Associations between body mass index and all-cause mortality: A systematic review and meta-analysis

Fasting insulin and c-reactive protein confound the association between mortality and body mass index. An increase in fat mass may mediate the associations between hyperinsulinemia, hyperinflammation, and mortality. The objective of this study was to describe the “average” associations between body mass index and the risk of mortality and to explore how adjusting for fasting insulin and markers of inflammation might modify the association of BMI with mortality. MEDLINE and EMBASE were searched for studies published in 2020. Studies with adult participants where BMI and vital status was assessed were included. BMI was required to be categorized into groups or parametrized as non-first order polynomials or splines. All-cause mortality was regressed against mean BMI squared within seven broad clinical populations. Study was modeled as a random intercept. β coefficients and 95% confidence intervals are reported along with estimates of mortality risk by BMIs of 20, 30, and 40 kg/m². Bubble plots with regression lines are drawn, showing the associations between mortality and BMI. Splines results were summarized. There were 154 included studies with 6,685,979 participants. Only five (3.2%) studies adjusted for a marker of inflammation, and no studies adjusted for fasting insulin. There were significant associations between higher BMIs and lower mortality risk in cardiovascular (unadjusted β −0.829 [95% CI −1.313, −0.345] and adjusted β −0.746 [95% CI −1.471, −0.021]), Covid-19 (unadjusted β −0.333 [95% CI −0.650, −0.015]), critically ill (adjusted β −0.550 [95% CI −1.091, −0.010]), and surgical (unadjusted β −0.415 [95% CI −0.824, −0.006]) populations. The associations for general, cancer, and non-communicable disease populations were not significant. Heterogeneity was very large (I² ≥ 97%). The role of obesity as a driver of excess mortality should be critically re-examined, in parallel with increased efforts to determine the harms of hyperinsulinemia and chronic inflammation.     

Lower extremity motor performance and body mass index in elderly people: the Italian Longitudinal Study on Aging

OBJECTIVES: To test the association between body mass index (BMI) and lower extremity motor performance in elderly people.
DESIGN: Multicenter, cross-sectional, observational study.
SETTING: A sample of individuals aged 65 and older recruited for the baseline survey of the Italian Longitudinal Study on Aging.
PARTICIPANTS: Two thousand six hundred seventy-two individuals (1,436 men, 1,236 women) independent with transfers and toileting and independent or requiring assistance for bathing or dressing.
MEASUREMENTS: Motor function was assessed using a Motor Performance Test (MPT), with a set of six tasks exploring lower extremity performance (LEP): rising once from a chair, turning in a half circle, tandem walking, standing on one leg, stair climbing, and walking 5 m.
RESULTS: The highest prevalence rates of difficulty in performing the tasks occurred in men and women, respectively, in tandem walking (14%, 28%), stair climbing (17.0%, 43%) and walking 5 m (15%, 30%). In both sexes, moderate (men: odds ratio (OR)=1.99, 95% confidence interval (CI)=1.16–3.43; women OR=2.07, 95% CI=1.18–3.65) and severe obesity (men: OR=3.45, 95% CI=1.21–9.89; women: OR=3.16, 95% CI=1.43–6.95) were each independently associated with overall motor performance impairment after adjusting for age, smoking, and comorbidity. Best performance was generally observed in the normal-weight and overweight groups.
CONCLUSION: The results confirm that, in both sexes, overweight is not related to motor impairment. Only in women, low BMI is associated with higher probability of overall motor performance impairment. These data suggest that moderate obesity should be distinguished from severe obesity when assessing the relationship between BMI and LEP.     

Body mass index and risk of all‐cause and cardiovascular mortality in hospitalized elderly patients with diabetes mellitus

Aims Obesity is linked to increased morbidity and mortality risk in both the general population and in patients with diabetes mellitus; however, recent reports suggest that, in hospitalized elderly individuals, the association between body mass index (BMI) and mortality may be inverse. The present study sought to investigate the association between BMI and survival in hospitalized elderly individuals with diabetes mellitus. Methods The medical records of 470 patients (226 males, mean age of 81.5 ± 7.0 years) admitted to an acute geriatric ward between 1999 and 2000 were reviewed. Of the 140 patients with diabetes mellitus, 122 had more than 6 months of follow‐up and were included in this analysis. Patients were followed up until 31 August 2004. Mortality data were extracted from death certificates. Results During a mean follow‐up of 3.7 ± 1.6 years, 69 (56.6%) subjects died, 31 (25.4%) from cardiovascular causes. Those who died from any cause had lower baseline BMI than those who survived (24.0 ± 4.0 vs. 27.1 ± 4.3 kg/m²; P < 0.0001). Similarly, those who died of cardiovascular causes had lower baseline BMI than those who did not (23.7 ± 3.6 vs. 25.9 ± 4.5, P = 0.01). BMI was inversely associated with all‐cause [relative risk (RR) 0.89, 95% confidence interval (CI) 0.83–0.96, P = 0.002] and cardiovascular death (RR 0.83, 95% CI 0.74–0.93, P = 0.002) even after controlling for age, sex, smoking, dyslipidaemia and reason for hospital admission. Conclusions In very elderly subjects with diabetes mellitus, increased BMI was associated with reduced mortality risk.     

Association between aortic calcification and total and cardiovascular mortality in older women

OBJECTIVES: To determine whether older women with abdominal aortic calcification had a greater cardiovascular and all-cause mortality, as such data are limited in older adults. DESIGN: Prospective cohort study with a mean follow-up of 13 years. SETTING: Community-based sample with four US clinical centres. SUBJECTS: A total of 2056 women aged > or =65 years with abdominal aortic calcification assessed on baseline radiographs. MAIN OUTCOME MEASURE: Mortality rate (all, cardiovascular, cancer or other cause) adjudicated from death certificates and hospital records. RESULTS: The prevalence of abdominal aortic calcification increased with age, ranging from 60% at age 65-69 years to 96% at 85 years and older. Participants with aortic calcification were more likely to die during follow-up of any cause (47% vs. 27%) or a cardiovascular-specific cause (18% vs. 11%, both P < 0.001) than those without aortic calcification. In age-adjusted analyses, aortic calcification was associated with a greater rate of all-cause and cause-specific mortality (cardiovascular, cancer, and other, all P < or = 0.01). In analyses adjusted for age and cardiovascular risk factors, aortic calcification was associated with an increased rate of all-cause mortality (HR: 1.37, 95% CI: 1.15-1.64), and noncardiovascular noncancer mortality (HR: 1.57, 95% CI: 1.17-2.11). The associations between aortic calcification and cancer mortality (HR: 1.44, 95% CI: 1.00-2.08) or cardiovascular mortality (HR: 1.18, 95% CI: 0.88-1.57) showed a similar pattern without reaching statistical significance, but was slightly stronger for mortality from coronary heart disease (HR: 1.53, 95% CI: 0.91-2.56). CONCLUSIONS: Abdominal aortic calcification in older women is associated with increased mortality. Future research should examine potential mechanisms for this association.     

Association of body mass index with blood pressure in 80-year-old subjects.

OBJECTIVE: Little data are available on the association between obesity and high blood pressure in elderly individuals, particularly in subjects over 80 years of age. The aim of the present study was to determine the association between body mass index (BMI) and blood pressure in 80-year-old subjects. METHODS: This study was part of the 8020 Data Bank Survey, which was designed to collect the baseline data of systemic and dental health conditions in 80-year-old subjects. We studied the cross-sectional association of BMI with blood pressures in 645 Japanese (258 men and 387 women), who were 80 years old. RESULTS: Mean systolic blood pressure rose from 146.6 mmHg in the first quintile of BMI to 147.5 mmHg in the second, 150.3 mmHg in the third, 151.6 mmHg in the fourth, and 156.4 mmHg in the fifth quintiles (test for trend, P = 0.006). Mean diastolic blood pressure rose from 75.8 mmHg in the lowest quintile of BMI to 81.8 mmHg in the highest (test for trend, P = 0.002). We performed multiple regression analysis, controlling for factors known to influence blood pressure values, such as sex, alcohol intake, current smoking status and serum glucose, total cholesterol and creatinine concentrations. The association between BMI and systolic and diastolic blood pressure, respectively, was highly statistically significant in all analyses. CONCLUSION: These results show that a close relationship is present between obesity and high blood pressure, even in very old subjects.     

Changes in body mass index in a Finnish population between 1972 and 1982

Population-based data on changes in body mass index are scarce. We have examined about 9700 people aged 30-59 years in two provinces of East Finland in 1972, 1977 and 1982. The age adjusted mean value of body mass index (kg m-2) in 1972 was 26.0 +/- 3.4 in men and 26.9 +/- 4.7 in women, increasing with age. During the 10-year follow-up the mean body mass index increased in men to 26.5 +/- 3.6 (P less than 0.001). In women we found a decrease in mean body mass index to 26.4 +/- 4.9 (P less than 0.001). The increase trend in body mass with age remained in women, while in men the age trend increased from survey to survey. The proportion of obese men also increased while in younger women a decrease was observed. The results of this study show the association between changes in physical activity, education etc. and the observed changes in the body mass index.     

Inverse relationship between body mass index and mortality in older nursing home residents: a meta‐analysis of 19,538 elderly subjects

Body mass index (BMI) and mortality in old adults from the general population have been related in a U‐shaped or J‐shaped curve. However, limited information is available for elderly nursing home populations, particularly about specific cause of death. A systematic PubMed/EMBASE/CINAHL/SCOPUS search until 31 May 2014 without language restrictions was conducted. As no published study reported mortality in standard BMI groups (<18.5, 18.5–24.9, 25–29.9, ≥30 kg/m²), the most adjusted hazard ratios (HRs) according to a pre‐defined list of covariates were obtained from authors and pooled by random‐effect model across each BMI category. Out of 342 hits, 20 studies including 19,538 older nursing home residents with 5,223 deaths during a median of 2 years of follow‐up were meta‐analysed. Compared with normal weight, all‐cause mortality HRs were 1.41 (95% CI = 1.26–1.58) for underweight, 0.85 (95% CI = 0.73–0.99) for overweight and 0.74 (95% CI = 0.57–0.96) for obesity. Underweight was a risk factor for higher mortality caused by infections (HR = 1.65 [95% CI = 1.13–2.40]). RR results corroborated primary HR results, with additionally lower infection‐related mortality in overweight and obese than in normal‐weight individuals. Like in the general population, underweight is a risk factor for mortality in old nursing home residents. However, uniquely, not only overweight but also obesity is protective, which has relevant nutritional goal implications in this population/setting.     

Associations between body mass index and mortality in acute-on-chronic liver failure patients

Introduction and objectivesThe association between the level of body mass index (BMI) and the mortality of patients with critical liver disease remains unclear. This study aimed to examine the association between BMI and hospital mortality of patients with acute-on-chronic liver failure (ACLF).MethodsClinical data from 146 ACLF patients were collected and analyzed. BMI was categorized into three groups: lower BMI (<18.5 kg/m²), normal BMI (18.5–24.9 kg/m²), and overweight (25.0–32.0 kg/m²). BMI and laboratory parameters were measured one day before, or on the day of the start of the treatment. Values of BMI and laboratory parameters were compared between survivors and non-survivors, and then hospital mortality rates were compared among patients with different BMI levels.ResultsThe prognosis of ACLF patients was significantly correlated with international normalized ratio (INR), albumin and BMI. The ACLF patients with low albumin level and high INR values tend to have a high mortality rate. Also, survival time was significantly shorter in the ACLF patients with lower BMI, while patients with normal and overweight values had longer survival time.ConclusionsA graded association between BMI and hospital mortality with a strong significant trend was found in ACLF patients in China.     

Larger body mass index and waist circumference are associated with lower mortality in Chinese long-term care facility residents

OBJECTIVES: To investigate the association between body mass index (BMI) and waist circumference (WC) and all‐cause mortality of Chinese residents in long‐term care facilities in Taiwan. DESIGN: Prospective cohort study. SETTING: Eight long‐term care facilities in Taiwan. PARTICIPANTS: Three hundred fifty‐four residents aged 60 and older (median 78.4, range 60–101; 156 men, 198 women) were recruited during the study period. MEASUREMENTS: Anthropometrics and metabolic parameters were measured at baseline. Mean BMI was 21.7±4.2 kg/m² (range 11.6–35.3 kg/m², and mean WC was 82.4±10.9 cm (range 55.0–124.0 cm). Mortality data were from the Department of Health in Taiwan. RESULTS: There were 219 deaths during the 5 years of follow‐up. After adjusting for age, sex, albumin, Karnofsky performance status scale, hypertension, and diabetes mellitus, subjects in the highest quartile of BMI (27.3± 2.8 kg/m²) and WC (96.7±7.4 cm) had a significantly lower mortality rate than did subjects in the lowest quartile (BMI, 16.7±1.7 kg/m²; WC, 69.6±4.2 cm). After further stratification according to central obesity status, the subjects in the two highest BMI quartiles had a lower mortality rate than those in the lowest BMI quartile but only in the central obesity group (≥90 cm in men or ≥80 cm in women). The adjusted relative risk for all‐cause mortality in the highest versus lowest BMI quartile was 0.17 (95% confidence interval=0.05–0.57). CONCLUSION: BMI and WC were negative predictors for all‐cause mortality in older Chinese adults living in long‐term care facilities. Participants with higher WC and BMI had lower all‐cause mortality.     

Low-density lipoprotein cholesterol and mortality in older people

OBJECTIVES: To investigate the role of low-density lipoprotein cholesterol (LDL-C) as a predictor of mortality in elderly subjects. DESIGN: Population-based prospective cohort study. SETTING: Two communities in northern Italy. PARTICIPANTS: Three thousand one hundred twenty Caucasian subjects aged 65 and older recruited in for the Cardiovascular Study in the Elderly and followed up for 12 years. MEASUREMENTS: Anthropometric measures: fasting plasma total cholesterol, triglyceride, high-density lipoprotein cholesterol, LDL-C, glucose, creatinine, and body mass index. Clinical measures: medical assessment, diabetes mellitus, hypertension, stroke, coronary disease, heart failure, and smoking and drinking habits. Vital status measures: death certificates from the Registry Office and causes of death according to the International Classification of Diseases. After plotting mortality rates using quartiles of LDL-C, relative hazard rates (RHRs) were calculated using multivariate Cox regression analyses. When the trend was nonlinear, the RHRs were further calculated for the 25th, 50th, and 75th percentiles of the distribution to confirm curvilinearity. RESULTS: The distribution of risk of total mortality in women and of fatal heart failure in all subjects was curvilinear (non J-shaped), decreasing nonlinearly with LDL-C. For total mortality in men and cardiovascular mortality in both sexes, the relationship with LDL-C was J-shaped. The risk of fatal myocardial infarction was J-shaped in men, whereas it increased linearly with higher LDL-C in women. In both sexes, the association between stroke mortality and LDL-C was not significant. CONCLUSION: This study adds to the uncertainty of the role of elevated levels of LDL-C as a risk factor for mortality in old people.     

Elevated body mass index and mortality risk in the elderly

The purpose of this report was to perform a systematic review and meta-analysis of the studies examining the impact of an elevated body mass index (BMI) on mortality risk in elderly (> or =65 years) men and women. A variance-based method of meta-analysis was used to summarize the relationships from available studies. The summary relative risk of all-cause mortality from the 26 analyses that included a risk estimate for a BMI within the overweight range was 1.00 (95% confidence intervals, 0.97-1.03). The summary relative risk of all-cause mortality for the 28 analyses that included a risk estimate for a BMI within the obese range was 1.10 (1.06-1.13). These calculations indicate that a BMI in the overweight range is not associated with a significantly increased risk of mortality in the elderly, while a BMI in the moderately obese range is only associated with a modest increase in mortality risk.