Hospital Controls versus Community Controls: Differences in Inferences Regarding Risk Factors for Hip Fracture

Abstract

In case-control studies using cases identified from persons admitted to hospitals, two types of controls are most often used: persons from the communities served by the hospitals and persons admitted to the same hospitals as those to which the cases were admitted. It is often unclear which is the more appropriate choice, and whether the use of one or the other type of control group will lead to biased conclusions. The purpose of the present analysis was to determine whether the choice of hospital controls versus community controls would influence conclusions regarding risk factors for hip fracture. Cases (n = 425), hospital controls (n = 312) and community controls (n = 454) were drawn from a case-control study of risk factors for hip fracture in women. Study participants were white and black women aged 45 years or older and living in New York City or Philadelphia, Pennsylvania, who were selected between September 1987 and July 1989. Using community controls but not hospital controls, investigators would have concluded that having a fall during the previous 6 months, current smoking, and moving during the previous year were associated with an increased risk of hip fracture. Associations of hip fracture risk with stroke and prior use of ambulatory aids were stronger using community controls, but associations with estrogen use and body mass index were not influenced by choice of control group. Community controls were quite similar to representative samples of community-dwelling elderly women, whereas hospital controls were somewhat sicker and more likely to be current smokers. The authors conclude that community controls comprise the more appropriate control group in case-control studies of hip fracture in the elderly.

Benzodiazepines and hip fractures in elderly people: case-control study

“…Much has been said about the choice of controls from the community or hospital,29 including for the study of hip fracture 30. Because the controls were admitted to hospital they were obviously ill and therefore had a higher probability of using drugs, perhaps including benzodiazepines, than a healthy control population.…”

Bone Mineral Density, Hip Axis Length and Risk of Hip Fracture in Men: Results from the Cornwall Hip Fracture Study

“…An alternative strategy would have been to select the controls from a hospital population; however, such a group, because of concurrent illness, may not be representative and it may be dif®cult to extrapolate the ®ndings to the general population. Moritz et al [17], in considering this issue, suggested community controls comprise the more appropriate control group in case±control studies of hip fracture in the elderly.…”

¿Es la etnia mapuche un factor de riesgo para padecer fractura de fémur proximal en adultos mayores?

“…Cuando se utilizó el concepto de raza con frecuencia la asociación fue modificada por el estrato social [9][10][11][12][13][14][15]23,24 . La raza es un grupo de individuos reunidos por algunas características genéticas comunes, cuyo valor para explicar la variabilidad humana es limitada dado la mayor importancia de la diversidad individual.…”

“…El menor acceso a la atención de salud de los miembros de la etnia mapuche con fractura de fémur proximal se balanceó utilizando controles hospitalarios, donde las dificultades de acceso son las mismas. Sin embargo, como se demostró en la revisión bibliográfica los controles hospitalarios son «más enfermos que los casos» 14 , lo que nos obligó a considerar en el análisis variables de control relacionadas con morbilidad. Otro factor que potencia el sesgo de muestreo es el alto índice de masculinidad de la población mapuche de la IX región (108,2 en Malleco y 103,2 en Cautín) que contrasta con el predominio del sexo femenino en chilenos con fractura de fémur proximal (índice de masculinidad en egresos por fractura de fémur proximal en 1985 66,6).…”

“…La masa ósea máxima que un individuo puede alcanzar es un atributo genético, posiblemente relacionado con la raza o etnia. En Estados Unidos los afroamericanos tienen una menor prevalencia de osteoporosis que mongoloides, caucásicos e hispanos [9][10][11][12][13][14][15][16] .…”