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8th February 2022
The mortality in heart disease patients has been found to be lowest for those with a body mass index (BMI) between 25 and 35 and which is higher that the level recommended in prevention guidelines. This was the conclusion of the Stabilisation of Atherosclerotic Plaque by Initiation of Darapladib Therapy (STABILITY) study by researchers from the Department of Medical Sciences, Uppsala Clinical Research, Sweden.
According to the World Health Organization (WHO), overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. Obesity is measured using BMI values and WHO defines someone as overweight if their BMI is greater than or equal to 25 and obese if their BMI is greater than or equal to 30. Based on these criteria, WHO estimates that in 2016, 39% of adults (18 years and older) were overweight and 13% were obese. Moreover, elevated BMI levels have been associated with numerous diseases and metabolic abnormalities including hyper-insulinaemia, insulin resistance, hypertension, dyslipidaemia, coronary heart disease and certain malignancies. However, despite the potential adverse cardiovascular sequelae associated with obesity, many studies and meta-analyses have demonstrated an obesity paradox in that the overweight and mildly obese having a better prognosis than do their leaner counterparts with the same level of cardiovascular disease.
The relationship between BMI and cardiovascular outcomes is therefore not straight forward and this relationship was further confused by the results of a 2019 study which concluded that while obesity was independently associated with increased risk for long-term mortality among patients with stable coronary artery disease, being overweight did not appear to confer an additional mortality risk.
For the present study, the Swedish team examined the association between BMI and mortality in heart disease patients based on data from the STABILITY study, a randomised, placebo-controlled trial evaluating the phospholipase A2 inhibitor in patients with stable coronary heart disease. Patient’s BMI was measured at baseline and the associations with cardiovascular outcomes were evaluated by Cox regression analysis with multivariable adjustments of several factors including gender, age, prior myocardial infarction, renal dysfunction, smoking status etc. The primary outcomes of interest were the composite of cardiovascular death, myocardial infarction and stroke whereas a secondary outcome was all-cause mortality.
Mortality in heart disease patients during follow-up
The study included 15,785 patients with a mean age of 64.9 years (18.7% female) and who were followed up for a mean of 3.7 years. In total, 1.5% of participants had a BMI < 20, 19.4% a BMI of 20 – 25, 42.8% a BMI of 25 – 30, 25.1% a BMI of 30 – 35 and 11.2% a BMI > 35.
In fully adjusted models, among those with the lowest BMI (< 20), there was a more than doubling of the risk of all-cause mortality (Hazard ratio, HR = 2.27, 95% CI 1.60 – 3.22), cardiovascular death (HR = 2.26) and heart failure (HR = 2.51) compared to those with a BMI of 25 – 30 which served as the reference point. Similarly, all-cause mortality was higher among those with a BMI of 20 – 25 (HR = 1.21) and cardiovascular mortality (HR = 1.26).
For the most obese patients (BMI > 35), the risk of all-cause mortality was higher than the reference group (HR = 1.18) and as was the risk for cardiovascular mortality (HR = 1.23).
In discussing their findings, the authors noted how mortality in heart disease was effectively U-shaped, i.e., the highest risks were in those with both the lowest and highest BMI values. They calculated that the lowest risk was for those with a BMI of 27 which was considered as ‘overweight’ in guidelines which advocate an ideal BMI of 20 to 25, suggesting how their data indicated that a slightly higher BMI was optimal.
Held C et al. Body Mass Index and Association With Cardiovascular Outcomes in Patients With Stable Coronary Heart Disease – A STABILITY Substudy J. Am Heart Assoc 2022
25th May 2021
Cancer of the breast is the most common form of cancer in women although with an early diagnosis, the 5-year survival prognosis ranges from 86 to 99%. Nevertheless, women who survive breast cancer have a 17% increased risk for a second cancer compared to the general population. One factor known to be associated with cancer is obesity with one US study estimating that 40% of all cancer diagnoses occurred in people who were either overweight or obese. However, while much attention has been paid to the effect of obesity on the development of an initial cancer, far less is known about how obesity impacts on the development of a second cancer. As a result, a team from Kaiser Permanente, Denver, US, sought to examine the association between body mass index (BMI) and a second cancer among women who survived invasive breast cancer. Data were extracted from an electronic database and a surveillance tumour registry which provided information on the incidence and type of secondary cancers that occurred. Height and weight measurements within two years prior through one year after the date of the initial breast cancer diagnosis were used to calculate the BMI. All women included had surgery as part of their initial breast cancer and had no evidence of a second cancer one year later. The study outcomes included all second cancers, cancers for which there was a known association with obesity (e.g., oesophageal adenocarcinoma), and ER-positive second breast cancers.
A total of 6481 women were included in the analysis with a mean age of 60.2 years, of whom 33.4% were classed as overweight or obese (33.8%) at the time of their initial breast cancer diagnosis. During a median follow-up of 88 months, 822 (12.7%) women developed a second cancer, of which 508 (61.8%) were obesity-related and 333 (40.5%) were breast cancer, the majority of which (69.4%) were ER-positive. The authors calculated that every 5 unit increase in BMI was associated with a 7% increased risk of developing any second cancer (relative risk, RR = 1.07, 95% CL 1.01–1.14), a 13% increased for an obesity-related cancer and by 15% for a second ER-positive breast cancer.
The authors calculated that the risk of a second cancer was increased by 5% for every 5 unit increase in BMI. They concluded that these data had important public health implications given the prevalence of obesity and underscored the need for effective preventative strategies.
Feigelson HS et al. Body Mass Index and Risk of Second Cancer Among Women with Breast Cancer. J Natl Cancer Inst 2021
2nd December 2020
Preliminary data has suggested that being overweight can contribute towards poorer health outcomes for those with COVID-19 and such patients are more likely to require mechanical ventilation. In contrast, far less attention has been paid to the possible relationship between low body mass index (BMI) and clinical outcomes. As a result, a team from the Department of Medicine, Donald and Barbara Zucker School of Medicine, New York, USA, set out to retrospectively analyse the overall association between different levels of BMI and outcomes for patients with COVID-19. The team included 10,861 patients admitted with COVID-19 into their hospital during March to the end of April 2020. The BMI was documented on admission to hospital as either self-reported or obtained from nursing staff. It was classified as follows with the BMI range in brackets: underweight (under 18.5kg/m2), normal (18.5 to 24.9), overweight (25 to 29.9) and obese class I (30 – 34), II (35 – 39) and III (40 or more). Data on patient outcomes were collected from electronic health records and the primary outcome used was the need for mechanical ventilation and death. All patients were followed until discharge, death or until early May 2020.
For the 10,861 patients with a median age of 65 years (59.6% male), 2.2% were classed as underweight, 23.1% normal, 37% overweight and 37.7% obese. In total, 2,220 (20.4%) patients required mechanical ventilation and 2,596 (23.9%) died. There were significant differences in both the need for mechanical ventilation and death among the different BMI categories. For instance, 12.4% of those classed as underweight and 73.8% of those classed as obese (all classes) required mechanical ventilation. In addition, 39.2% of those who were underweight died as did 62.9% of those in the obese category. Regression analysis revealed that patients who were underweight an increased risk of death (hazard ratio, HR = 1.46, 95% CI 1.17 – 1.81) which was actually higher than the risk for those with class III obesity (HR – 1.23, 95% CI 1.03 – 1.48). The reason for the increased risk of death among underweight patients was unclear but the authors speculated that this may have been related to increased frailty.
They concluded that the findings suggest that worse outcomes after COVID-19 are not restricted to obese patients and those who are underweight are also at a higher risk.
Kim T et al. Body Mass Index as a Risk Factor for Clinical Outcomes in Patients Hospitalised with COVID- 19 in New York. Obesity 2020 doi.org/10.1002/oby.23076