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, ISI0,120) 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/m(2) [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 ( >= 1 BP stage increase) and 18% had development of hypertension (systolic BP >= 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 ISI0,120 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.