Abstract
Plasma lipid testing is a key component of cardiovascular disease (CVD) screening. The last national survey of lipid levels was in 2009 and no studies have investigated lipids in the southern region of NZ. The aim of this study was to investigate changes in plasma lipid levels over time in Otago adults. We performed retrospective analysis of 883,793 community-requested lipid profiles from adults aged 18 to 100 years of age living in the Otago region from 1995-2021.
Over the 27-year period, mean total cholesterol (TC) levels fell from 6.38 mmol/L (95% CI 6.33-6.42) to 5.25 mmol/L (5.23-5.26) in women and from 6.17 mmol/L (6.14-6.21) to 4.83 mmol/L (4.81-4.84) in men. Low-density lipoprotein cholesterol shows a similar decline. High-density lipoprotein cholesterol (HDLc) peaked in 2006 at 1.66 mmol/L (1.65-1.66) for women and 1.36 mmol/L for men (1.36-1.37), declining to 1.57 mmol/L (1.56-1.58) and 1.26 mmol/L (1.26-1.26) respectively in 2021. Plasma triglycerides (TG) show a U-shaped distribution, falling to 1.39 mmol/L (1.38-1.40) for women and 1.55 mmol/L (1.53-1.56) for men in 2010, then increasing to 1.68 mmol/L (1.67-1.69) and 1.98 mmol/L (1.96-1.99) in 2021. Recent studies suggest TG to HDLc ratio (TG:HDLc) and remnant cholesterol (consisting of very low and intermediate density lipoprotein cholesterol) are strong risk factors for myocardial infarction, stroke and all-cause mortality. Both show U-shaped distributions in the Otago population, with 2021 mean values exceeding the recommended targets.
While traditional markers of CVD risk appear to be improving in Otago, increasing levels of alternative markers, TG:HDLc and remnant cholesterol, are concerning. There is a need for further monitoring and investigation of their association with CVD morbidity and mortality.