It’s like smoking. If you take identical twins and one smokes but the other doesn’t, the smoker is going to end up with a significantly higher white cell count. In Japan, for example, as smoking rates have steadily dropped, so has the normal white count range, such that about 8% of never smoking men would now be flagged as having abnormally low white counts if you used a cutoff like 4. But, that’s because most people were smoking before, when they set that cutoff. So, maybe 3 would be a better lower limit. The inflammation caused by smoking may actually be one of the reasons cigarettes increase the risk of heart attacks, strokes, and other inflammatory diseases. So, do people who have lower white counts have less heart disease, cancer, and overall mortality? Yes, yes, and yes. People with lower white blood cell counts live longer. “Even within the normal range,” every one point drop may be associated with a 20% drop in the risk of premature death.