More on HDL Levels and Human Longevity

You might recall that studies of centenarians turned up an association between reaching that age and levels of HDL, high density lipoprotein, a form of cholesterol transport mechanism. Here is another study demonstrating the same correlation for younger old people: "No previous researchers have sought to determine whether high-density lipoprotein (HDL) cholesterol levels are associated with survival to 85 years of age in a prospective cohort of aging men. We selected 652 men (mean age 65 years) enrolled in the VA Normative Aging Study who had [at least one] HDL cholesterol level documented during the study and who were old enough on the date of HDL cholesterol measurement to reach 85 years of age by [2008]. ... We used proportional hazards to determine hazard ratios (HRs) for mortality before age 85 years for each category of initial HDL cholesterol compared to the reference adjusting for co-morbidities, calculated low-density lipoprotein cholesterol, medications, smoking, body mass index, and alcohol consumption. Treating HDL cholesterol as a continuous predictor, we also determined the HR for each 10-mg/dl increment in HDL cholesterol. ... Each 10-mg/dl increment in HDL cholesterol was associated with a 14% [decrease] in risk of mortality before 85 years of age. In conclusion, after adjusting for other factors associated with longevity, higher HDL cholesterol levels were significantly associated with survival to 85 years of age." Which leads to the thought that if HDL is so good, why not test to see if artificially creating more of it in the body is beneficial?