Using explainable machine learning and fitbit data to investigate predictors of adolescent obesity.

Sociodemographic and lifestyle factors (sleep, physical activity, and sedentary behavior) may predict obesity risk in early adolescence; a critical period during the life course. Analyzing data from 2971 participants (M = 11.94, SD = 0.64 years) wearing Fitbit Charge HR 2 devices in the Adolescent Brain Cognitive Development (ABCD) Study, glass box machine learning models identified obesity predictors from Fitbit-derived measures of sleep, cardiovascular fitness, and sociodemographic status. Key predictors of obesity include identifying as Non-White race, low household income, later bedtime, short sleep duration, variable sleep timing, low daily step counts, and high heart rates (AUCMean = 0.726). Findings highlight the importance of inadequate sleep, physical inactivity, and socioeconomic disparities, for obesity risk. Results also show the clinical applicability of wearables for continuous monitoring of sleep and cardiovascular fitness in adolescents. Identifying the tipping points in the predictors of obesity risk can inform interventions and treatment strategies to reduce obesity rates in adolescents.

Physical Activity Fragmentation and Falls in Older Adults: Findings From the National Health and Aging Trends Study.

BACKGROUND: Physical activity (PA) may be an important fall prevention strategy. Current PA guidelines emphasize total PA dose, but daily patterning of PA is underappreciated. With aging, PA bouts become less frequent and shorter in duration (ie, more fragmented). PA fragmentation may be an indicator of fall risk, but the relationship is not well understood. This study examined daily PA accumulation and patterns with fall risk in older adults. METHODS: Participants (n = 685, 54.3% women, 61.5% aged 70-79 years) from the National Health and Aging Trends Study with wrist-worn accelerometry PA data from Round 11 (baseline) and sample person interviews with fall data from Round 12 (follow-up) were included. PA variables were categorized into tertiles and incident falls were defined as ≥1 self-reported fall in the year following the PA assessment between baseline and follow-up. A modified Poisson approach was used to estimate the relative risk of both PA accumulation and fragmentation with falls. RESULTS: Overall, 40.0% reported an incident fall. After adjustment for sociodemographic and health characteristics, those in the highest tertile of total PA accumulation had lower fall risk (aRR = 0.74, 95% CI: 0.57, 0.95) and those in the highest tertile of PA fragmentation had increased fall risk (aRR = 1.33, 95% CI: 1.03, 1.73). Models were attenuated after adjustment for physical functioning. CONCLUSIONS: PA fragmentation may identify fall risk in older adults. Longitudinal studies are needed to disentangle the temporal sequencing of the complex relationship between PA and physical functioning across the life course.

Association of physical activity and screen time with cardiovascular disease risk in the Adolescent Brain Cognitive Development Study.

BACKGROUND: According to the Physical Activity Guidelines Advisory Committee Scientific Report, limited evidence is available on sedentary behaviors (screen time) and their joint associations with physical activity (steps) for cardiovascular health in adolescence. The objective of this study was to identify joint associations of screen time and physical activity categories with cardiovascular disease (CVD) risk factors (blood pressure, hemoglobin A1c, cholesterol) in adolescence. METHODS: This study analyzed data from the Adolescent Brain Cognitive Development (ABCD) Study, comprising a diverse sample of 4,718 U.S. adolescents aged 10-15 years between 2018 and 2021. Steps were measured by a Fitbit wearable device and levels were categorized as low (1,000-6,000), medium (> 6,000-12,000), and high (> 12,000) averaged daily step counts. Self-reported recreational screen time hours per day were classified as low (0-4), medium (> 4-8), and high (> 8) hours per day. CVD risk factors including blood pressure, hemoglobin A1c, and cholesterol (total and HDL) were measured. RESULTS: The analytical sample averaged 6.6 h of screen time per day and 9,722 steps per day. In models including both screen time and steps, the high screen time category was associated with a 4.27 higher diastolic blood pressure percentile (95% CI 1.83-6.73) and lower HDL cholesterol (B= -2.85, 95% CI -4.77 to -0.94 mg/dL) compared to the low screen time category. Medium (B = 3.68, 95% CI 1.24-6.11) and low (B = 7.64, 95% CI 4.07-11.20) step categories were associated with higher diastolic blood pressure percentile compared to the high step category. The medium step category was associated with lower HDL cholesterol (B= -1.99, 95% CI -3.80 to -0.19 mg/dL) compared to the high step category. Findings were similar when screen time and step counts were analyzed as continuous variables; higher continuous step count was additionally associated with lower total cholesterol (mg/dL). CONCLUSIONS: Combinations of low screen time and high steps were generally associated with favorable cardiovascular health markers including lower diastolic blood pressure and higher HDL cholesterol, which can inform future adolescent health guidelines.

Sociodemographic Associations With Blood Pressure in 10-14-Year-Old Adolescents.

PURPOSE: To determine the association between sociodemographic characteristics and blood pressure among a demographically diverse population-based sample of 10-14-year-old US adolescents. METHODS: We conducted cross-sectional analyses of data from the Adolescent Brain Cognitive Development Study (N = 4,466), year two (2018-2020). Logistic and linear regression models were used to determine the association between sociodemographic characteristics (sex, race/ethnicity, sexual orientation, household income, and parental education) with blood pressure among early adolescents. RESULTS: The sample was 49.3% female and 46.7% non-White. Overall, 4.1% had blood pressures in the hypertensive range. Male sex was associated with 48% higher odds of hypertensive-range blood pressures than female sex (95% confidence interval [CI], 1.02; 2.14), and Black race was associated with 85% higher odds of hypertensive-range blood pressures compared to White race (95% CI, 1.11; 3.08). Several annual household income categories less than $100,000 were associated with higher odds of hypertensive-range blood pressures compared to an annual household income greater than $200,000. We found effect modification by household income for Black adolescents; Black race (compared to White race) was more strongly associated with higher odds of hypertensive-range blood pressures in households with income greater than $75,000 (odds ratio 3.92; 95% CI, 1.95; 7.88) compared to those with income less than $75,000 (odds ratio 1.53; 95% CI, 0.80; 2.92). DISCUSSION: Sociodemographic characteristics are differentially associated with higher blood pressure in early adolescents. Future research could examine potential mediating factors (e.g., physical activity, nutrition, tobacco) linking sociodemographic characteristics and blood pressure to inform targeted interventions.

Effectiveness of a paediatric weight management intervention for rural youth (iAmHealthy): Primary outcomes of a cluster randomised control trial.

BACKGROUND: Youth in rural areas are disproportionally affected by obesity. Given the unique barriers rural populations face, tailoring and increasing access to obesity interventions is necessary. OBJECTIVE: This paper evaluates the effectiveness of iAmHealthy, a family-based paediatric obesity intervention delivered to rural children, compared to a Newsletter Control. METHODS: Participating schools (n = 18) were randomly assigned to iAmHealthy or Newsletter Control. iAmHealthy consists of individual health coaching and group sessions delivered via televideo to a participant's home. The child and parent's body mass index (BMI), child physical activity and child dietary intake were assessed at baseline, post-treatment (8 months) and follow-up (20 months). Multilevel modeling estimated the effect of treatment at both time points. RESULTS: Parent and child dyads were recruited (n = 148) and randomised to iAmHealthy (n = 64) or the Control group (n = 84). The Control group had significant increases in child BMIz from baseline to follow-up. iAmHealthy youth had no significant changes in BMIz from baseline to post or follow-up. Child dietary intake, physical activity and parent BMI results are also discussed. CONCLUSIONS: This trial extends previous paediatric obesity work by simultaneously increasing convenience and dose of treatment. Results suggest iAmHealthy resulted in a change in BMIz trajectories and long-term health behaviour for youth.

TV Viewing From Young Adulthood to Middle Age and Cardiovascular Disease Risk.

INTRODUCTION: Few studies have longitudinally examined TV viewing trajectories and cardiovascular disease risk factors. The objective of this study was to determine the association between level and annualized changes in young adult TV viewing and the incidence of cardiovascular disease risk factors from young adulthood to middle age. METHODS: In 2023, prospective community-based cohort data of 4,318 Coronary Artery Risk Development in Young Adults study participants (1990-1991 to 2015-2016) were analyzed. Individualized daily TV viewing trajectories for each participant were developed using linear mixed models. RESULTS: Every additional hour of TV viewing at age 23 years was associated with higher odds of incident hypertension (AOR=1.16; 95% CI=1.11, 1.22), diabetes (AOR=1.19; 95% CI=1.11, 1.28), high triglycerides (AOR=1.17; 95% CI=1.08, 1.26), dyslipidemia (AOR=1.10; 95% CI=1.03, 1.16), and obesity (AOR=1.12; 95% CI=1.06, 1.17). In addition, each hourly increase in daily TV viewing was associated with higher annual odds of incident hypertension (AOR=1.26; 95% CI=1.16, 1.37), low high-density lipoprotein cholesterol (AOR=1.15; 95% CI=1.03, 1.30), high triglycerides (AOR=1.32; 95% CI=1.15, 1.51), dyslipidemia (AOR=1.22; 95% CI=1.11, 1.34), and obesity (AOR=1.17; 95% CI=1.07, 1.27) over the follow-up period. CONCLUSIONS: In this prospective cohort study, higher TV viewing in young adulthood and annual increases in TV viewing were associated with incident hypertension, high triglycerides, and obesity. Young adulthood as well as behaviors across midlife may be important time periods to promote healthful TV viewing behavior patterns.

Associations between occupational physical activity and left ventricular structure and function over 25 years in CARDIA.

AIMS: Leisure time physical activity (LTPA) confers cardiovascular health benefits, while occupational physical activity (OPA) may have paradoxically negative health associations. This study tested the explanatory hypothesis that unfavourable cardiac remodelling may result from chronic OPA-induced cardiovascular strain. METHODS AND RESULTS: Longitudinal associations of OPA and left ventricular (LV) structure and function were examined in 1462 participants {50.0% female, 56.4% White, aged 30.4 ± 3.4 years at baseline [Year 5 exam (1990-91)]} from the Coronary Artery Risk Development in Young Adults study. Left ventricular structure and function were measured as LV mass (LVMi), end-diastolic volume (LVEDVi), end-systolic volume (LVESVi), ejection fraction (LVEF), stroke volume (LVSVi), and e/a-wave ratio (EA ratio) via echocardiography at baseline and 25 years later. Occupational physical activity was reported at seven exams during the study period as months/year with 'vigorous job activities such as lifting, carrying, or digging' for ≥5 h/week. The 25-year OPA patterns were categorized into three trajectories: no OPA (n = 770), medium OPA (n = 410), and high OPA (n = 282). Linear regression estimated associations between OPA trajectories and echocardiogram variables at follow-up after adjusting for baseline values, individual demographic/health characteristics, and LTPA. Twenty-five-year OPA exposure was not significantly associated with LVMi, LVEDVi, LVSVi, or EA ratio (P > 0.05). However, higher LVESVi (ß = 1.84, P < 0.05) and lower LVEF (ß = -1.94, P < 0.05) were observed at follow-up among those in the high- vs. no-OPA trajectories. CONCLUSION: The paradoxically adverse association of OPA with cardiovascular health was partially supported by null or adverse associations between high OPA and echocardiogram outcomes. Confirmation is needed using more precise OPA measures.

This study tested the paradoxical notion that physical activity done for work may not have the same heart health benefits as expected for physical activity done during leisure time. Those who completed high amounts of physical activity at work had no beneficial changes and, in some cases, adverse changes to the structure and function of their hearts compared with those doing no activity at work during the same period. The adverse changes associated with physical activity at work were more apparent among men, those with greater than high school education levels, and those with low levels of physical activity outside of work.

Independent and joint associations of cardiorespiratory fitness and BMI with dementia risk: the Cooper Center Longitudinal Study.

OBJECTIVE: This study aimed to examine the association of midlife fitness and body mass index (BMI) with incident dementia later in life. DESIGN AND PARTICIPANTS: A cohort study of 6428 individuals (mean age 50.9±7.6 years) from the Cooper Center Longitudinal Study. MEASURES: Cardiorespiratory fitness and BMI were assessed twice (1970-1999) during visits to the Cooper Clinic, a preventive medicine clinic in Dallas, Texas. These measures were examined as continuous and categorical variables. As continuous variables, fitness and BMI were examined at baseline (averaged of two examinations) and as absolute change between exams (mean time 2.1±1.8 years). Variables were categorised: unfit versus fit and normal versus overweight/obese. Medicare claims data were used to obtain all-cause dementia incidence (1999-2009). Mean follow-up between midlife examinations and Medicare surveillance was 15.7 ((SD=6.2) years. Multivariable models were used to assess the associations between fitness, BMI and dementia. RESULTS: During 40 773 person years of Medicare surveillance, 632 cases of dementia were identified. After controlling for BMI and covariates, each 1-metabolic equivalent increment in fitness was associated with 5% lower (HR 0.95; 95% CI 0.90 to 0.99) dementia risk. In comparison, after controlling for fitness and covariates, each 1 kg/m2 increment in BMI was associated with a 3.0% (HR 1.03; 95% CI 1.00 to 1.07) higher risk for dementia, yet without significance (p=0.051). Similar findings were observed when the exposures were categorised. Changes in fitness and BMI between examinations were not related to dementia. Jointly, participants who were unfit and overweight/obese had the highest (HR 2.28 95% CI 1.57 to 3.32) dementia risk compared with their fit and normal weight counterparts. CONCLUSION: Lower midlife fitness is a risk marker for dementia irrespective of weight status. Being unfit coupled with overweight/obese status might increase one's risk for dementia even further.

Multimorbidity is associated with lower total 24-hour movement activity among US adults.

Objective: Having chronic conditions may result in reduced physical and cognitive function but less is known about multimorbidity with daily movement. We examined the association of multimorbidity and device-measured total daily movement in a nationally representative sample of US adults aged ≥ 30 years from the 2011-2014 National Health and Nutrition Examination Surveys. Methods: Any multimorbidity (≥2 conditions) and complex multimorbidity (≥3 conditions across ≥ 3 body systems) were quantified using 16 chronic conditions via self-report and/or clinical thresholds. Total movement over 24-hours (Monitor-Independent Movement Summary units [MIMS-units]) was measured using a wrist-worn device (ActiGraph GT3X). Multivariable linear regression examined the association of 1) each chronic condition, 2) number of conditions, 3) any multimorbidity, and 4) complex multimorbidity with total movement. Covariates included age, gender, race/ethnicity, educational attainment, and smoking status. Results: Among US adults (N = 7304, mean age: 53.2 ± 0.34 years, 53.2% female, 69.4% Non-Hispanic White), 62.2% had any multimorbidity with 34.2% having complex multimorbidity. After adjustment, a higher number of chronic conditions was associated with incrementally lower total movement (ß MIMS-units [95% CI] compared to those with no chronic conditions; one: -419 [-772, -66], two: -605 [-933, -278], three: -1201 [-1506, -895], four: -1908 [-2351, -1465], 5+: -2972 [-3384, -2560]). Complex multimorbidity presence was associated with -1709 (95% CI: -2062, -1357) and -1269 (-1620, -918) lower total movement compared to those without multimorbidity and multimorbidity but not complex, respectively. Conclusions: Multimorbidity was associated with lower 24-h movement among US adults and may be helpful for identifying adults at risk for low movement.

Moderate-to-vigorous intensity physical activity among U.S. adolescents before and during the COVID-19 pandemic: Findings from the Adolescent Brain Cognitive Development Study.

Only 16.1% percent of U.S. adolescents meet the recommendation of at least 60 minutes of moderate-to-vigorous intensity physical activity (MVPA) per day. Studies report declined levels of adolescent MVPA in early stages of the pandemic, but gaps remain in understanding changes beyond the initial three months of the pandemic. This study aims to describe and compare self-reported adolescent MVPA levels at multiple timepoints before and during the COVID-19 pandemic among 11,865 9-11-year-old U.S. adolescents from the Adolescent Brain Cognitive Development (ABCD) Study, including pre-pandemic (September 2016-October 2018), early (May, June, and August 2020), and later (October and December 2020, March 2021) stages of the pandemic. Poisson regression models with robust error variance were used to estimate crude and adjusted prevalence ratios (APRs) of the proportion of adolescents meeting national MVPA guidelines during early and later stages of the pandemic compared to pre-pandemic. The proportion of adolescents meeting MVPA guidelines decreased from pre (16.4%), early (11.0%), and later (4.7%) COVID-19 pandemic timepoints. Adolescent MVPA guideline adherence at early- and later-pandemic stages was 24% lower (APR 0.76, 95% CI 0.62, 0.93) and 68% lower (APR 0.32, 95% CI 0.24, 0.43) than pre-pandemic adherence, respectively. Weekly MVPA duration decreased throughout May 2020 to March 2021 (χ2 = 488.9, p < 0.0001). Study findings build upon existing evidence that the low achievement of national MVPA guidelines before the pandemic became even lower during the pandemic, demonstrating the need to support and improve access to adolescent MVPA opportunities during COVID-19 pandemic recovery efforts and in future pandemics.

Thirteen-Year Associations of Occupational and Leisure-Time Physical Activity with Cardiorespiratory Fitness in CARDIA.

PURPOSE: Differential effects on fitness are hypothesized to contribute to the opposing health effects of leisure-time physical activity (LTPA) and occupational physical activity (OPA). As such, this study examined cross-sectional and longitudinal associations of fitness with LTPA and OPA. METHODS: This study examined fitness associations with LTPA and OPA across 13 yr in the Coronary Artery Risk Development in Young Adults study (years 7 (baseline), 10, 15, and 20 (follow-up) examinations). Fitness was measured at baseline and follow-up via symptom-limited maximal graded exercise test (GXT) duration (in seconds), whereas LTPA and OPA were self-reported during each examination. Baseline and follow-up cross-sectional associations of LTPA (low, medium, high) and OPA (0, 1-6, and ≥6 months with OPA) with fitness were examined using linear regression. Longitudinal linear regression examined associations between 13-yr LTPA (low, medium, or high) and OPA (no, decreasing, or increasing) trajectories with fitness at follow-up, adjusted for baseline values. All models adjusted for center, sex, race, age, education, smoking history, alcohol intake, resting blood pressure, diabetes status, and body mass index. Stratified analyses examined associations by sex (female/male), race (Black/White), and LTPA groups. RESULTS: Compared with low, medium, and high LTPA were positively associated with fitness in all analyses ( P < 0.001). Reporting 1-6 or ≥6 months with OPA was negatively associated with fitness in cross-sectional follow-up models ( ß = -15.6 and -15.4, respectively; P ≤ 0.01). Longitudinally, those with increasing OPA had lower follow-up fitness compared with no OPA ( ß = -16.41, P < 0.01). Negative associations of OPA with fitness were not meaningfully different across sex and race groups. Significant LTPA-OPA interactions were observed ( P < 001). CONCLUSIONS: Physical activity research and public health promotion should consider domain-specific associations on cardiovascular health.

Physical Activity Over the Lifecourse and Cardiovascular Disease.

Despite improvements in cardiovascular care in recent decades, cardiovascular disease (CVD) remains a leading cause of death worldwide. At its core, CVD is a largely preventable disease with diligent risk factor management and early detection. As highlighted in the American Heart Association's Life's Essential 8, physical activity plays a central role in CVD prevention at an individual and population level. Despite pervasive knowledge of the numerous cardiovascular and noncardiovascular health benefits of physical activity, physical activity has steadily decreased over time and unfavorable changes in physical activity occur throughout people's lives. Here, we use a lifecourse framework to examine the evidence reporting on the association of physical activity with CVD. From in utero to older adults, we review and discuss the evidence detailing how physical activity may prevent incident CVD and mitigate CVD-related morbidity and death across all life stages.

Social epidemiology of Fitbit daily steps in early adolescence.

BACKGROUND: Sociodemographic disparities in adolescent physical activity have been documented but mostly rely on self-reported data. Our objective was to examine differences in device-based step metrics, including daily step count (steps d-1), by sociodemographic factors among a diverse sample of 10-to-14-year-old adolescents in the US. METHODS: We analyzed prospective cohort data from Year 2 (2018-2020) of the Adolescent Brain Cognitive Development (ABCD) Study (N = 6460). Mixed-effects models were conducted to estimate associations of sociodemographic factors (sex, sexual orientation, race/ethnicity, household income, parental education, and parental marital status) with repeated measures of steps d-1 over the course of 21 days. RESULTS: Participants (49.6% female, 39.0% racial/ethnic minority) accumulated an average of 9095.8 steps d-1. In mixed-effects models, 1543.6 more steps d-1 were recorded for male versus female sex, Black versus White race (328.8 more steps d-1), heterosexual versus sexual minority sexual orientation (676.4 more steps d-1), >$200,000 versus <$25,000 household income (1003.3 more steps d-1), and having married/partnered parents versus unmarried/unpartnered parents (326.3 more steps d-1). We found effect modification by household income for Black adolescents and by sex for Asian adolescents. CONCLUSIONS: Given sociodemographic differences in adolescent steps d-1, physical activity guidelines should focus on key populations and adopt strategies optimized for adolescents from diverse backgrounds. IMPACT: Sociodemographic disparities in physical activity have been documented but mostly rely on self-reported data, which can be limited by reporting and prevarication bias. In this demographically diverse sample of 10-14-year-old early adolescents in the U.S., we found notable and nuanced sociodemographic disparities in Fitbit steps per day. More daily steps were recorded for male versus female sex, Black versus White race, heterosexual versus sexual minority, >$100,000 versus <$25,000 household income, and having married/partnered versus unmarried/unpartnered parents. We found effect modification by household income for Black adolescents and by sex for Asian adolescents.

Higher blood pressure and weight observed among early adolescents during the COVID-19 pandemic.

The COVID-19 pandemic led to significant disruptions in the lifestyle behaviors of adolescents; however, there is a paucity of data on objective changes in health indicators of adolescents such as blood pressure, hypertension, and weight. The aim of this study is to quantify differences in blood pressure and weight before and during the COVID-19 pandemic among a demographically diverse national sample of early adolescents. We analyzed cross-sectional data from 2018 to 2020, corresponding to the second follow-up year (Year 2) of the Adolescent Brain Cognitive Development (ABCD) Study. Among 4,065 early adolescents (mean age 12.00, 49.4% female, 55.5% white), 3.4% vs 6.4% of adolescents had hypertension pre-pandemic vs during the pandemic (p < 0.001). The pandemic was associated with a 4.65 percentile (95% CI 2.65, 6.66) higher diastolic blood pressure, and a 1.68 kg (95% CI 0.51, 2.85) higher weight when adjusting for covariates. The pandemic was associated with a 1.97 higher odds of hypertension (95% CI 1.33, 2.92) compared to pre-pandemic when adjusting for covariates. Future studies should explore mechanisms and longitudinal trends in blood pressure among adolescents as they return to pre-pandemic lifestyle behaviors.

Analysis of Cardiorespiratory Fitness in Early Adulthood and Midlife With All-Cause Mortality and Fatal or Nonfatal Cardiovascular Disease.

Importance: Optimizing cardiovascular fitness is a prevention strategy against premature death and cardiovascular disease (CVD) events. Since this evidence has largely been established in older populations, the importance of cardiorespiratory fitness during earlier periods of adulthood remains unclear. Objective: To examine the association of early-adulthood cardiorespiratory fitness and percentage of early-adulthood cardiorespiratory fitness retained during midlife with subsequent risk of all-cause mortality and CVD-related morbidity and mortality overall as well as by sex and race. Design, Setting, and Participants: This retrospective population-based cohort study analyzed data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, an ongoing prospective cohort study conducted at field center clinics in Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California. Participants in the CARDIA study were aged 18 to 30 years when they completed the baseline graded exercise test protocol in 1985 to 1986 and have since undergone follow-up examinations biannually and every 2 to 5 years. Data were collected through August 31, 2020, and were analyzed in October 2022. Exposures: Cardiorespiratory fitness was estimated from a symptom-limited, maximal graded exercise test protocol conducted at baseline and at year 7 and year 20 follow-up examinations. Main Outcomes and Measures: All-cause mortality and combined fatal and nonfatal CVD events were obtained since year 20 of follow-up examinations through August 31, 2020. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) for each primary exposure with each outcome. Results: A total of 4808 participants (mean [SD] age at baseline, 24.8 [3.7] years; 2670 females [56%]; 2438 Black individuals [51%]) were included in the sample. During 68 751 person-years of follow-up, there were 302 deaths (6.3%) and 274 CVD events (5.7%) since year 20. Every 1-minute increment in cardiorespiratory fitness at baseline was associated with a lower risk of all-cause mortality in females (HR, 0.73; 95% CI, 0.64-0.82) and males (HR, 0.87; 95% CI, 0.80-0.96). Every 5% increment in cardiorespiratory fitness retained through year 20 was associated with a lower risk of all-cause mortality (HR, 0.89; 95% CI, 0.79-0.99), but no evidence of effect modification by race or sex was found. Every 1-minute increment in cardiorespiratory fitness at baseline was associated with a lower risk of fatal or nonfatal CVD (HR, 0.89; 95% CI, 0.82-0.96), and the estimated HR per 5% increment in cardiorespiratory fitness retained throughout midlife was 0.89 (95% CI, 0.78-1.00), with no evidence for interaction by race or sex. Conclusions and Relevance: This cohort study found that higher early-adulthood cardiorespiratory fitness and greater retention of early-adulthood cardiorespiratory fitness throughout midlife were associated with a lower risk of premature death and CVD events. Additional research is needed to clarify the association of cardiorespiratory fitness timing across the life course with risk of clinical outcomes.

Screen Time from Adolescence to Adulthood and Cardiometabolic Disease: a Prospective Cohort Study.

BACKGROUND: Previous studies have analyzed the relationship between screen time and cardiometabolic disease risk factors among adolescents, but few have examined the longitudinal effects of screen time on cardiometabolic health into adulthood using nationally representative data. OBJECTIVE: To determine prospective associations between screen time and later cardiometabolic disease over a 24-year period using a nationally representative adolescent cohort. DESIGN: Longitudinal prospective cohort data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) collected from 1994 to 2018. PARTICIPANTS: Adolescents aged 11-18 years old at baseline (1994-1995) followed for 24 years. MAIN MEASURES: Predictors: screen time (five repeated measures of self-reported television and video watching from adolescence to adulthood). OUTCOMES: Five repeated measures of body mass index (BMI); two repeated measures of waist circumference, hypertension, hyperlipidemia, and diabetes collected at 15- and 24-year follow-up exams. KEY RESULTS: For the 7105 adolescents in the sample (49.7% female, 35.0% non-white), the baseline adolescent average screen time per day was 2.86 ± 0.08 hours per day, which generally declined through 24-year follow-up. Average BMI at baseline was 22.57 ± 0.13 kg/m2, which increased to 30.27 ± 0.18 kg/m2 through follow-up. By 24-year follow-up, 43.4% of participants had obesity, 8.4% had diabetes, 31.8% had hypertension, and 14.9% had hyperlipidemia. In mixed-effects generalized linear models, each additional hour of screen time per day was associated with 0.06 (95% CI 0.04-0.09) within-person increase in BMI. Each additional hour of screen time per day was associated with higher within-person odds of high waist circumference (AOR 1.17, 95% CI 1.09-1.26), obesity (AOR 1.09, 95% CI 1.03-1.15), and diabetes (AOR 1.17, 95% CI 1.07-1.28). Screen time was not significantly associated with hypertension or hyperlipidemia. CONCLUSIONS: In this prospective cohort study, higher screen time in adolescence was associated with higher odds of select indicators of cardiometabolic disease in adulthood.

Prospective Association of Daily Steps With Cardiovascular Disease: A Harmonized Meta-Analysis.

BACKGROUND: Taking fewer than the widely promoted "10 000 steps per day" has recently been associated with lower risk of all-cause mortality. The relationship of steps and cardiovascular disease (CVD) risk remains poorly described. A meta-analysis examining the dose-response relationship between steps per day and CVD can help inform clinical and public health guidelines. METHODS: Eight prospective studies (20 152 adults [ie, ≥18 years of age]) were included with device-measured steps and participants followed for CVD events. Studies quantified steps per day and CVD events were defined as fatal and nonfatal coronary heart disease, stroke, and heart failure. Cox proportional hazards regression analyses were completed using study-specific quartiles and hazard ratios (HR) and 95% CI were meta-analyzed with inverse-variance-weighted random effects models. RESULTS: The mean age of participants was 63.2±12.4 years and 52% were women. The mean follow-up was 6.2 years (123 209 person-years), with a total of 1523 CVD events (12.4 per 1000 participant-years) reported. There was a significant difference in the association of steps per day and CVD between older (ie, ≥60 years of age) and younger adults (ie, <60 years of age). For older adults, the HR for quartile 2 was 0.80 (95% CI, 0.69 to 0.93), 0.62 for quartile 3 (95% CI, 0.52 to 0.74), and 0.51 for quartile 4 (95% CI, 0.41 to 0.63) compared with the lowest quartile. For younger adults, the HR for quartile 2 was 0.79 (95% CI, 0.46 to 1.35), 0.90 for quartile 3 (95% CI, 0.64 to 1.25), and 0.95 for quartile 4 (95% CI, 0.61 to 1.48) compared with the lowest quartile. Restricted cubic splines demonstrated a nonlinear association whereby more steps were associated with decreased risk of CVD among older adults. CONCLUSIONS: For older adults, taking more daily steps was associated with a progressively decreased risk of CVD. Monitoring and promoting steps per day is a simple metric for clinician-patient communication and population health to reduce the risk of CVD.

Quantifying physical activity across the midlife: Does consideration of perceived exertion matter?

Many questionnaires ascertain physical activity (PA) frequency, duration, and intensity to benchmark achievement of PA recommendations. However, most scoring algorithms utilize absolute intensity estimates when exertion may be influenced by age or health characteristics. This study quantified PA estimates with and without adjustments for perceived exertion and evaluated if differences were associated with individual-level characteristics. Women (n = 2,711) in the United States from the Study of Women's Health Across the Nation who completed ≥ 3 Kaiser Physical Activity Surveys (KPAS) across 8 biennial visits were included (baseline age: 46.4 ± 2.7 years). KPAS responses about activity mode and exertion were converted to metabolic equivalent of a task (METs) using the 2011 Compendium of Physical Activities to estimate absolute and perceived intensity-adjusted METs. Repeated measures (linear mixed effects) regression models were used to examine associations of sociodemographic and health-related characteristics with change in the difference between absolute MET estimates and perceived intensity-adjusted MET estimates. Older age (p < 0.001), Chinese (p < 0.001) and Japanese (p = 0.01) ethnicity, and current smoking (p = 0.001) were associated with positive differences between absolute and perceived intensity-adjusted MET estimates, which is suggestive of lower perceived-intensity physical activity. However, for most participants, absolute intensity-based estimates closely approximated perceived intensity-adjusted estimates over time. Traditional PA scoring techniques using absolute intensity estimates only may provide sufficient estimates of PA in longitudinal cohort studies of mid-life and older adult women.

Daily and hourly patterns of physical activity and sedentary behavior of older adults: Atherosclerosis risk in communities (ARIC) study.

This cross-sectional study of older adults ≥ 65 years describes daily and hourly patterns of accelerometer-derived steps, sedentary, and physical activity behaviors and examines differences by day of the week and sociodemographic and health-related factors to identify time-use patterns. Data were from 459 Atherosclerosis Risk in Communities (ARIC) study participants (60% female; mean ± SD age = 78.3 ± 4.6 years; 20% Black) who wore a hip accelerometer ≥ 4 of 7 days, for ≥ 10 h/day in 2016. We used linear mixed models to examine daily patterns of steps, sedentary, low light, high light, and moderate-to-vigorous intensity physical activity (MVPA). Differences by sex, median age (