Epidemiology and Health

Original Articles

Age-specific findings on lifestyle and trajectories of cognitive function from the Korean Longitudinal Study of Aging: Seungju lim, Eunyoung Yoo, Ickpyo Hong, Ji-Hyuk Park; Epidemiol Health. 2023;45:e2023098. Published online November 2, 2023; DOI: https://doi.org/10.4178/epih.e2023098

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Abstract Summary PDF: Abstract
OBJECTIVES
Few longitudinal studies have explored age-related differences in the relationship between lifestyle factors and cognitive decline. This study investigated lifestyle factors at baseline that slow the longitudinal rate of cognitive decline in young-old (55-64 years), middle-old (65-74 years), and old-old (75+ years) individuals.
METHODS
We conducted an 11-year follow-up that included 6,189 older adults from the Korean Longitudinal Study of Aging, which is a cohort study of community-dwelling older Koreans. Lifestyle factors, including physical activity, social activity (SA), smoking, and alcohol consumption were assessed at baseline. Cognitive function was measured at 2-year intervals over 11 years. Latent growth modeling and multi-group analysis were performed.
RESULTS
The influence of lifestyle factors on the rate of cognitive decline differed by age. Smoking at baseline (-0.05; 95% confidence interval [CI], -0.11 to -0.00, per study wave) accelerated cognitive decline in young-old individuals, whereas frequent participation in SA at baseline (0.02; 95% CI, 0.01 to 0.03, per study wave) decelerated cognitive decline in middle-old individuals. None of the lifestyle factors in this study decelerated cognitive decline in old-old individuals.
CONCLUSIONS
Cognitive strategies based on modifiable lifestyle factors such as smoking cessation in young-old individuals and frequent SA participation in middle-old age individuals may have great potential for preventing cognitive decline. Because the influence of lifestyle factors varied by age group, age-specific approaches are recommended to promote cognitive health.; Summary

Korean summary
본 연구는 국내 노인인구를 연령대별로 구분하여 연소노인(55-64세), 중고령노인(65-74세), 고령노인(75세+)의 인지저하 기울기를 가속 혹은 감속시키는 라이프스타일 요인을 파악하였다. '흡연'은 연소노인의 인지저하를 가속, '사회활동 참여 빈도'는 중고령노인의 인지저하를 감속시키는 것으로 나타났으며, 고령노인의 경우 유의미한 변수가 나타나지 않았다. 본 결과는 노인의 인지건강에 있어 연령대별 차별화된 라이프스타일 전략이 필요할 것을 시사한다.

Key Message
This study aimed to identify lifestyle factors that accelerate or decelerate the cognitive decline slope in the older population in South Korea, categorized by age groups: young-old adults (55-64), middle-old adults (65-74), and old-old adults (75+). The findings indicated that 'smoking' accelerates cognitive decline in young-old adults, while 'frequency of social activity participation' decelerates cognitive decline in middle-old adults. However, no significant lifestyle variables were identified for old-old adults. These results suggest the necessity of differentiated lifestyle strategies based on age groups for promoting cognitive health in the older population.

Long working hours and the risk of hypothyroidism in healthy Korean workers: a cohort study: Yesung Lee, Woncheol Lee, Hyoung-Ryoul Kim; Epidemiol Health. 2022;44:e2022104. Published online November 8, 2022; DOI: https://doi.org/10.4178/epih.e2022104

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Abstract Summary PDF Supplementary Material

Abstract

OBJECTIVES
Long working hours have been reported to cause various health problems, but are currently practiced in many countries. Building upon a previous cross-sectional study, the authors aimed to elucidate the causal relationship between long working hours and hypothyroidism through a longitudinal study.

METHODS

Data were collected at baseline from 45,259 participants without thyroid disease and with consistent weekly working hours (36-40, 41-52, 53-60, and >60 hours) during the follow-up period. Hypothyroidism was defined using the reference limits of serum thyroid-stimulating hormone and free thyroxine levels. By estimating hazard ratios (HRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression analysis, the risk of incident hypothyroidism was evaluated with 36-40 hours of work per week as the reference.

RESULTS

During 138,261.7 person-years of follow-up, 2,914 participants developed hypothyroidism (incidence density, 2.11/102 person-years). The multivariable-adjusted HRs of incident hypothyroidism for 41-52 hours, 53-60 hours, and >60 hours of work per week were 1.13 (95% CI, 1.03 to 1.24), 2.53 (95% CI, 2.17 to 2.95), and 2.57 (95% CI, 2.09 to 3.15), respectively. In dose-response analyses, long working hours had an approximately linear relationship with hypothyroidism incidence. The risk of incident hypothyroidism in those who worked 53-60 hours and >60 hours per week compared with the reference group was significantly higher among the older age group (≥36 years, stratified by median age), men, and daytime workers.

CONCLUSIONS

This large-scale cohort study demonstrated the association between long working hours and an increased risk of incident hypothyroidism with a dose-response relationship.

Summary

Korean summary
대규모 코호트연구를 통해 장시간노동을 수행한 노동자들에서 갑상선기능저하증의 위험이 높아지는 것을 확인할 수 있었다. 특히 연령, 성, 교대근무 유무에 따라 층화하여 분석한 결과에서 고연령, 남성, 교대근무를 하지 않는 노동자에서 관련성의 크기가 증가하였다.

Key Message
This large-scale cohort study (The Kangbuk Samsung Health Study), which used 45,259 participants without thyroid disease at baseline and estimated hazard ratios (HRs) using Cox proportional hazards regression analysis, demonstrated the association between long working hours and an increased risk of incident hypothyroidism with a dose-response relationship especially in older age group, men, and daytime workers.

Citations

Citations to this article as recorded by

Association between shift work and the risk of hypothyroidism in adult male workers in Korea: a cohort study
Seonghyeon Kwon, Yesung Lee, Eunhye Seo, Daehoon Kim, Jaehong Lee, Youshik Jeong, Jihoon Kim, Jinsook Jeong, Woncheol Lee
Annals of Occupational and Environmental Medicine.2023;[Epub] CrossRef

Cohort Profile

Cohort profile: Singapore’s nationally representative Retirement and Health Study with 5 waves over 10 years: Reuben Ng, Yi Wen Tan, Kelvin Bryan Tan; Epidemiol Health. 2022;44:e2022030. Published online February 21, 2022; DOI: https://doi.org/10.4178/epih.e2022030

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Abstract Summary PDF

Abstract

The Retirement and Health Study (RHS) is Singapore’s largest nationally representative cohort with over 15,000 participants (aged 45-85 years) followed across five timepoints in 10 years (2014-2024). Accounting for sample weights, the sample represents 1.2 million Singaporeans and permanent residents of a total population of 5.5 million. The RHS sought consent to link survey responses to relevant administrative data, enabling the cross-validation of self-reports with national databases. There are 10 sections in the RHS with over 400 questions, 50% of which are on respondents’ physical and mental health, healthcare utilization and insurance; the remaining 50% are about employment history, retirement adequacy, wealth, and household expenditure. The RHS was set up to provide microdata to compliment administrative data for whole-of-government policy making given that Singapore will reach super-aged status by 2026. Sample findings include a need for older adults to balance between immediate financial needs and investments regarding their pension funds. Also, 86% of older adults preferred to transit into partial retirement by reducing workloads. On the health front, existing studies utilising the RHS have revealed latent classes of disabilities, and that intentions to seek employment can mitigate disability developments. Another study reported that physical disability and social isolation was projected to increase, with ethnic disparities in social functioning. Overall, the RHS will be used for evidenced-informed policy agenda setting and evaluation across domains of health, finance, retirement adequacy, social and family development.

Summary

Key Message
The Retirement and Health Study (RHS) is Singapore’s largest nationally representative cohort with over 15,000 participants (aged 45-85 years) followed across five timepoints in 10 years (2014-2024). Sample findings include a need for older adults to balance between immediate financial needs and investments regarding their pension funds. Overall, the RHS will be used for evidenced-informed policy agenda setting and evaluation across domains of health, finance, retirement adequacy, social and family development.

Citations

Citations to this article as recorded by

Not Too Old for TikTok: How Older Adults Are Reframing Aging
Reuben Ng, Nicole Indran, Barbara J Bowers
The Gerontologist.2022; 62(8): 1207. CrossRef
A playbook for effective age advocacy on Twitter
Reuben Ng, Nicole Indran, Luyao Liu
Journal of the American Geriatrics Society.2022; 70(8): 2363. CrossRef
Ageism on Twitter during the COVID‐19 pandemic
Reuben Ng, Nicole Indran, Luyao Liu
Journal of Social Issues.2022; 78(4): 842. CrossRef
Media attention toward COVID-19 across 18 countries: The influence of cultural values and pandemic severity
Reuben Ng, Yi Wen Tan, Miguel A. Andrade-Navarro
PLOS ONE.2022; 17(12): e0271961. CrossRef

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