The essence ofthe scientific method is reproducing precisely the methods and patient cohortofthe original study, something most of us learn in 9th grade science.
The strengths ofthe Swedish study reviewed here include the large population based prospective cohort design along with the long period of follow up to validate the composition ofthe kidney stones.
The researchers looked at data on children featured in the British CohortStudy - a large group of people born in April 1970 - to look at the link between reading and maths scores at age 10, and earnings at ages 30, 34 and 38.
NicVAX was evaluated in a recent study in the American Journal of Psychiatry, in a small cohortof 11 smokers who smoked an average of 19 cigarettes per day, smoked for an average of 10 years, thereby meeting criteria for nicotine dependence.
Other limitations ofthe Swedish study reviewed here include the fact that it was based on an observational cohort and that we cannot obviously know the other lifestyle factors ofthecohort which may have contributed to stone formation.