It is well known that people die more commonly during cold seasons of the year, especially of cardiovascular and respiratory disease. Several studies on older people have shown that blood pressure, and measures of infammation, tend to be higher in colder weather. We do not know however if these things actually cause people to die in winter. Also, we do not know if these patterns also exist in children. We wish to investigate the seasonal relationship between blood pressure and inflammatory factors with outdoor temperature at the time these measurements have been made in the ALSPAC children and mothers. We will look at changes in these markers on repeated measures of the participants, to see if these measures are particularly raised during cold weather spells. We will link temperature data from the Meteorological Office to the dates when participants were measured. We will also use information about the participants such as their age, sex and socioeconomic status, to see if this modifies their response to cold weather. In the same way, we will use data the participants have provided about their housing, to see whether certain types of house protect people better (for example, houses with central heating, or insulation).