It's Absolutely Relative: The Effect of Age on the BMI-Mortality Relationship in Postmenopausal Women

Cross-sectional and longitudinal associations of obesity with disability between age 50 and 90 in the SHARE study

BACKGROUND

Obesity is associated with disability but whether age and ageing modify this association remains unclear. We examined whether this association changes between 50 and 90 years, and whether change in disability rates over 14 years differs by body mass index (BMI) categories.

METHODS

BMI and ADL-disability data on 28,453 individuals from 6 waves (2004-2018, SHARE study) were used to examine the cross-sectional absolute and relative associations, extracted at age 50, 60, 70, 80, and 90 years using logistic mixed models. Then baseline BMI and change in disability rates over 14-years were examined using logistic-mixed models.

RESULTS

At age 50, the probabilities of ADL disability in individuals with BMI 30-34.9 and ≥35 kg/m² were 0.07 (0.06, 0.09) and 0.11 (0.09, 0.12), increasing to 0.47 (0.44, 0.50) and 0.55 (0.50, 0.60) at age 90; the increase in both these groups was greater than that in the normal-weight group (p for increase with age<0.001). On the relative scale the OR at age 50 in these obesity groups was 2.37 (1.79, 3.13) and 5.03 (3.38, 7.48), decreasing to 1.51 (1.20, 1.89) and 2.19 (1.50, 3.21) at age 90; p for decrease with age=0.05 and 0.02 respectively. The 14-year increase in probability of disability was greatest in those with BMI≥35 kg/m² at age 50, 60, and 70 at baseline: differences in increase compared to normal weight were 0.08 (0.02, 0.14), 0.11 (0.07, 0.15), and 0.09 (0.02, 0.16) respectively.

CONCLUSIONS

ADL disability is increasingly prevalent with age in individuals with obesity. Relative measures of change obscure the association between obesity and disability due to age-related increase in disability rates in all groups.

Associations Between Mid- to Late-Life Body Mass Index and Chronic Disease-Free Survival: A Nationwide Twin Study

BACKGROUND

Some studies have linked late-life overweight to a reduced mortality risk compared to normal body mass index (BMI). However, the impact of late-life overweight and its combination with mid-life BMI status on healthy survival remains unclear. We aimed to investigate whether and to what extent mid- and/or late-life overweight are associated with chronic disease-free survival.

METHODS

Within the Swedish Twin Registry, 11 597 chronic disease-free twins aged 60-79 years at baseline were followed up for 18 years. BMI (kg/m2) was recorded at baseline and 25-35 years before baseline (ie, midlife) and divided as underweight (<20), normal (≥20-25), overweight (≥25-30), and obese (≥30). Incident chronic diseases (cardiovascular diseases, type 2 diabetes, and cancer) and deaths were ascertained via registries. Chronic disease-free survival was defined as years lived until the occurrence of any chronic diseases or death. Data were analyzed using multistate survival analysis.

RESULTS

Of all participants, 5 640 (48.6%) were overweight/obese at baseline. During the follow-up, 8 772 (75.6%) participants developed at least 1 chronic disease or died. Compared to normal BMI, late-life overweight and obesity were associated with 1.1 (95% CI, 0.3, 2.0) and 2.6 (1.6, 3.5) years shorter chronic disease-free survival. Compared to normal BMI through mid- to late life, consistent overweight/obesity and overweight/obesity only in mid-life led to 2.2 (1.0, 3.4) and 2.6 (0.7, 4.4) years shorter disease-free survival, respectively.

CONCLUSIONS

Late-life overweight and obesity may shorten disease-free survival. Further research is needed to determine whether preventing overweight/obesity from mid- to late life might favor longer and healthier survival.

Excessive Gestational Weight Gain and Long-Term Maternal Cardiovascular Risk Profile: The Study of Women's Health Across the Nation

Background: Excessive gestational weight gain (GWG) is consistently linked with maternal risk of obesity. However, the literature on its long-term cardiovascular risk is minimal and conflicting. We evaluated whether excessive GWG is associated with a high-risk cardiovascular profile among parous women in midlife. Materials and Methods: Participants were women in the multiethnic cohort Study of Women's Health Across the Nation with a history of live birth(s). Excessive GWG was defined according to Institute of Medicine guidelines and collected by self-recall. Outcomes were the atherosclerotic cardiovascular disease (ASCVD) risk score and C-reactive protein (CRP), measured at the study baseline when mean age was 47 years, and at 10 follow-up visits (1996-2017). We estimated the association of excessive GWG with outcomes through linear mixed model regression. Results: The analytic sample included 1318 women with 3049 singleton births. Over 40% (536) reported one or more pregnancies with excessive GWG. Longitudinal models estimated that at a mean age of 67, women with a history of excessive GWG had a 9.8% (9.2, 10.5) 10-year ASCVD risk, compared to 9.5% (8.9, 10.1) for those without, and mean CRP of 2.20 mg/L (1.89, 2.57) versus 1.85 mg/L (1.61, 2.14), respectively, adjusted for participant characteristics. Conclusions: In this multiethnic cohort of parous women, a history of excessive GWG was associated with a small, but statistically significant difference in ASCVD risk, and a moderate, statistically significant difference in CRP across midlife. More research is necessary to understand the mechanistic pathway between excessive GWG and long-term maternal cardiovascular health.

Age-dependent associations of body mass index with myocardial infarction, heart failure, and mortality in over 9 million Koreans

BACKGROUND

While obesity is a well-known cardiovascular risk factor, little is known whether age has a modifying effect.

AIM

To determine the age-dependent associations of BMI with cardiovascular outcomes.

METHODS

A population-based cohort of 9,278,433 Koreans without prior cardiovascular disease were followed up for the incidence of myocardial infarction (MI), heart failure (HF), and all-cause death. The effect of BMI with optimal normal weight (18.5-22.9 kg/m2) as reference was analyzed according to age groups [young (20-39 years), middle-aged (40-64 years), and elderly (≥65 years)] and age decades.

RESULTS

During 8.2 years, MI, HF, and all-cause death occurred in 65,607 (0.71%), 131,903 (1.42%), and 306,065 (3.30%), respectively. Associations between BMI and all outcomes were significantly modified by age (p-for-interaction < 0.001). There was a proportional increase in incident MI according to BMI in young subjects; this relationship became U-shaped in middle-aged subjects, and inversely proportional/plateauing in elderly subjects. A U-shaped relationship between BMI and incident HF was observed, but the impact of obesity was stronger in young subjects while the impact of underweight was stronger in middle-aged and elderly subjects. Meanwhile, lower BMI was associated with higher all-cause mortality in all ages, although this association was attenuated at young age, and pre-obesity was associated with the greatest survival benefit. These associations were independent of sex, smoking, physical activity, and comorbidities.

CONCLUSIONS

The impact of BMI on cardiovascular risk differs according to age. Weight loss may be recommended for younger overweight subjects, while being mildly overweight may be beneficial at old age.

DXA Versus Clinical Measures of Adiposity as Predictors of Cardiometabolic Diseases and All-Cause Mortality in Postmenopausal Women

OBJECTIVE

To investigate whether dual-energy x-ray absorptiometry (DXA) estimates of adiposity improve risk prediction for cardiometabolic diseases over traditional surrogates, body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) in older women.

PATIENTS AND METHODS

We analyzed up to 9744 postmenopausal women aged 50 to 79 years participating in the Women's Health Initiative who underwent a DXA scan and were free of cardiovascular disease and diabetes at baseline (October 1993 to December 1998) and followed through September 2015. Baseline BMI, WC, WHR, and DXA-derived percent total-body and trunk fat (%TrF) were incorporated into multivariable Cox proportional hazards models to estimate the risk of incident diabetes, atherosclerosis-related cardiovascular diseases (ASCVDs), heart failure, and death. Concordance probability estimates assessed the relative discriminatory value between pairs of adiposity measures.

RESULTS

A total of 1327 diabetes cases, 1266 atherosclerotic cardiovascular disease (ASCVD) cases, 292 heart failure cases, and 1811 deaths from any cause accrued during a median follow-up of up to 17.2 years. The largest hazard ratio observed per 1 standard deviation increase of an adiposity measure was for %TrF and diabetes (1.77; 95% CI, 1.66-1.88) followed by %TrF and broadly defined ASCVD (1.22; 95% CI, 1.15-1.30). These hazard ratios remained significant for both diabetes (1.47; 95% CI, 1.37-1.57) and ASCVD (1.22; 95% CI, 1.14-1.31) even after adjusting for the best traditional surrogate measure of adiposity, WC. Percentage of trunk fat was also the only adiposity measure to demonstrate statistically significant improved concordance probability estimates over BMI, WC, and WHR for diabetes and ASCVD (all P<0.05).

CONCLUSION

DXA-derived estimates of abdominal adiposity in postmenopausal women may allow for substantially improved risk prediction of diabetes over standard clinical risk models. Larger DXA studies with complete lipid biomarker profiles and clinical trials are needed before firm conclusions can be made.