Can the often volatile pattern of behavior (“Sinning against health as long as health is good; sacrificing everything for health when health is bad”) be brought into line with rationality? 

Or are individual preferences inconsistent, implying that medical experts should perhaps determine the appropriate amount of preventive behaviors?

 Can the economic concept of substitution be applied to health production even though situations can easily be envisioned in which only medical services (rather than one’s own health-enhancing efforts) offer the prospect of improvement?