Cohort studies

2021 ◽  
pp. 85-100
Author(s):  
Alvaro Muñoz ◽  
F. Javier Nieto

The simplest cohort design is to obtain exposure data at baseline and follow-up individuals to obtain data up to the point when the event of interest occurs. A richer design includes regularly scheduled visits at which data on exposures are updated. The exposures can be either fixed over time (e.g. race), change directly with time (e.g. age and calendar), or change at their own pace (e.g. biological markers). According to the scientific aims of a cohort study, disease occurrence can be measured as an event in person-time, time-to-endpoint of interest, or change in a biomarker repeatedly measured at follow-up visits. Analytical methods include survival analyses to handle censored observations and late entries due to incomplete observation of the development of events and origin, and longitudinal data analyses for the trajectories of markers of disease progression. Stratification, multivariate regression, and causal inference methods are key tools to accomplish comparability among exposed and unexposed groups. Identification of exposures and risk factors for disease provides a basis for prevention strategies. Data from cohort studies can be used to assess the effects of interventions by using data at the individual level to determine individual effectiveness or by comparing occurrence of disease in the population when typically none or only a few are intervened to determine population effectiveness.

2012 ◽  
Vol 12 (1) ◽  
pp. 1-27 ◽  
Author(s):  
ALAN L. GUSTMAN ◽  
THOMAS L. STEINMEIER ◽  
NAHID TABATABAI

AbstractStudies using data from the early 1990s suggested that while the progressive Social Security benefit formula succeeded in redistributing benefits from individuals with high earnings to individuals with low earnings, it was much less successful in redistributing benefits from households with high earnings to households with low earnings. Wives often earned much less than their husbands. As a result, much of the redistribution at the individual level was effectively from high earning husbands to their own lower earning wives. In addition, spouse and survivor benefits accrue disproportionately to women from high income households. Both factors mitigate redistribution at the household level. It has been argued that with the increase in the labor force participation and earnings of women, Social Security now should do a better job of redistributing benefits at the household level. To be sure, when we compare outcomes for a cohort with a household member age 51 to 56 in 1992 with those from a cohort born twelve years later, redistribution at the household level has increased over time. Nevertheless, as of 2004 there still is substantially less redistribution of benefits from high to low earning households than from high to low earning individuals.


2021 ◽  
Vol 53 (2) ◽  
pp. 283-317
Author(s):  
Justin J. Gengler ◽  
Bethany Shockley ◽  
Michael C. Ewers

Against the backdrop of fiscal reform efforts in Middle East oil producers, this article proposes a general framework for understanding how citizens relate to welfare benefits in the rentier state and then tests some observable implications using original survey data from the quintessential rentier state of Qatar. Using two novel choice experiments, we ask Qataris to choose between competing forms of economic subsidies and state spending, producing a clear and reliable ordering of welfare priorities. Expectations derived from the experiments about the individual-level determinants of rentier reform preferences are then tested using data from a follow-up survey. Findings demonstrate the importance of non-excludable public goods, rather than private patronage, for upholding the rentier bargain.


2020 ◽  
Author(s):  
Christopher James Hopwood ◽  
Ted Schwaba ◽  
Wiebke Bleidorn

Personal concerns about climate change and the environment are a powerful motivator of sustainable behavior. People’s level of concern varies as a function of a variety of social and individual factors. Using data from 58,748 participants from a nationally representative German sample, we tested preregistered hypotheses about factors that impact concerns about the environment over time. We found that environmental concerns increased modestly from 2009-2017 in the German population. However, individuals in middle adulthood tended to be more concerned and showed more consistent increases in concern over time than younger or older people. Consistent with previous research, Big Five personality traits were correlated with environmental concerns. We present novel evidence that increases in concern were related to increases in the personality traits neuroticism and openness to experience. Indeed, changes in openness explained roughly 50% of the variance in changes in environmental concerns. These findings highlight the importance of understanding the individual level factors associated with changes in environmental concerns over time, towards the promotion of more sustainable behavior at the individual level.


2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Fatemeh Koohi ◽  
Davood Khalili ◽  
Mohammad Ali Mansournia ◽  
Farzad Hadaegh ◽  
Hamid Soori

Abstract Background Understanding the distinct patterns (trajectories) of variation in blood lipid levels before diagnosing cardiovascular disease (CVD) might carry important implications for improving disease prevention or treatment. Methods We investigated 14,373 participants (45.5% men) aged 45–84 from two large US prospective cohort studies with a median of 23 years follow-up. First, we jointly estimated developmental trajectories of lipid indices, including low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) concentrations using group-based multi-trajectory modeling. Then, the association of identified multi-trajectories with incident CVD, heart failure, and all-cause mortality were examined using Cox proportional hazard model. Results Seven distinct multi-trajectories were identified. The majority of participants (approximately 80%) exhibited decreasing LDL-C but rising TG levels and relatively stable HDL-C levels. Compared to the individuals with healthy and stable LDL-C, HDL-C, and TG levels, those in other groups were at significant risk of incident CVD after adjusting for other conventional risk factors. Individuals with the highest but decreasing LDL-C and borderline high and rising TG levels over time were at the highest risk than those in other groups with a 2.22-fold risk of CVD. Also, those with the highest and increased triglyceride levels over time, over optimal and decreasing LDL-C levels, and the lowest HDL-C profile had a nearly 1.84 times CVD risk. Even individuals in the multi-trajectory group with the highest HDL-C, optimal LDL-C, and optimal TG levels had a significant risk (HR, 1.45; 95% CI 1.02–2.08). Furthermore, only those with the highest HDL-C profile increased the risk of heart failure by 1.5-fold (95% CI 1.07–2.06). Conclusions The trajectories and risk of CVD identified in this study demonstrated that despite a decline in LDL-C over time, a significant amount of residual risk for CVD remains. These findings suggest the impact of the increasing trend of TG on CVD risk and emphasize the importance of assessing the lipid levels at each visit and undertaking potential interventions that lower triglyceride concentrations to reduce the residual risk of CVD, even among those with the optimal LDL-C level.


Author(s):  
Md. Razib Alam ◽  
Bonwoo Koo ◽  
Brian Paul Cozzarin

Abstract Our objective is to study Canada’s patenting activity over time in aggregate terms by destination country, by assignee and destination country, and by diversification by country of destination. We collect bibliographic patent data from the Canadian Intellectual Property Office and the United States Patent and Trademark Office. We identify 19,957 matched Canada–US patents, 34,032 Canada-only patents, and 43,656 US-only patents from 1980 to 2014. Telecommunications dominates in terms of International Patent Classification technologies for US-only and Canada–US patents. At the firm level, the greatest number of matched Canada–US patents were granted in the field of telecommunications, at the university level in pharmaceuticals, at the government level in control and instrumentation technology, and at the individual level in civil engineering. We use entropy to quantify technological diversification and find that diversification indices decline over time for Canada and the USA; however, all US indices decline at a faster rate.


2021 ◽  
pp. 002202212110447
Author(s):  
Plamen Akaliyski ◽  
Christian Welzel ◽  
Michael Harris Bond ◽  
Michael Minkov

Nations have been questioned as meaningful units for analyzing culture due to their allegedly limited variance-capturing power and large internal heterogeneity. Against this skepticism, we argue that culture is by definition a collective phenomenon and focusing on individual differences contradicts the very concept of culture. Through the “miracle of aggregation,” we can eliminate random noise and arbitrary variation at the individual level in order to distill the central cultural tendencies of nations. Accordingly, we depict national culture as a gravitational field that socializes individuals into the orbit of a nation’s central cultural tendency. Even though individuals are also exposed to other gravitational forces, subcultures in turn gravitate within the limited orbit of their national culture. Using data from the World Values Survey, we show that individual values cluster in concentric circles around their nation’s cultural gravity center. We reveal the miracle of aggregation by demonstrating that nations capture the bulk of the variation in the individuals’ cultural values once they are aggregated into lower-level territorial units such as towns and sub-national regions. We visualize the gravitational force of national cultures by plotting various intra-national groups from five large countries that form distinct national clusters. Contrary to many scholars’ intuitions, alternative social aggregates, such as ethnic, linguistic, and religious groups, as well as diverse socio-demographic categories, add negligible explained variance to that already captured by nations.


2021 ◽  
pp. 1-6
Author(s):  
Meryem Grabski ◽  
Jon Waldron ◽  
Tom P. Freeman ◽  
Claire Mokrysz ◽  
Ruben J.J. van Beek ◽  
...  

<b><i>Background:</i></b> Monitoring emerging trends in the increasingly dynamic European drug market is vital; however, information on change at the individual level is scarce. In the current study, we investigated changes in drug use over 12 months in European nightlife attendees. <b><i>Method:</i></b> In this longitudinal online survey, changes in substances used, use frequency in continued users, and relative initiation of use at follow-up were assessed for 20 different substances. To take part, participants had to be aged 18–34 years; be from Belgium, Italy, the Netherlands, Sweden, or the UK; and have attended at least 6 electronic music events in the past 12 months at baseline. Of 8,045 volunteers at baseline, 2,897 completed the survey at both time points (36% follow-up rate), in 2017 and 2018. <b><i>Results:</i></b> The number of people using ketamine increased by 21% (<i>p</i> &#x3c; 0.001), and logarithmized frequency of use in those continuing use increased by 15% (<i>p</i> &#x3c; 0.001; 95% CI: 0.07–0.23). 4-Fluoroamphetamine use decreased by 27% (<i>p</i> &#x3c; 0.001), and logarithmized frequency of use in continuing users decreased by 15% (<i>p</i> &#x3c; 0.001, 95% CI: −0.48 to −0.23). The drugs with the greatest proportion of relative initiation at follow-up were synthetic cannabinoids (73%, <i>N</i> = 30), mephedrone (44%, <i>N</i> = 18), alkyl nitrites (42%, <i>N</i> = 147), synthetic dissociatives (41%, <i>N</i> = 15), and prescription opioids (40%, <i>N</i> = 48). <b><i>Conclusions:</i></b> In this European nightlife sample, ketamine was found to have the biggest increase in the past 12 months, which occurred alongside an increase in frequency of use in continuing users. The patterns of uptake and discontinuation of alkyl nitrates, novel psychoactive substances, and prescription opioids provide new information that has not been captured by existing cross-sectional surveys. These findings demonstrate the importance of longitudinal assessments of drug use and highlight the dynamic nature of the European drug landscape.


Author(s):  
Courtney A Polenick ◽  
Kira S Birditt ◽  
Angela Turkelson ◽  
Benjamin C Bugajski ◽  
Helen C Kales

Abstract Objectives Individuals often manage chronic conditions in middle and later life that may diminish well-being. Little is known, however, about discordant conditions (i.e., two or more conditions with competing self-management requirements) among older couples and their links to depressive symptoms. We considered discordant conditions at both the individual level and the couple level (i.e., between spouses), along with their long-term implications for depressive symptoms. Methods The U.S. sample included 1,116 middle-aged and older couples drawn from five waves (2006–2014) of the Health and Retirement Study. Longitudinal actor-partner interdependence models evaluated whether individual-level and couple-level discordant chronic health conditions were concurrently linked to depressive symptoms, and whether these associations became stronger over time. Models controlled for age, minority status, education, prior wave depressive symptoms, and each partner’s baseline report of negative marital quality and number of chronic conditions in each wave. Results Wives and husbands reported significantly greater depressive symptoms when they had individual-level discordant conditions about 2 years after baseline, and these links intensified over time. Beyond this association, husbands had significantly greater depressive symptoms when there were couple-level discordant conditions. Discussion Individual-level and couple-level discordant conditions may have lasting implications for depressive symptoms during midlife and older adulthood.


2020 ◽  
Vol 150 (5) ◽  
pp. 1240-1251 ◽  
Author(s):  
Amelia K Wesselink ◽  
Elizabeth E Hatch ◽  
Ellen M Mikkelsen ◽  
Ellen Trolle ◽  
Sydney K Willis ◽  
...  

ABSTRACT Background Phytoestrogens are plant-derived hormonally active compounds found in soy, cruciferous vegetables, nuts, and seeds. Although phytoestrogens have been associated with altered endogenous hormonal activity, luteal phase deficiency, and reduced endometrial decidualization, the literature reporting examinations of phytoestrogen intake and fertility presents mixed findings. Objectives We sought to evaluate prospectively the association between dietary phytoestrogen intake (isoflavones, lignans, and coumestans) and fecundability, the per-cycle probability of conception, in 2 cohorts of women planning pregnancy. Methods Pregnancy Study Online (PRESTO) and Snart Foraeldre (SF) are parallel web-based preconception cohort studies of women from North America and Denmark, respectively, who are trying to conceive. Participants complete an online baseline questionnaire on sociodemographic, lifestyle, and medical factors. We ascertained intake of individual phytoestrogens from validated FFQs. We measured fecundability using data on menstruation and pregnancy status from bimonthly follow-up questionnaires. We analyzed data from 4880 PRESTO and 2898 SF female study participants who had been attempting conception for ≤6 cycles at study entry. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% CIs. Results Phytoestrogen intake varied across cohorts, yet was associated with higher socioeconomic status and healthier behaviors in both cohorts. After adjustment for potential confounders, phytoestrogen intake was not substantially associated with fecundability in either cohort. We observed some evidence of improved fecundability with increasing isoflavone intake among women age ≥30 years in PRESTO (FR: 1.12; 95% CI: 0.94, 1.34, for comparison of ≥90th with &lt;25th percentile intake) and SF (corresponding FR: 1.19; 95% CI: 0.92, 1.55). Lignan intake was associated with slightly increased fecundability in SF (FR for comparison of 75th to 90th with &lt;25th percentile: 1.10; 95% CI: 0.96, 1.26), but decreased fecundability in PRESTO (FR for comparison of ≥90th with &lt;25th percentile: 0.83; 95% CI: 0.72, 0.97). Conclusions We did not observe strong associations between phytoestrogen intake and prospectively-measured fecundability among North American or Danish pregnancy planners.


2020 ◽  
pp. 001112872094096
Author(s):  
Erin A. Orrick ◽  
Alexander H. Updegrove ◽  
Alex R. Piquero ◽  
Tomislav Kovandzic

Research addressing the purported relationship between immigration and crime remains popular, but some gaps remain under-explored. One important gap involves disentangling differences in crime and punishment by immigrant status, as measured across different definitions of immigration status and in relation to U.S. natives, at the individual level. Using data from Texas, results show that native-born U.S. citizens are incarcerated for homicide at higher rates than almost all immigrant groups. While the incarceration rate for undocumented immigrants was 24% greater than the rate for all foreign-citizens, this rate was significantly less than that for U.S. citizens. Among the immigrant status classifications available in this study, all were associated with lower incarceration rates for homicide than that of U.S. citizens.


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