Reverse epidemiology

Reverse epidemiology is a term for a medical hypothesis which holds that obesity and high cholesterol may, counterintuitively, be protective and associated with greater survival in certain groups of people, such as very elderly individuals or those with certain chronic diseases. It further postulates that normal to low body mass index or normal values of cholesterol may be detrimental and associated with higher mortality in asymptomatic people.

The terminology was first proposed by Kamyar Kalantar-Zadeh in the journal Kidney International in 2003^[1] and in the Journal of American College of Physicians in 2004.^[2] It is a contradiction to prevailing concepts of prevention of atherosclerosis and cardiovascular disease; however, active prophylactic treatment of heart disease in otherwise healthy, asymptomatic people is and has been controversial in the medical community for several years.^[3][4]

Obesity survival paradox

Although the negative health consequences of obesity in the general population are well supported by the available evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox.^[5] The paradox was first described in 1999 in overweight and obese people undergoing hemodialysis,^[5] and has subsequently been found in those with heart failure, and peripheral artery disease (PAD).^[6]

In people with heart failure, those with a BMI between 30.0–34.9 had lower mortality than those with a normal weight. This has been attributed to the fact that people often lose weight as they become progressively more ill.^[7] Similar findings have been made in other types of heart disease. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, risk of further events is increased.^[8][9] Even after cardiac bypass surgery, no increase in mortality is seen in the overweight and obese.^[10] One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event.^[11] Another found that if one takes into account chronic obstructive pulmonary disease (COPD) in those with PAD the benefit of obesity no longer exists.^[6]

References

1. ^ Kalantar-Zadeh K, Block G, Humphreys MH, Kopple JD (March 2003). "Reverse epidemiology of cardiovascular risk factors in maintenance dialysis patients". Kidney Int. 63 (3): 793–808. doi:10.1046/j.1523-1755.2003.00803.x. PMID 12631061. 
2. ^ Kalantar-Zadeh K, Block G, Horwich T, Fonarow GC (April 2004). "Reverse epidemiology of conventional cardiovascular risk factors in patients with chronic heart failure". J. Am. Coll. Cardiol. 43 (8): 1439–44. doi:10.1016/j.jacc.2003.11.039. PMID 15093881. http://linkinghub.elsevier.com/retrieve/pii/S073510970400172X. 
3. ^ Naghavi M, Falk E, Hecht HS, Shah PK (December 2006). "The First SHAPE (Screening for Heart Attack Prevention and Education) Guideline". Crit Pathw Cardiol 5 (4): 187–190. doi:10.1097/01.hpc.0000249784.29151.54. PMID 18340236. 
4. ^ Pearson TA (2007). "The prevention of cardiovascular disease: have we really made progress?". Health Affairs 26 (1): 49–60. doi:10.1377/hlthaff.26.1.49. PMID 17211013. http://content.healthaffairs.org/cgi/pmidlookup?view=long&pmid=17211013. Retrieved 2008-08-11. 
5. ^ ^{a b} Schmidt DS, Salahudeen AK (2007). "Obesity-survival paradox-still a controversy?". Semin Dial 20 (6): 486–92. doi:10.1111/j.1525-139X.2007.00349.x. PMID 17991192. 
6. ^ ^{a b} U.S. Preventive Services Task Force (June 2003). "Behavioral counseling in primary care to promote a healthy diet: recommendations and rationale" (^{[dead link]}). Am Fam Physician 67 (12): 2573–6. PMID 12825847. http://www.aafp.org/afp/20030615/us.html. 
7. ^ Habbu A, Lakkis NM, Dokainish H (October 2006). "The obesity paradox: Fact or fiction?". Am. J. Cardiol. 98 (7): 944–8. doi:10.1016/j.amjcard.2006.04.039. PMID 16996880. 
8. ^ Romero-Corral A, Montori VM, Somers VK et al. (2006). "Association of bodyweight with total mortality and with cardiovascular events in coronary artery disease: A systematic review of cohort studies". Lancet 368 (9536): 666–78. doi:10.1016/S0140-6736(06)69251-9. PMID 16920472. 
9. ^ Oreopoulos A, Padwal R, Kalantar-Zadeh K, Fonarow GC, Norris CM, McAlister FA (July 2008). "Body mass index and mortality in heart failure: A meta-analysis". Am. Heart J. 156 (1): 13–22. doi:10.1016/j.ahj.2008.02.014. PMID 18585492. 
10. ^ Oreopoulos A, Padwal R, Norris CM, Mullen JC, Pretorius V, Kalantar-Zadeh K (February 2008). "Effect of obesity on short- and long-term mortality postcoronary revascularization: A meta-analysis". Obesity (Silver Spring) 16 (2): 442–50. doi:10.1038/oby.2007.36. PMID 18239657. 
11. ^ Diercks DB, Roe MT, Mulgund J et al. (July 2006). "The obesity paradox in non-ST-segment elevation acute coronary syndromes: Results from the Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the American College of Cardiology/American Heart Association Guidelines Quality Improvement Initiative". Am Heart J 152 (1): 140–8. doi:10.1016/j.ahj.2005.09.024. PMID 16824844.