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Abstract
Background: Blood serum lipid levels are often used as indicators of cardiovascular disease (CVD) risk, while diet quality has an established impact on blood serum lipid levels, including low- and high-density lipoproteins (LDL and HDL) and their corresponding apoproteins, apoB and apoA1 respectively, as well as triglycerides (TGs) and total cholesterol (TC). Diabetes mellitus (DM) is also an established risk factor for CVD, and dyslipidemia is a hallmark of accompanying metabolic disturbances, manifesting as hypertriglyceridemia, high serum levels of LDL, and lowered HDL. This study seeks to investigate the relation of diet quality, diabetes, and blood lipid levels, amongst American Indians (AIs) who participated in the Strong Heart Family Study (SHFS)—a longitudinal study of CVD and its risk factors in 12 AI communities in Arizona, North Dakota, South Dakota, and Oklahoma. To date no published studies have examined the relation of global diet quality, lipids, and diabetes in AIs.
Methods: This investigation included all SHFS participants who completed a baseline exam in 2001-2003 with available and plausible diet, lipids, and diabetes data. Block Food Frequency Questionnaires (FFQ) were used to estimate usual past-year dietary intake, and the Alternative Healthy Eating Index (AHEI) and Nettleton index were used to evaluate quality. Primary outcomes for analysis included TC (mg/dL), TG (mg/dL), HDL (mg/dL), LDL (mg/dL), and lipoproteins ApoA and ApoB. Covariates of interest included age, sex, site, BMI, waist circumference, energy intake, physical activity, systolic blood pressure, diastolic blood pressure, cigarette smoking, alcohol use, and prevalent diabetes. Generalized estimated equations (GEE) with an independence working correlation and robust standard errors and were used to estimate the cross-sectional associations of diet quality (as determined by both AHEI and the alternate index) with blood lipid level outcomes in the form of TC, TG, LDL, HDL, ApoA, and ApoB. For all analyses, potential modification of the association of diet quality with blood lipid levels by diabetes status was examined. Additional secondary analyses also examined the longitudinal association of diet quality in 2001-2003 with blood lipid levels in 2006-2009.
Results: Participants with diabetes had higher diet scores than those without diabetes (i.e., on average, participants with diabetes had scores 2.8 points higher for AHEI scoring and 2.3 points higher for Nettleton scoring when compared to participants without diabetes). Negative interactions with significance of diabetes and diet score on blood lipid outcomes were observed for TC (p < 0.01), LDL (p = 0.01), and ApoB (p < 0.01) for AHEI scores assessed, and TC (p < 0.01), LDL (p = 0.03}, and ApoB (p = 0.01) in Nettleton diet scoring. For longitudinal analyses, significant interactions of diabetes and diet scores on blood lipid outcomes occurred in TC only for both Nettleton (p = 0.03) and AHEI (p = 0.01) indices.
Conclusions: The interaction of diet quality and blood lipid status by diabetes status is significant in this cohort for TC, LDL, and ApoB outcomes. Given the disproportionate and increasing burden of T2DM, CVD, and associated mortality in AI populations, enabling resources that reduce population T2DM incidence while promoting greater glycemic control within individuals currently living with T2DM may reduce CVD risk and improve overall mortality within this population.
