Reasons for the increase in mortality due to coronary heart disease (CHD) in UK Indian
Asians are not well understood. In this study, we tested the hypotheses that elevated
plasma homocysteine concentrations are a risk factor for CHD in Indian Asians, and
explain part of their increased CHD risk, compared with Europeans.
We undertook two parallel case-control studies, one in Europeans and one in Indian
Asians. We recruited 551 male cases (294 European, 257 Indian Asian) and 1025 healthy
male controls (507 European, 518 Indian Asian). Fasting and post-methionine load homocysteine,
vitamin B12 and folate concentrations, and conventional CHD risk factors were measured.
Fasting homocysteine concentrations were 8% higher (95% CI 3-14) in cases compared
with controls, in both ethnic groups. The odds ratio of CHD for a 5 micromol/L increment
in fasting plasma homocysteine was 1.3 (1.1-1.6) in Europeans and 1.2 (1.0-1.4) in
Indian Asians. The association between fasting plasma homocysteine and CHD was independent
of conventional CHD risk factors in both ethnic groups. Post-load homocysteine concentrations
were not significantly different in cases compared with controls. Among the controls,
fasting homocysteine concentrations were 6% (2-10) higher in Indian Asians than in
Europeans. From the results we estimate that elevated homocysteine may contribute
to twice as many CHD deaths in Indian Asians, compared with Europeans. The differences
in homocysteine concentrations between the two ethnic groups were explained by lower
vitamin B12 and folate levels in Asians.
Plasma homocysteine is a novel and independent risk factor for CHD in Indian Asians,
and may contribute to their increased CHD risk. Raised homocysteine concentrations
in Indian Asians may be related to their reduced vitamin B12 and folate levels, implying
that the increased CHD risk in this group may be reduced by dietary vitamin supplementation.