Lijing L. Yan

Self-reported and measured sleep duration: how similar are they?

Background: Recent epidemiologic studies have found that self-reported duration of sleep is associated with obesity, diabetes, hypertension, and mortality. The extent to which self reports of sleep duration are similar to objective measures and whether individual characteristics influence the degree of similarity are not known. Methods: Eligible participants at the Chicago site of the Coronary Artery Risk Development in Young Adults Study were invited to participate in a 2003–2005 ancillary sleep study; 82% (n = 669) agreed. Sleep measurements collected in 2 waves included 3 days each of wrist actigraphy, a sleep log, and questions about usual sleep duration. We estimate the average difference and correlation between subjectively and objectively measured sleep by using errors-in-variables regression models. Results: Average measured sleep was 6 hours, whereas the average from subjective reports was 6.8 hours. Subjective reports increased on average by 34 minutes for each additional hour of measured sleep. Overall, the correlation between reported and measured sleep duration was 0.47. Our model suggests that persons sleeping 5 hours over-reported their sleep duration by 1.2 hours, and those sleeping 7 hours over-reported by 0.4 hours. The correlations and average differences between self-reports and measured sleep varied by health, sociodemographic, and sleep characteristics. Conclusion: In a population-based sample of middle-aged adults, subjective reports of habitual sleep are moderately correlated with actigraph-measured sleep, but are biased by systematic over-reporting. The true associations between sleep duration and health may differ from previously reported associations between self-reported sleep and health.Recent epidemiologic studies have found that sleep duration is associated with obesity, diabetes, hypertension and mortality. These studies have used self-reported habitual sleep duration, which has not been well validated. We model the extent to which self-reported habitual sleep reflects average objectively measured sleep. Eligible participants at the Chicago site of Coronary Artery Risk Development in Young Adults Study were invited to participate in a 2003-2004 ancillary sleep study; 82% (n=669) agreed. Sleep measurements collected in two waves included: 3-days of wrist actigraphy, a sleep log, and standard questions about usual sleep duration. Average measured sleep was 6 hours, and subjective reports averaged 0.80 hours longer than measured sleep. Subjective reports were not well calibrated, increasing on average by 31 minutes for each additional hour of measured sleep. Our model suggests that persons sleeping 5 and 7 hours over-reported, on average, by 1.3 and 0.3 hours respectively. Overall, there was a correlation of 0.45 between reported and measured sleep duration. The extent of overestimation, calibration and correlation varied by personal and sleep characteristics. Although asking about sleep duration seems uncomplicated, the correlation between self-reported and objectively-measured sleep in this population was moderate and systematically biased.

Cause-specific mortality for 240 causes in China during 1990–2013: a systematic subnational analysis for the Global Burden of Disease Study 2013

BACKGROUND China has experienced a remarkable epidemiological and demographic transition during the past three decades. Far less is known about this transition at the subnational level. Timely and accurate assessment of the provincial burden of disease is needed for evidence-based priority setting at the local level in China. METHODS Following the methods of the Global Burden of Disease Study 2013 (GBD 2013), we have systematically analysed all available demographic and epidemiological data sources for China at the provincial level. We developed methods to aggregate county-level surveillance data to inform provincial-level analysis, and we used local data to develop specific garbage code redistribution procedures for China. We assessed levels of and trends in all-cause mortality, causes of death, and years of life lost (YLL) in all 33 province-level administrative units in mainland China, all of which we refer to as provinces, for the years between 1990 and 2013. FINDINGS All provinces in mainland China have made substantial strides to improve life expectancy at birth between 1990 and 2013. Increases ranged from 4.0 years in Hebei province to 14.2 years in Tibet. Improvements in female life expectancy exceeded those in male life expectancy in all provinces except Shanghai, Macao, and Hong Kong. We saw significant heterogeneity among provinces in life expectancy at birth and probability of death at ages 0-14, 15-49, and 50-74 years. Such heterogeneity is also present in cause of death structures between sexes and provinces. From 1990 to 2013, leading causes of YLLs changed substantially. In 1990, 16 of 33 provinces had lower respiratory infections or preterm birth complications as the leading causes of YLLs. 15 provinces had cerebrovascular disease and two (Hong Kong and Macao) had ischaemic heart disease. By 2013, 27 provinces had cerebrovascular disease as the leading cause, five had ischaemic heart disease, and one had lung cancer (Hong Kong). Road injuries have become a top ten cause of death in all provinces in mainland China. The most common non-communicable diseases, including ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and cancers (liver, stomach, and lung), contributed much more to YLLs in 2013 compared with 1990. INTERPRETATION Rapid transitions are occurring across China, but the leading health problems and the challenges imposed on the health system by epidemiological and demographic change differ between groups of Chinese provinces. Localised health policies need to be implemented to tackle the diverse challenges faced by local health-care systems. FUNDING China National Science & Technology Pillar Program 2013 (2013BAI04B02) and Bill & Melinda Gates Foundation.

Association between sleep and blood pressure in midlife: the CARDIA sleep study.

BACKGROUND Epidemiological studies have reported an association between self-reported short sleep duration and high blood pressure (BP). Our objective was to examine both cross-sectional and longitudinal associations between objectively measured sleep and BP. METHODS This study is ancillary to the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study. Blood pressure was measured in 2000 and 2001 and in 2005 and 2006. Sleep was measured twice using wrist actigraphy for 3 consecutive days between 2003 and 2005. Sleep duration and sleep maintenance (a component of sleep quality) were calculated. Analyses included 578 African Americans and whites aged 33 to 45 years at baseline. Outcome measures were systolic BP (SBP) and diastolic BP (DBP) levels, 5-year change in BP, and incident hypertension. RESULTS After we excluded the patients who were taking antihypertensive medications and adjusted for age, race, and sex, shorter sleep duration and lower sleep maintenance predicted significantly higher SBP and DBP levels cross-sectionally as well as more adverse changes in SBP and DBP levels over 5 years (all P < .05). Short sleep duration also predicted significantly increased odds of incident hypertension (odds ratio, 1.37; 95% confidence interval, 1.05-1.78). Adjustment for 16 additional covariates, including snoring and daytime sleepiness, slightly attenuated the associations between sleep and BP. Sleep duration appeared to mediate the difference between African Americans and whites in DBP change over time (P = .02). CONCLUSION Reduced sleep duration and consolidation predicted higher BP levels and adverse changes in BP, suggesting the need for studies to investigate whether interventions to optimize sleep may reduce BP.

Cross-sectional and Longitudinal Associations Between Objectively Measured Sleep Duration and Body Mass Index The CARDIA Sleep Study

Numerous studies have found an association between shorter sleep duration and higher body mass index (BMI) in adults. Most previous studies have been cross-sectional and relied on self-reported sleep duration, which may not be very accurate. In the Coronary Artery Risk Development in Young Adults (CARDIA) Sleep Study (2000-2006), the authors examine whether objectively measured sleep is associated with BMI and change in BMI. They use several nights of wrist actigraphy to measure sleep among participants in an ongoing cohort of middle-aged adults. By use of linear regression, the authors examine whether average sleep duration or fragmentation is associated with BMI and 5-year change in BMI, adjusting for confounders. Among 612 participants, sleep duration averaged 6.1 hours and was grouped into 4 categories. Both shorter sleep and greater fragmentation were strongly associated with higher BMI in unadjusted cross-sectional analysis. After adjustment, BMI decreased by 0.78 kg/m(2) (95% confidence interval: -1.6, -0.002) for each increasing sleep category. The association was very strong in persons who reported snoring and weak in those who did not. There were no longitudinal associations between sleep measurements and change in BMI. The authors confirmed a cross-sectional association between sleep duration and BMI using objective sleep measures, but they did not find that sleep predicted change in BMI. The mechanism underlying the cross-sectional association is not clear.

Global Burden of Hypertension and Systolic Blood Pressure of at Least 110 to 115 mm Hg, 1990-2015

Importance Elevated systolic blood (SBP) pressure is a leading global health risk. Quantifying the levels of SBP is important to guide prevention policies and interventions. Objective To estimate the association between SBP of at least 110 to 115 mm Hg and SBP of 140 mm Hg or higher and the burden of different causes of death and disability by age and sex for 195 countries and territories, 1990-2015. Design A comparative risk assessment of health loss related to SBP. Estimated distribution of SBP was based on 844 studies from 154 countries (published 1980-2015) of 8.69 million participants. Spatiotemporal Gaussian process regression was used to generate estimates of mean SBP and adjusted variance for each age, sex, country, and year. Diseases with sufficient evidence for a causal relationship with high SBP (eg, ischemic heart disease, ischemic stroke, and hemorrhagic stroke) were included in the primary analysis. Main Outcomes and Measures Mean SBP level, cause-specific deaths, and health burden related to SBP (≥110-115 mm Hg and also ≥140 mm Hg) by age, sex, country, and year. Results Between 1990-2015, the rate of SBP of at least 110 to 115 mm Hg increased from 73 119 (95% uncertainty interval [UI], 67 949-78 241) to 81 373 (95% UI, 76 814-85 770) per 100 000, and SBP of 140 mm Hg or higher increased from 17 307 (95% UI, 17 117-17 492) to 20 526 (95% UI, 20 283-20 746) per 100 000. The estimated annual death rate per 100 000 associated with SBP of at least 110 to 115 mm Hg increased from 135.6 (95% UI, 122.4-148.1) to 145.2 (95% UI 130.3-159.9) and the rate for SBP of 140 mm Hg or higher increased from 97.9 (95% UI, 87.5-108.1) to 106.3 (95% UI, 94.6-118.1). Loss of disability-adjusted life-years (DALYs) associated with SBP of at least 110 to 115 mm Hg increased from 148 million (95% UI, 134-162 million) to 211 million (95% UI, 193-231 million), and for SBP of 140 mm Hg or higher, the loss increased from 5.2 million (95% UI, 4.6-5.7 million) to 7.8 million (95% UI, 7.0-8.7 million). The largest numbers of SBP-related deaths were caused by ischemic heart disease (4.9 million [95% UI, 4.0-5.7 million]; 54.5%), hemorrhagic stroke (2.0 million [95% UI, 1.6-2.3 million]; 58.3%), and ischemic stroke (1.5 million [95% UI, 1.2-1.8 million]; 50.0%). In 2015, China, India, Russia, Indonesia, and the United States accounted for more than half of the global DALYs related to SBP of at least 110 to 115 mm Hg. Conclusions and Relevance In international surveys, although there is uncertainty in some estimates, the rate of elevated SBP (≥110-115 and ≥140 mm Hg) increased substantially between 1990 and 2015, and DALYs and deaths associated with elevated SBP also increased. Projections based on this sample suggest that in 2015, an estimated 3.5 billion adults had SBP of at least 110 to 115 mm Hg and 874 million adults had SBP of 140 mm Hg or higher.

Consistently Stable or Decreased Body Mass Index in Young Adulthood and Longitudinal Changes in Metabolic Syndrome Components The Coronary Artery Risk Development in Young Adults Study

Background— Data are sparse regarding the association of stable body mass index (BMI) over the long term with metabolic syndrome components in young adults. Methods and Results— Participants in the Coronary Artery Risk Development in Young Adults Study, including white and black adults 18 to 30 years of age at the initial examination in 1985 to 1986, were stratified into groups by baseline BMI and change in BMI (stable/decreased, increased >2 kg/m2, or fluctuating) across all 6 examinations between years 0 and 15 of the study. Changes in metabolic syndrome components were compared between groups. Among 1358 men and 1321 women, 16.3% maintained a stable BMI, 73.9% had an increased BMI, and 9.8% had a fluctuating BMI. Over 15 years, participants with stable BMI had essentially unchanged levels of metabolic syndrome components, regardless of baseline BMI, whereas those with increased BMI had progressively worsening levels. For example, men with a baseline BMI of 20.0 to 24.9 kg/m2 and stable BMI during follow-up had a mean increase of only 15 mg/dL in fasting triglycerides over 15 years compared with 65 mg/dL (P<0.001) in those whose BMI increased. Incidence of metabolic syndrome at year 15 was lower in the stable BMI group (2.2%) compared with the increased BMI group (18.8%; P<0.001). Conclusions— Adverse progression of metabolic syndrome components with advancing age may not be inevitable. Young adults who maintained stable BMI over time had minimal progression of risk factors and lower incidence of metabolic syndrome regardless of baseline BMI. Greater public health efforts should be aimed at long-term weight stabilization.

Blood Pressure Differences Between Northern and Southern Chinese: Role of Dietary Factors: The International Study on Macronutrients and Blood Pressure

Blood pressure and prevalence of high blood pressure are greater for northern than southern Chinese. Reasons for these differences are unclear. Relationships of north–south blood pressure differences with multiple dietary factors were investigated in 839 Chinese participants, International Study on Macronutrients and Blood Pressure (INTERMAP), 561 northern, 278 southern, aged 40 to 59 years. Daily nutrient intakes were determined from four 24-hour dietary recalls and 2 timed 24-hour urine collections. Average systolic/diastolic pressure levels were 7.4/6.9 mm Hg higher for northern than southern participants. Southern participants had lower body mass index, sodium intake, sodium/potassium ratio, and higher intake of calcium, magnesium, phosphorus, and vitamins A and C. Considered singly, with control for age and gender, several dietary variables (eg, body mass index, urinary sodium/potassium ratio, urinary sodium, dietary phosphorus, and magnesium) reduced north–south blood pressure differences by ≥10%. Controlled for age and gender, nondietary variables had little effect on north–south blood pressure differences. With inclusion in regression models of multiple dietary variables (sodium, potassium, magnesium or phosphorus, body mass index), north–south blood pressure differences became much smaller (systolic −1.1, diastolic 1.6 mm Hg) and statistically nonsignificant. In conclusion, multiple dietary factors accounted importantly for north–south blood pressure differences. Efforts are needed to improve nutrition in China, especially in the north, as well as in other populations including those in the United States, for prevention and control of adverse blood pressure levels and major adult cardiovascular disease.

Twenty-year trends in the prevalence of disability in China

OBJECTIVE To evaluate changes in the age-adjusted prevalence of disability in transitional China from 1987 to 2006. METHODS Data from nationally representative surveys conducted in 1987 and 2006 were used to calculate age-adjusted disability prevalence rates by applying appropriate sample weights and directly adjusting to the age distribution of the 1990 Chinese population. Trends were assessed in terms of average annual percentage change. FINDINGS The estimated number of disabled people in China in 1987 and 2006 was 52.7 and 84.6 million, respectively, corresponding to a weighted prevalence of 4.9% and 6.5%. The age-adjusted prevalence of disability decreased by an average of 0.5% per year (average annual percentage change, AAPC: -0.5%; 95% confidence interval, CI: -0.7 to -0.4) during 1987-2006. However, it increased by an average of 0.3% (AAPC: 0.3%; 95% CI: 0.1 to 0.5) per year in males and by an average of 1.0% (AAPC: 1.0%; 95% CI: 0.8 to 1.2) per year among rural residents, whereas among females it showed an average annual decrease of 1.5% (AAPC: -1.5%; 95% CI: -1.7 to -1.3) and among urban residents, an average annual decrease of 3.9% (AAPC: -3.9%; 95% CI: -4.3 to -3.5). Despite significant declining trends for hearing and speech, intellectual and visual disabilities, the annual age-adjusted prevalence of physical and mental disabilities increased by an average of 11.2% (AAPC: 11.2%; 95% CI: 10.5 to 11.9) and 13.3% (AAPC: 13.3%; 95% CI: 10.7 to 16.2), respectively. CONCLUSION In China, the age-adjusted prevalence of disability has declined since 1987, with inconsistencies dependent on the type of disability. These findings call for continuing and specific efforts to prevent disabilities in China.

Research Misconduct in Low- and Middle-Income Countries

As part of a cluster of articles critically reflecting on the theme of “no health without research,” Richard Smith and colleagues lay out what is currently known about research misconduct in low- and middle-income countries, summarizing some high profile cases and making suggestions on ways forward.

A Cluster-Randomized Controlled Trial of a Simplified Multifaceted Management Program for Individuals at High Cardiovascular Risk (SimCard Trial) in Rural Tibet, China, and Haryana, India

Background— In rural areas in China and India, the cardiovascular disease burden is high but economic and healthcare resources are limited. This study (the Simplified Cardiovascular Management Study [SimCard]) aims to develop and evaluate a simplified cardiovascular management program delivered by community health workers with the aid of a smartphone-based electronic decision support system. Methods and Results— The SimCard study was a yearlong cluster-randomized, controlled trial conducted in 47 villages (27 in China and 20 in India). Recruited for the study were 2086 individuals with high cardiovascular risk (aged ≥40 years with self-reported history of coronary heart disease, stroke, diabetes mellitus, and/or measured systolic blood pressure ≥160 mm Hg). Participants in the intervention villages were managed by community health workers through an Android-powered app on a monthly basis focusing on 2 medication use and 2 lifestyle modifications. In comparison with the control group, the intervention group had a 25.5% (P<0.001) higher net increase in the primary outcome of the proportion of patient-reported antihypertensive medication use pre- and post-intervention. There were also significant differences in certain secondary outcomes: aspirin use (net difference: 17.1%; P<0.001) and systolic blood pressure (–2.7 mm Hg; P=0.04). However, no significant changes were observed in the lifestyle factors. The intervention was culturally tailored, and country-specific results revealed important differences between the regions. Conclusions— The results indicate that the simplified cardiovascular management program improved quality of primary care and clinical outcomes in resource-poor settings in China and India. Larger trials in more places are needed to ascertain the potential impacts on mortality and morbidity outcomes. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01503814.