Hypocholesterolemia

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Hypocholesterolemia is the presence of abnormally low (hypo-) levels of cholesterol in the blood (-emia). While hypercholesterolemia, the presence of high cholesterol, has been linked strongly with cardiovascular disease, it is much less certain whether low cholesterol levels are intrinsically harmful.

Contents

[edit] Classification

According to most authorities, only total cholesterol levels below 160 mg/dL or 4.1 mmol/l are to be classified as "hypocholesterolemia"[1].

[edit] Causes

Possible causes of low cholesterol are:[citation needed]

[edit] Role in disease

With the increased use of medication to suppress cholesterol, some have expressed concern that lowering cholesterol levels excessively will itself cause disease.

[edit] Specific disease entities

Demographic studies suggest that cholesterol levels form an U-shape curve when plotted against mortality; this suggests that low cholesterol is associated with increased mortality, mainly due to depression, cancer, hemorrhagic stroke and respiratory diseases.[3] It is possible that whatever causes the low cholesterol level also causes mortality, and that the low cholesterol is simply a marker of poor health.[1]

Links with depression have been supported by studies.[4] In contrast, no evidence was found for a link with hemorrhagic stroke (although higher cholesterol levels conferred a relative protection), and neither did statin drugs worsen the risk.[5].

The Heart Protection Study found no increase in either respiratory disease or neuropsychiatric illness in a large trial population taking a statin drug.[6]

[edit] Elderly

In the elderly, low cholesterol may confer a health risk that may not be offset by the beneficial effects of cholesterol lowering.[7] Similarly, for elderly patients admitted to hospital, low cholesterol may predict short-term mortality.[8]

[edit] Critical illness

In the setting of critical illness, low cholesterol levels are predictive of clinical deterioration, and are correlated with altered cytokine levels.[9]

[edit] References

  1. ^ a b Criqui MH. (1994). Very Low Cholesterol and Cholesterol Lowering. Leaflet 71-0059. American Heart Association.
  2. ^ Marini A, Carulli G, Azzarà A, Grassi B, Ambrogi F (1989). "Serum cholesterol and triglycerides in hematological malignancies". Acta Haematol. 81 (2): 75–9. PMID 2496554. 
  3. ^ Jacobs D, Blackburn H, Higgins M, et al (1992). "Report of the Conference on Low Blood Cholesterol: Mortality Associations". Circulation 86 (3): 1046–60. PMID 1355411. 
  4. ^ Suarez EC (1999). "Relations of trait depression and anxiety to low lipid and lipoprotein concentrations in healthy young adult women". Psychosom Med 61 (3): 273–9. PMID 10367605. 
  5. ^ Woo D, Kissela BM, Khoury JC, et al (2004). "Hypercholesterolemia, HMG-CoA reductase inhibitors, and risk of intracerebral hemorrhage: a case-control study". Stroke 35 (6): 1360–4. doi:10.1161/01.STR.0000127786.16612.A4. PMID 15087556. 
  6. ^ "MRC/BHF Heart Protection Study of cholesterol lowering with simvastatin in 20,536 high-risk individuals: a randomised placebo-controlled trial" (2002). Lancet 360 (9326): 7–22. doi:10.1016/S0140-6736(02)09327-3. PMID 12114036. 
  7. ^ Schatz IJ, Masaki K, Yano K, Chen R, Rodriguez BL, Curb JD (2001). "Cholesterol and all-cause mortality in elderly people from the Honolulu Heart Program: a cohort study". Lancet 358 (9279): 351–5. doi:10.1016/S0140-6736(01)05553-2. PMID 11502313. 
  8. ^ Onder G, Landi F, Volpato S, et al (2003). "Serum cholesterol levels and in-hospital mortality in the elderly". Am. J. Med. 115 (4): 265–71. doi:10.1016/S0002-9343(03)00354-1. PMID 12967690. 
  9. ^ Gordon BR, Parker TS, Levine DM, et al (2001). "Relationship of hypolipidemia to cytokine concentrations and outcomes in critically ill surgical patients". Crit. Care Med. 29 (8): 1563–8. doi:10.1097/00003246-200108000-00011. PMID 11505128. 
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