CHICAGO -- Sodium intake had a bigger-than-expected relationship with blood pressure in a twin study presented here.
Among 88 identical twin pairs enrolled in Milwaukee and East Lansing, Michigan, 37 had blood pressure (BP) that differed by ≥ 10 mm Hg between co-twins (who were both off antihypertensive medications). In these so-called "discordant" pairs, BPs averaged 138/85 mm Hg for one and 121/77 mm Hg for the other, according to Vidyka Kidambi, MD, of Milwaukee's Medical College of Wisconsin, and colleagues.
On average, twins with higher BP ate more sodium per the Block Sodium Screener (3,900 versus 3,261 mg/day) and had greater waist circumference (105 cm versus 98 cm), Kidambi showed in a poster at Hypertension 2018, jointly sponsored by the American Heart Association and the American Society of Hypertension.
Differences in sodium intake were significant independent of central adiposity, indicating significant sodium sensitivity in discordant twin pairs, the researchers concluded. They highlighted that the effect of about 500 mg less sodium per day suggests that modest decreases in sodium intake among sodium-sensitive individuals may be sufficient to see a reduction in BP. However, the study did not address other dietary factors or other parameters that may correlate with sodium intake and influence blood pressure.
"I'm not surprised that decreased sodium intake was associated with decreased BP," commented Matthew Denker, MD, of the Hospital of University of Pennsylvania. "But I was surprised by the effect size seen -- 17 mm Hg by my quick calculation. This greatly exceeds the typical numbers quoted," he told MedPage Today.
The twin study did not actually look at an intervention to lower sodium, pointed out Donald Lloyd-Jones, MD, of Northwestern University in Chicago. He said that the study had an "interesting design," even if it is already known from controlled studies that reducing sodium intake from usual levels will lower BP.
Lloyd-Jones and Denker were not involved in the study.
The twins included in the study were age 44 on average, and 63% were women, while 96% were Caucasian. BP was taken as an average of three measurements.
Kidambi disclosed no relevant relationships with industry.