The effect of age on the shape of the BMI-mortality relation and BMI associated with minimum all-cause mortality in a large Austrian cohort

Association of long-term exposure to various ambient air pollutants, lifestyle, and genetic predisposition with incident cognitive impairment and dementia

BACKGROUND

Long-term exposure to air pollution has been found to contribute to the development of cognitive decline. Our study aimed to assess the association between various air pollutants and cognitive impairment and dementia. Additionally, explore the modification effects of lifestyle and genetic predisposition.

METHODS

The exposure levels to various air pollutants, including particulate matter (PM) with diameters ≤ 2.5 (PM2.5), ≤ 10 (PM10), and between 2.5 and 10 μm (PM2.5-10) and nitrogen oxides (NO and NO2) were identified. An air pollution score (APS) was calculated to evaluate the combined exposure to these five air pollutants. A genetic risk estimate and healthy lifestyle score (HLS) were also generated. The Cox regression model adjusted by potential confounders was adopted to access the association between pollution exposure and cognitive decline, and several sensitivity analyses were additionally conducted to test the robustness.

RESULTS

The combined exposure to air pollutants was associated with an increased risk of incident cognitive decline. Compared with the low exposure group, the hazard ratio (HR) and 95% confidence interval (CI) for all-cause dementia, Alzheimer's dementia, vascular dementia, and mild cognitive impairment (MCI) in those exposed to the highest levels of air pollutants were respectively 1.07 (95% CI: 1.04 to 1.09), 1.08 (95% CI: 1.04 to 1.12), 1.07 (95% CI: 1.02 to 1.13), and 1.19 (95% CI: 1.12 to 1.27). However, the modification effects from genetic predisposition were not widely observed, while on the contrary for the healthy lifestyle. Our findings were proven to be reliable and robust based on the results of sensitivity analyses.

CONCLUSIONS

Exposure to air pollution was found to be a significant contributing factor to cognitive impairment and dementia, and this association was not easily modified by an individual's genetic predisposition. However, adopting a healthy lifestyle may help to manage the risk of cognitive decline related to air pollution.

Association Between Excess Sleep Duration and Risk of Stroke: A Population-Based Study

BACKGROUND

Excess sleep is associated with higher risk of stroke, but whether the risk is modified by age and if it remains elevated after accounting for the competing risk of death is not well understood.

METHODS

We used nine years of the Canadian Community Health Survey between 2000 to 2016 to obtain self-reported sleep duration and created a cohort of individuals without prior stroke, heart disease, or cancer. We linked to hospital records to determine subsequent admissions or emergency department visits for acute stroke until December 31, 2017. We used Cox proportional hazard models to determine the association between sleep duration and risk of stroke, assessing for modification by age and sex and adjusting for demographic, vascular, and social factors. We obtained cumulative incidence of stroke accounting for the competing risk of death.

RESULTS

There were 82,795 individuals in our cohort who met inclusion criteria and had self-reported sleep duration, with 1705 stroke events in follow-up. There was an association between excess sleep (≥10 h/night) and risk of stroke in those <70 years (fully adjusted hazard ratio 2.29, 95% CI 1.04-5.06), but not ≥70 years of age, with a similar association after accounting for the competing risk of death.

CONCLUSION

Sleep duration ≥10 h/night is associated with increased risk of stroke in those <70 years of age. The findings support current guidelines for 7-9 h of sleep per night. Further research is needed to elucidate the relationship between sleep and cerebrovascular disease.

Elevated body mass index increases the risk of cardiovascular events in hypertensive patients accompanied with obstructive sleep apnea: A cohort study

BACKGROUND

Effects of body mass index (BMI) on cardiovascular events are inconsistent. We aimed to investigate the association of BMI with cardiovascular events in hypertensives with obstructive sleep apnea (OSA).

METHODS

Hypertensives with OSA diagnosed with polysomnography between 2011 and 2013 in UROSAH cohort were followed up till Jan 2021. Outcomes were non-fatal cardiovascular events and cardiac death. Cox regression was used to estimate the relationship of continuous and categorical BMI with total and specific outcomes. Sensitivity analyses were performed by excluding those on OSA treatment or underweight patients. Stratified analyses were conducted by parameters including sex and age.

RESULTS

2239 hypertensives with OSA were included with 405 normal weight (BMI<25 kg/m²), 1164 overweight (25-29.9 kg/m²) and 670 obesity (≥30 kg/m²). 206 non-fatal cardiovascular events and 18 cardiac death were recorded during 6.6 years follow-up. Compared with normal weight group, overweight (HR=1.53, 95%CI: 1.01-2.32, P = 0.047) and obesity groups (1.85, 1.19-2.86, P = 0.006) showed increased risk for cardiovascular events, significant in obesity group and marginal in overweight group in fully-adjusted model. In specific events, obesity showed significantly elevated HR for non-fatal cardiovascular events (1.64, 1.04-2.60, P = 0.035). Continuous BMI showed significantly increased HR for total and specific events in all models. Sensitivity analysis yielded consistent results. In stratification analysis, stronger association between obesity and cardiovascular events was observed in the young (HR=5.97, P interaction=0.030).

CONCLUSIONS

BMI is in positive association with cardiovascular events in hypertensives with OSA, emphasizing importance of maintaining healthy BMI for prevention of adverse events in this population, on the basis of guideline-recommended treatment.

BMI trajectories, morbidity, and mortality in England: a two-step approach to estimating consequences of changes in BMI

OBJECTIVE

BMI is known to have an association with morbidities and mortality. Many studies have argued that identifying health risks using single BMI measures has limitations, particularly in older adults, and that changes in BMI can help to identify risks. This study identifies distinct BMI trajectories and their association with the risks of a range of morbidities and mortality.

METHODS

The English Longitudinal Study of Aging provides data on BMI, mortality, and morbidities between 1998 and 2015, sampled from adults over 50 years of age. This study uses a growth-mixture model and discrete-time survival analysis, combined using a two-step approach, which is novel in this setting, to the authors' knowledge.

RESULTS

This study identified four trajectories: "stable overweight," "elevated BMI," "increasing BMI," and "decreasing BMI." No differences in mortality, cancer, or stroke risk were found between these trajectories. BMI trajectories were significantly associated with the risks of diabetes, asthma, arthritis, and heart problems.

CONCLUSIONS

These results emphasize the importance of looking at change in BMI alongside most recent BMI; BMI trajectories should be considered where possible when assessing health risks. The results suggest that established BMI thresholds should not be used in isolation to identify health risks, particularly in older adults.

Body Mass Index Combined With Possible Sarcopenia Status Is Better Than BMI or Possible Sarcopenia Status Alone for Predicting All-Cause Mortality Among Asian Community-Dwelling Older Adults

Background

Body mass index (BMI) and sarcopenia are common indicators of nutritional status. Possible sarcopenia, defined as low muscle strength or performance, was recently introduced by the Asian Working Group for Sarcopenia (AWGS) in 2019. We investigated for association between all-cause mortality and BMI combined with possible sarcopenia severity in Asian older adults.

Methods

This study included a subpopulation (8,195 participants aged ≥60 years; male gender: 49.4%; mean age: 69.2 ± 6.8 years) from the Fourth Thai National Health Examination Survey (NHES-IV). BMI was classified using Asia-Pacific cut-offs. Possible sarcopenia was defined using quadriceps strength based on AWGS 2019 criteria, and possible sarcopenia severity was determined using study population quartile cut-offs. All-cause mortality data was derived from the national vital registry in 2020.

Results

The prevalence of underweight status and possible sarcopenia was 11.8 and 38.9%, respectively. Multivariate analysis showed underweight individuals with severe possible sarcopenia to be at highest risk for increased mortality [adjusted hazard ratio (aHR): 3.98, 95% confidence interval (CI): 2.89-5.48], and higher risk was found in men compared to women (aHR: 5.35, 95% CI: 1.19-8.97). Obese status without possible sarcopenia was an independent protective factor (aHR: 0.61, 95% CI: 0.38-0.97).

Conclusion

BMI combined with possible sarcopenia severity is a better predictor of mortality risk than either parameter alone.

A cutoff value for body composition on the severity of locomotive syndrome in Japanese older women: A cross-sectional study

We aimed to investigate the relationship between body compositions and locomotive syndrome in older women and derive body composition cutoff values to evaluate locomotive syndrome severity. In total, 236 women were included in this study. The percentage of body fat and skeletal muscle mass index was measured using multi-frequency bioelectrical impedance analysis. The locomotive syndrome severity (stage 0-3) was determined using the standup test, the two-step test, and a self-administered questionnaire. The receiver operating characteristic curve analysis indicated that the cutoff value for body fat percentage was 33.1% for locomotive syndrome stage 1 in women. This finding may aid in designing exercise and nutritional interventions to prevent locomotive syndrome in older women.

Vascular risk factors and stroke risk across the life span: A population-representative study of half a million people

Background:

The incidence of stroke in developed countries is increasing selectively in young individuals, but whether this is secondary to traditional vascular risk factors is unknown.

Methods:

We used the Canadian Community Health Survey from 2000 to 2016 to create a large population-representative cohort of individuals over the age of 30 and free from prior stroke. All analyses were stratified by age decile. We linked with administrative databases to determine emergency department visits or hospitalizations for acute stroke until December 2017. We calculated time trends in risk factor prevalence (hypertension, diabetes, obesity, and smoking) using meta-regression. We used Cox proportional hazard models to evaluate the association between vascular risk factors and stroke risk, adjusted for demographic, co-morbid, and social variables. We used competing risk regression to account for deaths and calculated population-attributable fractions. In a sensitivity analysis, we excluded those with prior heart disease or cancer.

Results:

We included 492,400 people in the analysis with 8865 stroke events over a median follow-up time of 8.3 years. Prevalence of hypertension, diabetes, and obesity increased over time while smoking decreased. Associations of diabetes, hypertension, and obesity with stroke risk were progressively stronger at younger age (adjusted hazard ratio for diabetes was 4.47, 95% confidence interval (CI) = 1.95–10.28 at age 30–39, vs 1.21, 95% CI = 0.93–1.57 at age 80+), although the obesity association was attenuated with adjustment. Smoking was associated with higher risk of stroke without a gradient across age deciles, although had the greatest population-attributable fraction at younger age. The hazard ratio for stroke with multiple concurrent risk factors was much higher at younger age (adjusted hazard ratio for 3–4 risk factors was 8.60, 95% CI = 2.97–24.9 at age 30–39 vs 1.61, 95% CI = 0.88–2.97 at age 80+) and results were consistent when accounting for the competing risk of death and excluding those with prior heart disease or cancer.

Conclusions:

Diabetes and hypertension were associated with progressively elevated relative risk of stroke in younger individuals and prevalence was increasing over time. The association of obesity with stroke was not significant after adjustment for other factors. Smoking had the greatest prevalence and population-attributable fraction for stroke at younger age. Our findings assist in understanding the relationship between vascular risk factors and stroke across the life span and planning public health measures to lower stroke incidence in the young.

Effect of Secular Trend, Age, and Length of Follow-up on Optimum Body Mass Index From 1985 Through 2015 in a Large Austrian Cohort

Background

Obesity and its health consequences will dominate health care systems in many countries during the next decades. However, the body mass index (BMI) optimum in relation to all-cause mortality is still a matter of debate.

Material and Methods

Data of the Vorarlberg Health Monitoring & Prevention Program (VHM&PP, 1985–2005) and data provided by the Main Association of Austrian Social Security Institutions (MAASSI, 2005–2015) were analyzed. Information was available on age, sex, smoking status, measured height and weight, and mortality. Generalized additive models were used to model mortality as a function of BMI, calendar time, age, and follow-up.

Results

In MAASSI (N = 282,216, 46.0% men), men and women were on average 2.7 years older than in VHM&PP (N = 185,361, 46.1% men). Average BMI was slightly higher in men (26.1 vs 25.7 kg/m²) but not in women (24.6 vs 24.7 kg/m²). We found an interactive effect of age and follow-up on the BMI optimum. Over age 35 years in men and 55 years in women, the BMI optimum decreased with length of follow-up. While keeping covariates fixed, BMI optimum increased slightly between 1985 and 2015 in men and women, 24.9 (95% CI, 23.9–25.9) to 26.4 (95% CI, 25.3–27.3), and 22.4 (95% CI, 21.7–23.1) to 23.3 (95% CI, 22.6–24.5) kg/m², respectively.

Conclusion

Age and length of follow-up have a pronounced effect on the BMI associated with the lowest all-cause mortality. After controlling for age and length of follow-up, the BMI optimum increased slightly over 30 years in this large study sample.

Association Between Physical Activity and Mortality Among Community-Dwelling Stroke Survivors

BACKGROUND AND OBJECTIVE

To determine the relationship between physical activity (PA) and mortality in community-dwelling stroke survivors.

METHODS

The Canadian Community Health Survey was used to obtain self-reported PA across 4 survey years and was linked to administrative databases to obtain prior diagnosis of stroke and subsequent all-cause mortality. PA was measured as metabolic equivalents (METs) per week and meeting minimal PA guidelines was defined as 10 MET-h/wk. Cox proportional hazard regression models and restricted cubic splines were used to determine the relationship between PA and all-cause mortality in respondents with prior stroke and controls, adjusting for sociodemographic factors, comorbidities, and functional health status.

RESULTS

The cohort included 895 respondents with prior stroke and 97,805 controls. Adhering to PA guidelines was associated with lower hazard of death for those with prior stroke (adjusted hazard ratio [aHR] 0.46, 95% confidence interval [CI] 0.29-0.73) and controls (aHR 0.69, 95% CI 0.62-0.76). There was a strong dose-response relationship in both groups, with a steep early slope and the vast majority of associated risk reduction occurring between 0 and 20 MET-h/wk. In the group of stroke respondents, PA was associated with greater risk reduction in those <75 years of age (aHR 0.21, 95% CI 0.10-0.43) compared to those ≥75 years of age (aHR 0.68, 95% CI 0.42-1.12).

DISCUSSION

PA was associated with lower all-cause mortality in an apparent dose-dependent manner among those with prior stroke, particularly in younger stroke survivors. Our findings support efforts towards reducing barriers to PA and implementation of PA programs for stroke survivors in the community.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that in community-dwelling survivors of stroke, adhering to physical activity guidelines was associated with lower hazard of death.

Association Between Excess Leisure Sedentary Time and Risk of Stroke in Young Individuals

Background and Purpose

The association between physical activity (PA) and lower risk of stroke is well established, but the relationship between leisure sedentary time and stroke is less well studied.

Methods

We used 9 years of the Canadian Community Health Survey between 2000 and 2012 to create a cohort of healthy individuals without prior stroke, heart disease, or cancer. We linked to hospital records to determine subsequent hospitalization or emergency department visit for stroke until December 31, 2017. We quantified the association between self-reported leisure sedentary time (categorized as <4, 4 to <6, 6 to <8, and 8+ hours/day) and risk of stroke using Cox regression models and competing risk regression, assessing for modification by PA, age, and sex and adjusting for demographic, vascular, and social factors.

Results

There were 143 180 people in our cohort and 2965 stroke events in follow-up. Median time from survey response to stroke was 5.6 years. There was a 3-way interaction between leisure sedentary time, PA, and age. The risk of stroke with 8+ hours of sedentary time was significantly elevated only among individuals <60 years of age who were in the lowest PA quartile (fully adjusted hazard ratio, 4.50 [95% CI, 1.64–12.3]). The association was significant across multiple sensitivity analyses, including adjustment for mood disorders and when accounting for the competing risk of death.

Conclusions

Excess leisure sedentary time of 8+ hours/day is associated with increased risk of long-term stroke among individuals <60 years of age with low PA. These findings support efforts to enhance PA and reduce sedentary time in younger individuals.

Shape of BMI-Mortality Risk Associations: Reverse Causality and Heterogeneity in a Representative Cohort of US Adults

OBJECTIVE

This study examines BMI-mortality associations and evaluates strategies intended to limit reverse causality. Heterogeneity in BMI-mortality risk associations across subgroups and causes of death is explored.

METHODS

A cohort of 654,382 adults from the US National Health Interview Survey was constructed. Associations between unit BMI levels and mortality were estimated using Cox proportional hazards models, including and excluding the first 5 years of follow-up, with and without controls for smoking or preexisting conditions, and including and excluding ever-smokers and individuals with preexisting conditions. Stratified analyses by individual characteristics were performed.

RESULTS

Addressing reverse causality led to reduced risk of mortality among those with low BMI levels (<18 kg/m² ). Excluding ever-smokers and individuals with preexisting conditions further led to increased risk among those with high BMI levels (between 33 kg/m² and >40 kg/m² ) and lowered the estimated nadir risk from 27 kg/m² to 23 kg/m² . After excluding ever-smokers and individuals with preexisting conditions, limiting the analysis to >5 years of follow-up produced no substantive changes. Heterogeneous results were observed across individual characteristics, particularly age and causes of death.

CONCLUSIONS

The exclusion of smokers and individuals with preexisting conditions alters the BMI-mortality risk association and results in a somewhat lower range of BMI with minimum mortality risk.

A novel decision model to predict the impact of weight management interventions: The Core Obesity Model

Aims

Models are needed to quantify the economic implications of obesity in relation to health outcomes and health-related quality of life. This report presents the structure of the Core Obesity Model (COM) and compare its predictions with the UK clinical practice data.

Materials and methods

The COM is a Markov, closed-cohort model, which expands on earlier obesity models by including prediabetes as a risk factor for type 2 diabetes (T2D), and sleep apnea and cancer as health outcomes. Selected outcomes predicted by the COM were compared with observed event rates from the Clinical Practice Research Datalink-Hospital Episode Statistics (CPRD-HES) study. The importance of baseline prediabetes prevalence, a factor not taken into account in previous economic models of obesity, was tested in a scenario analysis using data from the 2011 Health Survey of England.

Results

Cardiovascular (CV) event rates predicted by the COM were well matched with those in the CPRD-HES study (7.8-8.5 per 1000 patient-years across BMI groups) in both base case and scenario analyses (8.0-9.4 and 8.6-9.9, respectively). Rates of T2D were underpredicted in the base case (1.0-7.6 vs. 2.1-22.7) but increased to match those observed in CPRD-HES for some BMI groups when a prospectively collected prediabetes prevalence was used (2.7-13.1). Mortality rates in the CPRD-HES were consistently higher than the COM predictions, especially in higher BMI groups.

Conclusions

The COM predicts the occurrence of CV events and T2D with a good degree of accuracy, particularly when prediabetes is included in the model, indicating the importance of considering this risk factor in economic models of obesity.

Body mass index and risk of obesity-related conditions in a cohort of 2.9 million people: Evidence from a UK primary care database

Objective

Obesity rates in the United Kingdom are some of the highest in Western Europe, with considerable clinical and societal impacts. Obesity is associated with type 2 diabetes (T2D), osteoarthritis, cardiovascular disease, and increased mortality; however, relatively few studies have examined the occurrence of multiple obesity‐related outcomes in the same patient population. This study was designed to examine the associations between body mass index (BMI) and a broad range of obesity‐related conditions in the same large cohort from a UK‐representative primary care database.

Methods

Demographic data and diagnosis codes were extracted from the Clinical Practice Research Datalink GOLD database in January 2019. Adults registered for ≥ 3 years were grouped by BMI, with BMI 18.5–24.9 kg/m² as reference group. Associations between BMI and 12 obesity‐related outcomes were estimated using Cox proportional hazard models, adjusted for age, sex, and smoking.

Results

More than 2.9 million individuals were included in the analyses and were followed up for occurrence of relevant outcomes for a median of 11.4 years during the study period. Generally, there was a stepwise increase in risk of all outcomes with higher BMI. Individuals with BMI 40.0–45.0 kg/m² were at particularly high risk of sleep apnea (hazard ratio [95% confidence interval] vs. reference group: 19.8 [18.9–20.8]), T2D (12.4 [12.1–12.7]), heart failure (3.46 [3.35–3.57]), and hypertension (3.21 [3.15–3.26]).

Conclusions

This study substantiates evidence linking higher BMI to higher risk of a range of serious health conditions, in a large, representative UK cohort. By focusing on obesity‐related conditions, this demonstrates the wider clinical impact and the healthcare burden of obesity, and highlights the vital importance of management, treatment approaches, and public health programs to mitigate the impact of this disease.

Body mass index and all-cause mortality in older adults: A scoping review of observational studies

In older age, body composition changes as fat mass increases and redistributes. Therefore, the current body mass index (BMI) classification may not accurately reflect risk in older adults (65+). This study aimed to review the evidence on the association between BMI and all-cause mortality in older adults and specifically, the findings regarding overweight and obese BMI. A systematic search of the OVID MEDLINE and Embase databases was conducted between 2013 and September 2018. Observational studies examining the association between BMI and all-cause mortality within a community-dwelling population aged 65+ were included. Seventy-one articles were included. Studies operationalized BMI categorically (n = 60), continuously (n = 8) or as a numerical change/group transition (n = 7). Reduced risk of mortality was observed for the overweight BMI class compared with the normal BMI class (hazard ratios [HR] ranged 0.41-0.96) and for class 1 or 2 obesity in some studies. Among studies examining BMI change, increases in BMI demonstrated lower mortality risks compared with decreases in BMI (HR: 0.83-0.95). Overweight BMI classification or a higher BMI value may be protective with regard to all-cause mortality, relative to normal BMI, in older adults. These findings demonstrate the potential need for age-specific BMI cut-points in older adults.

Frequency and Types of Pathological Upper Gastrointestinal Endoscopy Findings in Clinically Healthy Individuals

BACKGROUND AND OBJECTIVE

Beyond its application for diagnostics in patients, esophagogastroduodenoscopy (EGD) is used to assess gastrointestinal drug effects in clinical trials, where the interpretation of any pathological findings depends on the respective background variability. The objective of this analysis was to characterize the occurrence of pathological findings in the upper gastrointestinal tract in symptom-free healthy individuals.

METHODS

A baseline EGD was performed in clinically healthy individuals in three clinical trials aimed to assess gastrointestinal tolerability of drugs. Pathological findings were described by type (redness, erosion, ulcer or other), number, size and location, and by clinical relevance as assessed by the endoscopist. Characteristics of volunteers were tested as potential covariates.

RESULTS

A total of 294 EGDs were assessed. Characteristics of individuals were as follows: 257 (87.4%) males, age (mean ± SD) 32.0 ± 8.1 years, body weight 76.0 ± 10.6 kg, body mass index (BMI) 24.0 ± 2.5 kg/m2, 200 consumed alcohol, 250 (of 290 where this information was available) consumed caffeine and 39 (of 152) were smokers, 30 (of 151) tested positive for H. pylori. Any pathological finding was present in 79.6%. Clinically relevant findings occurred in 44.2%, mainly erosions (39.1%). Nine stomach ulcers were observed. Only age and BMI had a statistically significant relationship to overall pathological findings [age 3.4 years higher (p = 0.027), and BMI 1.6 kg/m2 higher (p < 0.001); for clinically relevant vs no findings].

CONCLUSION

Upper gastrointestinal tract mucosal lesions, including those assessed as clinically relevant, are frequent in clinically healthy individuals, impeding the assessment of causality for both disease and drug effects on gastrointestinal health.

Predictors of long-term survival prior to permanent pacemaker implantation in octogenarians or older

Background

There is an increased need for permanent pacemaker (PPM) implantation for older patients with multiple comorbidities. The current guidelines recommend that, before implanting PPM, clinicians should discuss life expectancy with patients and their families as part of the decision-making process. However, estimating individual life expectancy is always a challenge.

Aims

We investigated predictors of long-term survival prior to PPM implantation in patients aged 80 or older.

Methods and results

From September 2004 to September 2015, 100 patients aged ≥ 80 years who received PPM implantation were included for retrospective survival analysis. The end point was all-cause mortality. Follow-up duration was 4.0 ± 2.7 years. By the end of the study, 54 patients (54%) had died. Of the 54 who died, 40 patients (74.1%) died of non-cardiac causes. Their survival rates at 1, 2, 3, 5, and 7 years were 90%, 76%, 54%, 32%, and 16%, respectively. Patients with a longer length of hospital stay before PPM implantation (LOS-B) [hazard ratio (HR) 1.03, 95% confidence interval (CI) 1.02–1.05, p < 0.001], estimated glomerular filtration rate (eGFR) < 30 ml/min/1.73 m² (HR 4.07, 95% CI 1.95–8.52, p < 0.001), body mass index (BMI) < 21 kg/m² (HR 2.50, 95% CI 1.16–5.39, p = 0.02), and dyspnea as the major presenting symptom (HR 2.88, 95% CI 1.27–6.55, p = 0.01) were associated with lower cumulative survival.

Conclusions

Longer LOS-B, lower eGFR and BMI, and dyspnea as the major presenting symptom are pre-PPM implantation predictors of long-term survival in patients aged 80 or older.

Body mass index and all cause mortality in HUNT and UK Biobank studies: linear and non-linear mendelian randomisation analyses

EDITOR'S NOTE

Please see the Editor's Note (doi: https://doi.org/10.1136/bmj.l1042) on Methodological Criticism and an Updated Analysis

OBJECTIVE

To investigate the shape of the causal relation between body mass index (BMI) and mortality.

DESIGN

Linear and non-linear mendelian randomisation analyses.

SETTING

Nord-Trøndelag Health (HUNT) Study (Norway) and UK Biobank (United Kingdom).

PARTICIPANTS

Middle to early late aged participants of European descent: 56 150 from the HUNT Study and 366 385 from UK Biobank.

MAIN OUTCOME MEASURES

All cause and cause specific (cardiovascular, cancer, and non-cardiovascular non-cancer) mortality.

RESULTS

12 015 and 10 344 participants died during a median of 18.5 and 7.0 years of follow-up in the HUNT Study and UK Biobank, respectively. Linear mendelian randomisation analyses indicated an overall positive association between genetically predicted BMI and the risk of all cause mortality. An increase of 1 unit in genetically predicted BMI led to a 5% (95% confidence interval 1% to 8%) higher risk of mortality in overweight participants (BMI 25.0-29.9) and a 9% (4% to 14%) higher risk of mortality in obese participants (BMI ≥30.0) but a 34% (16% to 48%) lower risk in underweight (BMI <18.5) and a 14% (-1% to 27%) lower risk in low normal weight participants (BMI 18.5-19.9). Non-linear mendelian randomisation indicated a J shaped relation between genetically predicted BMI and the risk of all cause mortality, with the lowest risk at a BMI of around 22-25 for the overall sample. Subgroup analyses by smoking status, however, suggested an always-increasing relation of BMI with mortality in never smokers and a J shaped relation in ever smokers.

CONCLUSIONS

The previously observed J shaped relation between BMI and risk of all cause mortality appears to have a causal basis, but subgroup analyses by smoking status revealed that the BMI-mortality relation is likely comprised of at least two distinct curves, rather than one J shaped relation. An increased risk of mortality for being underweight was only evident in ever smokers.

Reuniting overnutrition and undernutrition, macronutrients, and micronutrients

Over-nutrition and its late consequences are a dominant theme in medicine today. In addition to the health hazards brought on by over-nutrition, the medical community has recently accumulated a roster of health benefits with obesity, grouped under "obesity paradox." Throughout the world and throughout history until the 20^th century, under-nutrition was a dominant evolutionary force. Under-nutrition brings with it a mix of benefits and detriments that are opposite to and continuous with those of over-nutrition. This continuum yields J-shaped or U-shaped curves relating body mass index to mortality. The overweight have an elevated risk of dying in middle age of degenerative diseases while the underweight are at increased risk of premature death from infectious conditions. Micronutrient deficiencies, major concerns of nutritional science in the 20^th century, are being neglected. This "hidden hunger" is now surprisingly prevalent in all weight groups, even among the overweight. Because micronutrient replacement is safe, inexpensive, and predictably effective, it is now an exceptionally attractive target for therapy across the spectrum of weight and age. Nutrition-related conditions worthy of special attention from caregivers include excess vitamin A, excess vitamin D, and deficiency of magnesium.

Malnutrition among older adults living in Portuguese nursing homes: the PEN-3S study

OBJECTIVE

To characterise the nutritional status and to identify malnutrition-associated variables of older adults living in Portuguese nursing homes.

DESIGN

Cross-sectional study. Data on demographic and socio-economic characteristics, self-reported morbidity, eating-related problems, nutritional status, cognitive function, depression symptoms, loneliness feelings and functional status were collected by trained nutritionists through a computer-assisted face-to-face structured interview followed by standardised anthropometric measurements. Logistic regression was used to identify factors associated with being at risk of malnutrition/malnourished.

SETTING

Portuguese nursing homes.

SUBJECTS

Nationally representative sample of the Portuguese population aged 65 years or over living in nursing homes.

RESULTS

A total of 1186 individuals (mean age 83·4 years; 72·8 % women) accepted to participate. According to the Mini Nutritional Assessment, 4·8 (95 % CI 3·2, 7·3) % were identified as malnourished and 38·7 (95 % CI 33·5, 44·2) % were at risk of malnutrition. These percentages increased with age and were significantly higher for women. Logistic regression showed (OR; 95 % CI) that older adults reporting no or little appetite (6·5; 2·7, 15·3), those revealing symptoms of depression (2·6; 1·6, 4·2) and those who were more dependent in their daily living activities (4·7; 2·0, 11·1) were also at higher odds of being malnourished or at risk of malnutrition.

CONCLUSIONS

Malnutrition and risk of malnutrition are prevalent among nursing home residents in Portugal. It is crucial to routinely screen for nutritional disorders, as well as risk factors such as symptoms of depression and lower functional status, to prevent and treat malnutrition.

Sex-specific associations between adolescent categories of BMI with cardiovascular and non-cardiovascular mortality in midlife

Context

Most studies linking long-term consequences of adolescent underweight and obesity are limited to men.

Objective

To assess the sex-specific association of adolescent BMI with cardiovascular- and non-cardiovascular-related mortality in young adulthood and midlife.

Setting

A nationwide cohort.

Participants

927,868 women, 1,366,271 men.

Interventions

Medical examination data at age 17, including BMI, were linked to the national death registry.

Main outcomes

Death attributed to cardiovascular (CVD) and non-CVD causes.

Results

During 17,346,230 women-years and 28,367,431 men-years of follow-up, there were 451 and 3208 CVD deaths, respectively, and 6235 and 22,223 non-CVD deaths, respectively. Compared to low-normal BMI (18.5–22.0 kg/m²), underweight women had a lower adjusted risk for CVD mortality (Cox hazard ratio (HR) = 0.68; 95% CI 0.46–0.98) in contrast to underweight men (HR = 0.99; 0.88–1.13). The latter were at higher risk for non-CVD mortality (HR = 1.04; 1.00–1.09), unlike underweight women (HR = 1.01; 0.93–1.10). Findings, which persisted when the study sample was limited to those with unimpaired health, were accentuated for the obese with ≥ 30 years follow-up. Both sexes exhibited similarly higher risk estimates already in the high-normal BMI range (22.0 ≤ BMI < 25.0 kg/m²) with overall no interaction between sex and BMI (p = 0.62). Adjusted spline models suggested lower BMI values for minimal mortality risk among women (16.8 and 18.2 kg/m²) than men (18.8 and 20.0 kg/m²), for CVD and non-CVD death, respectively.

Conclusions

Underweight adolescent females have favorable cardiovascular outcomes in adulthood. Otherwise the risk patterns were similar between the sexes. The optimal BMI value for women and men with respect to future CVD outcomes is within or below the currently accepted low-normal BMI range.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0727-7) contains supplementary material, which is available to authorized users.

Overweight Without Central Obesity, Cardiovascular Risk, and All-Cause Mortality

OBJECTIVE

To assess the association of overweight without central obesity with risks of mortality.

PATIENTS AND METHODS

We included 14,299 participants in the Third National Health and Nutrition Examination Survey (from October 18, 1988, through October 15, 1994). According to their body mass index and waist circumference, participants were categorized into 7 anthropometric groups. Logistic regression models were used to assess the relation of cardiovascular risk factors (hypertension, diabetes, or hypercholesterolemia) and 10-year cardiovascular risk to anthropometric groups. Cox proportional hazards models were used to assess the risk of all-cause mortality, and competing-risks regression models were used for calculating cardiovascular and noncardiovascular mortality.

RESULTS

Compared with those with normal body mass index and waist circumference, overweight men without central obesity were more likely to have all 3 cardiovascular risk factors and a high cardiovascular risk, whereas women in this anthropometric group were more likely to have hypercholesterolemia. In proportional hazards models, overweight without central obesity was associated with lower all-cause mortality among men in the population with cardiovascular risk factors (hazard ratio, 0.71; 95% CI, 0.56-0.89; P=.004) and the general population (hazard ratio, 0.72; 95% CI, 0.60-0.87; P=.001), whereas results of these comparisons among women were not significant (P>.05). In competing risk analyses, overweight men without central obesity had a lower risk of noncardiovascular mortality, but not cardiovascular mortality.

CONCLUSION

Although overweight without central obesity was associated with cardiovascular risk factors and a high cardiovascular risk among men, men in this anthropometric group had a lower mortality risk.

Social and Behavioural Determinants of the Difference in Survival among Older Adults in Japan and England

BACKGROUND

A rapidly ageing population presents major challenges to health and social care services. Cross-country comparative studies on survival among older adults are limited. In addition, Japan, the country with the longest life expectancy, is rarely included in these cross-country comparisons.

OBJECTIVE

We examined the relative contributions of social and behavioural factors on the differences in survival among older people in Japan and England.

METHODS

We used data from the Japan Gerontological Evaluation Study (JAGES; n = 13,176) and the English Longitudinal Study of Ageing (ELSA; n = 5,551) to analyse all-cause mortality up to 9.4 years from the baseline. Applying Laplace regression models, the 15th survival percentile difference was estimated.

RESULTS

During the follow-up, 31.3% of women and 38.6% of men in the ELSA died, whereas 19.3% of women and 31.3% of men in the JAGES died. After adjusting for age and baseline health status, JAGES participants had longer survival than ELSA participants by 318.8 days for women and by 131.6 days for men. Family-based social relationships contributed to 105.4 days longer survival in JAGES than ELSA men. Fewer friendship-based social relationships shortened the JAGES men's survival by 45.4 days compared to ELSA men. Currently not being a smoker contributed to longer survival for JAGES women (197.7 days) and ELSA men (46.6 days), and having lower BMI reduced the survival of JAGES participants by 129.0 days for women and by 212.2 days for men.

CONCLUSION

Compared to participants in England, Japanese older people lived longer mainly because of non-smoking for women and family-based social relationships for men. In contrast, a lower rate of underweight, men's better friendship-based social relationships, and a lower smoking rate contributed to survival among participants in England.

Prevalence and Trends in Lifetime Obesity in the U.S., 1988-2014

INTRODUCTION

Estimates of obesity prevalence based on current BMI are an important but incomplete indicator of the total effects of obesity on a population.

METHODS

In this study, data on current BMI and maximum BMI were used to estimate prevalence and trends in lifetime obesity status, defined using the categories never (maximum BMI ≤30 kg/m²), former (maximum BMI ≥30 kg/m² and current BMI ≤30 kg/m²), and current obesity (current BMI ≥30 kg/m²). Prevalence was estimated for the period 2013-2014 and trends for the period 1988-2014 using data from the National Health and Nutrition Examination Survey. Predictors of lifetime weight status and the association between lifetime weight categories and prevalent disease status were also investigated using multivariable regression.

RESULTS

A total of 50.8% of American males and 51.6% of American females were ever obese in 2013-2014. The prevalence of lifetime obesity exceeded the prevalence of current obesity by amounts that were greater for males and for older persons. The gap between the two prevalence values has risen over time. By 2013-2014, a total of 22.0% of individuals who were not currently obese had formerly been obese. For each of eight diseases considered, prevalence was higher among the formerly obese than among the never obese.

CONCLUSIONS

A larger fraction of the population is affected by obesity and its health consequences than is suggested in prior studies based on current BMI alone. Weight history should be incorporated into routine health surveillance of the obesity epidemic for a full accounting of the effects of obesity on the U.S.

Central adiposity and the overweight risk paradox in aging: follow-up of 130,473 UK Biobank participants

Background: For older groups, being overweight [body mass index (BMI; in kg/m²): 25 to <30] is reportedly associated with a lower or similar risk of mortality than being normal weight (BMI: 18.5 to <25). However, this "risk paradox" is partly explained by smoking and disease-associated weight loss. This paradox may also arise from BMI failing to measure fat redistribution to a centralized position in later life.Objective: This study aimed to estimate associations between combined measurements of BMI and waist-to-hip ratio (WHR) with mortality and incident coronary artery disease (CAD).Design: This study followed 130,473 UK Biobank participants aged 60-69 y (baseline 2006-2010) for ≤8.3 y (n = 2974 deaths). Current smokers and individuals with recent or disease-associated (e.g., from dementia, heart failure, or cancer) weight loss were excluded, yielding a "healthier agers" group. Survival models were adjusted for age, sex, alcohol intake, smoking history, and educational attainment. Population and sex-specific lower and higher WHR tertiles were <0.91 and ≥0.96 for men and <0.79 and ≥0.85 for women, respectively.Results: Ignoring WHR, the risk of mortality for overweight subjects was similar to that for normal-weight subjects (HR: 1.09; 95% CI: 0.99, 1.19; P = 0.066). However, among normal-weight subjects, mortality increased for those with a higher WHR (HR: 1.33; 95% CI: 1.08, 1.65) compared with a lower WHR. Being overweight with a higher WHR was associated with substantial excess mortality (HR: 1.41; 95% CI: 1.25, 1.61) and greatly increased CAD incidence (sub-HR: 1.64; 95% CI: 1.39, 1.93) compared with being normal weight with a lower WHR. There was no interaction between physical activity and BMI plus WHR groups with respect to mortality.Conclusions: For healthier agers (i.e., nonsmokers without disease-associated weight loss), having central adiposity and a BMI corresponding to normal weight or overweight is associated with substantial excess mortality. The claimed BMI-defined overweight risk paradox may result in part from failing to account for central adiposity, rather than reflecting a protective physiologic effect of higher body-fat content in later life.

Sources of heterogeneity in studies of the BMI-mortality association

Background

To date, the amount of heterogeneity among studies of the body mass index-mortality association attributable to differences in the age distribution and length of follow-up has not been quantified. Therefore, we wanted to quantify the amount of heterogeneity attributable to age and follow-up in results of studies on the body mass index-mortality relation.

Methods

We used optima of the body mass index mortality association reported for 30 populations and performed meta-regression to estimate the amount of heterogeneity attributable to sex, ethnicity, mean age at baseline, percentage smokers, and length of follow-up.

Results

Ethnicity as single factor accounted for 36% (95% CI, 11–56%) of heterogeneity. Mean age and length of follow-up had an interactive effect and together accounted for 56% (95% CI, 24–74%) of the remaining heterogeneity. Sex did not significantly contribute to the heterogeneity, after controlling for ethnicity, age, and length of follow-up.

Conclusions

A considerable amount of heterogeneity in studies of the body mass index-mortality association is attributable to ethnicity, age, and length of follow-up.

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The BMI-mortality association varies considerably between study cohorts.

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We found ethnicity alone to account for 36% of the heterogeneity.

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Age and length of follow-up accounted for 56% of the remaining heterogeneity.

Association between body mass index and diabetes mellitus in tuberculosis patients in China: a community based cross-sectional study

BACKGROUND

We planned to determine the association of body mass index (BMI) with diabetes mellitus (DM) and impaired fasting glucose (IFG) in Chinese pulmonary tuberculosis (PTB) patients.

METHODS

3,505 newly-diagnosed PTB patients registered in PTB clinics in Linyi of China between September 2010 and March 2013 were enrolled. DM and IFG were identified based on fasting plasma glucose levels. ROC analysis was used to predict the ability of screening of BMI for DM and IFG in PTB patients.

RESULTS

Compared with 18.5-23.9 kg/m², patients with DM and IFG had significantly increased trends when BMI ≥ 24.0 kg/m², and aORs were 2.28 (95%CI 1.44-3.60) and 1.30 (95%CI 1.04-1.64), respectively. After adjustment for age, gender, and educational level, there was an increased odd in BMI ≥ 23.41 kg/m² for IFG, and a decreased odd in BMI < 19.82 kg/m² for DM (p < 0.05). The cut-offs of BMI for screening IFG and DM in PTB patients were 22.22 kg/m² (AUC 0.56) and 22.34 kg/m² (AUC 0.59).

CONCLUSIONS

In PTB patients, BMI is significantly associated with IFG and DM. However, the predictive power of BMI was not sufficient, so it may only be a limited screening tool for DM and IFG among PTB patients in China.

The Influence of Age the BMI and All-Cause Mortality Association: A Meta-Analysis

OBJECTIVES

To assess BMI range with the lowest mortality for those aged <65 years and those ≥65 years, utilising cohort studies that spanned the entire adult age range.

DESIGN

A two-stage random effects meta-analysis of studies that reported mortality in cohorts both ≥65 years and <65 years. Setting / Participants: Community living adults aged ≥65 and <65 years.

RESULTS

Eight studies were included with a total of 370 416 subjects (306 340 aged <65 years; 64 076 ≥65 years). In the older age group, mortality risk increased at BMIs lower than 22 (BMI range 21.0-21.9: hazard ratio (HR) (95% confidence interval (CI)): 1.05 (1.03, 1.07)), which was not seen in younger adults. In the younger group, mortality increased from BMI range 28.0-28.9 (HR (95% CI): 1.13 (1.00, 1.29)), but mortality did not tend to increase significantly in the older group at BMIs above 23.

CONCLUSION

The recommended healthy weight range is appropriate for younger and middle aged adults but a higher BMI range should be recommended for older adults based on mortality.

Being overweight in early adulthood is associated with increased mortality in middle age

Observational analyses of the association between body mass index (BMI) and all-cause mortality often suggest that overweight is neutral or beneficial, but such analyses are potentially confounded by smoking or by reverse causation. The use of BMI measured in early adulthood offers one means of reducing the latter problem. We used a cohort who were first measured while 16-24 year old students at Glasgow University in 1948-1968 and subsequently re-measured in 2000-2003, offering a rare opportunity to compare BMI measured at different ages as a predictor of mortality. Analysis of the later BMI measurements suggested that overweight was beneficial to survival, while analysis of BMI measured in early adulthood suggested that overweight was harmful and that the optimum BMI lay towards the lower end of the recommended range of 18.5-25 kg m^-2. We interpret the association with later BMI as being probably distorted by reverse causality, although it remains possible instead that the optimum BMI increases with age. Differences when analyses were restricted to healthy non-smokers also suggested some residual confounding by smoking. These results suggest that analyses of BMI recorded in middle or old age probably over-estimate the optimum BMI for survival and should be treated with caution.

Reverse Epidemiology of Traditional Cardiovascular Risk Factors in the Geriatric Population

Traditional risk factors of cardiovascular death in the general population, including body mass index (BMI), serum cholesterol, and blood pressure (BP), are also found to relate to outcomes in the geriatric population, but in an opposite direction. Some degrees of elevated BMI, serum cholesterols, and BP are reportedly associated with lower, instead of higher, risk of death among the elderly. This phenomenon is termed "reverse epidemiology" or "risk factor paradox" (such as obesity paradox) and is also observed in a variety of chronic disease states such as end-stage renal disease requiring dialysis, chronic heart failure, rheumatoid arthritis, and AIDS. Several possible causes are hypothesized to explain this risk factor reversal: competing short-term and long-term killers, improved hemodynamic stability in the obese, adipokine protection against tumor necrosis factor-α, lipoprotein protection against endotoxins, and lipophilic toxin sequestration by the adipose tissue. It is possible that the current thresholds for intervention and goal levels for such traditional risk factors as BMI, serum cholesterol, and BP derived based on younger populations do not apply to the elderly, and that new levels for such risk factors should be developed for the elderly population. Reverse epidemiology of conventional cardiovascular risk factors may have a bearing on the management of the geriatric population, thus it deserves further attention.

Associations of pre-diagnostic body mass index with overall and cancer-specific mortality in a large Austrian cohort

PURPOSE

Although obesity is a well-known risk factor for several cancers, its role on cancer survival is poorly understood.

METHODS

Within the VHM&PP cohort, 8,673 cancer patients (42.2% women) were followed over a median time of 11.9 years. Cox proportional hazard models were used to estimate the association of pre-diagnostic overweight (BMI 25.0-29.9 kg/m(2)) and obesity (BMI ≥ 30.0 kg/m(2)) with all-cause and cancer-specific mortality. Cubic restricted splines were additionally modeled.

RESULTS

During 71,126 person-years, 4,571 deaths were observed. Compared to normal weight, overweight was associated with statistically significantly decreased all-cause mortality (HR 0.93; 95% CI 0.87-0.997) and cancer-specific mortality (HR 0.91; 95% CI 0.84-0.99). Underweight was statistically significantly associated with 28% increased overall mortality, in particular in men [HR 2.02 (95% CI 1.43-2.83) vs. HR 0.96 (95% CI 0.71-1.30) in women]. J-shaped associations were found between BMI and mortality with the nadir around a BMI of 25 kg/m(2). Analysis by cancer site showed though not statistically significantly that overweight was associated with reduced mortality, while obesity was associated with increased cancer-specific mortality except cancers of the upper digestive tract. In patients with local stage colorectal cancers, obesity was associated with increased all-cause (vs. normal weight HR 1.90; 95% CI 1.03-3.52) and cancer-specific mortality (HR 3.17; 95% CI 1.29-7.81).

CONCLUSION

Overweight patients have a better overall prognosis, while for obesity no association and for underweight worse prognosis were found. Our results on common cancers indicate that there are tumor- and stage-specific differences.