Relations of insulin sensitivity to longitudinal blood pressure tracking: Variations with baseline age, body mass index, and blood pressure

Background - The relations of insulin sensitivity (IS) to hypertension incidence may vary according to baseline age, body mass index (BMI), and blood pressure (BP). Methods and Results - We investigated the relations of IS (insulin sensitivity index, ISI_0,120) to 4-year incidence of hypertension and BP progression in 1933 nonhypertensive Framingham Study participants (median age, 51 years; 56% women). Analyses were stratified by age (less than versus greater than or equal to median), BMI (<25 [normal], 25 to <30 [overweight], ≥30 kg/m² [obese]), and BP category (systolic BP≥130 or diastolic BP≥85, "high normal" per the sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High BP [JNC-VI] versus BP<130/85 mm Hg). On follow-up, 41% of participants had BP progression (2:1 BP stage increase) and 18% had development of hypertension (systolic BP2:140 or diastolic BP>90 mm Hg or antihypertensive medication use). In younger (<51 years) people with normal BMI and baseline BP<130/85 mm Hg, the second-to-fourth ISI_0,120 quartiles were associated with lower multivariable-adjusted odds for hypertension incidence (0.27; 95% CI, 0.09 to 0.83; P<0.05) and BP progression (0.37; 95% CI, 0.18 to 0.77; P<0.01) relative to the lowest (most insulin resistant) quartile. IS was not related to BP progression or hypertension incidence in older individuals, in obese participants, or in people with BP≥ 130/85 mm Hg. Conclusions - In our large community-based sample, reduced IS predicted BP tracking principally in younger people with normal BMI and BP< 130/85 mm Hg. Effect modification by age, BMI, and baseline BP may explain variation in the results of prior clinical investigations relating IS to hypertension incidence.