What does this paragraph mean?

Type D personality is an established independent risk marker in patients with CHD, prospectively associated with worse clinical and patient-reported outcomes, although substantial heterogeneity exists between studies. Research findings have attributed large parts of this heterogeneity to the disease stage, specificity of the outcome measure, and sample age. It is important to consider the mechanistic pathways through which a risk factor is likely to exert its effect when choosing endpoints. Otherwise, it might erroneously dilute the importance of the risk factor.