Cross sectional studies: advantages and disadvantages

A cross sectional study design was used to investigate the extent of chronic fatigue and the associated psychosocial exposures in a developing country. The setting was a primary health centre catchment area in Goa, India. Participants were women aged 18-50 years. The primary outcome was reporting of fatigue for at least six months. Data on the primary outcome and psychosocial exposures were obtained by a structured interview. The psychosocial exposures that were investigated included mental health and gender disadvantage factors. The presence of anaemia was determined from a blood sample.1

The sampling frame consisted of 8595 eligible women listed in family health registers. In total, 3000 randomly sampled women were invited to participate and 2494 (83%) consented. Recruitment took place from November 2001 to May 2003. It was reported that 12.1% (95% confidence interval 10.8 to 13.4%) of women experienced chronic fatigue. Those psychosocial exposures most strongly associated with chronic fatigue were poor mental health and sexual violence by the husband.

Which of the following statements, if any, are true?

• a) The study was longitudinal by design

• b) It was possible to estimate the prevalence of chronic fatigue in women aged 18-50 years

• c) It was possible to estimate the incidence of chronic fatigue in women …