Light sets the brain’s daily clock by regional quickening and slowing of the molecular clockworks at dawn and dusk

How daily clocks in the brain are set by light to local environmental time and encode the seasons is not fully understood. The suprachiasmatic nucleus (SCN) is a central circadian clock in mammals that orchestrates physiology and behavior in tune with daily and seasonal light cycles. Here, we have found that optogenetically simulated light input to explanted mouse SCN changes the waveform of the molecular clockworks from sinusoids in free-running conditions to highly asymmetrical shapes with accelerated synthetic (rising) phases and extended degradative (falling) phases marking clock advances and delays at simulated dawn and dusk. Daily waveform changes arise under ex vivo entrainment to simulated winter and summer photoperiods, and to non-24 hr periods. Ex vivo SCN imaging further suggests that acute waveform shifts are greatest in the ventrolateral SCN, while period effects are greatest in the dorsomedial SCN. Thus, circadian entrainment is encoded by SCN clock gene waveform changes that arise from spatiotemporally distinct intrinsic responses within the SCN neural network.

Race Differences in Trajectories of Hopelessness Among U.S. Older Adults: Do Social Conditions Matter?

Despite being a risk factor for cardiovascular disease, suicidal ideation, and mortality among U.S. older adults, research on hopelessness and how it changes over time are lacking. Although hopelessness generally increases with age, levels of hopelessness may be influenced by race/ethnicity and social or economic factors. This study uses longitudinal data from 8,359 individuals from the Health and Retirement Study to examine race differences in trajectories of hopelessness from 2006 to 2018. We used linear mixed models to estimate trajectories of hopelessness for blacks, whites and Hispanics age 51 and older. The model was fit with a natural spline cubic function to model changes in time trends of hopelessness and the interaction between time and race. Models controlled for demographic characteristics, socioeconomic status, health status, and psychosocial factors that influence hopelessness. We found that older Hispanics have the highest levels of hopelessness, followed by non-Hispanic blacks and non-Hispanic whites. Trajectories of hopelessness were non-linear and differed by race. For older whites, hopelessness increased from 2006-2010 and then decreased until 2018. For older blacks, it decreased the entire time period but did so at a decreasing rate; and, for older Hispanics, hopelessness decreased from 2006-2012 and then increased thereafter. Our study shows that hopelessness generally decreased over time among older adults between 2006 and 2018 in race-specific ways, despite generally increasing with age. These findings suggest that race, age and period effects differentially influence trajectories of hopelessness. Factors contributing to these differences may be related to concurrent social and economic conditions.

Considerations on the Impact of SARS-CoV-2 on Travel Motivations

Travel demand is driven by various motives, which can be subject to changes. Trend study data show, that some motivations shift over time based on age, birth cohort or time-period. It is expected that the external shock of the SARS-CoV-2 pandemic affects travel motivations of an entire population across ages and cohorts. However, and interestingly, survey results show that there are hardly any period effects on travel motives during the pandemic. There are two possible explanations which require further investigation: Either motivations are much more stable than expected, or motivations are instantly adjusted according to the available options to avoid cognitive dissonance between increased desires and reduced opportunities as well as limited abilities to travel.

The dynamics of attitudes toward immigrants: Cohort analyses for Western EU member states

Public opinion climates on immigrants are subject to certain dynamics. This study examines two mechanisms for such dynamics in Western EU member states for the 2002–2018 period. First, the impact of cohort replacement and, second, the impact of periodic threat perceptions, namely, changing macroeconomic conditions and shifts in immigration rates. To date, empirical research on anti-immigrant sentiments rarely combines these two concepts simultaneously to disentangle the interplay of period and cohort effects and determine the factors for long- and short-term attitude changes in societies. Motivated by this gap in the literature, I conduct multiple linear regression analyses of pooled data from all waves of the European Social Survey to show that the process of cohort replacement has led to a substantially more positive opinion climate toward immigrants since the 2000s. However, results indicate that in the future, this positive development is likely to come to a halt since younger cohorts no longer hold significantly more immigrant-friendly attitudes than their immediate predecessors. Furthermore, we observe different period effects to impact cohorts’ attitudes. Fixed-effects panel analyses show that the effect of changing macroeconomic conditions on cohorts’ attitudes is low. Changes in immigration rates, however, lead to significantly more dismissive attitudes when immigrants originate from the Global South as opposed to when they enter from EU countries. These insights suggest that it is less economic or cultural threat perceptions, but ethnic prejudice that plays a key role for natives to oppose immigration. Overall, findings suggest that it is not either cohort or period effects driving large-scale attitude changes, but rather we observe an interplay of both.

STABILITY AND CHANGES IN PARTY IDENTIFICATION IN TAIWAN: AN EXAMINATION OF LIFE CYCLE, COHORT, AND PERIOD EFFECTS

This article builds on the theoretical debate over age, period, and cohort effects (APC) and explores how these factors might affect Taiwan's partisan stability. We conducted a two-level multinomial logit random effects model using survey data from 1991 to 2020 to disentangle the APC effects. Our findings challenge Converse's core assumption that partisanship strengthens with age. As a new democracy, Taiwan's party affiliations remain fluid, and we do find evidence of period effects, particularly associated with cross-Strait crises that favor the DPP. However, generational replacement is the most significant factor driving party identity changes in Taiwan. With generational replacement, the Kuomintang is burdened by the image of a century-old party. The Democratic Progressive Party (DPP) had previously fared better among young cohorts but has recently lost its support from millennials. The youngest generation increasingly refuses to associate with the traditional political parties. It seems reasonable to expect that the new generational forces will restructure the Blue–Green cleavage and expand the ideological diversity of Taiwan's party system.

Age period cohort analysis of chewing ability in Korea from 2007 to 2018

There have been marked improvements in oral health in Korea during the past 10 years, including chewing ability. We sought to disentangle age, period, and cohort effects in chewing ability between 2007 and 2018. We analyzed data from the Korea National Health and Nutrition Examination Survey. The main variable was chewing difficulty, which was assessed among participants aged 20 years and older. APC analysis revealed three trends in chewing difficulty: (1) there was an increase in chewing difficulty starting at around 60 years of age (age effect), (2) there was a steady decrease in chewing difficulty during the observation period (period effect), and (3) chewing ability improved with each successive generation born after 1951 (cohort effect). Regarding recent improvements in chewing ability, cohort effects were somewhat more important than period effects.

Decomposing Employment Trends of Disabled Workers

This paper estimates Age–Period–Cohort models on employment rates of Dutch Disability Insurance (DI) applicants. We find that the substantial decrease in employment between 1999 and 2013 is explained by year-of-application cohort effects and that period effects are negligible. In turn, application cohort effects partly stem from increasing shares of applicants without permanent contracts. Changes in application cohort effects are largely confined to the years following two DI reforms that increased self-screening among workers. We next analyze changes in employment rates of awarded and rejected applicants and follow a Difference-in-Differences approach. Assuming common compositional cohort effects, we infer negligible effects of changes in benefit conditions.

Getting a Grip on Secular Changes: Age-Period-Cohort modeling of grip strength in the English Longitudinal Study of Ageing

Background Grip strength is a popular and valuable measure in studies of physical functional capabilities in old-age. The influence of historical trends and differential period-specific exposures can complicate the interpretation of biomarkers of aging and health and requires careful analysis and interpretation of ageing, birth cohort, and period effects. The current study evaluates the effects of aging, period, and cohort on grip strength in a population of adults and older adults. Methods We use >27,000 observations for individuals ≥50 years of age, born in approximately 1910-1960, from the English Longitudinal Study of Aging to examine a variety of multilevel and cross-classified modeling approaches to evaluate age, period, and cohort effects. Our results extended Hierarchical Age Period Cohort modeling and compared our results with a set of nine sub-models with explicit assumptions to determine the most reliable modeling approach. Results Findings suggest grip strength is primarily related to age, with minimal evidence of either period and/or cohort effects. Each year’s increase in a person’s age was associated with a 0.40-kilogram decrease in grip strength, though this decline differs by gender. Conclusions We conclude that as a population ages, grip strength declines at a systematic and predictable rate equal to -0.40-kilograms per year (approximately -.50-kg for men and -.30-kg for women) in residents of England aged 50 and older. Age-effects were predominant and most consistent across methodologies. While there was some evidence for cohort effects, such effects were minimal and therefore indicative that grip strength is a consistent physiological biomarker of aging.