Monday, January 21, 2013

The HUNT2 study: Is Cholesterol bad for you?

Does Cholesterol cause heart disease? The common man think it does. Most doctors also believe the same. Unfortunately there have been no studies that specifically test the relationship 

Norway conducted a 10 year long study named HUNT2. The results were published in 2011.

The Study followed up 52,087 people between 20-74 years of age, between years 1995-2007. They specifically looked at the mortality (ie the number of people who died), and its relation to the total cholesterol values. They also checked the mortality for Ischemic Heart Disease (IHD) and CardioVascular Disease (CVD). CVD is for all heart diseases and IHD is specifically for reduced supply to the heart which results in heart attacks.

There are 3 graphs which we will see below. The graphs show the mortality rate at different Cholesterol values. The values are given in mmol/litre, instead of the mg/dl that we are used to. The conversion would be 5 -> 193; 6 -> 232 ; 7 -> 270. Remember that people are asked to keep their Cholesterol values below 200mg/dl.

The first graph is for Total Mortality.

For men the best value was 193-232, the worst was below 193. Above 232 the death instances increased but not as much as they increased below 193. I have no idea why there are no range for 5.0 and less.
br /> For women, total deaths were lowest above 270mg/dl, it was a nearly linear reverse relationship with total cholesterol. The worst result was below 193.

The second graph is mortality risk by CVD.

For men the best value was again 193-232, the worst was above 232. Above 232 the death instances increased more than below 193.

For women the best result was between 232-270. The worst result was below 193. Between 193-232 was slightly worse than 232-270.

Last graph is mortality risk due to IHD.

IHD for men does give a worst outcome when the Total Cholesterol level increases beyond 232mg/dl. But 193-232 range is slightly better than the lower than 193 case.

For women again the worst case is to have lower than 193mg/dl.

From the conclusion
Based on epidemiological analysis of updated and comprehensive population data, we found that the underlying assumptions regarding cholesterol in clinical guidelines for CVD prevention might be flawed: cholesterol emerged as an overestimated risk factor in our study, indicating that guideline information might be misleading, particularly for women with ‘moderately elevated’ cholesterol levels in the range of 5–7 mmol L. Our findings are in good accord with some previous studies. A potential explanation of the lack of accord between clinical guidelines and recent population data, including ours, is time trend changes for CVD/IHD and underlying causal (risk) factors.
‘Know your numbers’ (a concept pertaining to medical risk factor levels, including cholesterol) is currently considered part of responsible citizenship, as well as an essential element of preventive medical care. Many individuals who could otherwise call themselves healthy struggle conscientiously to push their cholesterol under the presumed ‘danger’ limit (i.e. the recommended cut-off point of 5 mmol L), coached by health personnel, personal trainers and caring family members. Massive commercial interests are linked to drugs and other remedies marketed for this purpose. It is therefore of immediate and wide interest to find out whether our results are generalizable to other populations.
This paper shows us that the current guidelines are flawed at least in the Norway. Is it possible that the commercial interest have somehow influenced the too low cholesterol guidelines?

It seems important for women to keep their cholesterol numbers HIGHER, even if it might not be very clear for men. It seems that the best range for men is between 190 to 230, while for women the best range is bigger from 230-270.

Similar range (200-240) can be seen in the following graph. The graph was constructed using the Mortality data from WHO (2002) and Total Cholesterol data from BHF-HeartStats (2005). The data is per country in both the cases. Its a big image, and blogger does not provide zoom facility, so right click and open in new tab.

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