. Decision to admit patients was modeled using step-wise discriminant analysis. Clinicians examined different numbers of patients and admitted at different rates. In one hospital one group of clinicians appears to rely primarily on diagnosis and another group on other variables, predominately previous history, and social or referral factors. The most influential background variable was self-referral which favored not admitting patient. The most influential diagnoses were schizophrenia and affective disorder which favored admission. In another hospital the most important variables in most models were legal status of admission, number of previous hospitalizations, violence and suicide as presenting problems and referral source. All variables except referral source favored admission. Some referral sources favored admission and others did not. In the last hospital studied the most salient variable was self-referral which favored not admitting patient. Decisions in one hospital were not modeled because no clinician met study inclusion criteria. There appears to be variability between clinicians in what information they use to make their decisions in the psychiatric emergency room and what percent of patients they admit.

Decision Making↗

PubMed1996

Translating research findings into health policy.

Evidence of the influence of research on health policy is paradoxical. While there is scant evidence that research has had any impact on the direction or implementation of widespread health reforms, research on evidence-based medicine has dramatically increased, despite limited evidence that it has affected clinical practice. These developments have occurred in the context of a general decline in state intervention and provision and a post-modern questioning of researchers' authority. Models of the relationship between research and policy range from one where empirical research rationally informs decision-making, through research incrementally affecting policy, to an "enlightenment" or "infiltration" model, which may operate on a conceptual level. Health research that contributes to large-scale socio-political change may require more methodological pluralism and greater focus on key institutional structures. Case studies reviewed suggest that dissemination is enhanced if researchers involve managers and policy-makers in the development of the framework for and focus of research and if investigators assume a responsibility for seeing their research translated into policy. Public health research is more influential if topical, timely, well-funded and carried out by a collaborative team that includes academics. Evaluations are more influential if, in addition, they are commissioned by health authorities but based on local collection of data, and instruments and incentives to implement policy are available. In some areas, such as the recent policy focus on careers in the community, researchers were largely responsible for raising this policy issue, whereas in other areas, such as the relationship between unemployment and health, researchers are just one of the groups of experts making competing claims about causality. In conclusion, clear research findings are not always a passport to policy, but researchers can reframe the way health policy issues are seen, and collaboration with policy-makers initially can enhance implementation later.

Communication Barriers↗

PubMed1995

Periodically modulated inhibition and its postsynaptic consequences--II. Influence of modulation slope, depth, range, noise and of postsynaptic natural discharges.

This paper examines the relation, or "synaptic coding", between the discharges of inhibitory fibres whose instantaneous firing rate is modulated periodically and pacemaker postsynaptic neurons using crayfish synapses and point process statistics. Several control parameters were varied individually, and the other maintained constant as far as possible: it extends the preceding publication that described the general features and varied only the modulation frequency [Segundo et al. (1995) Neuroscience 68, 657-692]. Statistics were mainly cycle histograms and Lissajous diagrams (with presynaptic and post-synaptic histograms on the abscissae and ordinate, respectively), complemented occasionally by displays of intervals along time and of interval differences along order ("basic graphs" and "recurrence plots", respectively). The postsynaptic influence of modulated inhibitory discharges is characteristically sensitive to all control parameters examined. (1) The frequency was reported in the companion paper [Segundo et al. (1995) Neuroscience 68, 657-692]. (2) The average slope per half-cycle, controlled via either frequency or depth, acts by way of its magnitude and sign in ways revealed by hysteretic loops. Hysteresis increases and varies as the modulation's steepness increases: it is minor and with a single clockwise loop at small slopes, but major and multi-looped at the larger ones. Slopes, because of their different postsynaptic consequences, were separated into the categories of "steep", "gentle" and "abrupt" if around, respectively, 1.0, 30.0 and 150.0 s-2. The influence of slopes in restricted portions of the cycle depends on their position on the inhibitory rate scale. (3) The modulation's range acts by way of its depth and of its position on the inhibitory rate scale. Deeper ranges, when compared with the shallower ones they contain, induce effects similar to those of shallower modulations with their central portion, plus effects peculiar to them at extreme rates. Changes in range position from the centre to the extremes of the inhibitory rate scale are influential (e.g., saturations appear). Changes within the centre can be highly influential, particularly when ranges are narrow and close to the postsynaptic natural rate, and modulation frequencies are low: relations between corresponding rates can be linear increasing, linear decreasing or piecewise linear. Changes around extreme rates are negligible, however, and saturations are present. (4) The usual modulations whose individual cycles did not differ from the cycle histogram were compared to others with the same cycle histograms but whose individual cycles had an unpredictable fast variability referred to as "noise".(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Alcohol and drug abusers' reasons for seeking treatment.

Clients at two different treatment facilities were asked at assessment how influential each of 10 possible reasons were in their decision to change their alcohol or drug use. Clients at both facilities most often endorsed "weighing the pros and cons of drinking or drug use" and a "warning from spouse." Client's reasons for seeking treatment were also examined in relation to treatment compliance. Three reasons--"weighing the pros and cons," "hitting rock bottom," and experiencing a "major lifestyle change"--were predictive of treatment compliance. Clients who rated any of these reasons as influential were more likely to enter and complete treatment. Although more research is needed, knowledge of clients' reasons for seeking treatment might be useful in treatment matching.

Adult↗

PubMed1988

Adolescent drug taking: role of family and peers.

To study the influence of family and peers on drug-taking behavior in adolescents, confidential self-reports were obtained from 3333 London adolescents about their use of solvents and illicit drugs. They were also asked about their perception of their best friend's and any family member's use of drugs. The results show that both family and peer's use of drugs were influential. However, peers were more influential than family regardless of whether they took drugs or not and both factors can also have a synergistic effect. The implications of the findings are discussed.

Adolescent↗

PubMed2005

Childhood friends who smoke: do they influence adolescents to make smoking transitions?

This study investigated longitudinally the extent to which childhood friends who smoke influence adolescents' smoking transitions, and compared that influence with that of parents who smoke. In a sample of 4744 children, results showed that the probability, per close friend, that a smoking close friend influenced the adolescent to make the first transition to trying smoking was 38% (95% CI: 28%, 46%); to make the second transition from trying to monthly smoking, 10% (95% CI: 5%, 15%); and to make the third transition from monthly to daily smoking, 11% (95% CI: 5%, 17%). Compared to parents' smoking, close friends' smoking was 12% (p=0.03) more influential for the first transition, no different for the second transition (p=0.53), and 16% (p=0.01) less influential for the third transition. Results provide new evidence suggesting that childhood close friends who smoke influence not only initiation but also escalation of adolescents' smoking. Results also confirmed the important role of parents' smoking. Targeting both childhood close friends' and parents' smoking would be valuable in prevention research.

Adolescent↗