Blood pressure data analysis from NHANES dataset.
By: João Guilherme
Tags: Python, Data Visualization, Pandas, Science, Blood Pressure

Speaking about sex differences in BP, I highly recommend the following article for further understanding of the data:

https://academic.oup.com/ajh/article/31/12/1247/5123934, and further explanation on the effects of aging in BP in both sexes, I recommend this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4768730/.

Overall, the analysis of the NHANES dataset showed that the difference between diastolic (t= -2.47) and systolic BP (t = 3.1) in the age band [0–10 years] is small compared to other age bands. This is observed, between many reasons, by a low sexual differentiation in this pre-puberty period. The difference between males and females in systolic BP reach it’s maximum value on the age band of [20–30 years] (t= 37.31) and diastolic BP on the age band of [30–40 years] (t=19.68), both BP being higher in males compared to females (this is why the t value is positive, once the variable 1 is always the male group compared to the variable 2 female).

After the greatest difference in systolic BP in the [20–30 years], the difference drops through years reaching a negative t value of -1.9 in the age band of [60–70 years]. The negative t value is saying that, on our sample, the mean systolic BP of females is higher than males. The diastolic BP difference between males and females also reduces over years. Many factors contributes to this observed result. One of those factors may be drop of sexual hormones in females, as they get older.

Using the “t age” values observed for systolic BP, we can see that males have high increase in BP, specially between the age bands of [10–20 years](t = 33.16) and [20–30 years](t=34.71) which slows down in older groups, for example [70–80 years] (t=4.17). Females, on the other hand, start with slower increase in systolic BP in the age bands[10–20 years](t=23.85) and [20–30 years](t=17.47). Then females increases their t values in the age band of [40–50 years](t=20.9), reaching the point of a higher mean systolic BP on the age band of [60–70 years] (speaking about the sample only).

Using the “t age” values for diastolic BP, I would highlight brief observations. First of all, it’s interesting to note the shape of “U” of data over years for both sexes, increasing until age band of [40–50 years] and reducing after this age band.

The purpose of calculating “t male” and “t female” was observe variations between diastolic and systolic BP in males or females respectively between age bands. In the first age band [0–10 years] we observe a “t female” of 104.14 and “t male” of 103.36, which increases in age band of [10–20 years] and falls as age increases. This was not an expected result once the difference between means increase after 40 years old. But, we also see a continuous increase in the standard deviation of the variables as the groups get older, especially on systolic BP.

It is important to highlight that many biases might be contained is this data analysis. For example, smoking, HDL, cholesterol, obesity, nutrition behaviour, alcohol consumption and diabetes were not explored between age bands and gender and might influence BP.

In resume, the difference between males and females are minimal in BP between 0–10 years old. The difference becomes clear between 10–40 years old, with males having greater systolic and diastolic BP. Those differences are reduced between 40–70 years old and swap between 70–80 years old in matters of systolic BP, and are reduced in matters of diastolic BP. Both genders suffers an increase of systolic BP as they get older. Both genders suffers increase in diastolic BP as they get older until 40–50 years, after this point, diastolic BP is reduced.