Cholesterol in the bloodstream is carried within protein-rich packages known as ‘lipoproteins’. These come in two main types, so-called ‘low-density lipoprotein-cholesterol’ (LDL-C) and ‘high-density lipoprotein-cholesterol’ (HDL-C). Conventional wisdom has it that LDL-C is responsible for dumping cholesterol on the inside of arteries, and is dubbed ‘bad cholesterol’ as a result. On the other hand, HDL-cholesterol is said to be a sign of cholesterol being cleared from the inside of arteries, as is generally thought of as ‘good cholesterol’.
I was interested to read a recent study in which the associations between LDL- and HDL-C levels and degree of arterial disease were assessed in a group of individuals age 80 and over [1]. Arterial disease was assessed via calcium scoring. This test is believed to provide an accurate measure of the degree of build up of ‘atherosclerotic plaque’ on the inside of the arteries around the heart.
In this study, low levels of HDL-C were associated with higher calcium scores (and therefore the degree of arterial disease). This finding is consistent with conventional wisdom. However, this study also found that there was no association at all found between LDL-C levels and calcium scores in this population. This result does ask questions about the general assumption that higher levels of LDL-C are a ‘bad sign’ in older individuals.
In fact, there is evidence to the contrary. For instance, in a study published earlier this year, higher levels of both total cholesterol and LDL-C were found to be associated with a reduced risk of death in individuals aged 85 followed for 10 years [2].
In another study published last year, researchers assessed the levels of cholesterol and risk of death in almost 120,000 adults living in Denmark [3]. The researchers found that having higher than recommended levels of total cholesterol was associated with a reduced risk of death.
For instance, in men aged 60-70, compared with those of total cholesterol levels of less than 5.0 mmol/l, those with total cholesterol levels of 5.00-5.99 had a 32 per cent reduced risk of death. For those with levels 6.0-7.99 mmol/l, risk of death was 33 per cent lower. Even in individuals with levels with 8.00 mmol/l and above, risk of death was no higher than it was for those with levels less than 5.0 mmol/l.
The results were similar for women too. In women aged 60-70, levels of 5.0-5.99 and 6.0-7.99 were associated with a 43 and 41 per cent reduced risk of death respectively.
In individuals aged 70 and over, the results were similar, except here, levels of total cholesterol of 8.00 mmol/l or more were associated with a reduced risk of death too (in both men and women).
In short, we are misguided if we assumed that higher levels of cholesterol are a sign of increased death risk. In older individuals, there is evidence that the reverse is true.
References:
1. Freitas WM, et al. Low HDL cholesterol but not high LDL cholesterol is independently associated with subclinical coronary atherosclerosis in healthy octogenarians. Aging Clin Exp Res. 2014 Jun 7. [Epub ahead of print]
2. Takata Y, et al. Serum total cholesterol concentration and 10-year mortality in an 85-year-old population. Clin Interv Aging. 2014;9:293-300
3. Association of lipoprotein levels with mortality in subjects aged 50 + without previous diabetes or cardiovascular disease: A population-based register study. Scandinavian Journal of Primary Health Care 2013;31(3):172-180
