These children were compared with a randomly selected, age matched population consisting of 14575 children.
Perhaps a more precise way of defining the health-care burden directly attributable to cancer would be to compare hospitalisation of any kind among cancer survivors with that observed in a randomly selected age- and sex-matched subset of the cancer-free population (or, more practically, the general population).
Age, weight, and height were highly multicollinear (r >0.80); therefore, we selected age as an independent variable representing all three characteristics.
The main strengths of the present study are as follows: (1) the long average follow-up period of 10 years; (2) the use of an older sample of randomly selected age- and sex-stratified non-institutionalized individuals from the community; and (3) the use of serum FA levels to assess DHA or EPA status.
Thus, the selected age distribution of the sample was age 7 to 11 years.
Another limitation may be the selected age group.
In a cross-sectional population-based serosurveillance study conducted in 2006-07, from a randomly selected age-stratified sample of 7,903 persons, serum IgG-Ptx concentrations were analyzed using a fluorescent bead-based multiplex immuno assay.
A randomly selected, age-matched cohort of 7,832 subjects without cancer was selected for comparison.
Recently, Alsowaidi et al. reported indirectly that in a randomly selected, age-stratified cohort of adolescent school children and their caretakers in the UAE, with a median age of 30 years (range 8 - 93 years), a 7.3% prevalence of comorbid allergic rhinitis asthma, lower in immigrants and with increasing age [ 13].
By season and gender, controls were matched using a greedy algorithm to select age matches by selecting the closest match first, within a 5-year age range, then the closest remaining match and so on (STATA, gmatch).
