Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Period Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1979

Periodate oxidation analysis of carbohydrates. XIII. Simultaneous gas chromatographic determination of the aldehydes in the periodate oxidation products of non-dialyzable urinary carbohydrate materials as diethyl dithioacetals.

The aldehydes in the periodate oxidation products of non-dialyzable urinary carbohydrate materials were determined simultaneously by gas chromatography of their diethyl dithioacetal derivatives. The yields of aldehydes for normal male urine varied considerably among subjects, but their molar ratios were almost constant. The average values for glyceraldehyde/glyoxal and lactaldehyde/glyoxal molar ratios were 0.41 and 0.27, respectively. The average amount of L-fucose at the non-reducing terminals of carbohydrate chains, as estimated from the yield of lactaldehyde, was about 5 mg/day.

Aldehydes↗
PubMed2004

Twin deliveries in the United States over three decades: an age-period-cohort analysis.

OBJECTIVE: Time is an important variable in understanding the recent increase in twin deliveries in the United States. Therefore, this study was designed to estimate the influences of maternal age, period (year) of delivery, and maternal-birth-year cohort on trends in rates of twin deliveries. METHODS: United States natality data were used to assess trends in twin pregnancies resulting in live births. This age-period-cohort analysis included 7, 5-year maternal-age groups (15-19 through 45-49 years), 6 twin delivery periods (1975, 1980, 1985, 1990, 1995, and 2000), and 12, 5-year maternal birth cohorts (1926-1930 through 1981-1985). The independent effects of maternal age, twin delivery period, and maternal birth cohort on twin delivery rates for blacks and whites were modeled using Poisson regression techniques. RESULTS: Our study assessed 95,042 blacks and 401,989 whites with twin deliveries. Twin deliveries increased by 46% for blacks and 62% for whites from 1975 to 2000, with the largest increase occurring in the year 2000. For blacks, maternal age had the strongest impact on the increasing twin delivery rates, followed by period of delivery. For whites, the greatest effect was due to period of delivery, followed by maternal birth year cohort and, lastly, maternal age. CONCLUSION: Our data confirm the importance of nature's biologic contribution of maternal aging to twin delivery rates, but suggest that recent changes in the environment surrounding pregnancy (nurture) also influence twin delivery rates. The relative contributions of biologic versus environmental influences appear to differ among blacks and whites.

Adolescent↗
PubMed2001

Rates of preterm delivery among Black women and White women in the United States over two decades: an age-period-cohort analysis.

The authors assessed the influence of age, period, and cohort effects on rates of preterm delivery in the United States. Rates of preterm delivery for singleton births (<37 weeks) in seven age groups (15-19, 20-24,., 45-49 years), five periods (1975, 1980, 1985, 1990, 1995), and 11 maternal birth cohorts (1926-1930, 1931-1935,., 1976-1980) were examined. Over the 20-year study interval, preterm delivery increased by 3.6% among Blacks (from 15.5% in 1975 to 16.0% in 1995) and by 22.3% among Whites (from 6.9% to 8.4%). Among Black primigravid women, rates of preterm delivery increased from 1975 to 1990 and began to decline thereafter; among Whites, the rates increased between 1975 and 1995. In Blacks, women aged 25-29 years had the lowest rates for the first and second births, and women aged 30-34 years had the lowest rate for subsequent births. In Whites, the age groups with the lowest preterm delivery rates were 20-24 years for first births and 25-29 years for subsequent births. Cohort-specific rates of preterm delivery remained fairly constant across age strata and periods for Whites, but a small trend was apparent for Blacks aged 30-44 years. The consistency of the observed age effects across periods and cohorts suggests that the age effect is partly due to biologic factors. The presence of period effects might be linked to the increased survival of premature infants or to increased viability among births occurring at lower lengths of gestation.

Adolescent↗
PubMed1995

[Infiltrating transitional carcinoma of the bladder. (1st part). Preoperative or neoadjuvant chemotherapy. Our experience with 38 patients followed-up for a prolonged period].

Analysis of the evolution of 37 patients treated with neoadjuvant chemotherapy + radical cystectomy and bilateral lymphadenectomy. Patients were followed until death, and survivors between 43 and 68 months. Twenty-six patients died. Twenty of them within 24 months after treatment and 6 after 2 years. Five did not undergo surgery due to fast tumour progression during the interval scheduled for cytostatics administration. Bladder removal was rejected in 5 cases after a significant loco-regional progression was shown by laparotomy. Initially, bladder was preserved in 12 patients after TUR + chemotherapy, and in 8 patients when cCR was observed: 1 died due to a disease unrelated cause. 1 was lost after 16 months with no evidence of vesical cancer or metastasis. 3 presented distant dissemination. 3 are alive and have no evidence of tumour. 1 pCR died of metastasis. 1 cPR required radical cystectomy and died of metastasis. Of the 2 cases defined as sCR, one had to undergo radical cystectomy and remains disease-free while the other one died of metastasis. Radical cystectomy was performed in 15 cases. Three remain tumour-free, 2 were lost. to follow-up and 10 died (3 for disease-unrelated causes and 7 as a consequence of their condition). Nodes affectation were present in 54%. Metastasis was found in 57.3% and 17.3% had local relapse. The pre-operative chemotherapy regime examined has not contributed to prolong the metastasis-free interval in the group of patients studied.

Carcinoma, Transitional Cell↗
PubMedDate not supplied

[Age-period-cohort analysis of mortality caused by traffic accidents in Spain].

OBJECTIVE: To study the evolution of traffic accidents mortality in Spain and its possible application to an age-period-cohort analysis, as well as the effect of selected road safety measures. MATERIAL AND METHODS: Road accidents rates of mortality were obtained, and five-year interval age rates for each sex, which allows the study of specific rates of age by birth cohorts. To determine the association between the selected road safety measures and mortality. Poisson regression models were adjusted. RESULTS: Two waves emerge in the evolution of traffic accidents. There was no clear effect with respect to age, nor was there a cohort effect for men or women. As to the road safety measures, we discuss the consistency between the selected models and graphic results. The compulsory use of helmet and of crossing lights is significantly associated to a reduction in mortality (RR 0.73, p < 0.05). CONCLUSIONS: Road accidents mortality shows a slight increase in the studies period. This rate performance cannot be sufficiently explained by age effects, diagnostic period nor birth cohort, however, road safety measures are considered positive.

Accidents, Traffic↗
PubMed2005

Age-period-cohort analysis of Swiss suicide data, 1881-2000.

At the end of the 19(th) century, male suicide rates in Switzerland were as high as the respective rates in recent decades, whereas female suicide rates were distinctly lower. An age-period-cohort analysis was performed to provide more information about the gender-specific changes over the last century. Suicide mortality has been reported in Switzerland since 1876 when the standardised registration of mortality data began. The analysed data cover the period 1881-2000. The statistical analyses were based on log-linear models and data aggregated by 10-year age-intervals and 10-year period intervals. The results indicate similar age and period effects in males and females. The estimates representing age-specific risk increase steadily with age, with intermediate plateaus in the 20s and the 50s. The period-specific estimates follow the economic cycles. The birth cohort effects are stronger in males and weaker in females. In the males' estimates, there is a peak in cohorts born around 1840 and a low in cohorts born some 60-100 years later. The estimates increased again in generations born after World War II. In females, the birth cohort estimates are low in cohorts born in the first half of the 19(th) century and increase until the first half of the 20(th) century. Birth cohort effects remain an intriguing topic in epidemiology of suicide. A better understanding of birth cohort effects might open new doors to suicide prevention.

Age Distribution↗
PubMed1997

Secular trend and age-period-cohort analysis of prostate cancer mortality in Taiwan.

PURPOSE: We evaluated the secular mortality trend of prostate cancer in Taiwan from 1964 through 1994. MATERIALS AND METHODS: Analyses were based on vital statistics. Relative risks associated with each of the age, period and cohort effects on secular mortality were estimated from a log-linear Poisson model. RESULTS: Age adjusted mortality rates increased more than 2-fold during the last 30 years in Taiwan. Age-period-cohort analysis showed that the age effect was the strongest. CONCLUSIONS: Factors related to aging are the main reason for the increase in prostate cancer mortality in Taiwan during the least 3 decades.

Adult↗
PubMed2004

Increasing risk of gastroschisis in Norway: an age-period-cohort analysis.

The prevalence of gastroschisis in Norway, as reported to the Medical Birth Registry of Norway, increased regularly and sixfold from 0.5 to 2.9 per 10,000 births during 1967-1998. The prevalence was also consistently higher among children of younger mothers. The authors used age-period-cohort analysis to assess effects of both parents' age and year of birth (parental cohorts). Mother's and father's age were included in three different regression models. Apart from a significantly higher risk at a young maternal age, the authors also found higher risk at a young paternal age (1.6-fold per 10 years' reduction in father's age, 95% confidence interval: 1.0, 2.4). The time trend was highly significant regardless of whether it was ascribed to period, mother's year of birth, or father's year of birth. However, when father's year of birth was used to describe the time trend, no apparent additional effect of father's age was found, only for mother's age. The time trend is likely caused by environmental factors. Persistently increasing risks among children of young mothers may hypothetically be related to lifestyle factors. A contribution to risk also from fathers born in more recent years or from young fathers increases the likelihood that a factor related to modern lifestyles of young couples may be related to risk.

Adult↗
PubMed1996

Age-period-cohort analysis of the incidence of schizophrenia in Scotland.

Studies examining a possible decline in the incidence of schizophrenia over the last two to three decades have paid little attention to the possible role of birth cohort effects. We collected data on a Scottish national sample of all schizophrenic patients, admitted for the first time between 1966 and 1990 (N = 11348; male = 6301). In an Age-Period-Cohort analysis, a full model, incorporating three factors, had a substantially better fit to the data than other models (especially, an Age-Period model), providing clear evidence of the presence of a cohort effect. After adjustment for the effects of age and period, there was a 55% reduction in the rate of schizophrenia in men and a 39% fall in the number of women over the 50-year birth period from 1923 to 1973. The marked decline in the first admission rates observed in Scotland cannot, however, be attributed entirely to this cohort effect. Rather, a greater proportion of the declining first admission rates (88%) is ascribed to the period effect (i.e. artefactual or causally related cross-sectional effects). Nevertheless, the fact that a birth-cohort effect accounts for part of the declining incidence, suggests that causal environmental factors operating early in life have been diminishing in intensity.

Adolescent↗
PubMed2001

Combined FEM and Green's function analysis of periodic SAW structure, application to the calculation of reflection and scattering parameters.

Because of more and more stringent requirements on SAW filter performances, it is important to compute, with very good accuracy, the SAW propagation characteristics, which include the calculation of reflection and scattering parameters. For that reason, the analysis of periodic structures on a semi-infinite piezoelectric substrate is one of the most important problems being investigated by SAW researchers. For infinite periodic grating modeling, we developed numerical mixed FEM/BEM (finite element method-boundary element method) models using an efficient interpolation basis function that takes into account the singularity at both edges of each electrode. In this paper, a review of the numerical program that has been developed during the past few years will be presented. For an infinite periodic grating, it is convenient to solve the propagation problem in the Fourier domain (wave number space and harmonic excitation), and important efforts have been spent to properly integrate the so-called periodic harmonic Green function. Using this numerical model together with the general P- matrix formalism, it is possible to compute all of the basic parameters with a very good accuracy. These consist of the single strip reflectivity, acoustic wave-phase velocity, and position offset between reflection and transduction centers. Simulations and comparisons with experiments are shown for each model.

Journal Article↗
PubMed2006

The constrained space orbital variation analysis for periodic ab initio calculations.

The constrained space orbital variation (CSOV) method for the analysis of the interaction energy has been implemented in the periodic ab initio CRYSTAL03 code. The method allows for the partition of the energy of two interacting chemical entities, represented in turn by periodic models, into contributions which account for electrostatic effects, mutual polarization and charge transfer. The implementation permits one to carry out the analysis both at the Hartree-Fock and density functional theory levels, where in the latter the most popular exchange-correlation functionals can be used. As an illustrating example, the analysis of the interaction between CO and the MgO (001) surface has been considered. As expected by the almost fully ionic character of the support, our periodic CSOV results, in general agree with those previously obtained using the embedded cluster approach, showing the reliability of the present implementation.

Journal Article↗
PubMed2004

Variations in the risk of disability pension in Norway 1970-99. A gender-specific age-period-cohort analysis.

AIMS: A study was undertaken to investigate whether cohort or period effects could explain the varying and generally increasing incidence of disability pension in Norway between 1970 and 1999. METHODS: The study used data from a complete national register of new disability cases in Norway, including all cases of disability pension in the 16-60 age group categorized according to age and gender for each year from 1970 to 1999. The population at risk was defined for each year from census data and number of individuals already receiving disability pension. Data were organized in five-year age groups, five-year time periods and corresponding overlapping nine-year birth cohorts. Age- and gender-specific rates were displayed graphically for periods and cohorts. Separate Poisson regression models were fitted for age periods and age cohorts. Finally a combined age, period, and cohort model was applied. RESULTS: The overall incidence was 7.4/1,000 non-disabled persons per year for women and 6.0/1,000 for men. For women 52.1% of the cases were in the 51-60 age group, whereas the corresponding figure for men was 57.6%. Statistical analysis showed an increasing trend for both genders, more pronounced for women than men. All time periods deviated significantly from the trend, either upwards or downwards. Age-cohort models showed less variation, but recent cohorts had higher than expected rates, especially for men. CONCLUSIONS: Further studies should investigate why Norwegian women were more affected by the period effects than men. An increasing incidence of disability pension among recent cohorts is a major challenge for the Norwegian welfare system.

Adolescent↗
PubMed1998

Age-period-cohort analysis of chronic disease rates. I: Modelling approach.

Age-Period-cohort models are widely used by epidemiologists to analyse trends in disease incidence and mortality. The interpretation of such models is fraught with difficulty in view of the exact linear dependency between the three variables. It is the purpose of this paper to review, compare and contrast some of the more common approaches to this problem based on Poisson regression and a linear model for the log rates. Also the results of using the different approaches on a single series of data on breast cancer incidence among females in Scotland from 1960-1989 are presented for comparison. Recommendations as to the merits and drawbacks of the approaches are also given in the conclusions. Models which are based upon the estimable contrasts such as local curvatures and deviations from linearity are most suitable.

Adolescent↗
PubMed1996

Incidence of multiple sclerosis in Møre and Romsdal, Norway from 1950 to 1991. An age-period-cohort analysis.

We have examined the time trends in multiple sclerosis incidence over the past four decades from 1950 to 1991 in Møre and Romsdal County, Norway. Incidence rates by year of birth, year of onset and year of diagnosis according to sex, age and clinical course were studied. All patients with multiple sclerosis diagnosed by August 1992 were included, giving a total of 419 patients (171 men, 248 women) with onset of multiple sclerosis in the period 1950-91. Mean age at onset was 33.2 years, and mean age at diagnosis was 39.2 years. The incidence rate by year of onset increased from 2.87 per 100 000 in the period 1950-54 (men 3.06, women 2.67) to 5.57 per 100 000 in 1985-91 (men 3.75, women 7.94) (P<0.001). The incidence was particularly high in the period from 1975 to 1985. Major period- or cohort-effects in incidence, apart from the general increasing trend, could not be identified by an age-period-cohort analysis.

Adolescent↗
PubMedDate not supplied

Age-period-cohort analysis of breast cancer mortality.

The objective of this study is to develop a hypothesis about the carcinogenesis of breast cancer from a descriptive analysis. This study is an application of the age-period-cohort model (APC model) on the mortality rate of breast cancer in Taiwan over the period from 1964 to 1991. Age-specific and age-adjusted mortality rates are described and then age, period, and cohort effects are separately analysed. (Female) breast cancer mortality data in Taiwan from 1964 to 1991 were abstracted from the annual reports of the Taiwan Provincial Department of Health. The population data in Taiwan from 1964 to 1991 were abstracted from the demographic data in Taiwan compiled by the Ministry of Interior, R.O.C. The results show that both age-adjusted and age-specific mortality rates of breast cancer are increasing over the study period and with birth cohorts. The bimodal pattern becomes more apparent in later periods. The Clemmensen's hook is five years later both in the descriptive study and the APC analysis. The findings suggest a possible role of later life overnutrition as the major period effed (promoter) and a change in reproductive behavior as the cohort effect (initiator). The application of the APC model also denotes the possible role of later life overnutrition and a change in reproductive behavior after the birth cohort of 1929. These findings may help us develop hypotheses of carcinogenesis of breast cancer.

Adult↗
PubMed1999

An age-period-cohort analysis of 50,875 AIDS cases among injecting drug users in Europe.

BACKGROUND: The long average incubation time from HIV infection to AIDS makes it difficult to estimate recent HIV transmission from AIDS incidence data. Age-period-cohort (APC) analysis can separate out the effects of age, calendar time and birth cohort to provide a clearer picture of transmission trends. METHODS: AIDS incidence data from 1981 to 1994 among intravenous drug users (IDU) for 12 Western European countries were used. Yearly incidences per 100,000 population or 100,000 person-years were calculated by age at diagnosis and 5-year birth cohort (1950-1954, 1955-1959, 1960-1964, 1965-1969 and 1970-1974), and corrected for reporting delay. Incidence patterns were compared between birth cohorts and countries. RESULTS: For most countries the impact was greatest on the cohort born 1960-1964. Comparing incidence patterns in the 1965-1969 to 1960-1964 cohorts suggest the epidemic has plateaued at low to intermediate levels in Austria, Greece and the North-Western European countries, and at high levels in France, Italy and Switzerland. For most countries transmission amongst the 1970-1974 as compared to the 1965-1969 cohorts could not be assessed due to small numbers and short follow-up time. In Spain the epidemic was uncontrolled with a high incidence among recent birth cohorts. In Portugal the epidemic was still at an early and expanding phase. CONCLUSIONS: The APC analysis revealed large country differences in the dynamics of the HIV/AIDS epidemic among IDU. Full interpretation of these differences is dependent on information from other sources about the local public health response and trends in drug injecting behaviours. Earlier introduction of the virus and higher prevalence of injecting drug use may explain some of the generally higher incidence in Southern European countries, but the larger part of it is most likely explained by local characteristics of drug users, such as younger age and more frequent sharing of needles and syringes, and a less effective public health response.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Cerebrovascular disease mortality in Spain, 1955-1992: an age-period-cohort analysis.

The purpose of this study was to assess the contributions of period and birth cohort effects to changes in cerebrovascular disease (CVD) mortality in Spain over the period 1955-1992. Poisson regression models were fitted to age-and sex-specific CVD mortality rates obtained from National Vital Statistics. In the period 1955-1975, CVD mortality remained stable. In the period 1975-1992, CVD mortality declined by 54% (rate ratio, RR: 0.46; 95% confidence interval, CI: 0.43-0.49) in males and 62% (RR: 0.38; 95% CI: 0.34-0.42) in females. The cohort effect was very small up to the generation born in 1905, moving clearly downward thereafter. CVD mortality for subjects born in the period 1945-1949 was lower than for those born in the period 1905-1909 by 68% (RR: 0.32; 95% CI:0.16-0.63) in males and 82% (RR: 0.18; 95% CI: 0.07-0.45) in females. Among the possible partial explanations for these effects are the decline in ischemic heart disease and rheumatic fever mortality, the drop in salt and alcohol intake, the reduction in smoking among males and blood pressure among females, and the widespread use of antihypertensive treatments in Spain over the last 20 years.

Adult↗
PubMed1989

Suicide in England and Wales 1946-1985: an age-period-cohort analysis.

Four decades of suicide mortality data for England and Wales were analysed within an age-period-cohort framework. Marked differences in results were found by sex. The analysis of the male data showed that the risk of suicide increased with age until men were in their mid-fifties (after allowing for period and cohort effects), and that suicide risk declined for males born from 1876 to 1915, but had increased over 4-fold for certain later-born cohorts. Female suicide risk was found to decline with later nativity (after adjusting for age and period effects). The identification of period effects in terms of known changes in the carbon monoxide (CO) content of domestic gas successfully accounted for temporal variation in male suicide risk, but fitted less well to the data for females.

Adult↗