Introduction: Fatty acids (FAs) are essential components of cell membranes and play an integral role in membrane fluidity. The lipophilic index (LI, defined as the sum of the products between FA percentage and melting points (°C) of each FA, divided by the total percentage of FAs) is a novel index that captures the overall FA profile and reflects lipoprotein fluidity. Limited studies have evaluated the relationship between plasma LI and CHD risk, and none has assessed this association among postmenopausal women.
Hypothesis: Higher plasma LI is associated with increased CHD risk among postmenopausal women.
Methods: In a nested case-control study in Women’s Health Initiative Observational Study, we measured levels of plasma phospholipid FAs, expressed as molar percentage (mol%), in 1214 matched CHD cases (including myocardial infarction and coronary death) and controls. Multivariate conditional logistic regression was used to calculate ORs for CHD risk between each quartiles (based on controls) of LI after adjusting for confounders.
Results: The mean age of the women was 67.8±6.8 years, average BMI was 27.6±6.0, 89.5% were White, 6.6% were current smokers, 41.2% were hypertensive, and 15.2% had dyslipidemia. The median plasma LI among cases and controls were 22.5 and 22.1, respectively. Palmitic acid (16:0) and stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), and docosahexaenoic acid (22:6) were the most common saturated, monounsaturated, n-6 and n-3 polyunsaturated FAs, respectively. The association between quartiles of LI and CHD risk are shown in Table below. After multivariate adjustment in the parsimonious model, plasma LI was significantly associated with an increased risk of CHD: OR=1.61 (95% CI 1.25-2.07, P for trend<0.01) comparing extreme quartiles. This association was attenuated to 1.57 (1.22 - 2.03, P for trend<0.01) in the fully adjusted model.
Conclusion: Our study indicated that higher plasma LI, which represents lower FA fluidity, was associated with higher risk of CHD among postmenopausal women.