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The importance of body mass index and weight-change in patients with coronary artery disease

Kennedy, Linn LU (2006)
Abstract
High body mass index (BMI) is associated with cardiovascular risk factors such as hypertension, dyslipidemia, and insulin resistance. Obesity is also an independent risk factor for coronary artery disease (CAD) and can cause structural as well as functional changes in the heart. High BMI is associated with increased mortality in the population. Weight-loss from a state of overweight or obesity may reverse some of the alternations associated with excess weight. However, the survival benefit of weight-loss among the population is still uncertain.



The aims of this thesis were to examine the prognostic importance of BMI and weight-change in patients with CAD. A total of 12 550 patients with CAD, 94% with prior acute... (More)
High body mass index (BMI) is associated with cardiovascular risk factors such as hypertension, dyslipidemia, and insulin resistance. Obesity is also an independent risk factor for coronary artery disease (CAD) and can cause structural as well as functional changes in the heart. High BMI is associated with increased mortality in the population. Weight-loss from a state of overweight or obesity may reverse some of the alternations associated with excess weight. However, the survival benefit of weight-loss among the population is still uncertain.



The aims of this thesis were to examine the prognostic importance of BMI and weight-change in patients with CAD. A total of 12 550 patients with CAD, 94% with prior acute myocardial infarction (AMI), were included in our post-hoc analyses. Patients were recruited from 3 large clinical trials in which weight and height were measured. Mean follow-up ranged from 6 months to 5.4 years. Patients were categorized into 4 groups according to baseline BMI: underweight (< 22.00 kg/m2), normal-weight (22.00-24.99 kg/m2), overweight (25.00-29.99 kg/m2), obese (>/= 30 kg/m2). Patients were divided into 3 groups with regard to weight-change; weight-loss, weight-stability and weight-gain. Weight-change was pre-defined as weight-gain or weight-loss from baseline of > 0.1 kg per baseline BMI-unit. Consequently, for a patient with a BMI of 25 kg/m2, a change of > ±2.5 kg was categorized as a weight-change. This corresponds to 3-3.5% change in total body-weight. Weight-change was assessed after 3-12 months.



One of the main findings in this thesis was that among patients with CAD, being overweight or obese was not associated with increased mortality or morbidity risk, compared to being normal-weight. Being underweight was significantly associated with increased mortality risk compared to being normal-weight. The prognostic impact of BMI was related to time of follow-up as well as the inherent risk of the patient. It seems that obesity might be hazardous during longer period of follow-up and when the inherent risk of the patient is low.



Another finding is that the association between BMI and prognosis was related to treatment with neurohormonal blockade, i.e. ACE inhibitors and betablockers. Increased activation of the renin angiotensin system and the sympathetic nervous system is common in patients with CAD. Being overweight or obese was associated with decreased survival among patients not receiving neurohormonal blockade. Among patients receiving neurohormonal blockade, overweight and obese patients did not have increased mortality compared to normal-weight patients.



Weight-loss was not associated with survival benefits among patients with CAD. Compared to weight-stability, weight-loss was rather associated with increased mortality, independent of baseline BMI. Weight-gain had similar risk compared to weight-stability. The reasons for these observations are likely multifactorial. Importantly, our findings do not preclude a benefit of weight-loss in response to exercise training as part of a cardiac rehabilitation program.



Our observations expand the knowledge about how BMI and body weight-change are related to the prognosis in patients with stable CAD and following AMI. These findings reinforce the need for a better understanding of the importance of BMI and the complexity of weight-change to the prognosis among these patients. Our data do not indicate that obesity is a negative factor in patients with CAD today, whereas underweight is. Further, our observations indicate that weight-loss in patients with established CAD should render every doctor's attention and underlying reasons should be explored. These associations and their causes should be further assessed in future investigations. Meanwhile, we believe that our main focus should be on preventing obesity early in life. In other words, obesity should be prevented rather than treated. (Less)
Abstract (Swedish)
Popular Abstract in Swedish

Det är välkänt att övervikt och fetma är starkt associerade med sjukliga förändringar i hjärtkärlsystemet och ökar risken att drabbas av hjärtkärlsjukdom och förtida död. Trots att viktnedgång hos överviktiga kan leda till en tillbakagång av sjukliga förändringar i hjärta och kärl, har man dock inte klart visat att viktnedgång leder till minskad risk att drabbas av hjärtkärlsjukdom eller till förbättrad överlevnad.



Denna avhandling har studerat hur övervikt/fetma och viktförändring är relaterade till överlevnad hos patienter med kranskärlssjukdom. Totalt har ca 12 550 patienter ingått i analyserna och nästan samtliga har haft hjärtinfarkt. Patienterna har hämtats från 3 stora... (More)
Popular Abstract in Swedish

Det är välkänt att övervikt och fetma är starkt associerade med sjukliga förändringar i hjärtkärlsystemet och ökar risken att drabbas av hjärtkärlsjukdom och förtida död. Trots att viktnedgång hos överviktiga kan leda till en tillbakagång av sjukliga förändringar i hjärta och kärl, har man dock inte klart visat att viktnedgång leder till minskad risk att drabbas av hjärtkärlsjukdom eller till förbättrad överlevnad.



Denna avhandling har studerat hur övervikt/fetma och viktförändring är relaterade till överlevnad hos patienter med kranskärlssjukdom. Totalt har ca 12 550 patienter ingått i analyserna och nästan samtliga har haft hjärtinfarkt. Patienterna har hämtats från 3 stora vetenskapliga studier i vilka längd och vikt mätts vid upprepade tillfällen. Analyserna avseende den prognostiska betydelsen av övervikt/fetma respektive viktförändring har varit sk. efterhandsanalyser. Detta innebär att studierna i vilka patienterna deltagit inte ursprungligen varit ämnade för dessa analyser. Dessa studier har i stället gjorts för att undersöka effekter av olika läkemedel på överlevnad och sjuklighet vid kranskärlssjukdom, särskilt efter hjärtinfarkt. Uppföljningstiden i de 3 studierna har varierat mellan ca 6 månader och 5.4 år i medeltal.



Patienterna har indelats i olika grupper beroende på sk. body mass index (BMI), dvs. kroppsvikt justerad för kroppslängd. Undervikt har definierats som BMI < 22 kg/m2, normalvikt som 22-24.99 kg/m2, övervikt som 25-29.99 kg/m2, och fetma som minst 30 kg/m2. Patienterna har också indelats i olika grupper beroende på viktförändring. Viktnedgång har definierats som en viktminskning om mer än 0.1 kg per BMI i utgångsläget. Vid en BMI på 25 i utgångsläget har således en viktminskning om mer än 2.5 kg krävts för att räknas som en viktminskning. Motsvarande definition har tillämpats för viktuppgång. Viktförändringen har uppmätts under 3-12 månader.



Ett tydligt fynd är att övervikt/fetma inte visat sig innebära någon ökad risk jämfört med normal vikt hos patienter med kranskärlssjukdom. Underviktiga patienter har däremot uppvisat klart försämrad överlevnad. Det förefaller dock som om fetma skulle kunna vara en riskfaktor på längre sikt. Det är också möjligt att fetma kan vara en riskfaktor hos de patienter som är minst sjuka av sin kranskärlssjukdom.



Ett annat fynd är att sambandet mellan BMI och prognos tycks påverkas av behandling med läkemedel som motverkar effekterna av aktivering av stresshormonella system. De läkemedel som avses är sk. ACE hämmare och betablockerare. Aktivering av stresshormonella system är mycket vanlig efter hjärtinfarkt. Således sågs ett samband mellan övervikt/fetma och försämrad överlevnad hos patienter som inte erhöll någon behandling med ACE hämmare eller betablockerare, medan något sådant samband inte sågs bland patienter som erhöll sådan behandling. I dag behandlas patienter med kranskärlssjukdom, särskilt efter hjärtinfarkt, vanligen med dessa typer av läkemedel.



Ytterligare ett fynd är att viktnedgång inte var relaterad till någon förbättrad prognos. Inte ens hos överviktiga/feta patienter sågs något sådant samband. Snarare var det så att viktnedgång var relaterad till sämre överlevnad, medan viktuppgång inte var relaterad till sämre överlevnad. Orsakerna till dessa observationer kan vara många och dessa fynd utesluter inte att viktnedgång som resultat av sunt leverne, innefattande lagom motion och bra kost, kan minska sjuklighet och förbättra överlevnad bland överviktiga/feta individer med kranskärlssjukdom. Dock bör orsakerna till viktnedgång utrönas hos patienter med kramskärlssjukdom. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Coats, Andrew, Faculty of Medicine, University of Sydney, Australia
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Medicine (human and vertebrates), Cardiovascular system, Medicin (människa och djur), Kardiovaskulära systemet, prognosis, coronary artery disease, body mass index
publisher
Department of Clinical Sciences, Lund University
defense location
Medicinska Klinikens aula, ingång 35, Universitetssjukhuset MAS, Malmö
defense date
2006-05-23 13:00:00
ISBN
91-85481-96-3
language
English
LU publication?
yes
additional info
The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Emergency medicine/Medicine/Surgery (013240200)
id
ba7043d6-13c8-4767-939b-d31d7ce36478 (old id 546766)
date added to LUP
2016-04-01 16:03:58
date last changed
2018-11-21 20:38:27
@phdthesis{ba7043d6-13c8-4767-939b-d31d7ce36478,
  abstract     = {High body mass index (BMI) is associated with cardiovascular risk factors such as hypertension, dyslipidemia, and insulin resistance. Obesity is also an independent risk factor for coronary artery disease (CAD) and can cause structural as well as functional changes in the heart. High BMI is associated with increased mortality in the population. Weight-loss from a state of overweight or obesity may reverse some of the alternations associated with excess weight. However, the survival benefit of weight-loss among the population is still uncertain.<br/><br>
<br/><br>
The aims of this thesis were to examine the prognostic importance of BMI and weight-change in patients with CAD. A total of 12 550 patients with CAD, 94% with prior acute myocardial infarction (AMI), were included in our post-hoc analyses. Patients were recruited from 3 large clinical trials in which weight and height were measured. Mean follow-up ranged from 6 months to 5.4 years. Patients were categorized into 4 groups according to baseline BMI: underweight (&lt; 22.00 kg/m2), normal-weight (22.00-24.99 kg/m2), overweight (25.00-29.99 kg/m2), obese (&gt;/= 30 kg/m2). Patients were divided into 3 groups with regard to weight-change; weight-loss, weight-stability and weight-gain. Weight-change was pre-defined as weight-gain or weight-loss from baseline of &gt; 0.1 kg per baseline BMI-unit. Consequently, for a patient with a BMI of 25 kg/m2, a change of &gt; ±2.5 kg was categorized as a weight-change. This corresponds to 3-3.5% change in total body-weight. Weight-change was assessed after 3-12 months.<br/><br>
<br/><br>
One of the main findings in this thesis was that among patients with CAD, being overweight or obese was not associated with increased mortality or morbidity risk, compared to being normal-weight. Being underweight was significantly associated with increased mortality risk compared to being normal-weight. The prognostic impact of BMI was related to time of follow-up as well as the inherent risk of the patient. It seems that obesity might be hazardous during longer period of follow-up and when the inherent risk of the patient is low.<br/><br>
<br/><br>
Another finding is that the association between BMI and prognosis was related to treatment with neurohormonal blockade, i.e. ACE inhibitors and betablockers. Increased activation of the renin angiotensin system and the sympathetic nervous system is common in patients with CAD. Being overweight or obese was associated with decreased survival among patients not receiving neurohormonal blockade. Among patients receiving neurohormonal blockade, overweight and obese patients did not have increased mortality compared to normal-weight patients.<br/><br>
<br/><br>
Weight-loss was not associated with survival benefits among patients with CAD. Compared to weight-stability, weight-loss was rather associated with increased mortality, independent of baseline BMI. Weight-gain had similar risk compared to weight-stability. The reasons for these observations are likely multifactorial. Importantly, our findings do not preclude a benefit of weight-loss in response to exercise training as part of a cardiac rehabilitation program.<br/><br>
<br/><br>
Our observations expand the knowledge about how BMI and body weight-change are related to the prognosis in patients with stable CAD and following AMI. These findings reinforce the need for a better understanding of the importance of BMI and the complexity of weight-change to the prognosis among these patients. Our data do not indicate that obesity is a negative factor in patients with CAD today, whereas underweight is. Further, our observations indicate that weight-loss in patients with established CAD should render every doctor's attention and underlying reasons should be explored. These associations and their causes should be further assessed in future investigations. Meanwhile, we believe that our main focus should be on preventing obesity early in life. In other words, obesity should be prevented rather than treated.},
  author       = {Kennedy, Linn},
  isbn         = {91-85481-96-3},
  language     = {eng},
  publisher    = {Department of Clinical Sciences, Lund University},
  school       = {Lund University},
  title        = {The importance of body mass index and weight-change in patients with coronary artery disease},
  year         = {2006},
}