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At least 163 records · Page 9Linked to original sources
PubMed1994

Objective detection of 40 Hz auditory evoked potentials: phase coherence vs. magnitude-squared coherence.

The relative performance of phase coherence (PC) and magnitude-squared coherence (MSC) for detection of steady-state evoked potentials was studied using 40 Hz auditory evoked potentials (AEPs) in 10 normal human subjects. In addition, simulation experiments were carried out to determine the effects of signal amplitude and phase variability on detection performance. All simulations showed MSC performance to be better than PC performance, with further improvements when MSC was supplemented with weighted averaging. However, human 40 Hz AEP data showed essentially identical detection performance for PC and MSC, with or without weighted averaging. These data support a "phase aggregation" model (at least near threshold) over the more usual model in which an AEP signal is added to a stationary noise. Human data collected under "no-stimulus" conditions agree well with theoretical distributions for both PC and MSC. For equal test time, long analysis periods (with less averaging) yielded equal performance to short analysis periods (with more averaging), for both PC and MSC.

Acoustic Stimulation↗
PubMed2006

Period estimates of cancer patient survival are more up-to-date than complete estimates even at comparable levels of precision.

BACKGROUND AND OBJECTIVE: Period analysis provides more up-to-date estimates of cancer patient survival than traditional methods, but there is a trade-off between up-to-dateness and precision. Our objective was to compare the performance of period and complete analysis in terms of up-to-dateness and precision of survival estimates. STUDY DESIGN AND SETTING: Five-year relative survival data actually observed for patients diagnosed with 1 of 20 common forms of cancer in Finland in 36 overlapping 5-year periods between 1958-1962 and 1993-1997 were compared with period estimates and various variants of complete estimates of 5-year relative survival potentially available during these periods. RESULTS: At comparable levels of up-to-dateness, survival estimates from period analysis were more precise than survival estimates from complete analysis. At comparable levels of precision, period analysis provided more up-to-date survival estimates than did complete analysis. CONCLUSION: These results further encourage more widespread use of period analysis as a standard tool for up-to-date monitoring of cancer patient survival by population-based cancer registries.

Finland↗
PubMed2004

Temporal trends of dengue fever/dengue hemorrhagic fever in Bangkok, Thailand from 1981 to 2000: an age-period-cohort analysis.

The aim of this study was to examine the effects of age, time period, and birth cohorts with dengue fever/dengue hemorrhagic fever (DF/DHF) in Bangkok, Thailand over the period 1981-2000. The age group at greatest risk for DF/DHF was 5-9 years old. The period effect shows a remittent pattern, with significant increases in 1986-1990 and 1996-2000. The birth cohort group showed a significant decreasing trend from the 1961-1965 group to the 1991-1995 group (R2 = 0.7620) with a decreasing rate of 0.1. We concluded that the temporal trend of DF/DHF is decreasing; especially for DHF.

Adolescent↗
PubMed1997

Age-period-cohort analysis of cervical cancer mortality in Taiwan, 1974-1992.

OBJECTIVES: To develop a hypothesis about the carcinogenesis of cervical cancer from a descriptive analysis. METHODS: The mortality data of cervical cancer were analyzed over the period from 1974 to 1992 among Taiwanese women using a log-linear Poisson model modified from the method of Osmond and Gardner to examine the effects of age, calendar period of death, and birth cohort on cervical cancer mortality. RESULTS: This age-period-cohort model provides a summary guide for interpretation of cancer mortality trends. According to this model, age was found to be the strongest factor predicting cervical cancer mortality. Women in 50-54 age group have 89.3-fold risk of cervical cancer compared to those in the 30-34 age group. The cohort effect is also of particular interest because the generation at greatest risk for cervical cancer is the one born between 1893 and 1938, and a dramatically declining trend is observed thereafter for 1938-1963 birth cohort. Interest has emerged about the increasing trend in recent cohorts (after 1963 birth cohort). However calendar time only has a slight effect in the APC analysis. The model also identified a possible role of female sex hormones as the age effect, promiscuous sexual activity as the period effect (promoter) and the change in reproductive behavior as the cohort effect (initiator). CONCLUSIONS: These results may help to develop a hypothesis of carcinogenesis of cervical cancer in Taiwan.

Adult↗
PubMed1978

Periodicity measures for repeated random auditory patterns.

Random auditory patterns were repliated according to defined rules, converted toauditory pulse trains, and presented to listeners. Three ined: the threshold fraction of repeated elements necessary for a fixed level of discrimination from a nonrepeated pattern; the accuracy of periodicity matching; and periodicity magnitude ratings. A short-term periodicity analysis over successive replications appears to be more representative of the behavioral measures than a long-term periodicity analysis. Of the signal measures of periodicity examined, the maximum autocorrelation, irrespective of delay, most closely reflects behavioral measures of periodicity strength.

Auditory Perception↗
PubMed1996

Age-period-cohort analysis of suicide mortality rates in Spain, 1959-1991.

BACKGROUND: Although there is evidence that suicide rates may be increasing in Spain, formal epidemiological studies have been limited to specific cities or counties. The objective of this study was to investigate nationwide trends in suicide mortality from 1959 to 1991 in Spain, with emphasis on age, period, and cohort effects. METHODS: Age- and sex-specific suicide mortality rates from 1959 until 1991 were obtained from official vital statistics tables from the Instituto Nacional de Estadística, the official registry of vital statistics in Spain. Poisson regression and graphical methods were used to model and estimate age, period and cohort effects. RESULTS: Suicide mortality rates increased with age, with a proportional increment for each decade of life of 45% (95% confidence interval: 45-46%). In both males and females, age-adjusted suicide mortality rates decreased from 1959 until the late 1970s and early 1980s. In 1982, trends started to increase, returning to the levels of 1959 in less than 6 years. Cohort effects were small for cohorts born prior to 1940. For cohorts born after 1950, suicide rates increased markedly. CONCLUSIONS: The increase in suicide mortality in younger cohorts and the high rates of suicide in the elderly demand further investigation to establish causal mechanisms and preventive strategies.

Adolescent↗
PubMed1997

Trends of liver cirrhosis mortality in Europe, 1970-1989: age-period-cohort analysis and changing alcohol consumption.

BACKGROUND: Since the mid 1970s, a striking reduction in alcohol-related problems has been observed in many Western countries. Liver cirrhosis mortality is considered to be a major indicator of alcohol-related problems in the general population. The aim of the present study is to describe liver cirrhosis mortality trends in European countries between 1970 and 1989. METHODS: This is a descriptive study on liver cirrhosis mortality in 25 European countries, and in four grouped European regions. A Poisson log-linear age-period-cohort model is used to clarify whether the recent trend in mortality represents a short-term fluctuation or an emerging long-term trend. In addition, a descriptive comparison between trends in per capital alcohol consumption and liver cirrhosis mortality is conducted. RESULTS: In the whole European population and in that of Western and Southern Europe increasing period effects were observed until the second half of the 1970s followed by a decline in the next periods. In Eastern Europe the decline in period effects started in the first half of the 1980s, whereas in Northern Europe an increasing period effect was observed until the second half of the 1970s, followed by a stabilization. Similar trends were observed for per capita alcohol consumption. The age effect analysis showed a continuously rising effect in Eastern Europe, whereas an attenuation of the effect at around age 65 years was observed in Western Europe. Intermediate patterns were observed in Southern and Northern Europe. The birth cohort effect suggested that in the Western and Southern populations mortality could continue to decrease over the next decade, while in Eastern and Northern mortality is still rising and this will probably continue for the next decade. CONCLUSIONS: The age-period-cohort analysis allows targeting of health care and prevention programmes based on future trends. Aetiological and prognostic factors act differently in Europe. A better understanding of the trends would require more detailed information on alcoholism treatment rates, alcohol habits, viral hepatitic infections and other factors involved in the aetiopathogenesis of the disease.

Adult↗
PubMed2006

Is there an association between SV40 contaminated polio vaccine and lymphoproliferative disorders? An age-period-cohort analysis on Norwegian data from 1953 to 1997.

Between 1955 and 1963, an estimated number of 150 million people in various parts of the world, including Norway, received poliomyelitis vaccine possibly contaminated with infectious simian virus 40 (SV40). Human studies have investigated the hypothesised association between SV40 and various cancers, but the results have so far been contradicting. The aim of the present study was to examine Norwegian cancer incidence data to assess a possible association between birth cohorts assumed to have been subjected to the vaccine and the incidence rate of lymphoproliferative disorders (excluding Hodgkin's lymphoma), further subdivided into non-Hodgkin's lymphoma (NHL), lymphocytic leukemia and plasma cell neoplasms. Between 1953 and 1997, the incidence rate of lymphoproliferative diseases combined increased about 3-fold in both males and females. Subgroup analysis showed that this increase was largely attributable to NHL. Age-period-cohort modelling of the subgroups, as well as of all groups combined, showed that the cohort effect was more prominent than the period effect. However, the variations in incidence patterns across the birth cohorts did not fit with the trends that would be expected if a SV40 contaminated vaccine did play a causative role. Thus, our data do not support the hypothesis of an association between the vaccine and any subgroup of lymphoproliferative diseases.

Adult↗
PubMed1998

Hospitalization parameters in patients infected with HIV: an analysis of the period 1992-1997.

The course of several hospitalization parameters of HIV-infected patients in a general hospital during the past 6 years was analyzed. There was a decrease observed in the number of non-AIDS diagnosed patients admitted during the observation period, but this decrement was noted only in the past 2 years in AIDS patients. This decline was not accounted for by a decrease in the incidence of AIDS patients seen each year, and was very probably due to the efficacy of antiretroviral combination therapy. The average length of stay of both AIDS and non-AIDS diagnosed patients decreased markedly during the first 3 years to stabilize during the remaining observation period. An analysis of the mode in which the patients were seen for the first time in the hospital (admitted from the emergency department because of complications of advanced HIV infection or attended in the outpatient clinic) revealed that, after a steady decrease from 1985 to 1995 in the relative proportion of patients hospitalized (p < 0.0001), there was an inversion of the downward trend in the past two years (p = 0.04). Most of the patients admitted during these 2 years were persons who did not know that they were infected with HIV. This observation reinforces the need for education campaigns and voluntary HIV testing which are particularly directed toward persons with high risk factors for the infection, in order to provide medical care before complications of advanced HIV infection appear.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Peak and nadir experiences and their consequences described by pediatric oncology nurses.

Pediatric oncology nurses experience role-related stressors, some of which are inherent to the speciality, and their consequences. Despite these difficulties, nurses continue in the specialty. One variable that helps to explain their continued commitment is "meaning", or what pediatric oncology nurses find to be most significant and satisfying in their roles. One technique for determining meaning in a role is to inquire about the peak (significant and positive) and nadir (significant and negative) role-related experiences and the consequences of both kinds of experiences. The purpose of this study was to identify the peak and nadir experiences of pediatric oncology nurses and the short- and long-term consequences of those experiences. Using an interview format that consisted of four open-ended questions and a convenience sampling plan, five nurses interviewed 26 nurses from one pediatric cancer center and 38 nurses from a national sample. The interviewers completed an initial training session on interviewing and repeated that training two more times during data collection. Written or taped oral consent was obtained at the time of each interview. Using a content analytical technique (Krippendorff, 1980), four nurses independently coded each interview. Agreement ratings ranged from 75% to 100% per coded theme for an overall agreement level of 92%. Training for the coding process occurred initially and periodically throughout the analysis period. Fifteen different themes for peak experiences were identified, the majority of which reflect the nurses' experience with patients dying, or with patients recovering and living normal lives, or with the close relationships that develop between nurses and patients. Multiple short- and long-term consequences were identified and included changes in (1) values (becoming less judgmental), (2) behaviors (giving more empathic care), and (3) perspective (accepting limitations of care). Twenty-three different nadir themes were identified. A shared characteristic of several of these themes is the nurses' regret over a perceived inadequacy in handling a situation. Another common element is witnessing patient suffering and feeling unable to adequately relieve the suffering or provide comfort to the patient. The short-term consequences of nadir experiences tend to be negative and include guilt, anger, or dread. The long-term consequences tend to be positive and similar to the long-term consequences of peak experiences. Study findings indicate that pediatric oncology nurses do find meaning in their roles and that those who continue in the speciality are able to experience positive long-term consequences. Study findings will be used to develop a new scale to measure role-related meaning and to develop interventions designed to assist nurses in finding meaning in their roles even during particularly stressful periods.

Adult↗
PubMed2001

Age-period-cohort analysis of dentist use in Spain from 1987 to 1997. An analysis based on the Spanish National Health Interview Surveys.

The aim was to determine whether the effects of age, period (from 1987 to 1997), or cohort (birth-cohort) are the most plausible explanations for the variation in dentist utilisation over time in Spain. On the basis of three sequential Spanish National Health Surveys, the trend in the percentage of people visiting the dentist within the previous 3 months was analysed by means of a standard cohort table and by the CLAYTON & SCHIFFLERS method. The percent of people visiting the dentist grew from 13.6% in 1987, to 17.2% in 1997. Visual examination of the cohort table, together with the fit of the age-cohort model, indicates that cohort succession may be the best explanation for the increase. The younger the cohort, the higher the dental visit rate; this relationship was strongest for people born after 1977. The model also indicates that the rates of dental visiting tend to increase up to middle age, and then tend to decrease with age.

Adolescent↗
PubMed1996

Age-period-cohort analysis of motor vehicle mortality in Taiwan, 1974-1992.

The aim of this study was to examine the effects of age, calendar period of death and birth cohort in motor vehicle mortality in Taiwan over the period 1974-1992. A log-linear model modified from the method of Osmond and Gardner (Stat. Med. 1: 245-259; 1982) was used. Age turned out to be a significant predictor of motor vehicle mortality. The most risky group (over 70 years) had 27.1 and 16.3 times the mortality of the least risky group (5-9 years, 10-14 years) for males and females respectively. The period effect showed a continuously increasing mortality trend since 1974 in females. The pattern in males is similar except that it has slightly leveled off in recent years. The birth cohorts at the highest risk of motor vehicle death were those born between 1979 and 1983 for both sexes. However, males born between 1929 and 1933 also had a high mortality. This analysis provided a better understanding of the trend of mortality from motor vehicle crashes.

Accidents, Traffic↗
PubMed1994

Age-period-cohort analysis of pulmonary tuberculosis mortality in Taiwan: 1961 to 1990.

The specific aim of this study was to examine the effects of age, calendar period of death, and birth cohort in pulmonary tuberculosis (TB) mortality in Taiwan during the period 1961 to 1990. A log-linear Poisson regression model modified from the method of Osmond and Gardner was used and 79,881 deaths (58,025 males and 21,856 females) were included in the analysis. Birth cohort is the most significant predictor of pulmonary TB mortality according to the model. The earliest birth cohort from 1891 had a pulmonary TB mortality 17,327 and 6,186 times those born from 1986 for males and females, respectively. There was also a significant age effect. The youngest age group of zero to four years had a pulmonary TB mortality 7.10 and 5.87 times those for the age group of five to nine years for males and females, respectively. The oldest age group of 70 to 74 years had a risk of pulmonary TB mortality 2.89 and 1.88 times those for the five- to nine-year age groups for males and females, respectively. Parameters of the period factor showed a decreasing pulmonary TB mortality from 1961 to 1990 that was less significant than those of age or cohort. In addition to the improvement in medical measures that influenced the effect of calendar year on TB mortality, year of birth is an important determinant in the trend of TB mortality in Taiwan. The result shows that the major focus for TB mortality in Taiwan is in the age groups born between 1891 and 1921.

Adolescent↗
PubMed2007

Melanoma incidence in central Italy will go on increasing also in the near future: a registry-based, age-period-cohort analysis.

The aim of the study was to evaluate malignant melanoma incident trends in central Italy by means of an age-period-cohort approach. A total of 1977 malignant melanoma (15-84 years) incidents in the area of the Tuscany Cancer Registry between 1987 and 2001 were analysed. Poisson regression has been used to estimate age, cohort and period effect. A nonlinear regression model was used to estimate the expected number of new cases in the period 2002-2006. Incidence rates increased in all age, period and cohort groups. The model that best fitted the data included age and 'drift'. The linear effect ('drift') showed, in each age group, an increase of the risk of malignant melanoma diagnosis of about 36.6% every 5 years of period or cohort. For the period 2002-2006, 1112 new cases were predicted with a standardized rate (age 15-84 years) of 19.2x100.000. In the Tuscany Cancer Registry area, no clues for malignant melanoma incidence rates levelling off were documented. Growing rates and number of malignant melanoma are expected in the near future.

Adolescent↗
PubMed1994

Bifurcation analysis pf periodic SEIR and SIR epidemic models.

The bifurcations of the periodic solutions of SEIR and SIR epidemic models with sinusoidally varying contact rate are investigated. The analysis is carried out with respect to two parameters: the mean value and the degree of seasonality of the contact rate. The corresponding portraits in the two-parameter space are obtained by means of a numerical continuation method. Codimension two bifurcations (degenerate flips and cusps) are detected, and multiple stable modes of behavior are identified in various regions of the parameter space. Finally, it is shown how the parametric portrait of the SEIR model tends to that of the SIR model when the latent period tends to zero.

Data Interpretation, Statistical↗
PubMed2004

Analysis of periodic fluctuations of the height of Swedish soldiers in 18th and 19th centuries.

This paper investigates the periodicity of the adult height of Swedish soldiers of the 18th and 19th centuries using spectral analysis. The height data are left truncated due to the enforcement of minimum height requirement. Hence, we use a truncated regression model using maximum likelihood estimation. We isolate the various frequency components, assess their importance, and perform sensitivity analysis by means of fitting several alternative models.

Body Height↗