Changes in the rate of some cardiovascular diseases of seafarers before and after the voyage (n = 230) Research results Disease Before voyage After voyage p n% n% Arrhythmia 91 39.57 96 41.74 > 0.05 Ischemic heart disease 10 43.50 14 6.09 > 0.05 Hypertension 82 35.65 127 45.36 0.039 Hypertension grade 1 48 17.14 50 17.86 > 0.05 Hypertension grade 2 37 13.21 51 18.21 < 0.001 Hypertension grade 3 13 4.65 26 9.29 < 0.001 Note: Research results from Table 3.5 show that among the diseases of the circulatory system of seafarers working on ocean-going ships, hypertension is the highest proportion, mainly degree 1 and 2, followed by arrhythmia.