My fiance and I recently discovered that we are related through our great-grandfathers, who were brothers. Are there any inherited health risks for third cousins like ourselves?

First-cousin marriages put children at risk because they increase the chances of children carrying two recessive genes that can lead to illness. This risk is diminished with each generation away from the common ancestor. If you are worried, you can ask for advice from your local genetic institute. However, in Iceland, where the isolation of the population led to relatives marrying, there may have been advantages for distant cousin partners. There, in studies of cousin and non-related marriages from 1800 to 1965, the third- and fourth-cousin marriages were most successful in rearing healthy children.

Do people have fewer heart attacks now than a generation ago? If so, how come, when more people today are obese?

There has been a 60% fall in the numbers of heart attacks in British men in the past 25 years. The improvement is due to millions stopping smoking, better control of high blood pressure and a big change in the pattern of cholesterol in the blood. However, the gradual rise in obesity in younger and middle-aged adults may change this for the worse as they reach their 60s. There was a similar fall in heart attacks in North America until the late 90s, but the obesity epidemic started sooner there and numbers are rising again. We are about 10 years behind them, so we can't be complacent.

· Do you have a question for Dr Smith? Email doctordoctor@theguardian.com