Biomedical subjects

C A Prescott

Publications and source records attributed to C A Prescott.

At least 55 records · Page 3Linked to original sources

PubMed2000

Burow's solution in the treatment of active mucosal chronic suppurative otitis media: determining an effective dilution.

Burow's solution (13 per cent aluminium acetate) has been found to inhibit in vitro the growth of most commonly occurring bacteria found in the discharging ear. An in vitro study has shown that the minimum inhibitory concentration of Burow's solution for these organisms lies between a 1:80 and a 1:160 dilution. This paper reports on a clinical trial that incorporated 67 discharging ears to establish the most effective strength of aluminium acetate solution. There was no statistical difference in the effectiveness of full strength Burow's solution compared to 3.25 per cent aluminium acetate solution (a quarter strength Burow's solution). Response rates of 80.8 per cent and 75 per cent respectively following a two-week treatment period were achieved using these two solutions. A 1.3 per cent aluminium acetate solution (1/10 strength Burow's solution) was found to be markedly inferior. Bacteriological and audiological profiles were recorded for each patient.

Acetates↗

PubMed1999

An evaluation of the 'voice test' as a method for assessing hearing in children with particular reference to the situation in developing countries.

In developing countries with limited no or access to standard audiometric methods a 'voice test' is a potential non-technological alternative method of assessing hearing. A three level 'voice test' was developed, refined and standardised-accurate response to a whispered voice equating with normal hearing, to a conversational voice with mild hearing loss and to a loud voice to moderate/severe hearing loss. In a hospital based study 177 children were voice tested in sound treated rooms and then tested using standard audiometric procedures to determine precise hearing thresholds. In this situation the voice test had a specificity of 95.9% and a sensitivity of 80%. When the test was evaluated on 201 children aged 3-8 years, first voice tested and then tested with standard audiometry in the classrooms of their pre-primary schools it was found to have a specificity of 97.8% and a sensitivity of 83.3%. With this degree of accuracy in detecting hearing impairment and given the simplicity required to administer the test, it is felt that such a test could be recommended for use by primary health care workers in developing countries where access to standard audiometric methods for assessing hearing are not available.

Audiometry↗

PubMed1999

Cholesteatoma in children--the experience at The Red Cross War Memorial Children's Hospital in South Africa 1988-1996.

This review of experience with cholesteatoma in children, describes the presentation and features of the disease from a tertiary institution in a 'developing country'. A total of 24 out of 96 cholesteatomas in 81 children (M:F = 44:37) aged 2-12 years initially presented with mastoiditis, with intracranial complications in seven children. Three of the cholesteatomas were congenital, 56 arose from retraction pockets-11 pars flaccida, 45 pars tensa 21 were associated with either a central perforation or total atelectasis and one originated at a ventilation tube site. Open cavity surgery was undertaken in all cases-atticotomy in 14, open mastoid cavity in 82 ears. It was not always possible to preserve reasonably normal pre-operative hearing nor was it possible to improve hearing loss. Twenty-six out of 81 children did not return for follow-up. Even with open cavity surgery, recurrence of cholesteatoma occurred. Late diagnosis, extensive disease, a high rate of complications and poor follow-up are the features of this disease in 'developing' countries.

Audiometry↗

PubMed1999

A population-based twin study of lifetime major depression in men and women.

BACKGROUND: Women report higher rates of major depression (MD) than men. Although genetic factors play an important etiologic role in MD, we are uncertain whether genetic factors are of equal importance in men and women, and whether the same genetic factors predispose men and women to MD. METHODS: We obtained, by telephone interview, a lifetime history of MD, defined by the DSM-III-R, from 3790 complete male-male, female-female, and male-female twin pairs, identified through a population-based registry. Results were analyzed using probandwise concordance, odds ratios, and biometrical twin modeling. RESULTS: The odds ratios (plus tetrachoric correlations) for lifetime MD were as follows: (1) male-male monozygotic, 3.29 (+0.37); (2) male-male dizygotic, 1.86 (+0.20); (3) female-female monozygotic, 3.02 (+0.39); (4) female-female dizygotic, 1.59 (+0.18); and (5) male-female dizygotic, 1.39 (+0.11). In the best-fitting twin model, the heritability of liability to MD was the same in men and women and equal to 39%, while the remaining 61% of the variance in liability was due to individual-specific environment. We rejected, with only modest confidence, the hypothesis that the genetic risk factors for MD were the same in men and women. The best-fitting model estimated the genetic correlation in the liability to MD in the 2 sexes to be +0.57. While we found no evidence to suggest a violation of the equal environment assumption, MD was less common in women from opposite-sex vs same-sex twin pairs. CONCLUSIONS: Major depression is equally heritable in men and women, and most genetic risk factors influence liability to MD similarly in the 2 sexes. However, genes may exist that act differently on the risk for MD in men vs women.

Adolescent↗

PubMed1999

Clinical characteristics of major depression that predict risk of depression in relatives.

BACKGROUND: Major depression (MD) is both clinically and etiologically heterogeneous. We attempt to relate clinical and etiologic heterogeneity by determining those features of MD that reflect a high familial liability to depressive illness. METHODS: Our sample, 3786 personally interviewed twin pairs from a population-based registry, contained 1765 people with a lifetime history of MD by DSM-III-R criteria, of whom 639 (36.2%) had affected co-twins. We examine, using Cox proportional hazard models, the clinical features of MD in affected twins that predicted the risk for MD in the co-twin. Control variables were zygosity, age at interview, and sex of the twin and co-twin. RESULTS: The best-fitting model contained 4 significant predictors: number of episodes, duration of longest episode, recurrent thoughts of death or suicide, and level of distress or impairment. These 4 clinical features were similarly predictive of the risk for MD in the co-twins of male and female twins and predicted risk of illness more strongly in monozygotic than in dizygotic twins. Variables that did not uniquely predict risk of MD in the co-twin included age at onset and number of depressive symptoms. For number of episodes, the best-fitting model indicated an inverted U-shaped function with greatest co-twin risk for MD with 7 to 9 lifetime episodes. CONCLUSIONS: The clinical features of MD in epidemiologic samples can be meaningfully related to the familial vulnerability to illness. Familial MD is best characterized by intermediate levels of recurrence, long duration of episodes, high levels of impairment, and recurrent thoughts of death or suicide. These clinical features probably reflect a high genetic liability to depressive illness.

Adult↗

PubMed1999

A population-based twin study in women of smoking initiation and nicotine dependence.

BACKGROUND: The development of drug dependence requires prior initiation. What is the relationship between the risk factors for initiation and dependence? METHODS: Using smoking as a model addiction, we assessed smoking initiation (SI) and nicotine dependence (ND) by personal interview in 1898 female twins from the population-based Virginia Twin Registry. We developed a twin structural equation model that estimates the correlation between the liability to SI and the liability to ND, given SI. RESULTS: The liabilities to SI and ND were substantially correlated but not identical. Heritable factors played an important aetiological role in SI and in ND. While the majority of genetic risk factors for ND were shared with SI, a distinct set of familial factors, which were probably partly genetic, solely influenced the risk for ND. SI was associated with low levels of education and religiosity, high levels of neuroticism and extroversion and a history of a wide range of psychiatric disorders. ND was associated with low levels of education, extroversion, mastery, and self-esteem, high levels of neuroticism and dependency and a history of mood and alcohol use disorders. CONCLUSIONS: The aetiological factors that influence SI and ND, while overlapping, are not perfectly correlated. One set of genetic factors plays a significant aetiological role in both SI and ND, while another set of familial factors, probably in part genetic, solely influences ND. Some risk factors for SI and ND impact similarly on both stages, some act at only one stage and others impact differently and even in opposite directions at the two stages. The pathway to substance dependence is complex and involves multiple genetic and environmental risk factors.

Adult↗

PubMed1999

The assessment of dependence in the study of stressful life events: validation using a twin design.

BACKGROUND: In the assessment of stressful life events (SLEs), researchers have often tried to evaluate whether individual events are dependent or independent of the respondent's behaviour. We sought to validate this evaluation using a twin methodology. We predicted that dependent SLEs would be more heritable than independent SLEs. METHODS: We explored, by twin modelling, the resemblance in two pairs of past-year personal and network SLEs rated individually, by trained interviewers, on a four-point dependence-independence scale. We examined results from two waves of interviews with 785 female-female twin pairs ascertained from a population based registry. RESULTS: Twin model-fitting found no evidence for genetic effects on personal or network independent SLEs. However, familial-environmental factors played an important role in the aetiology of network independent SLEs. For personal and network dependent SLEs, by contrast, three of four analyses suggested a significant aetiological role for genetic factors with estimated heritabilities ranging from 19 to 51%. CONCLUSIONS: Our results support the validity of interviewer assessments of dependence versus independence of SLEs. As predicted, these assessments were relatively successful at distinguishing SLEs that were influenced by genetic factors from those that were not.

Adult↗

PubMed1999

Fears and phobias: reliability and heritability.

BACKGROUND: Familial factors, which are partly genetic, influence risk for phobias. Prior family and twin studies, however, were based on a single lifetime assessment, which may be only moderately reliable. METHODS: We obtained, 8 years apart, two assessments of lifetime history of five unreasonable fears and phobias (agoraphobia and social, situational, animal and blood-injury phobia) from face-to-face and telephone interviews from 1708 individual female twins from a population-based registry. We also obtained, 1 month apart, test retest reliability on 192 twins. We fitted, using the program Mx, a measurement model that estimates the role of genetic and environmental risk factors correcting for measurement error. RESULTS: Short-term reliability of the five phobias was modest (mean kappa = 0.46), but higher than long-term stability (mean kappa = 0.30). Unreliability occurred both for subject recall of unreasonable fears and for interviewer assessment of which fears constituted phobias. Examining fears and phobias together, in a multiple threshold model, results suggested that twin resemblance was due solely to genetic factors, with estimated total heritabilities, corrected for unreliability, of: any 43%, agoraphobia 67%, animal 47%, blood/injury 59%, situational 46% and social 51%. With the exception of animal phobia, similar results were obtained analysing phobias alone. CONCLUSIONS: Lifetime histories of unreasonable fears and phobias assessed at personal interview have substantial unreliability. Correcting for unreliability, the liability to fears and their associated phobias is moderately heritable. Individual-specific environmental experiences play an important role in the development of phobias, while familial-environmental factors appear to be of little aetiological significance.

Adult↗

PubMed1999

Sex differences in the sources of genetic liability to alcohol abuse and dependence in a population-based sample of U.S. twins.

BACKGROUND: There are substantial sex differences in all levels of alcohol involvement among U.S. adults. The goal of this study was to test whether the magnitude and sources of genetic and environmental influences on liability for alcohol abuse and dependence differ for men and women. METHODS: Structured personal interviews were used to assess DSM-III-R- and DSM-IV-defined alcohol abuse and dependence among 5091 male and 4168 female twins (including 1546 identical, 1128 same-sex fraternal, and 1423 opposite-sex pairs) born in Virginia between 1934 and 1974. Twin correlations were analyzed using structural equation modeling. RESULTS: The magnitude of twin-pair resemblance was similar across several definitions of alcoholism and was substantially higher among identical than fraternal pairs. The proportion of population variation in liability attributed to genetic factors was substantial among both women (55-66%) and men (51-56%), and we found little evidence of a role of environmental factors shared by family members. In all definitions studied, we could reject a model that the genetic sources of liability in the two sexes overlap completely. CONCLUSION: In this first population-based study of alcoholism among male and female twins from the U.S., we found that genetic factors play a major role in the development of alcoholism in both sexes, that the magnitudes of genetic influence were equally high for men and women, and that the genetic sources of vulnerability are partially, but not completely, overlapping in men and women.

Adolescent↗

PubMed1999

Hallucinogen, opiate, sedative and stimulant use and abuse in a population-based sample of female twins.

OBJECTIVE: Rates of illicit psychoactive substance use and abuse in women have increased substantially over the last 50 years. However, we understand little about the aetiology of these behaviors in women, and almost nothing about the role of familial-environmental and genetic factors. METHODS: We obtained, by means of blind telephone interviews with 1934 individual twins from female-female adult pairs ascertained through a population-based registry, including both members of 500 MZ and 326 DZ pairs, a history of lifetime illicit use, abuse and dependence, as defined by DSM-IV, of hallucinogens, opiates, sedatives and non-cocaine stimulants. RESULTS: Lifetime prevalences for substance use ranged from 3.3% for opiates to 10.4% for hallucinogens. Rates of abuse (ranging from 0.7% for opiates to 3.2% for stimulants) and dependence (ranging from 0.2% for hallucinogens to 1.4% for stimulants) were substantially lower. Significant twin resemblance was found for hallucinogen use, opiate use, sedative use and stimulant use, abuse and symptoms of dependence. The results of twin-model fitting suggested that twin resemblance for hallucinogen and stimulant use was due to both genetic and familial environmental factors, while twin resemblance for opiate and sedative use as well as stimulant abuse and symptoms of dependence was solely the result of genetic factors. Heritability of liability ranged from 21% to 72%. Twin resemblance for substance use, abuse and dependence could not be explained by the similarity of the twins' environment in childhood, adolescence or adulthood. CONCLUSION: Although limited by the rarity in women of these forms of substance use and misuse, our results none the less suggest that familial factors, which are at least in part genetic, strongly influence the vulnerability to hallucinogen, opiate, sedative and stimulant use and abuse in women.

Adult↗

PubMed1999

Genetic and environmental contributions to alcohol abuse and dependence in a population-based sample of male twins.

OBJECTIVE: Most twin and adoption studies of alcoholism have ascertained cases through treatment settings or archival data; these subjects may differ from affected subjects identified epidemiologically. The authors studied the importance of genetic influences on risk of alcohol-related disorders in a new population-based twin sample. METHOD: Structured personal interviews were used to assess DSM-III-R-defined and DSM-IV-defined alcohol abuse and dependence among 3,516 twins from male-male pairs born in Virginia between 1940 and 1974. RESULTS: The magnitude of resemblance among twin pairs was similar across several definitions of alcoholism and was substantially higher among 861 identical pairs than among 653 fraternal pairs. On the basis of a liability threshold model, 48%-58% of the variation in liability was attributed to additive genetic factors, with the remainder attributed to environmental influences not shared by family members. When a treatment-based proband concordance model was used, evidence for shared environmental as well as genetic influences emerged. CONCLUSIONS: In this first population-based study of male twins from the United States, it was found that genetic factors played a major role in the development of alcoholism among males, with similar influence for alcohol abuse and alcohol dependence. Prior findings implicating the influence of common environment may be attributable to sampling strategy; in this population-based sample, environmental factors shared by family members appear to have had little influence on the development of alcoholism in males.

Adolescent↗

PubMed1999

Caffeine intake, tolerance, and withdrawal in women: a population-based twin study.

OBJECTIVE: Caffeine is by far the most commonly consumed psychoactive substance. The use and abuse of most other licit and illicit psychoactive drugs have been shown to be substantially heritable. However, the impact of genetic factors on caffeine consumption, heavy use, intoxication, tolerance, and withdrawal is largely unknown. METHOD: Caffeine consumption, in the form of brewed coffee, instant coffee, tea, and caffeinated soft drinks, as well as caffeine intoxication, tolerance, and withdrawal, were assessed by personal interviews of 1,934 individual twins from female-female pairs ascertained from the population-based Virginia Twin Registry. The sample included both members of 486 monozygotic and 335 dizygotic pairs. Twin resemblance was assessed by probandwise concordance, odds ratios, and tetrachoric correlations. Biometrical model fitting was also performed. RESULTS: The resemblance in twin pairs for total caffeine consumption, heavy caffeine use, caffeine intoxication, caffeine tolerance, and caffeine withdrawal was substantially greater in monozygotic than in dizygotic twin pairs. Model fitting suggested that twin resemblance for these measures could be ascribed solely to genetic factors, with estimated broad heritabilities of between 35% and 77%. CONCLUSIONS: Caffeine is an addictive psychoactive substance. Similar to previous findings with other licit and illicit psychoactive drugs, individual differences in caffeine use, intoxication, tolerance, and withdrawal are substantially influenced by genetic factors.

Adult↗

PubMed1999

Causal relationship between stressful life events and the onset of major depression.

OBJECTIVE: Stressful life events are associated with the onset of episodes of major depression. However, exposure to stressful life events is influenced by genetic factors, and these factors are correlated with those that predispose to major depression. The aim of this study was to clarify the degree to which stressful life events cause major depression. METHOD: The authors assessed the occurrence of 15 classes of stressful life events and the onset of DSM-III-R major depression over a 1-year period in female twins ascertained from a population-based registry. The sample contained 24,648 person-months and 316 onsets of major depression. Stressful life events were individually rated on contextual threat and dependence (the degree to which the stressful life event could have resulted from the respondent's behavior). The nature of the relationship between stressful life events and major depression was tested by 1) discrete-time survival analysis examining the relationship between dependence and the depressogenic effect of stressful life events and 2) a co-twin control analysis. RESULTS: While independent stressful life events were significantly associated with onsets of depression, when level of threat was controlled, the association was significantly stronger for dependent events. The odds ratio for onset of major depression in the month of a stressful life event was 5.64 in all subjects, 4.52 within dizygotic pairs, and 3.58 within monozygotic pairs. CONCLUSIONS: Stressful life events have a substantial causal relationship with the onset of episodes of major depression. However, about one-third of the association between stressful life events and onsets of depression is noncausal, since individuals predisposed to major depression select themselves into high-risk environments.

Adult↗

PubMed1999

Genetic and environmental risk factors in the aetiology of illicit drug initiation and subsequent misuse in women.

BACKGROUND: Subsequent to initial exposure to the use of a psychoactive substance, psychoactive substance use disorder (PSUD) may or may not develop. AIMS: To investigate the relationship between the risk factors for initiation and the subsequent misuse of psychoactive substances. METHOD: The lifetime history of illicit substance use and misuse was obtained by telephone interview with 1934 members of female-female twin pairs. We apply a novel model, which estimates the role of genetic and environmental risk factors that influence initiation and those specific to misuse, to three classes of illicit psychoactive substances. RESULTS: The individual-specific environment and family environment influenced the probability of initiation, but only individual-specific environment had an impact on the probability of subsequent misuse. Genetic factors which influence the risk of initiation and of misuse were identified. CONCLUSIONS: Aetiological factors that influence drug initiation and subsequent misuse are correlated but not identical. Family environment is an important determinant of risk for drug experimentation. Two classes of genetic risk factors act on the liability to PSUD: those that influence the probability of initiation and those that influence the risk of misuse.

Adult↗

PubMed1999

Chorion type as a possible influence on the results and interpretation of twin study data.

The estimation of genetic effects from twin studies usually relies upon the equal environment assumption--that monozygous (MZ) and dizygous (DZ) twin pairs experience equal similarity of their environments from prenatal experiences through adulthood. However, the sharing of a chorion may make a subset of identical twins more similar, or in some cases, more different, than twins that do not share a chorion. Recent studies suggest monochorionic MZ twins resemble one another more than dichorionic MZ twins in cognitive abilities, personality, and risk for psychiatric disorder. To the extent that prenatal environment affects these characteristics, the traditional twin method will yield biased estimates of genetic and environmental influences. We develop models for quantifying this bias and estimating the influence of chorion type on estimates of heritability.

Bias↗

PubMed1999

Clarifying the relationship between religiosity and psychiatric illness: the impact of covariates and the specificity of buffering effects.

Previous analyses in a large population-based sample of female twins indicated that three dimensions of religiosity--personal devotion, personal conservatism and institutional conservatism--were, in different ways, significantly related to current depressive symptoms and substance use and lifetime psychiatric and substance use disorders. Furthermore, personal devotion, but neither personal conservatism nor institutional conservatism, buffered the depressogenic effects of stressful life events (SLEs). We here explore further these results, using linear, logistic and Cox regression models. Eight personality and six demographic variables had distinct patterns of association with the three dimensions. Personal devotion was positively associated with years of education, age, and optimism and negatively correlated with neuroticism. Personal conservatism was negatively associated with education, income, age, mastery and positively correlated with neuroticism. Institutional conservatism was negatively correlated with self-esteem and parental education. Covarying for these 14 variables produced little change in their association with psychiatric and substance use outcomes. The impact of the dimensions of religiosity differed as a function of the SLE category. High levels of both personal devotion and institutional conservatism protected against the depressogenic effects of death and personal illness. High levels of personal conservatism were associated with increased sensitivity to relationship problems. These results suggest that the association between religiosity and low risk for symptoms of depression and substance use may be in part causal. The relationship between dimensions of religiosity and response to SLEs is complex but probably of importance in clarifying the nature of the coping process.

Adaptation, Psychological↗

PubMed1999

Age at first drink and risk for alcoholism: a noncausal association.

Prior research indicates risk for alcoholism is increased among individuals who begin to drink at an early age. We replicate and extend these findings, addressing causal and noncausal explanations for this association. Structured psychiatric interviews, including assessment of lifetime DSM-IV alcohol abuse and alcohol dependence (AD), were conducted with 8746 adult twins ascertained through a population-based twin registry. We found strong evidence for an association between early drinking onset and risk for AD, but less evidence for an association with alcohol abuse. The results of twin-pair analyses suggest that all of the association between early drinking and later AD is due to familial sources, which probably reflect both shared environmental and genetic factors. These results suggest the association between drinking onset and diagnosis is noncausal, and attempts to prevent the development of AD by delaying drinking onset are unlikely to be successful.

Adolescent↗

PubMed1998

The antibacterial activity of acetic acid and Burow's solution as topical otological preparations.

At present there are no topical otological preparations on the World Health Organisation's essential drug list, largely due to the ototoxic potential of preparations containing aminoglycoside antibiotics. Acetic acid and Burow's solution have long been used in the treatment of the discharging ear. The aim of this study was to ascertain the antibacterial activity of these two preparations against the most commonly occurring bacteria isolated from discharging ears in our department. Twenty fresh isolates of each of the following organisms--Pseudomonas aeruginosa, Staphylococcus aureus, Proteus mirabilis and Streptococcus pyogenes--were plated onto blood agar and tested against one per cent, two per cent and three per cent acetic acid and Burow's solution (13 per cent aluminium acetate). The activity of each agent was ascertained by the size of the zone of inhibition of bacterial growth. Burow's solution showed significantly larger average zones of inhibition than acetic acid (p < 0.001). The two per cent and three per cent acetic acid as well as the Burow's solution were active against all the organisms tested.

Acetates↗