Validity and reproducibility of the PERSIAN Cohort food frequency questionnaire: assessment of major dietary patterns.

BACKGROUND: Dietary patterns, encompassing an overall view of individuals' dietary intake, are suggested as a suitable means of assessing nutrition's role in chronic disease development. The aim of this study was to evaluate the validity and reproducibility of a food frequency questionnaire (FFQ) designed for use in the Prospective Epidemiological Research Studies in IrAN (PERSIAN), by comparing major dietary patterns assessed by the FFQ with a reference method. METHODS: Study participants included men and women who enrolled in the PERSIAN Cohort Study at seven of the eighteen centers. These centers were chosen to include dietary variations observed among the different Iranian ethnic populations. Two FFQ were completed for each participant over a one-year study period (FFQ1 upon enrollment and FFQ2 at the end of the study), with 24 interviewer-administered 24-hour dietary recalls (24 h) being completed monthly in between. Spearman correlation coefficients (SCC) were used comparing FFQs 1 and 2 to the 24 h to assess validity, while FFQ1 was compared to FFQ2 to assess reproducibility of the questionnaire. RESULTS: Three major dietary patterns-Healthy, Low Protein/High Carb and Unhealthy-were identified, accounting for 70% of variance in the study population. Corrected SCC ranged from 0.31 to 0.61 in the validity and from 0.34 to 0.57 in reproducibility analyses, with the first two patterns, which accounted for over 50% of population variance, correlated at above 0.5 in both parameters, showing acceptable findings. CONCLUSIONS: The PERSIAN Cohort FFQ is suitable for identification of major dietary patterns in the populations it is used for, in order to assess diet-disease relationships.

Different operationalizations of the 2018 WCRF/AICR cancer prevention recommendations and risk of cancer.

BACKGROUND: The standardized scoring system assessing adherence to the 2018 World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) cancer prevention recommendations assigns equal weight for each recommendation, thereby giving higher weight to dietary factors collectively (5 points) than adiposity (1 point) and physical activity (1 point). An alternative score assigning equal weights to the adiposity, physical activity, alcohol, and other dietary (composite) recommendations may better predict cancer associations. METHODS: We examined associations between standardized and alternative scores with cancer risk in two US prospective cohorts. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression. RESULTS: During 28 years of follow-up, 16,342 incident cancer cases in women and 8729 cases in men occurred. Individuals in the highest versus lowest quintile of the standardized score had a reduced overall cancer risk (women: HR = 0.89, 95% CI: 0.85, 0.94; men: HR = 0.87, 95% CI: 0.81, 0.94). Results were slightly stronger for the alternative score (women: HR = 0.83, 95% CI: 0.79, 0.87; men: HR = 0.81, 95% CI: 0.75, 0.86). Similar patterns were observed for obesity-related, alcohol-related, smoking-related, and digestive system cancers. CONCLUSIONS: Greater adherence to the WCRF/AICR cancer prevention recommendations was associated with lower cancer risk. A score assigning equal weights to the adiposity, physical activity, alcohol, and all remaining diet components yielded stronger associations than the standardized score.

Validation of the Rapid Prime Diet Quality Score Screener (rPDQS), A Brief Dietary Assessment Tool With Simple Traffic Light Scoring.

BACKGROUND: Dietary pattern is a determinant of chronic disease, but nonregistered dietitian nutritionist (non-RDN) clinicians rarely assess diet because of barriers such as time constraints and lack of valid, brief diet quality assessment tools. OBJECTIVE: The study aimed to evaluate the relative validity of a brief diet quality screener using both a numeric scoring system and a simple traffic light scoring system. DESIGN: A cross-sectional study was conducted using the CloudResearch online platform to compare participants' responses to the 13-item rapid Prime Diet Quality Score screener (rPDQS) and the Automated Self-Administered 24-hour (ASA24) Dietary Assessment Tool. PARTICIPANTS/SETTING: The study was conducted in July and August 2021 and included 482 adults ≥18 years of age or older sampled to be representative of the US population. MAIN OUTCOME MEASURES: All participants completed the rPDQS and an ASA24; of these, 190 completed a second ASA24 and rPDQS. Responses to rPDQS items were coded using both traffic light (eg, green = healthiest intake, red = least healthy intake) and numeric (eg, consume < 1 time a week, consume ≥ 2 times per day) scoring methods and were compared with food group equivalents and Healthy Eating Index-2015 (HEI-2015) scores estimated from ASA24s. STATISTICAL ANALYSES: Deattenuated Pearson correlation coefficients were calculated to account for within-person variation in 24-hour diet recalls. RESULTS: Overall, 49% of participants were female, 62% were ≥35 years, and 66% were non-Hispanic White, 13% non-Hispanic Black, 16% Hispanic/Latino, and 5% Asian. For both food groups to encourage (eg, vegetables, whole grains) and to consume in moderation (eg, processed meats, sweets), there were statistically significant associations with intakes assessed by rPDQS, using both traffic light and numeric scoring methods. Total rPDQS scores correlated with the HEI-2015, r = 0.75 (95% confidence interval [CI] = 0.65, 0.82). CONCLUSIONS: The rPDQS is a valid, brief diet quality screener that identifies clinically relevant patterns of food intake. Future research is needed to test whether the simple traffic light scoring system is an effective tool that can help non-RDN clinicians provide brief dietary counseling or make referrals to registered dietitian nutritionists, as needed.

Excess mortality associated with elevated body weight in the USA by state and demographic subgroup: A modelling study.

Background: The obesity epidemic in the USA continues to grow nationwide. Although excess weight-related mortality has been studied in general, less is known about how it varies by demographic subgroup within the USA. In this study we estimated excess mortality associated with elevated body weight nationally and by state and subgroup. Methods: We developed a nationally-representative microsimulation (individual-level) model of US adults between 1999 and 2016, based on risk factor data from 6,002,012 Behavioral Risk Factor Surveillance System respondents. Prior probability distributions for hazard ratios relating body-mass index (BMI) to mortality were informed by a global pooling dataset. Individual-level mortality risks were modelled accounting for demographics, smoking history, and BMI adjusted for self-report bias. We calibrated the model to empirical all-cause mortality rates from CDC WONDER by state and subgroup, and assessed the predictive accuracy of the model using a random sample of data withheld from model fitting. We simulated counterfactual scenarios to estimate excess mortality attributable to different levels of excess weight and smoking history. Findings: We estimated that excess weight was responsible for more than 1300 excess deaths per day (nearly 500,000 per year) and a loss in life expectancy of nearly 2·4 years in 2016, contributing to higher excess mortality than smoking. Relative excess mortality rates were nearly twice as high for women compared to men in 2016 (21·9% vs 13·9%), and were higher for Black non-Hispanic adults. By state, overall excess weight-related life expectancy loss ranged from 1·75 years (95% UI 1·57-1·94) in Colorado to 3·18 years (95% UI 2·86-3·51) in Mississippi. Interpretation: Excess weight has substantial impacts on mortality in the USA, with large disparities by state and subgroup. Premature mortality will likely increase as obesity continues to rise. Funding: The JPB Foundation, NIH, CDC.

Measurement Error Affecting Web- and Paper-Based Dietary Assessment Instruments: Insights From the Multi-Cohort Eating and Activity Study for Understanding Reporting Error.

Few biomarker-based validation studies have examined error in online self-report dietary assessment instruments, and food records (FRs) have been considered less than food frequency questionnaires (FFQs) and 24-hour recalls (24HRs). We investigated measurement error in online and paper-based FFQs, online 24HRs, and paper-based FRs in 3 samples drawn primarily from 3 cohorts, comprising 1,393 women and 1,455 men aged 45-86 years. Data collection occurred from January 2011 to October 2013. Attenuation factors and correlation coefficients between reported and true usual intake for energy, protein, sodium, potassium, and respective densities were estimated using recovery biomarkers. Across studies, average attenuation factors for energy were 0.07, 0.07, and 0.19 for a single FFQ, 24HR, and FR, respectively. Correlation coefficients for energy were 0.24, 0.23, and 0.40, respectively. Excluding energy, the average attenuation factors across nutrients and studies were 0.22 for a single FFQ, 0.22 for a single 24HR, and 0.51 for a single FR. Corresponding correlation coefficients were 0.31, 0.34, and 0.53, respectively. For densities (nutrient expressed relative to energy), the average attenuation factors across studies were 0.37, 0.17, and 0.50, respectively. The findings support prior research suggesting different instruments have unique strengths that should be leveraged in epidemiologic research.

Sustainable food systems and nutrition in the 21st century: a report from the 22nd annual Harvard Nutrition Obesity Symposium.

Food systems are at the center of a brewing storm consisting of a rapidly changing climate, rising hunger and malnutrition, and significant social inequities. At the same time, there are vast opportunities to ensure that food systems produce healthy and safe food in equitable ways that promote environmental sustainability, especially if the world can come together at the UN Food Systems Summit in late 2021 and make strong and binding commitments toward food system transformation. The NIH-funded Nutrition Obesity Research Center at Harvard and the Harvard Medical School Division of Nutrition held their 22nd annual Harvard Nutrition Obesity Symposium entitled "Global Food Systems and Sustainable Nutrition in the 21st Century" in June 2021. This article presents a synthesis of this symposium and highlights the importance of food systems to addressing the burden of malnutrition and noncommunicable diseases, climate change, and the related economic and social inequities. Transformation of food systems is possible, and the nutrition and health communities have a significant role to play in this transformative process.

Diet cost and quality using the Healthy Eating Index-2015 in adults from urban and rural areas of Mexico.

OBJECTIVE: To assess the association between diet cost and quality by place of residence. DESIGN: We analysed cross-sectional data of the National Health and Nutrition Survey-2012. Diet cost was estimated by linking dietary data, obtained from a 7-d SFFQ, with municipality food prices, which were derived from a national expenditure survey. Diet quality was assessed using the Healthy Eating Index-2015 (HEI-2015). Association between quintiles of diet cost and HEI-2015 was assessed using linear regression analysis. SETTINGS: Mexico. PARTICIPANTS: 2438 adults (18-59 years). RESULTS: Diet cost was positively associated with diet quality (HEI-2015) in urban but not in rural areas. Compared with quintile (Q1) of cost, the increment in diet quality score was 1·17 (95 % CI -0·06, 4·33) for Q2, 2·14 (95 % CI -0·06, 4·33) for Q3, 4·70 (95 % CI 2·62, 6·79) for Q4 and 6·34 (95 % CI 4·20, 8·49) for Q5 (P-trend < 0·001). Individuals in rural v. urban areas on average have higher quality diets at lower cost with higher intakes of whole grains and beans and lower intakes of Na, added sugars and saturated fats. Living in the South, being indigenous and having low socio-economic status were also associated with higher quality diets. CONCLUSIONS: Diet cost was positively associated with diet quality, but only in urban areas. Further studies are needed to understand the relation between diet cost and quality in rural areas. To improve overall diet quality in Mexico, strategies that aim to reduce the cost of high-quality diets should consider the heterogeneity by place of residence.

Exploration of Machine Learning and Statistical Techniques in Development of a Low-Cost Screening Method Featuring the Global Diet Quality Score for Detecting Prediabetes in Rural India.

BACKGROUND: The prevalence of type 2 diabetes has increased substantially in India over the past 3 decades. Undiagnosed diabetes presents a public health challenge, especially in rural areas, where access to laboratory testing for diagnosis may not be readily available. OBJECTIVES: The present work explores the use of several machine learning and statistical methods in the development of a predictive tool to screen for prediabetes using survey data from an FFQ to compute the Global Diet Quality Score (GDQS). METHODS: The outcome variable prediabetes status (yes/no) used throughout this study was determined based upon a fasting blood glucose measurement ≥100 mg/dL. The algorithms utilized included the generalized linear model (GLM), random forest, least absolute shrinkage and selection operator (LASSO), elastic net (EN), and generalized linear mixed model (GLMM) with family unit as a (cluster) random (intercept) effect to account for intrafamily correlation. Model performance was assessed on held-out test data, and comparisons made with respect to area under the receiver operating characteristic curve (AUC), sensitivity, and specificity. RESULTS: The GLMM, GLM, LASSO, and random forest modeling techniques each performed quite well (AUCs >0.70) and included the GDQS food groups and age, among other predictors. The fully adjusted GLMM, which included a random intercept for family unit, achieved slightly superior results (AUC of 0.72) in classifying the prediabetes outcome in these cluster-correlated data. CONCLUSIONS: The models presented in the current work show promise in identifying individuals at risk of developing diabetes, although further studies are necessary to assess other potentially impactful predictors, as well as the consistency and generalizability of model performance. In addition, future studies to examine the utility of the GDQS in screening for other noncommunicable diseases are recommended.

Transdisciplinary research and clinical priorities for better health.

Modern medicine makes it possible for many people to live with multiple chronic diseases for decades, but this has enormous social, financial, and environmental consequences. Preclinical, epidemiological, and clinical trial data have shown that many of the most common chronic diseases are largely preventable with nutritional and lifestyle interventions that are targeting well-characterized signaling pathways and the symbiotic relationship with our microbiome. Most of the research priorities and spending for health are focused on finding new molecular targets for the development of biotech and pharmaceutical products. Very little is invested in mechanism-based preventive science, medicine, and education. We believe that overly enthusiastic expectations regarding the benefits of pharmacological research for disease treatment have the potential to impact and distort not only medical research and practice but also environmental health and sustainable economic growth. Transitioning from a primarily disease-centered medical system to a balanced preventive and personalized treatment healthcare system is key to reduce social disparities in health and achieve financially sustainable, universal health coverage for all. In this Perspective article, we discuss a range of science-based strategies, policies, and structural reforms to design an entire new disease prevention-centered science, educational, and healthcare system that maximizes both human and environmental health.

Does the High Prevalence of Vitamin D Deficiency in African Americans Contribute to Health Disparities?

African Americans have higher incidence of, and mortality from, many health-related problems than European Americans. They also have a 15 to 20-fold higher prevalence of severe vitamin D deficiency. Here we summarize evidence that: (i) this health disparity is partly due to insufficient vitamin D production, caused by melanin in the skin blocking the UVB solar radiation necessary for its synthesis; (ii) the vitamin D insufficiency is exacerbated at high latitudes because of the combination of dark skin color with lower UVB radiation levels; and (iii) the health of individuals with dark skin can be markedly improved by correcting deficiency and achieving an optimal vitamin D status, as could be obtained by supplementation and/or fortification. Moderate-to-strong evidence exists that high 25-hydroxyvitamin D levels and/or vitamin D supplementation reduces risk for many adverse health outcomes including all-cause mortality rate, adverse pregnancy and birth outcomes, cancer, diabetes mellitus, Alzheimer's disease and dementia, multiple sclerosis, acute respiratory tract infections, COVID-19, asthma exacerbations, rickets, and osteomalacia. We suggest that people with low vitamin D status, which would include most people with dark skin living at high latitudes, along with their health care provider, consider taking vitamin D3 supplements to raise serum 25-hydroxyvitamin D levels to 30 ng/mL (75 nmol/L) or possibly higher.

Comprehensive Assessment of Diet Quality and Risk of Precursors of Early-Onset Colorectal Cancer.

BACKGROUND: The role of poor diet quality in the rising incidence of colorectal cancer (CRC) diagnosed younger than age 50 years has not been explored. Based on molecular features of early-onset CRC, early-onset adenomas are emerging surrogate endpoints. METHODS: In a prospective cohort study (Nurses' Health Study II), we evaluated 2 empirical dietary patterns (Western and prudent) and 3 recommendation-based indexes (Dietary Approaches to Stop Hypertension [DASH], Alternative Mediterranean Diet [AMED], and Alternative Healthy Eating Index [AHEI]-2010) with risk of early-onset adenoma overall and by malignant potential (high-risk: ≥1 cm, tubulovillous or villous histology, high-grade dysplasia, or ≥3 adenomas), among 29 474 women with 1 or more lower endoscopy before age 50 years (1991-2011). Multivariable logistic regressions were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: We documented 1157 early-onset adenomas with 375 at high risk. Western diet was positively associated, whereas prudent diet, DASH, AMED, and AHEI-2010 were inversely associated with risk of early-onset adenoma. The associations were largely confined to high-risk adenomas (the highest vs lowest quintile: Western, OR = 1.67, 95% CI = 1.18 to 2.37; prudent, OR = 0.69, 95% CI = 0.48 to 0.98; DASH, OR = 0.65, 95% CI = 0.45 to 0.93; AMED, OR = 0.55, 95% CI = 0.38 to 0.79; AHEI-2010, OR = 0.71, 95% CI = 0.51 to 1.01; all Ptrend ≤ .03), driven by those identified in the distal colon and rectum (all Ptrend ≤ .04, except AMED: Ptrend = .14). CONCLUSION: Poor diet quality was associated with an increased risk of early-onset distal and rectal adenomas of high malignant potential. These findings provide preliminary but strong support to the role of diet in early-onset CRC.

The vitamin D for COVID-19 (VIVID) trial: A pragmatic cluster-randomized design.

OBJECTIVES: To determine the effect of vitamin D supplementation on disease progression and post-exposure prophylaxis for COVID-19 infection. We hypothesize that high-dose vitamin D3 supplementation will reduce risk of hospitalization/death among those with recently diagnosed COVID-19 infection and will reduce risk of COVID-19 infection among their close household contacts. METHODS: We report the rationale and design of a planned pragmatic, cluster randomized, double-blinded trial (N = 2700 in total nationwide), with 1500 newly diagnosed individuals with COVID-19 infection, together with up to one close household contact each (~1200 contacts), randomized to either vitamin D3 (loading dose, then 3200 IU/day) or placebo in a 1:1 ratio and a household cluster design. The study duration is 4 weeks. The primary outcome for newly diagnosed individuals is the occurrence of hospitalization and/or mortality. Key secondary outcomes include symptom severity scores among cases and changes in the infection (seroconversion) status for their close household contacts. Changes in vitamin D 25(OH)D levels will be assessed and their relation to study outcomes will be explored. CONCLUSIONS: The proposed pragmatic trial will allow parallel testing of vitamin D3 supplementation for early treatment and post-exposure prophylaxis of COVID-19. The household cluster design provides a cost-efficient approach to testing an intervention for reducing rates of hospitalization and/or mortality in newly diagnosed cases and preventing infection among their close household contacts.

Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations.

While dietary factors are important modifiable risk factors for type 2 diabetes (T2D), the causal role of carbohydrate quality in nutrition remains controversial. Dietary glycemic index (GI) and glycemic load (GL) have been examined in relation to the risk of T2D in multiple prospective cohort studies. Previous meta-analyses indicate significant relations but consideration of causality has been minimal. Here, the results of our recent meta-analyses of prospective cohort studies of 4 to 26-y follow-up are interpreted in the context of the nine Bradford-Hill criteria for causality, that is: (1) Strength of Association, (2) Consistency, (3) Specificity, (4) Temporality, (5) Biological Gradient, (6) Plausibility, (7) Experimental evidence, (8) Analogy, and (9) Coherence. These criteria necessitated referral to a body of literature wider than prospective cohort studies alone, especially in criteria 6 to 9. In this analysis, all nine of the Hill's criteria were met for GI and GL indicating that we can be confident of a role for GI and GL as causal factors contributing to incident T2D. In addition, neither dietary fiber nor cereal fiber nor wholegrain were found to be reliable or effective surrogate measures of GI or GL. Finally, our cost-benefit analysis suggests food and nutrition advice favors lower GI or GL and would produce significant potential cost savings in national healthcare budgets. The high confidence in causal associations for incident T2D is sufficient to consider inclusion of GI and GL in food and nutrient-based recommendations.

Bicycle Facilities Safest from Crime and Crashes: Perceptions of Residents Familiar with Higher Crime/Lower Income Neighborhoods in Boston.

While studies of bicyclist's perceptions of crime and crash safety exist, it is also important to ask lower-income predominantly-minority residents what bicycle-route surface or context they perceive as safest from crime and crashes. With their insights, their chosen bike environments could be in engineering guidelines and built in their neighborhoods to improve residents' health and lessen their risk of exposure to crime or crashing. This study involved two populations in Boston: (a) community-sense participants (eight groups-church/YMCA n = 116); and (b) street-sense participants (five groups-halfway house/homeless shelter/gang members n = 96). Participants ranked and described what they saw in 32 photographs of six types of bicycle environments. Quantitative data (Likert Scale 0⁻6 with 0 being low risk of crime/crash) involved regression analysis to test differences. Qualitative comments were categorized into 55 themes for surface or context and if high or low in association with crime or crashes. For crime, two-way cycle tracks had a significantly lower score (safest) than all others (2.35; p < 0.01) and share-use paths had a significantly higher score (least safe) (3.39; p < 0.01). For crashes, participants rated shared-use paths as safest (1.17) followed by two-way cycle tracks (1.68), one-way cycle tracks (2.95), bike lanes (4.06), sharrows (4.17), and roads (4.58), with a significant difference for any two groups (p < 0.01) except between bike lane and sharrow (p = 0.9). Street-sense participants ranked all, except shared-use paths, higher for crime and crash. For surface, wide two-way cycle tracks with freshly painted lines, stencils, and arrows were low risk for crime and a cycle track's median, red color, stencils, and arrows low risk for crash. For context, clean signs, balconies, cafes, street lights, no cuts between buildings, and flowers were low risk for crime and witnesses, little traffic, and bike signals low risk for crash. As bicycle design guidelines and general Crime Perception Through Environmental Design (CPTED) principles do not include these details, perhaps new guidelines could be written.

Effect of Monthly High-Dose Vitamin D on Mental Health in Older Adults: Secondary Analysis of a RCT.

OBJECTIVES: To test the effect of monthly high-dose vitamin D supplementation on mental health in pre-frail older adults. DESIGN: Ancillary study of a 1-year double-blind randomized clinical trial conducted in Zurich, Switzerland. SETTING AND PARTICIPANTS: A total of 200 community-dwelling adults 70 years and older with a prior fall event in the last year. Participants were randomized to receive 24 000 IU vitamin D3 (considered standard of care), 60 000 IU vitamin D3 , or 24 000 IU vitamin D3 plus 300 µg calcifediol per month. MEASURES: The primary end point was the Mental Component Summary (MCS) of the SF-36. Secondary end points were the SF-36 Mental Health (MH) subscale and the Geriatric Depression Scale (GDS-15). RESULTS: Participants' mean age was 78 years (67% women), and 58% were vitamin D deficient (<20 ng/mL). Over time, primary and secondary end points did not differ significantly among the three treatment groups or in subgroups by vitamin D status at baseline. Given the lack of a true placebo group, we explored in a predefined observational analysis the change in mental health scales by achieved 25(OH)D levels at 12 months. After adjusting for confounders, participants achieving the highest 25(OH)D quartile (Q) at 12 months (44.7-98.9 ng/mL) had the greatest improvements in MCS (Q4 = 0.79 vs Q1 = -2.9; p = .03) and MH scales (Q4 = 2.54 vs Q1 = -3.07; p = .03); these associations were strongest among participants who were vitamin D deficient at baseline. No association was found for GDS (p = .89). CONCLUSIONS: For mental health, our study suggests no benefit of higher monthly doses of vitamin D3 compared with the standard monthly dose of 24 000 IU. However, irrespective of vitamin D treatment dose, achieving higher 25(OH)D levels at 12-month follow-up was associated with a small, clinically uncertain but statistically significant improvement in mental health scores.

Harnessing University Strengths in Multisectoral Collaborations for Planetary Health.

Although significant achievements in human health have been made globally, progress has been made possible, in part, through unconstrained use of natural resources. As the health of our planet worsens, human health is also endangered. Scholars and policymakers from diverse disciplines highlighted complex, multisectoral approaches for addressing poor dietary intake, over- and undernutrition, and chronic diseases in sub-Saharan Africa at the Agriculture, Nutrition, Health, and the Environment in Africa Conference held at Harvard University on 6-7 November 2017. A planetary health approach to addressing these challenges offers a unique opportunity to advance solutions for environmental and social factors that influence agriculture, nutrition, and overall health in the larger context of rapid population growth and transitions in food systems and livelihoods. This paper outlines 3 key avenues for universities to promote science at the intersection of public health and the environment in sub-Saharan Africa.

Associations of Sedentary Time with Energy Expenditure and Anthropometric Measures.

PURPOSE: To investigate associations between accelerometer-determined sedentary time (ST) in prolonged (≥30 min) and nonprolonged (<30 min) bouts with physical activity energy expenditure (PAEE) from doubly labeled water. Additionally, associations between ST and body mass index (BMI) and waist circumference were examined. METHODS: Data from 736 women and 655 men age 43 to 82 yr were analyzed. Participants wore the Actigraph GT3X for 7 d on two occasions approximately 6 months apart, and the average of the measurements was used. Physical activity energy expenditure was estimated by subtracting resting metabolic rate and the thermic effect of food from doubly labeled water estimates of total daily energy expenditure. Cross-sectional associations were analyzed using isotemporal substitution modeling. RESULTS: Reallocation of prolonged ST to nonprolonged was not associated with increased PAEE and only significantly associated with lower BMI (ß = -0.57 kg·m; 95% confidence interval, -0.94 to -0.20) and waist circumference (ß = -1.61 cm; 95% confidence interval, -2.61 to -0.60) in men. Replacing either type of ST with light or moderate-to-vigorous physical activity was significantly associated with higher PAEE, and lower BMI and waist circumference in both women and men. CONCLUSIONS: Limiting time spent sedentary as well as decreasing ST accumulated in prolonged bouts may have beneficial effects on BMI and waist circumference. Replacing any type of ST with activities of light or higher intensity may also have a substantial impact on PAEE.

Physical Activity Assessment with the ActiGraph GT3X and Doubly Labeled Water.

PURPOSE: To compare the degree to which four accelerometer metrics-total activity counts per day (TAC per day), steps per day (steps per day), physical activity energy expenditure (PAEE) (kcal·kg·d), and moderate- to vigorous-intensity physical activity (MVPA) (min·d)-were correlated with PAEE measured by doubly labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. METHODS: This analysis included 684 women and 611 men age 43 to 83 yr. Participants wore the Actigraph GT3X on the hip for 7 d twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. RESULTS: Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical axis counts. After adjusting for weight, age, accelerometer wear time, and fat free mass, the correlation between TAC per day based on triaxial counts and DLW-determined PAEE was 0.44 in women and 0.41 in men. Correlations for steps per day and accelerometer-estimated PAEE with DLW-determined PAEE were similar. After adjustment for within-person variation in DLW-determined PAEE, the correlations for TAC per day increased to 0.61 and 0.49, respectively. Correlations between MVPA and DLW-determined PAEE were lower, particularly for modified bouts of ≥10 min. CONCLUSIONS: Accelerometer measures that represent total activity volume, including TAC per day, steps per day, and PAEE, were more highly correlated with DLW-determined PAEE than MVPA using traditional thresholds and should be considered by researchers seeking to reduce accelerometer data to a single metric.