HC Statistics

Average prevalence of “sickness”

Despite the large number of illnesses defined by the International Statistical Classification of Diseases and Related Health Problems (ICD) disease coding system, health systems need to know how many encounters they are likely to experience each month. One gauge for this is the prevalence of sickness in the population. A paper by White et al. (1961) estimates this figure as follow:

Data from this survey for a four-year period (1946-1947 to 1949-1950) show variations in the mean monthly sickness rates with age, sex and season between extremes of 51 and 89 per 100 adults (sixteen years of age and over), as shown in Table 1. The annual mean monthly rates are rather constant at about 68, sug- gesting that in a broad-based population survey, 68 adults out of every 100, in an average month, will experience at least one episode of ill health or injury that they can recall at the end of that month.

The authors also investigate the typical number of physician visits, hopsitalizations, and referrals to academic medical centers. They find that:

In summary, it appears that within an average month in Great Britain or the United States, for every 1000 adults (sixteen years of age and over) in the population, about 750 will experience what they recognize and recall as an episode of illness or injury. Two hundred and fifty of the 750 will consult a physician at least once during that month. Nine of the 250 will be hospitalized, 5 will be referred to another physician, and 1 will be sent to a university medical center within that month. Expressed in other terms, 0.75 of the adult population experience sickness each month, 0.25 consult a physician, 0.009 are hospitalized, 0.005 are referred to another physician,and 0.001 are referred to a university medical center. In an average month, 0.009/0.75, or 0.012, of the “sick” adults in the community, are seen on hospital wards, and 0.001/0.75, 0.004, are seen at university medical centers.


  • KERR L. WHYYE, MD, T. FRANKLIN WILLIANIS, MD, AND BERNARD G. GREENBERG, PHD. The Ecology of Medical Care. The New England Journal of Medicine 265:885-892, 1961.

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