Coronary risk factors, diet and vitamins as possible explanatory factors of the Swedish north–south gradient in coronary disease: a comparison between two MONICA centres

OBJECTIVE: To investigate whether differences in serum lipids, diet, plasma vitamins or other risk factors explain the higher incidence of cardiovascular disease in the northern parts of Sweden, compared to Göteborg on the west coast. DESIGN: A comparison between the two Swedish MONICA populations in northern Sweden (NSW) and in Göteborg (GOT) in 1990. SETTING: Norrbotten and Västerbotten counties in the north of Sweden and the city of Göteborg on the west coast. SUBJECTS: In the north 1583 men and women aged 25-64 years were investigated, and in Göteborg 1574 men and women. Plasma vitamins were examined in a subsample of men aged 40-49 (n = 259). MAIN OUTCOME MEASURES: Serum lipids, blood pressure, anthropometric measurements, smoking habits, physical activity, diet, education, and plasma vitamins. RESULTS: NSW men and women had mean serum total cholesterol of 6.30 (standard deviation 1.23) mmol L-1 and 6.12 (1. 33) mmol L-1, compared to 5.75 (1.14) mmol L-1 and 5.67 (1.24) mmol L-1 in GOT men and women (P = 0.0001). NSW men and women were shorter and had higher body mass index than in Göteborg. Cigarette smoking was slightly more prevalent amongst GOT men and women. Göteborg men and women more often had more than compulsory school education, compared to NSW men and women, whereas there were no differences in physical activity during leisure time. There were no differences in vegetable consumption, whereas fruit was consumed more frequently by NSW women compared to GOT women, with a higher intake of fibre and ascorbate. Consumption of wine and total alcohol consumption were higher in Göteborg, whereas NSW men and women drank significantly more coffee. In the subsample of men (aged 40-49) who had plasma vitamins measured, men in Göteborg had slightly higher mean retinol concentrations (P = 0.005) and lutein and zeaxanthine levels (P = 0.006 and 0.009, respectively) compared to northern men, but there were no differences with respect to alpha- or beta-carotene, ascorbic acid or lipid-adjusted vitamin E. NSW men had slightly higher plasma iron and magnesium concentrations (P = 0.005 and 0.001, respectively). CONCLUSION: The largest and most consistent differences between Göteborg and northern Sweden were found for serum cholesterol, probably reflecting differences in intake of saturated fat. The differences in serum cholesterol may explain a substantial part of the differences in coronary heart disease morbidity and mortality. We found no consistent differences concerning vegetable and fruit consumption. More alcohol was consumed in Göteborg. Differences in education and childhood conditions, as reflected in differences in height, may contribute to the north-south gradient with respect to CHD incidence and mortality.