AlmostClever wrote:95% of 9,000 patients is not enough proof to show correlation?
Did I read that right?
What the abstract actually reported was the hazard ratio. This is a measure of the relative risk of some event in one group compared to another group.
Participants reporting one or more vascular comorbidities at diagnosis had an increased risk of ambulatory disability, and risk increased with the number of vascular conditions reported (hazard ratio [HR]/condition for early gait disability 1.51; 95% confidence interval [CI] 1.41–1.61).
Vascular comorbidity at any time during the disease course also increased the risk of ambulatory disability (adjusted HR for unilateral walking assistance 1.54; 95% CI 1.44–1.65).
What the first statement means is that MS patients with one or more vascular comorbidities at the time of diagnosis had a 1.51 times greater risk for ambulatory disability. The second statement indicates that having a vascular comorbidity at any time during the course of MS disease resulted in 1.54 times the risk of ambulatory disability.
The 95% CI numbers that are reported indicate the 95% confidence interval for the two hazard ratio numbers. The 95% CI functions essentially like error bars on the reported data. In effect, the first hazard ratio was found to vary from 1.41 to 1.61 with a mean of 1.51 and the second hazard ratio was found to vary from 1.44 to 1.65 with a mean of 1.54. The 95% CI indicates that 95% of the calculated hazard ratios lie under the center of the bell curve, the population of hazard ratios, with a value of 1.41 to 1.61 (for the first case), and that 2.5% of the data lie at either end of the extremes of the bell curve. The 95% CI is plus or minus 2 standard deviations from the mean on the bell curve.
Anyway, that's my best interpretation from my college biostatistics course which was about 16 years ago. Clear as mud (or at least slightly better I hope).