yes you can. there are very similar but i'd say that 'relations' can be used to describe domains that are more personal, e.g. familial relations, sexual relations, working relations, whereas 'associations' sounds more formal to me.

ASSOCIATIONS: a. A mental connection or relation between thoughts, feelings, ideas, or sensations. b. A remembered or imagined feeling, emotion, idea, or sensation linked to a person, object, or idea. RELATIONS: a) The mutual dealings or connections of persons, groups, or nations in social, business, or diplomatic matters: international relations. b) A logical or natural association between two or more things; relevance of one to another; connection:. Eg:the relation between smoking and heart disease. so, I would prefer to say that "the relation between various factors and heart disease" is the right way.