Researchers found that diarrhoea and dehydration during infancy make hypertension in later life more likely.
The study looked at links between the summer temperatures in the UK between 1919 and 1940 and the current health of UK women born during that period.
The researchers wanted to see if there were any long-term health consequences of the dehydration which was common in the summer months when access to water was not always guaranteed, and when methods of preventing and treating dehydration were less sophisticated. Epidemics of diarrhoea during hot summers were not uncommon.
Animal experiments have shown that dehydration during infancy increases sodium retention. Researchers thought the same would be true in humans.
In addition, a previous study found that hospital admission for dehydration in the first six months of life was associated with higher BP at age seven.
To test the theory in adults, the researchers interviewed and examined the records of 3,964 women aged 60-79 years.
Each woman had her town or city of birth recorded, so that records on the weather during the first three years of life could be found. The mean summer temperature and rainfall of July to September were retrieved.
The researchers found that the average temperature during the first summer of life was positively associated with systolic BP.
An extra 1.3 deg C in the mean temperature during the first summer of life was associated with a 1.12mmHg increase in systolic BP, while an extra 34mm of rainfall during the first summer was associated with a drop of 1.65mmHg systolic BP.
They did not find any effect of summer temperature or rainfall on diastolic BP.
'The physiologic processes that control systolic BP may be more strongly influenced by exposures during early life than those that control diastolic BP,' the researchers concluded.
- Am J Epidemiol 2006;163:608-14