TOKYO, June 8 : Japan's economy lost momentum in the January-March quarter from the previous three months over sluggish capital expenditure, revised gross domestic product (GDP) data showed on Monday, pointing to challenges ahead due to the Middle East conflict. The GDP figures released by the Cabinet Office showed the economy expanded an annualised 1.8 per cent in the first quarter, compared with the initially estimated 2.1 per cent. Economists' median forecast was for 1.3 per cent growth.