The world faces numerous threats to public health which are beyond the control of those who suffer. But some of the biggest killers are self-inflicted. Bad diet, smoking, alcohol consumption and lack of exercise are contributing to what has been described as a 'slow-motion disaster'. Unhealthy lifestyles are driving more people into hospital at an early age. The problem goes beyond the suffering of the patient - the economic cost to society can be huge if the problem is not tackled. It is encouraging therefore that world leaders met recently to put the problem on the international agenda. The summit held by the United Nations on non-communicable diseases such as cancer, lung and heart disease is a timely wake-up call. The treatment cost for these diseases is estimated at US$30 trillion globally in 20 years; equal to nearly half of the world domestic product last year. World Health Organisation chief Dr Margaret Chan Fung Fu-chun, from Hong Kong, urged governments to intervene with policies to fight this modern epidemic. There are numerous ways in which people can be encouraged to adopt a healthier lifestyle. A spiralling medical bill drains away public resources and pushes more people into poverty in developing countries. Hong Kong is fortunate enough to have an enviable budget surplus most years. But that does not mean the threat is irrelevant to us. The recurrent public spending on health care has reached HK$40 billion this year, about 15.5 per cent of the budget. The problems arising from an ageing population have already prompted the government to make a belated move to prepare for a voluntary health insurance scheme. Hong Kong is rightly respected for its high medical standards. But we can save medical expenditure - and lives - if fewer people needlessly develop serious illnesses. More should be done to nurture a healthy lifestyle.