Primary health care is crucial when it comes to diagnosis and treatment of common diseases, and health counselling. Body height, body weight and waist circumference are easy to measure enabling calculation of body mass index, body surface area, waist-to-height ratio, and waist-to-hip ratio. However, in clinical practice and guidelines little attention has been paid to differences in body size among individuals except in relation to overweight and obesity. A difference between men and women that has received little attention is the smaller body size of women on average.

The aim of this thesis was to assess the association between body surface area and 24-hour ambulatory blood pressure monitoring in participants from the Helsinki Birth Cohort Study population (n = 534, mean age 61 years, 51% women), and plasma glucose concentrations in an oral glucose tolerance test (n = 2659, mean age 58 years, 56% women) and ankle brachial index (n = 972, mean age 59 years, 53% women) in participants from Harjavalta Risk Monitoring for Cardiovascular Disease Project population considering unexplained sex differences. BSA was calculated using the Mosteller formula (weight (kg) × height (cm) / 3600)0.5.

Body surface area was positively associated with blood pressure even after adjustment for confounding factors. However, blood pressure load per body surface area was significantly higher among women. Body surface area showed an inverse association with 2-hour post-load plasma glucose concentration in an oral glucose tolerance test. The smaller body surface area was the higher was proportion of new pre-diabetes or diabetes diagnoses. Body surface area also had a negative association with 2-hour post-load plasma glucose concentration in subjects with normal glucose tolerance. Body surface area had a positive association with ankle-brachial index and difference in ankle-brachial index between women and men was modified by body surface area. This partially explains why women have lower ankle-brachial index. In conclusion, body size should be considered in epidemiological studies especially when comparing glucose metabolism, blood pressure or ABI between men and women. Moreover, an OGTT may not be an appropriate diagnostic method to detect glucose disorders.