Birth weight modifies the association between a healthy Nordic diet and office blood pressure in old age

A healthy diet reduces risk for high blood pressure. A small body size at birth increases risk for high blood pressure. Our aim was to study whether birth weight modifies the association between a healthy Nordic diet, characterized by high intake of Nordic vegetables, fruits, and berries, whole-grain rye, oat, and barley, and rapeseed oil, and blood pressure. Finnish men and women (n = 960) born in 1934–1944 attended clinical visits including clinical measurements, and questionnaires in 2001–2004 and 2011–2013. Linear regression was applied to investigate the interactions between birth weight and Nordic diet (measured by the Baltic sea diet score (BSDS)) on blood pressure change during the 10-year follow-up. Baseline Nordic diet and birth weight showed a significant interaction on systolic blood pressure (SBP) (p = 0.02), and pulse pressure (PP) (p < 0.01) over a 10-year follow-up. In the lowest birth weight category (women < 2951 g, men < 3061 g), predicted SBP decreased across BSDS thirds (lowest (T1): 155 mmHg, highest (T3): 145 mmHg, p for linearity = 0.01) as did predicted PP (T1: 71 mmHg, T3: 63 mmHg, p < 0.01). In the middle birth weight category, predicted SBP increased across BSDS thirds (T1: 151 mmHg, T3: 155 mmHg, p = 0.02) as did predicted PP (T1: 67 mmHg, T3: 71 mmHg, p < 0.01). In the highest birth weight category, no associations were found. Higher adherence to a healthy Nordic diet was associated with lower SBP and PP in individuals with low birth weight but with higher SBP and PP in those with average birth weight.