Helsinki Policemen Study

Background/Question:

The Helsinki Policemen Study investigated the association between blood glucose level and risk of coronary heart disease (CHD). The study was one of the first prospective epidemiological studies to demonstrate “an association of hyperinsulinemia to the risk of coronary heart disease.” [1] The researchers collected glucose and insulin data on middle-aged police officers in Helsinki, Finland over two examination periods to track the incidence of CHD.

Population and Methods:

The first examination took place from 1966 to 1967 in a cohort of 1326 men aged 30 years or older (98.4% response rate) employed by the Helsinki police or the National Police Force in Helsinki. At baseline, they were given complete physical examinations by a physician, blood and urine samples were collected for cholesterol, hematocrit and glucose measurements; physiologic function tests were performed and socio-demographic data were recorded [2].

A second examination of the subjects took place five years later, from 1971 to 1972, and included a clinical examination, BMI measurement, skin-fold thickness, blood pressure, blood samples for blood glucose and serum cholesterol, oral blood glucose tests, the Rose cardiovascular questionnaire and a questionnaire on medical history, smoking status and physical activity level [1]. The cohort was followed for an average of 22.3 years, with individual follow-up periods ranging from 21.9 to 22.9 years [1]. The study found that it appeared the “predictive value [of blood glucose level] diminished with lengthening follow-up time.” [1]

Results:

Within the Helsinki Policemen cohort, blood glucose level predicted coronary heart disease. In a 1979 study of glucose tolerance and coronary heart disease, researchers observed that 10-year CHD mortality rates for policemen in the highest 1-hour and 2-hour post-load blood glucose levels were 87.7/1000 and 76.7/1000 respectively, compared to the lowest levels, with mortality rates at 35.2/1000 and 54.8/1000, respectively. [2] However, when blood glucose was included in a multivariate analysis including smoking, cholesterol, blood pressure, age, body mass and smoking status, it showed no significant association. [2]

In a 1998 study of insulin activity, “the age-adjusted hazard ratios for a major CHD event, comparing men in the highest area under the curve of insulin quintiles with those in the combined 4 lower quintiles during 5-, 10-, 15-, and 22- year follow-up periods, were 3.29 (95% CI 1.56-6.91), 2.72 (95% CI 1.67-4.42) , 2.14 (95% CI 1.43-3.21), and 1.61 (95% CI 1.14-2.27) respectively.”

Conclusions/Discussion:

The Helsinki Policemen study, along with the Busselton and Paris Prospective Studies was among the first of its kind to show an association between high blood glucose and risk for CHD [1]. The authors conclude that the association may only provide predictive value in the short-term.

Since the Helsinki Policemen results have been published, the Atherosclerosis Research In Communities (ARIC), Rancho Bernardo, and San Luis Valley Diabetes Studies, among others, have published contrary findings [3-4]. Among the ARIC cohort, fasting insulin levels were not predictive of CHD risk among men although presence of diabetes did convey a high risk of CHD. [3] In a five year follow-up of the Rancho Bernardo study cohort, fasting insulin level was unrelated to the risk of cardiovascular disease. [4] However, a meta-analysis of the association between plasma insulin and cardiovascular mortality based on data from eleven European prospective studies, including the Helsinki Policemen Study, showed that during the 8.8-year follow-up the hazard ratio of CVD mortality for the highest vs the lowest quartile for fasting insulin, adjusting for age and other risk factors, was 1.54 (1.16-2.03) in men and 2.06 (1.45-4.90) in women. For 2-h insulin these ratios were 0.85 (0.60-1.21) and 1.36 (0.53-3.45) [5]. (KP/HB)