Missingness in blood pressure medication data
Hi, I have a question regarding blood pressure medication variables (captured in field IDs 6177 and 6153)
In my analytical sample, these variables have a substantial amount of missing data, with over 50% of participants coded as NA. It also appears that the answers provided to these variables/questions were reviewed again during the nurse interview, which makes the extent of missingness in fields 6177 and 6153 difficult to understand.
I'd appreciate any guidance on the following:
1) Are there any known reasons why fields 6177 and 6153 contain missingness?
2) How is the missingness in these types of variables usually interpreted? - Should NAs be treated as genuine missing data, or can it be assumed that participants who are NA were not taking antihypertensive medication (or any of the other medication categories captured by these fields)?
3) Are there alternative fields that could be used, that may provide more complete information on blood pressure medication use?
Any insight on what might be driving this missingness in these variables would be really helpful
Thank you
Comments
4 comments
Hi Tahsina,
Field 6177 holds data for males, while field 6153 holds equivalent data for females. You can see this in the Showcase page for each field, which says Sexed:Males only or Sexed:Females only. Field 6153 also includes data about “exogenous hormones” (HRT), which would not be relevant to Males.
Thank you for using the forum.
Hi Rachael,
Thank you for your response. My query was more about the extent of missingness I'm observing in these variables. I was wondering whether there is any known explanation for the NA values in these variables, how those NAs are typically interpreted, and whether alternative fields could be used for antihypertensive medication that might provide more complete data.
Thank you
Depending on how your dataset was obtained and combined, you might expect to see NA values in field 6177_i0 for all females (slightly over half of all participants are female), and NA values in field 6153_i0 for all males.
80% of UKB participants have not attended an imaging visit, and therefore have no values for any fields at _i2 or _i3. For more on instances see What is an instance index? – UK Biobank .
If a value is NA or missing for field 6177, this would usually mean that the participant was not asked that question at the relevant visit, either because it was not applicable to them or because they did not attend that visit at all.
Fields 6177 and 6153 relate to answers that participants provided during an in-person visit to a UKB assessment centre. UKB also has some Linked Health Data for some participants, which was provided by the National Health Service (NHS). For example, there is GP (primary care) Prescription data in Record Table gp_scripts, described in Field 42039 on Showcase. See also Category 3000 and Resource 596 . Please note that this is only available for 45% of participants, and only up till 2017. Record table gp_scripts is within the Parquet database on the UKB-RAP, in entity (sub-table) gp_scripts.
One further complication is that fields 6177 and 6153 are arrayed. This is because it is possible for a single participant to answer both “Cholesterol-lowering medication” and “Blood pressure medication”. The two different answers are saved in different Array indeces. Since most participants will not answer with multiple medications, most participants will have NA in all but the first array index.
That is: I would expect all female participants to have a value in Field 6153_i0_a0, but most female participants to have no value in Field 6153_i0_a1.
Please sign in to leave a comment.