Birth Weight, Weight Change During Life Course, and Adult Blood Pressure / Hypertension in Hong Kong Female Nurses

Background: There is much evidence that body weight at any stage of life is significantly associated with blood pressure (BP). In the last two decades, some experts have suggested that low birth weight (BW) should be considered as a new risk factor for developing hypertension (HTN). Only a few studies comprehensively investigated the associations between BP and BW and body weight during the life course, especially in Chinese populations.;Objectives: To determine whether BW, weight at young adulthood (age 18), and current weight have independent associations with adult BP / HTN. To describe the trend of weight change during the life course and its association with adult BP and HTN. To determine the time point or period at which body weight has the largest effect on the adult BP / HTN. To examine whether there are interaction effects of BW, weight at age 18, and current weight on adult BP / HTN.;Subjects and Methods: The study population was drawn from female nurses aged 35 to 65 years who are members of the Association of Hong Kong Nursing Staff (AHKNS). This study consisted of three parts. A pilot study was conducted in advance to determine whether a mail survey was feasible in the target population. Following the pilot study, the formal study was established, and a self-administered questionnaire to collect the information on early life exposures and later life outcomes was mailed to the nurses. Additionally, during the formal study, face to face body measurements were conducted in a sub group of participants to verify the validity of some self-reported variables.;Results: 1253 nurses participated in the study. The mean age was 45.7 years, the mean BW and current BMI was 3.01kg and 22.0kg/m 2 respectively. 80.9% of participants had weight gain during adult life, ranged from 0.18kg to 36.29kg. The highest BP existed in the participants who were in the heaviest 10% both at birth and at present (SBP: 131.5 mmHg, DBP: 80.0 mmHg). According to linear regression analysis, a significant inverse association between BW and BP (P<0.05) was found in the BW <3 .5kg group. Current weight and weight at age 18 were both positively associated with BP (both P<0.05). Adult weight change (current weight -- weight at age 18) and weight gain before adulthood (weight at age 18 -- birth weight) were both positively associated with BP (both P0.05), but a significant interaction was found between current weight and weight at age 18 (P>0.05). A further curve estimation showed a quadratic curvilinear association (like a "J" shape, P<0.05) between BW and BP. The BW-systolic BP relationship was strengthened in the current overweight / obesity group (coefficient B: -3.70) and the age ≥ 45 years group (coefficient B: -3.61). Similar results were found using logistic regression analyses for HTN.;Conclusions: There is a weak negative association characterized as "J" shape between BW and adult BP. The effect of BW on BP is independent of weight at older ages. Being over weight / obese at current amplifies the effect of BW on BP. Body weight at age 18 and at current are both positively associated with BP. Current weight has the greatest effect on BP. Weight gain during life course has an independently positive association with BP. Maintaining an optimal body weight during the life course is important.