Strong Period Effect Research Articles

Changes in mortality due to major alcohol-related diseases in four Nordic countries, France and Germany between 1980 and 2009: a comparative age-period-cohort analysis.

To investigate age, period and cohort effects on time trends of alcohol-related mortality in countries with different drinking habits and alcohol policies. Age-period-cohort (APC) analyses on alcohol-related mortality were conducted in Denmark, Finland, Norway, Sweden, France and Germany. Cases included alcohol-related deaths in the age range 20-84 years between 1980 and 2009. Mortality data were taken from national causes of death registries and covered the ICD codes alcoholic psychosis, alcohol use disorders, alcoholic liver disease and toxic effect of alcohol. In all countries changes across age, period and cohort were found to be significant for both genders [effect value with confidence interval (CI) shown in Supporting information, Table S1]. Period effects pointed to an increase in alcohol-related mortality in Denmark, Finland and Germany and a slightly decreasing trend in Sweden, while in Norway an inverse U-shaped curve and in France a U-shaped curve was found. Compared with the cohorts born before 1960, the risk of alcohol-related mortality declined substantially in cohorts born in the 1960s and later. Pairwise between-country comparisons revealed more statistically significant differences for period (P < 0.001 for all 15 comparisons by gender) than for age [P < 0.001 in seven (men) and four (women) of 15 comparisons] or cohort [P < 0.01 in two (men) and three (women) of 15 comparisons]. Strong period effects suggest that temporal changes in alcohol-related mortality in Denmark, Finland, Norway, Sweden, France and Germany between 1980 and 2009 were related to secular differences affecting the whole population and that these effects differed across countries.

Smoothed Lexis Diagrams With Applications to Lung and Breast Cancer Trends in Taiwan

Cancer surveillance research often begins with a rate matrix, also called a Lexis diagram, of cancer incidence derived from cancer registry and census data. Lexis diagrams with 3- or 5-year intervals for age group and for calendar year of diagnosis are often considered. This simple smoothing approach suffers from a significant limitation; important details useful in studying time trends may be lost in the averaging process involved in generating a summary rate. This article constructs a smoothed Lexis diagram and indicates its use in cancer surveillance research. Specifically, we use a Poisson model to describe the relationship between the number of new cases, the number of people at risk, and a smoothly varying incidence rate for the study of the incidence rate function. Based on the Poisson model, we use the standard Lexis diagram to introduce priors through the coefficients of Bernstein polynomials and propose a Bayesian approach to construct a smoothed Lexis diagram for the study of the effects of age, period, and cohort on incidence rates in terms of straightforward graphical displays. These include the age-specific rates by year of birth, age-specific rates by year of diagnosis, year-specific rates by age of diagnosis, and cohort-specific rates by age of diagnosis. We illustrate our approach by studying the trends in lung and breast cancer incidence in Taiwan. We find that for nearly every age group the incidence rates for lung adenocarcinoma and female invasive breast cancer increased rapidly in the past two decades and those for male lung squamous cell carcinoma started to decrease, which is consistent with the decline in the male smoking rate that began in 1985. Since the analyses indicate strong age, period, and cohort effects, it seems that both lung cancer and breast cancer will become more important public health problems in Taiwan. Supplementary materials for this article are available online.

Age differences in mammography screening reconsidered: life course trajectories in 13 European countries.

Breast cancer is the most common cause of cancer mortality among European women. To reduce mortality risk, early detection through mammography screening is recommended from the age of 50 years onwards. Although timely initiation is crucial for cancer prognosis, the temporal dimension has largely been ignored in research. In cross-sectional research designs, it is not clear whether reported age differences reflect 'true' age effects and/or presumed period effects resulting from evolving knowledge and screening programmes. We use longitudinal data from the survey of Health, Ageing and Retirement (SHARELIFE, 2008), which enables to cast light on age differences by providing retrospective information on the age at which women commenced regular mammography screening. Moreover, the cross-national dimension of the SHARE permits framing the results within the context of nationally implemented screening programmes. By means of the Kaplan-Meier procedure, we examine age trajectories for five 10-year birth cohorts in 13 European countries (n = 13 324). Birth cohorts show very similar age trajectories for each country. Along with the observation that large country differences and country-specific deviations coincide with screening programme characteristics, this suggests strong period effects related to implemented national screening programmes. Age differences in mammography screening generally reflect the period effects of national screening policies. This leaves little room for economic theories about human health capital that leave out the institutional context of preventive health care provision.

The incidence of esophageal adenocarcinoma continues to rise: analysis of period and birth cohort effects on recent trends

During the past four decades, the incidence of esophageal adenocarcinoma (EAC) has increased markedly in Western populations. Recent reports have suggested that the rate of increase has slowed or plateaued. Using data from cancer registries in Australia, the United States and Sweden, we examined incidence trends for esophageal and gastric cardia tumors between 1984 and 2008 using joinpoint analyses and age-period-cohort models. EAC incidence continues to undergo statistically significant annual increases in Australia and the United States, although the rate of increase has slowed. Among men, incidence increased annually by 2.2% [95% confidence interval (CI) 1.5% to 2.9%] between 1994 and 2008 in Australia and 1.5% (95% CI 0.2% to 2.8%) between 1998 and 2008 in the United States. EAC incidence among men remained unchanged in Sweden between 2001 and 2008 (P = 0.52). EAC incidence among women showed significant linear increases between 1984 and 2008. Age-period-cohort models suggested strong effects for both period and birth cohort on EAC incidence in Australia and the United States, and a strong period effect for Sweden. EAC incidence continues to increase in Australia and the United States. The continued increases, even among more recent birth cohorts, suggest that EAC incidence will continue to rise during coming decades.

Incidence of thyroid cancer in Italy, 1991–2005: time trends and age–period–cohort effects

BackgroundIn Italy, some of the highest incidence rates (IRs) of thyroid cancer (TC) worldwide have been reported. Patients and methodsTC cases <85 years of age reported to Italian cancer registries during 1991–2005 were included. Age-standardized IRs were computed for all TC and age–period–cohort effects were estimated for papillary TC. ResultsIRs of TC were twofold higher in 2001–2005 than in 1991–1995 (18 and 8 per 100000 women, 6 and 3 per 100000 men, respectively). Increases were similar in the two sexes and nearly exclusively due to papillary TC. Increases of papillary TC by birth cohort were found in both sexes and among all age groups between 20 and 79 years. Age–period–cohort models showed a strong period effect in both sexes (rate ratio for 2001–2009 versus 1991–1995 = 2.5 in women and 2.3 in men), although IRs peaked at an earlier age in women (45–49 years) than men (65–69 years). ConclusionThe strength of the period effect in both sexes and the earlier onset in women than men strongly implicated increased medical surveillance in the upward trends of papillary TC incidence in Italy. The consequences of the current intense search for TC on morbidity and possible overtreatment, especially among young women, should be carefully evaluated.

COLFORD ET AL. RESPOND

In his letter, Hunter raises interesting issues: treatment-period interaction and carry-over effects in an AB–BA crossover trial.1 The treatment effect (active versus sham water filtration devices), stratified by sequence, suggests interaction: sequence active–sham (relative risk [RR] = 1.23; 95% confidence interval [CI] = 1.03, 1.48) and sequence sham–active (RR = 0.61; 95% CI = 0.50, 0.74). These estimates, however, are confounded by a strong period effect: highly credible gastrointestinal illness (HCGI) incidence declines in both study arms with time (Figure 1). An observed secular decline over time in incidence and prevalence (that is, a period effect) of self-reported outcome has been noted in studies of gastrointestinal illness.2–6 The cause remains unknown; hypotheses are that the decline is caused by genuine health improvement over time simply from participation (“Hawthorne Effects”) or by bias in self-reported outcomes. The decline due to bias could result from over-reporting early, under-reporting late (because of respondent fatigue), or both. Irrespective of the cause, the active filtration device appears harmful in sequence active–sham because incidence is higher in period 1 and lower in period 2. The device appears protective for sequence sham–active for this same reason. When a period effect is observed in an AB–BA cross-over trial, the only way to estimate an unbiased effect is to average treatment effects over the sequences.7 FIGURE 1 Decline of highly credible gastrointestinal illness (HCGI) over time, by study arm: Sonoma Water Evaluation Trial, Sonoma County, CA, 2001–2006. Hunter notes that the pattern in our study is consistent with a scenario in which participants randomized to sequence active–sham lose long-term immunity while using active water filtration and subsequently experience elevated levels of HCGI in period 2 while using sham water filtration (e.g., untreated water). This hypothesis merits consideration, but unfortunately we cannot test it directly. A carry-over effect results when the treatment in period 1 continues to influence the outcome in period 2. Indeed, with an AB–BA cross-over design it is impossible to distinguish carry-over effect from treatment-period interaction, and our results are also consistent with treatment-period interaction.7 A possible cause leading to a larger treatment effect in period 2 than in period 1 could be greater device use by participants remaining in the study. However, objective measures of device use based on our data suggest lower device use in period 2 (see supplemental Table A2 from the original study).1 Furthermore, parallel slopes of HCGI episodes per person-year observed in period 2 (Figure 1) do not support a carry-over effect. We suggest a rigorous alternative design to test carry-over effect: a 4-arm crossover trial (AA–AB–BA–BB) with participants rerandomized at crossover. If the treatment effect in single-treatment sequences mirrored the mixed-treatment sequences (majority of the protective effect in period 2) this would not support a carry-over effect. If the carry-over effect were observed, the specific cause would require further investigation, possibly measurement of participants' immunologic responses to specific putative pathogens.

Social disparities in BMI trajectories across adulthood by gender, race/ethnicity and lifetime socio-economic position: 1986-2004.

The prevalence of obesity and overweight is rapidly increasing in industrialized countries, with long-term health and social consequences. There is also a strong social patterning of obesity and overweight, with a higher prevalence among women, racial/ethnic minorities and those from a lower socio-economic position (SEP). Most of the existing work in this area, however, is based on cross-sectional data or single cohort studies. No national studies to date have examined how social disparities in obesity and overweight differ by age and historical period using longitudinal data with repeated measures. We used panel data from the nationally representative Monitoring the Future Study (1986-2004) to examine social disparities in trajectories of body mass index (BMI) over adulthood (age 18-45). Self-reported height and weight were collected in this annual US survey of high-school seniors, followed biennially since 1976. Using growth curve models, we analysed BMI trajectories over adulthood by gender, race/ethnicity and lifetime SEP (measured by parents' education and respondent's education). BMI trajectories exhibit a curvilinear rate of change from age 18 to 45, but there was a strong period effect, such that weight gain was more rapid for more recent cohorts. As a result, successive cohorts become overweight (BMI>25) at increasingly earlier points in the life course. BMI scores were also consistently higher for women, racial/ethnic minority groups and those from a lower SEP. However, BMI scores for socially advantaged groups in recent cohorts were actually higher than those for their socially disadvantaged counterparts who were born 10 years earlier. Results highlight the importance of social status and socio-economic resources for maintaining optimal weight. Yet, even those in advantaged social positions have experienced an increase in BMI in recent years.

Societal Transition, Policy Changes and Family Formation: Evidence from Hungary

The paper uses the Hungarian Generations and Gender Survey ‘Turning Points in the Life-course’ (HGGS) to describe recent changes in union formation, onset of childbearing, leaving home and cohabitation. By estimating survivor functions and semi-parametric hazard regression models with time-varying covariates for the timing of first union and first birth, we find a long delay among the youngest cohorts, but also remarkably strong period effects. Reduced employment, increased educational enrolment, and a higher level of uncertainty are important drivers behind these changes. Moreover, our evidence suggests that certain policy changes during the transition have exacerbated this effect, having an asymmetric impact on family formation – depending on the social status of individuals.

Continuity and Change in Attitudes Toward Abortion: Poland and the United States

In this study, we seek to describe and explain changes in mass abortion attitudes in Poland and the United States. Both countries exhibit modest, but significant, declines in support for legal abortion during the 1990s and early years of the twenty-first century. When compositional, structural, and period effects are estimated separately, both countries exhibit strong pro-life period effects beginning in the late 1990s. In Poland, compositional effects exert pro-choice pressure but are counteracted by strong pro-life structural effects. By contrast, compositional effects in the United States are rather weak, but strong pro-choice structural effects are offset by pro-life period effects. The latter result is attributed to strategic framing of the abortion issue by pro-life elites.A version of this paper was presented at the annual meeting of the American Political Science Association, Chicago, September 2004. Thanks are due David Damore, Kenneth Fernandez, Sheila Lambert, Jonathan Strand, Matthew Wetstein, and Melanie Young for valuable comments and assistance.

Impact of Physician Sitting Versus Standing During Inpatient Oncology Consultations: Patients' Preference and Perception of Compassion and Duration. A Randomized Controlled Trial

The purpose of this study was to determine the impact of physician sitting versus standing on the patient's preference of physician communication style, and perception of compassion and consult duration. Sixty-nine patients were randomized to watch one of two videos in which the physician was standing and then sitting (video A) or sitting and then standing (video B) during an inpatient consultation. Both video sequences lasted 9.5 minutes. Thirty-five patients (51%) blindly preferred the sitting physician, 16 (23%) preferred the standing, and 18 (26%) had no preference. Patients perceived that their preferred physician was more compassionate and spent more time with the patient when compared with the other physician. There was a strong period effect favoring the second sequence within the video. The patients blinded choice of preference ( P = 0.003), perception of compassion ( P = 0.0016), and other attributes favored the second sequence seen in the video. The significant period effect suggests that patients prefer the second option presented, notwithstanding a stated preference for a sitting posture (55/68, 81%). Physicians should ask patients for their preference regarding physician sitting or standing as a way to enhance communication.

Constrained standing: Evaluating the foot/floor interface

A methodological study was conducted to provide a multivariate evaluation of the foot/floor interface in constrained standing. Measures of body movement (from force platform and video recording), leg muscle EMGs, reported exertion/discomfort and task performance were taken during a two-hour task. Factor Analysis showed four major factors named Body Movement, Muscle Contraction, Perceived Fatigue and Task Errors. Most measures showed strong effects of time on task (Period Effect), indicating cumulative fatigue. Hard-soled shoes where marginally worse than soft soled shoes on a number of measures. Mat thickness had little effect. To test the methodology a commercial mat was evaluated in a separate experiment. Strong period effects were again obtained, but again the mat had little effect on any measures. Implications for a measurement methodology are discussed

Materialist and Postmaterialist Values and Social Structure in the Nordic Countries: A Comparative Study

The discussion on political value change in advanced industrial society is related to the value dimension which Ronald Inglehart has conceptualized as the materialist/postmaterialist dimension. According to Inglehart, the silent revolution is a gradual value change from materialist to postmaterialist values, from giving greatest priority to values which reflect a preoccupation with physical sustenance and safety values towards a heavier emphasis on belonging, self-expression, and quality of life values. The explanations for the value change rest on two hypotheses which Inglehart labels the scarcity hypothesis and the socialization hypothesis. The scarcity hypothesis is based on the assumption that an individual's values reflect the socioeconomic environment. People tend to place high priority on whatever needs are in short supply. The scarcity hypothesis is, as Inglehart remarks, very similar to the diminishing marginal utility theory in economics. As the basic economic and physical security of individuals is met, values reflecting these needs are given a lower priority in relation to other, conflicting values.' From this perspective we would expect that changes in economic conditions would almost immediately cause change in value priorities. A prolonged period of economic growth and high prosperity would lead to postmaterialist values, whereas economic decline would lead to the opposite. According to the scarcity hypothesis, strong period effects should be present with regard to different generations' value priorities. The socialization hypothesis contradicts somewhat the scarcity perspective. The relationship between socioeconomic factors and individual value priorities is not one of immediate adjustment. Early socialization tends to have an impact on adult social and political values. The socialization perspective is based on the notion of a basic human personality structure which tends to crystallize before the time an individual reaches adulthood. According to this hypothesis there will be a sizable time-lag between changes in the socioeconomic environment and changes in the political value profile. Ten to fifteen years after a change in economic conditions, the age cohorts that had spent their formative years in prosperity would enter the electorate. Although Inglehart emphasizes that the theoretical framework behind the silent revolution is based on both hypotheses,2 most of his theoretical discussion is based on the socialization perspective, which he more specifically relates to Abraham Maslow's well-known theory of a need hierarchy underlying human motivation. Maslow's theory is based on the assumption that people tend to fulfill needs in hierarchical order. Greatest

First Births in America: Changes in the Timing of Parenthood.

Americans today are becoming parents at older ages; more of them are also remaining childless. This book addresses what causes some members of the population to choose delay or permanent childlessness how far they pervade American society and how their parenthood schedules compare with those in other developed countries. The authors bring a wide variety of data sources to bear on the question of whether these delays will be greater and permanent childlessness more widespread in the future; they employ vital registration data cross-sectional studies and longitudinal surveys. It is concluded that few young Americans intend to remain childless but that the competition of educational and career goals and the presence of unfavorable economic conditions lead to postponement of childbearing. Similar parenthood schedules were recorded during the Great Depression. The authors refute the prediction that present trends will continue in the future. Strong period effects have occurred and are likely to occur again; they are unpredictable by their very nature. Although period changes in parenthood timing appear to affect virtually all sectors of the American population there are also important exceptions. Recent divergence between white and black behavior is 1 and the persistence of very early parenthood in both good and poor times is another. Contrasts with Japan show that the parenthood schedules of contemporary Americans are not an inevitable outcome of the forces of economic development and modernization. Rather the American pattern is 1 possible response that is consistent with its culture institutions and past history.

Comment on barbara devaney’s “An analysis of variations in U.S. Fertility and female labor force participation trends”

Devaney presents an extension of the basic Easterlin relative income/fertility model incorporating wages (following Butz and Ward 1977) work experience and education as potential determinants of fertility but preserving the models underlying cohort approach and its essential indifference to period fertility behavior. In the Devaney model period effects occur principally with respect to the timing of fertility. When confronting a strong period effect such as the fertility decline across all cohorts in the 1960s Devaney gives it a cohort interpretation. The result is a series of highly significant regression coefficients that offer the appearance of new knowledge yet may have only traced historical coincidences. That the Easterlin relative income hypothesis and Devaney revision intended as predictors of cohort behavior are necessarily quantified on period data has implications neither Easterlin nor she addresses. The most important is that the measures juxtapose different economic periods. Thus the Easterlin relative income changes for males 20-24 derive from the slowly growing incomes at those ages during the 1950s (when they should have done better by Easterlin theory) more rapid but uneven increases in the 1960s and a downturn in the 1970s. Set against incomes for ages 45-54 at slightly earlier dates they produce a pattern of slippage after the mid-1950s recovery in the late 1960s and renewed slippage throughout the 1970s. The Devaney relative income measured by deviations from an exponential trend line for lifetime income produces a pattern of continuous slippage beginning somewhat earlier. One can speculate on the appearance these relative income measures would have assumed if the Eisenhower and Nixon to Carter economies had been moderately stronger or the Kennedy-Johnson economy weaker. The more salient fact is that there are no strong period income effects of an Easterlin or Devaney type that are not directly related to economic recessions. Devaneys inclusion of a period variable (wages) in her version of the model does not resolve the Easterlin paradox that distinct cohort behavior can be imputed from its absence.